Dr Rajiv Desai

Plane Crash

May 28, 2021 by Dr Rajiv Desai

Plane Crash:

“Flying is not inherently dangerous, but to an even greater extent than the sea, it is terribly unforgiving ….”
—Captain A. G. Lumplugh, British Aviation Insurance Group 

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Section-1 

Prologue:

Flight is, and always will be a marvel of human achievement. The opportunity to “spread your wings” and fly is an unbelievable privilege and experience. Airways have undergone a drastic evolution in the past decade, with airplanes becoming the most widely used means of transport across the globe. This is primarily because of the higher reliability, least travel time and a better cost effectiveness of the airways over other modes of transport. In addition to that, airports are traditionally considered as the country’s signature monuments. It showcases to an outsider, the first and the last impression of the country. Commercial aviation transports more than four billion passengers annually on airliners. Aviation is a critical part of national economy, providing for the movement of people and goods throughout the world and enabling economic growth. As volume of air transportation is increasing rapidly, the safety of aviation becomes an important problem for many countries. Accident of an airplane leads loss of human life and it also influences the reputation and the economy of air transportation industry of the country.    

The safe operation of an airplane depends on the reliable performance of systems that provide thrust, lift, stability, control, collision avoidance, navigation, and cabin environment. The wellbeing of crew, passengers, and bystanders may be threatened by the failure of any one these systems to perform their designed function. Nearly all airplane accidents are cause by several contributing factors. There is almost never a single, simple cause. Human factors are contributing or causal in most accidents. This can be pilots, designers, controllers, mechanics or operator management. Over the years, airplanes have become more reliable, better-designed and maintained. A structural failure accident is indeed rare. Weather can certainly contribute to accidents, but pilots can deviate around thunderstorms, fly to an alternate airport or elect not to fly in certain weather (such as freezing rain), so it’s hard to say that weather “causes” an accident. However, weather conditions can make flying or landing much more challenging. More recently, a Lion Air flight crashed in October 2018, as well as an Ethiopian Airlines flight in 2019. The 2018 and 2019 crashes raised questions about malfunctions of sensors and software of the Boeing 737 Max airplane used in both flights, and many airlines responded by grounding the airplane.

The airplane has revolutionized our existence. It has cut journeys that used to take weeks and months into just a few hours. The busiest day recorded in aviation is 24 July 2019, with more than 225,000 flights on that day. It’s also extremely safe, but people continue to fear it. The likelihood of dying in a plane crash (or even being in one) is so slim it’s almost pointless to quantify. According to 2015 statistics from The Economist, the probability of your plane going down is around one in 5.4 million. More recent numbers from the probability-calculating app Am I Going Down? in April 2018, give you odds as good as 20 million to one that you’ll make it safely from point A to point B. Even traveling by car is more deadly than hopping on a plane. Nonetheless plane crashes are catastrophic, killing more people at once, which grabs more attention and makes people more sensitive to them. With the development of economic globalization and economic, political, and cultural exchanges worldwide and the acceleration of turnover, the global civil aviation transportation industry continuously develops, and flight safety is increasingly taken seriously. Paying high attention to civil aviation accidents, the public easily lose confidence in civil aviation transportation, thus seriously restricting the development of civil aviation. Therefore, it is necessary to make in-depth study for improvement of the safety skill of airlines and reduction of the probability of aviation accidents. This article discusses and analyzes plane crash involving private planes and civilian airlines, and not helicopter crash or military aircraft crash. The focus is on plane crash involving commercial airline.     

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Abbreviations and synonyms:

FAA = Federal Aviation Administration

NTSB = National Transportation safety Board

GPWS = Ground Proximity Warning System

ICAO = International Civil Aviation Organization

Knot = kn = kt = one nautical mile per hour = 1.852 km/h = 1.15078 mph = 0.514 m/s

PIC = Pilot in command 

GA = general aviation

POH = Pilot Operating Handbook

ETOPS = Extended range Twin-engine Operational Performance Standard

CL = center of lift = center of pressure = CP

CG = center of gravity

AOA = angle of attack

CVR = Cockpit Voice Recorder

FDR = Flight Data Recorder

ILS = instrument landing system

IFR = Instrument flight rules

VFR = visual flight rules

VMC = visual meteorological conditions

IMC = instrument meteorological conditions

RVSM = Reduced Vertical Separation Minima

ACAS = Airborne Collision Avoidance System

TCAS = Traffic Collision Avoidance System 

ATC = Air traffic controller 

ADS-B = Automatic Dependent Surveillance Broadcast

CRM = cockpit/crew resource management

CFIT = Controlled flight into terrain

LOC-I = Loss of control in-flight

HFACS = Human Factors Analysis and Classification System

TFH = total flight hours

ALAR = Approach-and-Landing Accidents Reduction

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Section-2

Introduction and Terminology: 

Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere (i.e., air flight or aviation) or through the vacuum of outer space (i.e., spaceflight). This can be achieved by generating aerodynamic lift associated with gliding or propulsive thrust, aerostatically using buoyancy, or by ballistic movement. Many things can fly, from animal aviators such as birds, bats and insects, to natural gliders/ parachuters such as patagial animals, anemochorous seeds and ballistospores, to human inventions like aircraft (airplanes, helicopters, airships, balloons, etc.) and rockets which may propel spacecraft and spaceplanes.

An aircraft is any machine that can fly. An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), gliders, paramotors and hot air balloons. The human activity that surrounds aircraft is called aviation. The science of aviation, including designing and building aircraft, is called aeronautics. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. An airplane is a specific type of aircraft that has fixed wings and is heavier than air that is capable of sustained, powered, and controlled flight.  Aviation began in the 18th century with the development of the hot air balloon, an apparatus capable of atmospheric displacement through buoyancy. Some of the most significant advancements in aviation technology came with the controlled gliding flying of Otto Lilienthal in 1896; then a large step in significance came with the construction of the first powered airplane by the Wright brothers in the early 1900s. Since that time, aviation has been technologically revolutionized by the introduction of the jet which permitted a major form of transport throughout the world.

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General Aviation (GA):

Although GA is typically characterized by recreational flying, it encompasses much more. Besides providing personal, business, and freight transportation, GA supports diverse activities such as law enforcement, forest fire fighting, flight instruction, air ambulance, agriculture, logging, fish and wildlife spotting, and other vital services flown in a variety of aircraft of all sizes and types, including airplanes, helicopters, balloons, and gliders. The majority of civil aviation crashes, deaths, and injuries are attributed to general aviation operations. General aviation aircraft are as varied as their pilots and the types of operations flown. The following aircraft categories and classes are included in each year’s Nall Report:

• Piston single-engine
• Piston multiengine
• Turboprop single-engine
• Turboprop multiengine
• Experimental
• Amateur-built
• Turbojet

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Difference between Commercial Aviation and General Aviation:

Civil (non-military) flight operations are usually categorized as commercial or general aviation.

Commercial aviation concerns scheduled flights from larger tarmac airports that involve the transportation of passengers or cargo. When you purchase a ticket to fly on a plane, your travel falls into this category. Pilots who fly commercial aircraft are held to higher medical and safety standards, and they are required to hold the appropriate licensure and training before they can operate large commercial planes.

General aviation, on the other hand, includes a wide range of aircraft. All nonscheduled flights that are not operated by commercial airlines or by the military are identified as general aviation. It’s easier to get a license to fly general aviation aircraft, and the safety standards aren’t as quite as high as those for commercial pilots.

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A Part 121 carrier is a regularly scheduled air carrier in the U.S. In addition to scheduled air operators, the FAA provides designations for private operators (Part 91), foreign air carriers and foreign registered operators of U.S. aircraft (Part 129), and commuter and on-demand operators (Part 135), among others. According to the FAA regulations, there are differences between part 121, and 135, 129, and 91. Each of these parts regulates a certain area of operations. Knowing these regulations is obligatory for the operator and mastering it significantly increases the general aviation sector safety.

General aviation, governed by 14CFR Part 91 regulations, includes all civilian aviation with the exclusion of operations involving paid passenger transport—the latter covered under the comparable 14CFR Part 121 and 135 rules. Although accidents for the airlines (14CFR Part 121) have dramatically declined over recent decades (Aviation Safety Institute, 2012; Li & Baker, 2007), such a decrease is not as evident for general aviation, although preliminary data (NTSB, 2014b) indicate a decline for the most recent year (2013). Still, general aviation accounts for the overwhelming majority (94%) of civil aviation fatalities in the United States (Li & Baker, 2007), and represents an unresolved safety challenge for aviation. Furthermore, general aviation accidents carry an associated annual cost of $1.6 to $4.6 billion to individuals and institutions affected (e.g., family and nonfamily incurring injury and/or loss of life, insurance companies, accident investigation costs) when taking into account hospital costs, loss of pay with a fatal accident, and loss of the aircraft (Sobieralski, 2013). In all likelihood, these costs would be even higher if litigation costs were assessed as well.

Most studies on general aviation accidents to date (Bazargan & Guzhva, 2011; Bennett & Schwirzke, 1992; Groff & Price, 2006; Li & Baker, 1999; Li, Baker, Grabowski, & Rebok, 2001; Rostykus, Cummings, & Mueller, 1998; Shao, Guindani, & Boyd, 2014) have focused on the pilot either in terms of pilot error, or corresponding risk factors such as pilot flight experience, certification, demographics, and flight conditions. This is not surprising since the airman has been faulted in 55–85% of general aviation accidents (Li et al., 2001; Shkrum, Hurlbut, & Young, 1996). Therefore, the remaining general aviation accidents likely have pilot-independent causes, and it is hypothesized that maintenance errors represent such a subset.

Although general aviation airplane crashes typically generate much media coverage, they are infrequent occurrences. In 1992 there were 39.6 million flight departures and 2075 crashes. In 78% of the crashes there were no deaths and in 68% there were no injuries. Airplanes are designed with features that can dissipate the kinetic energy of the occupants and minimize injury in the event of a crash landing. If a crash landing is necessary, pilots are taught to keep the plane under control, to land in an upright position at the slowest possible speed, and to avoid obstacles as much as possible.

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Knot:

A nautical mile is a unit of measurement used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as one minute (1/60 of a degree) of latitude along any line of longitude. Today the international nautical mile is defined as exactly 1852 meters (6076 ft; 1.151 mi). The derived unit of speed is the knot, one nautical mile per hour.

The knot is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.15078 mph or 0.514 m/s). The ISO standard symbol for the knot is kn. The same symbol is preferred by the Institute of Electrical and Electronics Engineers (IEEE); kt is also common, especially in aviation, where it is the form recommended by the International Civil Aviation Organization (ICAO). The knot is a non-SI unit. The knot is used in meteorology, and in maritime and air navigation.

Although the unit knot does not fit within the SI system, its retention for nautical and aviation use is important because the length of a nautical mile, upon which the knot is based, is closely related to the longitude/latitude geographic coordinate system. As a result, nautical miles and knots are convenient units to use when navigating an aircraft or ship. A vessel travelling at 1 knot along a meridian travels approximately one minute of geographic latitude in one hour.

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Pilot in command (PIC);

The pilot in command (PIC) of an aircraft is the person aboard the aircraft who is ultimately responsible for its operation and safety during flight. This would be the captain in a typical two- or three-pilot aircrew, or “pilot” if there is only one certificated and qualified pilot at the controls of an aircraft. The PIC must be legally certificated (or otherwise authorized) to operate the aircraft for the specific flight and flight conditions, but need not be actually manipulating the controls at any given moment. The PIC is the person legally in charge of the aircraft and its flight safety and operation, and would normally be the primary person liable for an infraction of any flight rule.

The strict legal definition of PIC may vary slightly from country to country. The International Civil Aviation Organization, a United Nations agency, definition is: “The pilot responsible for the operation and safety of the aircraft during flight time.” Flight time for airplanes is defined by the U.S. FAA as “Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing.” This would normally include taxiing, which involves the ground operation to and from the runway, as long as the taxiing is carried out with the intention of flying the aircraft.

The Pilot in Command must hold the rank of Captain, and typically sits in the left seat. The second in command can be a First Officer or another Captain, and will occupy the right seat. The term first officer has been in use for decades by most airlines, it has its roots in nautical terminology for the second-in-command. During World War II, the Air Force (then the Army Air Corps) began using the term “co-pilot” and the term name eventually became common. First officer is a more descriptive designation and is consistent with the Navy and maritime industries. In older, larger airliners, there was a second officer or flight engineer. During the days of propeller airliners, the flight engineer was a specially qualified maintenance technician, due to the complexity of operating large radial engines. When jets arrived, most flight engineers were pilots specially trained to operate aircraft systems.

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Flight Time Requirements:  

The FAA requires 1,500 hours to fly as an airline pilot, which can be earned in about two years. The rule requires first officers — also known as co-pilots — to hold an Airline Transport Pilot (ATP) certificate, requiring 1,500 hours total time as a pilot.

Type of license	Total Hours Required
Private Pilot License	40 Hours
Commercial Pilot Certificate	250 Hours
Airline Transport Pilot Certificate	1,500 Hours

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A commercial pilot in typical airline service is allowed, at maximum, to fly about (1) 100 hours of flight time in any 28 consecutive days; (2) 900 hours of flight time in any calendar year; and. (3) 1,000 hours of flight time in any 12 consecutive calendar months. This does not include other duty time (like time between flights), and can be lower based on airline internal rules or contracts.

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Section-3

Risk of flying:

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Risks of travel:  

Transport is a classic case of the public perception of risk being at variance with the actual numbers. The public perception is a highly volatile matter particularly in mass transport, where one incident can cause a large number of fatalities. Another feature of transport risk is that the impact of the numbers is very dependent on how you represent them. Basically, there are several possible ways of quoting transport risk; in terms of distance travelled, number of journeys or time of travel. Interested parties tend to choose the form of presentation that suits their own purposes.

The air transport industry, for example, will almost always choose a per km basis, which is optimum for them, as most fatalities occur on landing and take-off, while the intervening distances are large. Land based transport organisations, in contrast, will tend to select fatalities per number of journeys or hours of travel, since the risks are uniformly spread. Thus both are able to demonstrate that theirs is the safest form of transport. The actual statistics are given below (taken from an article by Roger Ford in Modern Railways, Oct 2000 and based on a DETR survey). They record the number of fatalities per billion km, journeys or hours of travel.

Billion km	Billion journeys	Billion hours
Air 0.05	Bus 4.3	Bus 11.1
Bus 0.4	Rail 20	Rail 30
Rail 0.6	Van 20	Air 30.8
Van 1.2	Car 40	Water 50
Water 2.6	Foot 40	Van 60
Car 3.1	Water 90	Car 130
Pedal cycle 44.6	Air 117	Foot 220
Foot 54.2	Pedal cycle 170	Pedal cycle 550
Motorcycle 108.9	Motorcycle 1,640	Motorcycle 4,840

Clearly, the one thing that stands is that, whichever way you look at it, motorcycles are disastrously the most dangerous form of transport. Bus and rail are the safest form of transport by any measure and air is safest only when risk is calculated against distance travelled.

Take the claims about flying being the safest form of transport. If you plot the number of fatal accidents against distance travelled, you end up with 0.05 deaths per billion kilometers for commercial aircraft versus 0.6 deaths per billion kilometers for rail travel. What the airlines don’t tell you is that this form of comparison effectively dilutes the accident rate for aircraft. Aircraft usually travel huge distances while cars and trains don’t. And while the risk of having a fatal accident in a car or train is spread more or less evenly across the journey time, the opposite is true for planes: 70 per cent of all aircraft accidents take place at takeoff and landing, which is only 4 per cent of journey time.

A better measure is to plot the number of deaths against the time travelled. This is fairer, since many car and train journeys last as long as plane journeys. But it still doesn’t take into account the concentration of accidents around takeoff and landing.

The most accurate method is to compare the number of deaths with the number of journeys made. So accurate, in fact, that this is the measure used by the industry and its insurers. This makes much more sense, because what matters to the individual is the journey, not how long it took or how far it went. Also, it enables comparison of different types of jet, both long haul and short haul. By this measure, air travel takes on a rather different complexion. Deaths per billion passenger journeys are, on average, 117 for airliners compared with 40 for cars, and 20 for trains. Only motorbikes, at 1,640 deaths per billion passenger journeys, are riskier than aircraft on this basis.

Of course, as any insurance expert will tell you, a person’s actual risk depends on their exposure. The real reason why air travel is relatively safe is because many of us use it so rarely.

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A US National Safety Council study showed flying to be 22 times safer than travelling by car. On average, 21,000 people die on the road in the US in a 6-month period. This is approximately the same amount of all commercial air travel fatalities worldwide in 40 years!

In 1990, five hundred million airline passengers were transported an average distance of eight hundred miles, through more than seven million takeoffs and landings, in all kinds of weather conditions, with a loss of only thirty-nine lives. During that same year the National Transportation Safety Board’s report shows that over forty-six thousand people were killed in auto accidents. A sold-out 727 jet would have to crash every day of the week, with no survivors, to equal the highway deaths per year in the U.S.

Let me put it in another way:

83% of U.S. adults drive a car at least several times a week. Adult population of U.S. in 1990 was about 174 million. 83% of 174 million is 144 million. So about 144 million people drove car several times a week, say 5 times a week. That comes to about 102 million people drove car once a day. So about 37,230 million people drove car in 1990. That is 37,230 million car journeys in 1990. 7 million plane journeys resulted in 39 deaths. So 37,230 million plane journeys would result in 207,424 deaths. But 37,230 million car journeys caused 46,000 deaths. So car travel is safer than airplane travel when you calculate risk against number of journeys.  

However, journey number safety logic falters when we compare number of deaths versus number of people travelled. 39 deaths for 500 million people travelled by air in 1990. If 37,230 million people travelled by air, about 2903 death would occur by air, much lesser than 46,000 deaths by car. You are 16 times safer in a plane than in a car. If each car journey carried two-person, 74,460 million people travelled by car in 1990. If 74,460 million people travelled by air, about 5,806 deaths would occur by air still lesser than 46,000 deaths by car. So air travel trumps car travel when you compare number of fatalities to number of people travelled but not when you compare number of fatalities to number of journeys.

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Even after reading the stats, you’re still nervous at check-in, you’re not alone. Aviophobia, or the fear of flying, affects an estimated 6.5% of the population. The fear of flying can be debilitating, resulting in sufferers missing out on family events or holidays and – in some cases – work promotions. It’s no surprise that so many people have a fear of flying. Even young birds, born with wings and a natural instinct to fly are nervous, so given we don’t have wings and our natural instinct is to walk, it’s no surprise that we’re fearful of being on board a huge chunk of metal travelling at 35,000 feet and some 500 miles an hour! Researchers in psychology like Paul Slovic and Baruch Fischhoff have found that when we have control (like when we’re driving) we’re less afraid, and when we don’t have control (like when we’re flying) we’re more afraid. Driving affords more personal control, making it feel safer. In addition, plane crashes are catastrophic, killing more people at once, which grabs more attention and makes people more sensitive to them. Car crashes happen every day and spread the loss over time, making their combined effects less noticeable.

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Plane crash statistics:   

Plane crashes are rare. Hull loss is defined as “an event in which an aircraft is destroyed or damaged beyond economical repair.”  In the ten years from 2008 to 2017, there were 1,410 hull loss accidents worldwide involving fixed-wing aircraft with six or more seats, yet from those accidents, only 8,530 people died. That means on the average flight, you have a 4.5-million-to-one chance of dying, making it the second-rarest event behind winning the lottery. For comparison, an estimated 1.25 million people worldwide die from road accidents every year. Apart from one or two outlier years, both the number of airline accidents and deaths have been on a sustained downward trend since the mid-1990s.

The number of aircraft accidents has been on a sustained downward trend for over 20 years as seen in the graph below:

Commercial air travel is regarded as one of the safest forms of transport in the world. Worldwide, commercial aviation transports more than four billion passengers annually on airliners and transports more than 200 billion ton-kilometers of cargo safely at their destinations. In 2020, due to the coronavirus pandemic, the number of scheduled passengers boarded by the global airline industry dropped to only 1.8 billion people. This represents a 55 percent loss in global air passenger traffic.

Remember: 

Aircraft are taking off around the world at a rate of over 400 departures per hour – and that’s only scheduled commercial traffic.

The number of flights performed globally by the airline industry increased steadily since the early 2000s and reached 38.9 million in 2019.

US Commercial flight carriers are conducting about 5,670 passenger flights daily in 2019. Roughly 100,000 flights take off and land every day all over the globe.

The global commercial air transport fleet stood at nearly 24,000 aircraft in 2015. That number grew 3.9 percent annually between 2015 and 2020 to 29,003 aircraft.

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Graph below shows countries and regions with the highest number of fatal civil airliner accidents from 1945 through March 6, 2021

As a result of continued annual growth in global air traffic passenger demand, the number of airplanes that are involved in accidents is on the increase. Although the United States is ranked among the 20 countries with the highest quality of air infrastructure, the U.S. also reports the highest number of civil airliner accidents worldwide. At 861, the United States is the country with the highest number of fatal civil airliner accidents.

The year 2014 is memorable in the aviation’s safety performance for the tragic disappearance of Malaysia Airlines’ flight MH370 and the shooting down of MH17, which lead to 298 fatalities. 

In terms of flight stages, final approach and landing is the most common time for an accident to occur, with takeoff and initial climb being the distant second. However, accidents during landing and takeoff are the most survivable – they occur close to airports where the aircraft are already travelling low and slow and emergency services can respond with a moment’s notice.

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Which type of flying is safer:  

Type of Flight	Fatalities per million flight hours
Airliner (Scheduled and nonscheduled Part 121)	0.00597
Commuter Airline (Scheduled Part 135)	6.10
General Aviation (private Part 91)	11.00

Source: Bureau of Transportation Statistics

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Odds of being involved in a fatal accident:

	Odds of being on a fight that results in at least one fatality	Odds being killed on a single flight
Flying on airlines with good safety records	1 in 10 million	1 in 19.8 million
Flying on airlines with poor safety records	1 in 1.5 million	1 in 2.0 million

Source: OAG Aviation & PlaneCrashInfo.com accident 

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It is important to remember that thousands of airplanes take off every day. Comparatively speaking, plane crashes are quite rare. Here are some of the basics about how frequently crashes happen, when, where, and why.

-1. Either almost everyone survives a plane accident or almost no one does

A thorough US government analysis of 1983–2000 plane accidents found that most accidents have really high survival rates of 81 to 100 percent. But in a handful of accidents, just 0 to 20 percent of people survive.

-2. Planes are crashing less often and killing fewer people

The worst year for plane deaths was 1972, according to this International Business Times analysis. The data do tend to fluctuate from year to year, but it’s clear that we’re not living in the most dangerous time for flying.

-3. Deaths per plane passenger have been going down

The Economist did a nice analysis of recent trends and came to this conclusion: “Over the past four decades fatalities on airplanes—be it from accidents or terrorism—have declined even as the number of travelers has increased almost ten-fold.” This chart below also shows that the majority of deaths are because of accidents, not terrorist attacks.

-4. The safest part of the plane might be the back. Or maybe not.

In 2007, Popular Mechanics went through 36 years of fatal US crashes to try to find where the people who survived them sat. They concluded that the back of the plane was better. However, because such crashes are so rare, there were only 20 crashes available for analysis. And that makes it unclear if this is just a statistical fluke in a small data set. The magazine’s story also included a quotation from the FAA, which said that there’s no way to know which area is safest. But since it’s unlikely that sitting in the back will harm you, you may as well go for it if you want.

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Factors contributing to air accidents are shown in the graph below: 

In the early days of flight, approximately 80 percent of accidents were caused by the machine and 20 percent were caused by human error. Today that statistic has reversed. Approximately 80 percent of airplane accidents are due to human error (pilots, air traffic controllers, mechanics, etc.) and 20 percent are due to machine (equipment) failures.    

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Section-4

Airplane:  

An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spectrum of uses for airplanes includes recreation, transportation of goods and people, military, and research. Worldwide, commercial aviation transports more than four billion passengers annually on airliners and transports more than 200 billion ton-kilometers of cargo annually, which is less than 1% of the world’s cargo movement. Most airplanes are flown by a pilot on board the aircraft, but some are designed to be remotely or computer-controlled such as drones.

The Wright brothers invented and flew the first airplane in 1903, recognized as “the first sustained and controlled heavier-than-air powered flight”. They built on the works of George Cayley dating from 1799, when he set forth the concept of the modern airplane (and later built and flew models and successful passenger-carrying gliders).  Between 1867 and 1896, the German pioneer of human aviation Otto Lilienthal also studied heavier-than-air flight. Following its limited use in World War I, aircraft technology continued to develop. Airplanes had a presence in all the major battles of World War II. The first jet aircraft was the German Heinkel He 178 in 1939. The first jet airliner, the de Havilland Comet, was introduced in 1952. The Boeing 707, the first widely successful commercial jet, was in commercial service for more than 50 years, from 1958 to at least 2013.

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Aircraft Categories:

Airplane – Engine-driven, fixed-wing aircraft

Lighter-Than-Air – Aircraft that uses a gas that is lighter than air in order to rise and remain in the air.

Powered Parachute – A powered type of aircraft that has a flexible wing, frame and wheels. The wing is not in the proper position or ready to provide lift until the aircraft is moving.

Rotorcraft – Flight is maintained by one or more spinning rotors.

Weight-Shift-Control – Also known as a hang glider. This aircraft contains a motor but is only directionally controlled by changes in the center of gravity rather than by control surfaces.

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Classification of Airplanes:

The following information is from FAA Advisory Circular AC 23.1309-1D.

As listed in the AC, the four certification classes of Part 23 airplanes are:

• Class I airplanes, which typically are single reciprocating engine airplanes under 6,000 pounds.
• Class II airplanes, which typically are multiple reciprocating engine, multiple turbine engine and single turbine engine airplanes under 6,000 pounds.
• Class III airplanes, which typically are all Part 23 aircraft equal to or more than 6,000 pounds.
• Class IV airplanes, which typically are commuter category airplanes.

All weights are based on maximum certificated gross takeoff weight. According to the FAA Small Airplane Directorate, the maximum certificated gross takeoff weight is at the time of initial certification; that is, the maximum certificated gross takeoff weight as listed on the original type certificate data sheet. For example, an aircraft for which its initial certification was as a Class II airplane below 6000 pounds would not automatically rise to a Class III aircraft because of the installation of an aftermarket STC that included a gross weight increase to more than 6,000 pounds.

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Airframe:

The structural parts of a fixed-wing aircraft are called the airframe. The parts present can vary according to the aircraft’s type and purpose. Early types were usually made of wood with fabric wing surfaces. When engines became available for powered flight around a hundred years ago, their mounts were made of metal. Then as speeds increased more and more parts became metal until by the end of WWII all-metal aircraft were common.

Aluminum is ideal for aircraft manufacture because it’s lightweight and strong. Aluminum is roughly a third the weight of steel, allowing an aircraft to carry more weight and or become more fuel efficient. Furthermore, aluminum’s high resistance to corrosion ensures the safety of the aircraft and its passengers. The airframe of a typical modern commercial transport aircraft is 80 percent aluminum by weight. Aluminum alloys are the overwhelming choice for the fuselage, wing, and supporting structures of commercial airliners and military cargo/transport aircraft. In modern times, increasing use of composite materials has been made.

Figure below shows a typical airplane with its major components listed.  Many external airplane components are constructed of metal alloys, although composites made of materials such as carbon fiber and a variety of fiberglass resins are becoming more popular as technology improves.

Typical structural parts include:

-One or more large horizontal wings, often with an airfoil cross-section shape. The wing deflects air downward as the aircraft moves forward, generating lifting force to support it in flight. The wing also provides stability in roll to stop the aircraft from rolling to the left or right in steady flight.

-A fuselage, a long, thin body, usually with tapered or rounded ends to make its shape aerodynamically smooth. The fuselage joins the other parts of the airframe and usually contains important things such as the pilot, payload and flight systems.

-A vertical stabilizer or fin is a vertical wing-like surface mounted at the rear of the plane and typically protruding above it. The fin stabilizes the plane’s yaw (turn left or right) and mounts the rudder, which controls its rotation along that axis.

-A horizontal stabilizer or tailplane, usually mounted at the tail near the vertical stabilizer. The horizontal stabilizer is used to stabilize the plane’s pitch (tilt up or down) and mounts the elevators, which provide pitch control.

-The stabilizers’ job is to provide stability for the aircraft, to keep it flying straight. The vertical stabilizer keeps the nose of the plane from swinging from side to side, which is called yaw. The horizontal stabilizer prevents an up-and-down motion of the nose, which is called pitch.

-Landing gear, a set of wheels, skids, or floats that support the plane while it is on the surface. Planes take off and land on sturdy wheels and tires, which are rapidly retracted into the undercarriage (the plane’s underbody) by hydraulic rams to reduce drag (air resistance) when they’re in the sky.  On seaplanes, the bottom of the fuselage or floats (pontoons) support it while on the water.

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Wings:

The wings of a fixed-wing aircraft are static planes extending either side of the aircraft. When the aircraft travels forwards, air flows over the wings, which are shaped to create lift. This shape is called an airfoil and is shaped like a bird’s wing.

Airplanes have flexible wing surfaces which are stretched across a frame and made rigid by the lift forces exerted by the airflow over them. Larger aircraft have rigid wing surfaces which provide additional strength.

Whether flexible or rigid, most wings have a strong frame to give them their shape and to transfer lift from the wing surface to the rest of the aircraft. The main structural elements are one or more spars running from root to tip, and many ribs running from the leading (front) to the trailing (rear) edge.

Early airplane engines had little power, and lightness was very important. Also, early airfoil sections were very thin, and could not have a strong frame installed within. So, until the 1930s, most wings were too lightweight to have enough strength, and external bracing struts and wires were added. When the available engine power increased during the 1920s and 30s, wings could be made heavy and strong enough that bracing was not needed any more. This type of unbraced wing is called a cantilever wing.

The number and shape of the wings varies widely on different types. A given wing plane may be full-span or divided by a central fuselage into port (left) and starboard (right) wings. Occasionally, even more wings have been used, with the three-winged triplane achieving some fame in WWI. The four-winged quadruplane and other multiplane designs have had little success.

A monoplane has a single wing plane, a biplane has two stacked one above the other, a tandem wing has two placed one behind the other. When the available engine power increased during the 1920s and 30s and bracing was no longer needed, the unbraced or cantilever monoplane became the most common form of powered type. The distance between a wing root and wing tip the length of the wing. Wing span is the distance from one wing tip to the other wing tip. To be aerodynamically efficient, a wing should be straight with a long span from side to side but have a short chord (high aspect ratio). But to be structurally efficient, and hence light weight, a wing must have a short span but still enough area to provide lift (low aspect ratio). In aeronautics, the aspect ratio of a wing is the ratio of its span to its mean chord. It is equal to the square of the wingspan divided by the wing area. Thus, a long, narrow wing has a high aspect ratio, whereas a short, wide wing has a low aspect ratio.

At transonic speeds (near the speed of sound), it helps to sweep the wing backwards or forwards to reduce drag from supersonic shock waves as they begin to form. The swept wing is just a straight wing swept backwards or forwards.

The delta wing is a triangle shape that may be used for several reasons. As a flexible Rogallo wing, it allows a stable shape under aerodynamic forces and so is often used for ultralight aircraft and even kites. As a supersonic wing, it combines high strength with low drag and so is often used for fast jets.

A variable geometry wing can be changed in flight to a different shape. The variable-sweep wing transforms between an efficient straight configuration for takeoff and landing, to a low-drag swept configuration for high-speed flight. Other forms of variable planform have been flown, but none have gone beyond the research stage.

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Wing Dihedral is the upward angle of an aircraft’s wing, from the wing root to the wing tip. The amount of dihedral determines the amount of inherent stability along the roll axis. Although an increase of dihedral will increase inherent stability, it will also decrease lift, increase drag, and decreased the axial roll rate. As roll stability is increased, an aircraft will naturally return to its original position if it is subject to a brief or slight roll displacement. Most large airliner wings are designed with dihedral.

On low-wing aircraft, the center of gravity is above the wing and roll stability is less pronounced. This factor requires the use of greater dihedral angles in low-wing airplanes. On high-wing aircraft, the center of gravity is below the wing, so less dihedral is required.

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Fuselage:

The fuselage, from the French word “fuselé” meaning “spindle shaped”, is the portion of the airplane used to literally join, or fuse, the other parts together.  It is commonly thought of as the body of the aircraft and holds the passengers and cargo safely inside. A fuselage is a long, thin body, usually with tapered or rounded ends to make its shape aerodynamically smooth. The pilots of manned aircraft operate them from a cockpit located at the front or top of the fuselage and equipped with controls and usually windows and instruments. A plane may have more than one fuselage, or it may be fitted with booms with the tail located between the booms to allow the extreme rear of the fuselage to be useful for a variety of purposes.

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Cockpit:

The cockpit, sometimes referred to as the Flight Deck, is where the pilots sit.  It contains the flight controls, which move the airplane, as well as all the buttons and switches used to operate the various systems.

A yoke, alternatively known as a control wheel or a control column, is a device used for piloting some fixed-wing aircraft. The pilot uses the yoke to control the attitude of the plane, usually in both pitch and roll. Rotating the control wheel controls the ailerons and the roll axis. Fore and aft (in front of and behind) movement of the control column controls the elevator and the pitch axis. Aft describes the direction of movement within an aircraft; that is, towards the tail. Example: “Let’s go aft”. Meaning to pull back on the yoke. When the yoke is pulled back the nose of the aircraft rises. When the yoke is pushed forward the nose is lowered. When the yoke is turned left the plane rolls to the left and when it is turned to the right the plane rolls to the right.

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Nose of an airplane:

The nose of an airplane is very important to flight. Like the tip of an arrow, it decides where the plane is going to go. All of the elements of flight depend on keeping the nose pointed in the right direction. It also pays a key role in limiting drag around the aircraft. It slices through the air, allowing it to flow around the aircraft in a gentle way that won’t slow it down. In that way, it’s very important in keeping the plane efficient.

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Windshield:

The windshield on smaller aircraft is usually made from polycarbonate, a type of plastic, while pressurized airplanes use a sandwich of plastic and glass layers, called a laminate, up to 20mm thick.  This is necessary to absorb the impact of birds, insects and other debris that may collide with the windshield as the airplane flies at close to the speed of sound.

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Engine:

An airplane has at least one, or as many as eight engines, which provide the thrust needed to fly.  There are many different makes and models on aircraft today but all perform the same basic function of taking the air that’s in front of the aircraft, accelerating it and pushing it out behind the aircraft. Jet powered aircraft perform this function by compressing the air using turbines, while propeller-powered aircraft use a propeller mounted to the engine. In general, the propeller works like a big screw, pulling the aircraft forward while pushing the air behind it.

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Antenna:

There are numerous radio antennas located around an aircraft, their size and position corresponding to the type of work each antenna must perform and the frequencies being transmitted or received. The GPS antenna, for example, is always mounted to the top of an airplane. This is because the GPS satellites are in Space, and therefore always above the aircraft. As a general rule, longer antennas are used for radio communication and navigation (VHF frequencies), while shorter antennas are reserved for higher frequency data such as the GPS signals and the transponder, which provides air traffic control with information about the aircraft’s position and altitude.

These days, the skies are packed with planes that fly by day, by night, and in all kinds of weather. Radio, radar, and satellite systems are essential for navigation. There are at least two or three radio systems on the aircraft to enable communication with the ground, air traffic control etc. Special procedures exist for what to do if a plane loses the ability to communicate.

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Empennage:

This name stems from the French word “empenner,” meaning “to feather an arrow”.  The empennage is the name given to the entire tail section of the aircraft, including both the horizontal and vertical stabilizers, the rudder and the elevator.  As a combined unit, it works identically to the feather on the arrow, helping guide the aircraft to its destination.

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Horizontal Stabilizer and Elevator:

At the rear of the fuselage of most aircraft one finds a horizontal stabilizer and an elevator. The stabilizer is a fixed wing section whose job is to provide stability for the aircraft, to keep it flying straight. The horizontal stabilizer is quite simply an upside-down wing, designed to provide a downward force (push) on the tail.  Airplanes are traditionally nose-heavy and this downward force is required to compensate for that, keeping the nose level with the rest of the aircraft. The horizontal stabilizer prevents up-and-down, or pitching, motion of the aircraft nose. The elevator is the small moving section at the rear of the stabilizer that is attached to the fixed sections by hinges. Because the elevator moves, it varies the amount of force generated by the tail surface and is used to generate and control the pitching motion of the aircraft. There is an elevator attached to each side of the fuselage. The elevators work in pairs; when the right elevator goes up, the left elevator also goes up.

The elevator is used to control the position of the nose of the aircraft and the angle of attack of the wing. Changing the inclination of the wing to the local flight path changes the amount of lift which the wing generates. This, in turn, causes the aircraft to climb or dive. During takeoff the elevators are used to bring the nose of the aircraft up to begin the climb out. During a banked turn, elevator inputs can increase the lift and cause a tighter turn. That is why elevator performance is so important for fighter aircraft.

The elevators work by changing the effective shape of the airfoil of the horizontal stabilizer. Changing the angle of deflection at the rear of an airfoil changes the amount of lift generated by the foil.

Both the horizontal stabilizer and the elevator contribute to pitch stability, but only the elevators provide pitch control. They do so by decreasing or increasing the downward force created by the stabilizer:

• an increased downward force, produced by up elevator, forces the tail down and the nose up. At constant speed, the wing’s increased angle of attack causes a greater lift to be produced by the wing, accelerating the aircraft upwards. The drag and power demand also increase;
• a decreased downward force at the tail, produced by down elevator, causes the tail to rise and the nose to lower. At constant speed, the decrease in angle of attack reduces the lift, accelerating the aircraft downwards.

The lift force (F) is applied at center of pressure of the horizontal stabilizer which is some distance (L) from the aircraft center of gravity.

This creates a torque T = F X L on the aircraft and the aircraft rotates about its center of gravity.

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Vertical Stabilizer and Rudder:

The vertical stabilizer is designed to stabilize the left-right motion of the aircraft.  While most aircraft use a single stabilizer, some models, such as the Lockheed C-69 Constellation, use multiple, smaller stabilizers.

The rudder is attached to the vertical stabilizer, located on the tail of the aircraft.  It works identically to a rudder on a boat, helping to steer the nose of the aircraft left and right; this motion is referred to as yaw.  Unlike the boat however, it is not the primary method of steering.  Its main purpose is to counteract certain types of drag, or friction, ensuring that the aircraft’s tail follows the nose, rather than sliding out to the side.

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Aileron:

The ailerons are located at the rear of the wing, typically one on each side.  They work opposite to each other, meaning that when one is raised, the other is lowered.  Their job is to increase the lift on one wing while reducing the lift on the other.  By doing this, they roll the aircraft sideways, causing the aircraft to turn. This is the primary method of steering a fixed-wing aircraft.

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Flap:

The wings have additional hinged, rear sections near the body that are called flaps. Flaps are a “high lift / high drag” device mounted on the trailing edge of the wing. Not only do they improve the lifting ability of the wing at slower speeds by changing the camber, or curvature of the wing, but when extended fully they also create more drag.  This means an aircraft can descend (or lose altitude) faster, without gaining airspeed in the process.

Slat:

A slat is a “high lift” device typically found on jet-powered aircraft.  Slats are similar to the flaps except they are mounted on the leading edge of the wing. They also assist in changing the camber, or curvature of the wing, to improve lifting ability at slower speeds.

Spoiler:

The spoiler’s function is to disrupt, or spoil, the flow of air across the upper surface of the wing. They are usually found on larger aircraft, which can have two types installed.  The in-flight spoilers are small and designed to reduce the lifting capability of the wing just enough to allow the aircraft to descend quicker without gaining airspeed.  Although the flaps can also perform this function, the spoiler is intended to be used temporarily, while the flaps are typically used for longer durations such as during the approach and landing.  The ground spoilers typically deploy automatically on landing and are much larger than their in-flight cousins.  They are used to completely destroy the lifting ability of the wing upon landing, ensuring that the entire weight of the airplane rests firmly on the wheels, making the brakes more effective and shortening the length of runway needed to stop the aircraft.

Raising spoilers on only one wing causes a rolling motion. Spoilers cause torque, just as rudders, elevators, and ailerons do.  

Flaps are deployed downward on takeoff and landing to increase the amount of force produced by the wing. On some aircraft, the front part of the wing will also deflect. Slats are used at takeoff and landing to produce additional force. The spoilers are also used during landing to slow the plane down and to counteract the flaps when the aircraft is on the ground.

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Struts:

The struts are part of the undercarriage, more commonly known as the landing gear. Their function is to absorb the impact of the landing as the aircraft touches the ground. Each strut contains a shock absorber (a collection of springs), hydraulic oil and gasses which work together to reduce the impact felt by the passengers. On some aircraft, such as those used by student pilots, the struts are made entirely out of spring steel.  This type of steel is treated in such a way that it can absorb the shock of landings repeatedly, bending automatically back into shape.

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Wheels:

The wheels are another part of the undercarriage, or landing gear.  While most aircraft have a minimum of three wheels, larger aircraft require many more to support their immense weight. Typically aircraft wheels are filled with nitrogen instead of air. This is because the pressure of nitrogen gas changes very little with changes in altitude or temperature, which is something aircraft constantly experience.

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Wingtip:

A wing tip (or wingtip) is the part of the wing that is most distant from the fuselage of a fixed-wing aircraft. Because the wing tip shape influences the size and drag of the wingtip vortices, tip design has produced a diversity of shapes, including:

Squared-off

Aluminium tube bow

Rounded

Hoerner style

Winglets

Drooped tips

Raked wingtips

Tip tanks

Sails

Fences

End plates

Winglets have become popular additions to high-speed aircraft to increase fuel efficiency by reducing drag from wingtip vortices. Its purpose is to reduce the drag (or air resistance) the wing produces as it pushes through the air. This not only allows the airplane to fly faster, but also means it burns less fuel, allowing it to fly longer distances without refueling.

In lower speed aircraft, the effect of the wingtip shape is less apparent, with only a marginal performance difference between round, square, and Hoerner style tips. The slowest speed aircraft, STOL aircraft, may use wingtips to shape airflow for controlability at low airspeeds.

Wing tips are also an expression of aircraft design style, so their shape may be influenced by marketing considerations as well as by aerodynamic requirements.

Wing tips are often used by aircraft designers to mount navigation lights, anti-collision strobe lights, landing lights, handholds, and identification markings.

Wing tip tanks can act as a winglet and distribute weight more evenly across the wing spar.

On fighter aircraft, they may also be fitted with hardpoints, for mounting drop tanks and weapons systems, such as missiles and electronic countermeasures. Wingtip mounted hose/drogue systems allow Aerial refueling of multiple aircraft with separation.

Aerobatic aircraft use wingtip mounted crosses for visual attitude reference. Wingtip mounted smoke systems and fireworks highlight rolling aerobatic maneuvers. Some airshow acts feature the pilot touching or dragging the wingtip along the ground.

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Fuel tank:

You need fuel to power a plane—lots of it. An Airbus A380 holds over 310,000 liters (82,000 US gallons) of fuel, which is about 7,000 times as much as a typical car! The fuel is safely packed inside the plane’s huge wings. Fuel is stored in the wings of aircraft for primarily 3 reasons:

-1. Fuel acts as a counter stress for the wings shortly after takeoff when the great stress of the aircraft’s mass acts on them. This prevents a large change in the wing dihedral angle. This effect is so great on the Boeing 747, that if only the center tank was filled (leaving the wing tanks empty) and the plane would take off, the wings would simply snap. Due to this reason, fuel is first consumed from the center tank and then the wing tanks. Conversely, during refueling, the wing tanks are filled initially and then the center tanks.

-2. Keeps the center of gravity more or less in the desired position. If the tanks are at the nose or tail of the aircraft, there will be a large change of momentum as fuel is filled or consumed. Longitudinal center of gravity is vital for an aircraft’s stability, and any large change in its position is not conducive for flying.

-3. The weight of the fuel provides rigidity to the wing, thereby reducing wing flutter. Flutter is the vibration of the wings due to the airflow. Large flutter is so hazardous that it can even result in total collapse of the wings.

Note:

All aircraft carry more fuel than they need for the flight in case of bad weather conditions. They need enough to allow them to circle (in what’s called a holding pattern), or possibly divert to another airport.

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Pressurized cabins:  

Air pressure falls with height above Earth’s surface—that’s why mountaineers need to use oxygen cylinders to reach extreme heights. The summit of Mount Everest is just under 9 km (5.5 miles) above sea level, but jet planes routinely fly at greater altitudes than this and military planes have flown almost three times higher! That’s why passenger planes have pressurized cabins: ones into which heated air is steadily pumped so people can breathe properly. Military pilots avoid the problem by wearing face masks and pressurized body suits.

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Autopilot:

Autopilot is an automatic flight control system that keeps an aircraft in level flight or on a set course. It can be directed by the pilot, or it may be coupled to a radio navigation signal. Autopilot reduces the physical and mental demands on a pilot and increases safety. The common features available on an autopilot are altitude and heading hold.

The autopilot helps the aircraft to fly automatically. There are still two pilots but they do not have to hold on to all the controls. There are normally two autopilot systems, because without them the plane would need to be ‘hand-flown’. Pilots are able to do this easily, but it is impractical for a long flight. It would also mean that certain complex approaches in bad weather may be prohibited. Pilots usually engage the autopilot shortly after takeoff and disengage it a few miles from the landing runway.

Pilots command the autopilot to do several different functions: fly a heading, navigate to a radio station or waypoint, climb/descent, hold altitude and occasionally fly a holding pattern. Autopilots do what the pilots tell them to; they are not autonomous. Landings are usually done manually by the pilot. Some airplanes can auto land but this is done most frequently in very low visibility conditions and requires a significant amount of preprogramming and monitoring. 

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The figure above shows the parts of an airplane and their functions.

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How much wiring is there on a plane?

An average Boeing 747 aircraft has over 150 miles (240 kilometers) of wires inside its body, or roughly the distance between Amsterdam and the south of Belgium. The longest wiring, however, that can be found in an airplane is in the double-decker plane Airbus A380 — its 320 miles of cables would stretch as far as Leicester to Glasgow. 

Why are passenger windows on airplanes round?

The windows on an airplane are round for a reason. After a series of accidents in the early days of commercial flying, the engineers uncovered that having square windows with sharp corners compromised the safety of the aircraft. On the other hand, round windows used since then can take the repeated pressure during a flight.

How long does the oxygen in an emergency mask last?

The oxygen masks provided from above your seat in case of an emergency are designed to give out only 15 minutes of oxygen, enough to allow the pilot to lower the altitude of the plane to a level where the outside air pressure is breathable (around 10,000 feet or 3,000 meters).

How long was a flight from London to Singapore in the 1930s?

Today’s flight from London to Singapore takes roughly 12 hours, which might seem like a lifetime to some people. Back in 1934, the same route would have taken eight days and included 22 stopovers to refuel the plane, such as Athens, Baghdad, Calcutta, and Bangkok, among others.

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Use of computers:

Since the mid-1960s, computer technology has been continually developed to the point at which aircraft and engine designs can be simulated and tested in myriad variations under a full spectrum of environmental conditions prior to construction. As a result, practical consideration may be given to a series of aircraft configurations, which, while occasionally and usually unsuccessfully attempted in the past, can now be used in production aircraft. These include forward swept wings, canard surfaces, blended body and wings, and the refinement of specialized airfoils (wing, propeller, and turbine blade). With this goes a far more comprehensive understanding of structural requirements, so that adequate strength can be maintained even as reductions are made in weight.

Complementing and enhancing the results of the use of computers in design is the pervasive use of computers on board the aircraft itself. Computers are used to test and calibrate the aircraft’s equipment, so that, both before and during flight, potential problems can be anticipated and corrected. Whereas the first autopilots were devices that simply maintained an aircraft in straight and level flight, modern computers permit an autopilot system to guide an aircraft from takeoff to landing, incorporating continuous adjustment for wind and weather conditions and ensuring that fuel consumption is minimized. In the most advanced instances, the role of the pilot has been changed from that of an individual who continuously controlled the aircraft in every phase of flight to a systems manager who oversees and directs the human and mechanical resources in the cockpit.

The use of computers for design and in-flight control is synergistic, for more radical designs can be created when there are on-board computers to continuously adapt the controls to flight conditions. The degree of inherent stability formerly desired in an aircraft design called for the wing, fuselage, and empennage (tail assembly) of what came to be conventional size and configurations, with their inherent weight and drag penalties. By using computers that can sense changes in flight conditions and make corrections hundreds and even thousands of times a second—far faster and more accurately than any pilot’s capability—aircraft can be deliberately designed to be unstable. Wings can, if desired, be given a forward sweep, and tail surfaces can be reduced in size to an absolute minimum (or, in a flying wing layout, eliminated completely). Airfoils can be customized not only for a particular aircraft’s wing or propeller but also for particular points on those components.

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High-lift device:

In aircraft design and aerospace engineering, a high-lift device is a component or mechanism on an aircraft’s wing that increases the amount of lift produced by the wing. The device may be a fixed component, or a movable mechanism which is deployed when required. Common movable high-lift devices include wing flaps and slats. Fixed devices include leading-edge slots, leading edge root extensions, and boundary layer control systems.

The size and lifting capacity of a fixed wing is chosen as a compromise between differing requirements. For example, a larger wing will provide more lift and reduce the distance and speeds required for takeoff and landing, but will increase drag, which reduces performance during the cruising portion of flight. Modern passenger jet wing designs are optimized for speed and efficiency during the cruise portion of flight, since this is where the aircraft spends the vast majority of its flight time. High-lift devices compensate for this design trade-off by adding lift at takeoff and landing, reducing the distance and speed required to safely land the aircraft, and allowing the use of a more efficient wing in flight. The high-lift devices on the Boeing 747-400, for example, increase the wing area by 21% and increase the lift generated by 90%. 

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Flight Instruments:

Flight instruments help pilots keep an eye on conditions. To the untrained eye, a panel of flight instruments may seem like a smorgasbord of dials. But all these crucial gauges provide a pilot with critical data during the flight. The six most basic flight instruments, as found in a simple prop-driven plane, are as follows:

Airspeed indicator: An air speed indicator (ASI) is a device for measuring the forward speed of the aircraft. The ASI uses the aircraft pitot-static system to compare pitot and static pressure and thus determine forward speed of an aircraft in kilometers per hour (km/h), knots (kn), miles per hour (MPH) and/or meters per second (m/s).

Altimeter: As the name implies an altimeter measures altitude. The indicator in this case is a barometer, which measures air pressure.

Attitude indicator:  The attitude indicator (AI) is a flight instrument that informs the pilot of the aircraft orientation relative to Earth’s horizon, and gives an immediate indication of the smallest orientation change. By use of a gyroscope, the indicator provides spatial clarity even in disorienting flight conditions.

Heading indicator: The heading indicator simply tells the pilot in which direction the plane is heading. The device depends on both a gyroscope and a magnetic compass, however, as both are susceptible to different errors during flight.

Turn coordinator: A typical turn coordinator indicates the plane’s yaw or roll rate while also indicating the rate of coordination between the plane’s bank angle and the rate of yaw. This device depends on a gyroscope, as well as an inclinometer ball in a glass cylinder to indicate when the aircraft is skidding or slipping.

Variometer: Also known as a vertical speed indicator, this device indicates the rate of a plane’s rate of climb or descent. Working along similar lines as the altimeter, the variometer depends on atmospheric pressure readings to determine how swiftly altitude changes are occurring.

The total number of flight instruments has increased over the years with the speed, altitude, range and overall sophistication of the aircraft.

In the general aviation (GA) community, an automated aircraft is generally comprised of an integrated advanced avionics system consisting of a primary flight display (PFD), a multifunction display (MFD) including an instrument certified global positioning system (GPS) with traffic and terrain graphics, and a fully integrated autopilot. This type of aircraft is commonly known as an advanced avionics aircraft. In an advanced avionics aircraft, the PFD is displayed on the left computer screen and the MFD is on the right screen. Automation is the single most important advance in aviation technologies. Electronic flight displays (EFDs) have made vast improvements in how information is displayed and what information is available to the pilot. Pilots can access onboard information electronically that includes databases containing approach information, primary instrument display, and moving maps that mirror sectional charts, or display modes that provide three-dimensional views of upcoming terrain. These detailed displays depict airspace, including temporary flight restrictions (TFRs). MFDs are so descriptive that many pilots fall into the trap of relying solely on the moving maps for navigation.

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Phases of Flight:

More phases are needed in the event a plane is flying at low altitudes or experiences complications in the air.

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Attitude of airplane:

The aircraft attitude is the orientation of an aircraft with respect to the horizon. There are 3 components to the aircraft’s attitude. They are pitch, roll and yaw.

-1. Pitch

Pitch is the vertical relationship between the nose and horizon. Since the pilot/cockpit and nose of the aircraft are all moving together, the pitch attitude is seen as the ratio of visible sky to ground in the view ahead. The exact ratio of sky to ground visible in the forward window will vary from one aircraft type to another. In a typical light aircraft, the ratio might be 2/3 ground and 1/3 sky when the aircraft is in the cruise attitude.

Increasing the pitch attitude (nose up) (making more sky visible)

-Airspeed will decrease

-Rate of climb will increase (or rate of descent will decrease)

-Load Factor will increase

Decreasing the pitch attitude (nose down) (making more ground visible)

-Airspeed will increase

-Rate of descent will increase (or rate of climb will decrease)

-Load Factor will decrease

-2. Roll

Roll or bank is how much the nose “tilts” to the left or right. It can also be thought of as the angle the horizon makes in the window. The bank angle ranges from 0 to about 30 degrees under normal circumstances. Larger bank angles are used in aerobatics or air combat. Glider pilots will commonly use bank angles of up to 45 to 60 degrees.

Changing the bank attitude directly affects:

-Bank angle

-Rate of turn

When the aircraft banks, the lift of the wings no longer acts vertically, and so the force directly upwards is reduced (by the cosine of the bank angle). If left uncorrected this will result in the aircraft descending. The nose will also usually drop. In order to maintain level flight the pilot will apply back-pressure to the stick while the wings are banked to raises the elevators. This changes the lift characteristics of the stabilizer, deflecting air up and pushing the tail down (known as rotation). This in turn changes the angle of attack of the wing, which produces more lift. This will maintain level flight. The airspeed will usually decrease slightly as a result of this. For steeper bank angles an aircraft pilot will usually increase the power setting to keep the speed up.

-3. Yaw

Yaw refers to the direction in which the nose of the aircraft is pointing. It is the left-right movement of the nose across the horizon. It is possible for the nose of the aircraft to be pointing in a different direction from that in which the aircraft is moving. This usually occurs in a turn, and is called slip (if the aircraft is moving sideways into the turn) or skid (if it is moving outwards). Yaw is almost impossible to detect by visual references. In fixed-wing aircraft it is detected by references to the slip indicator. Gliders usually have a piece of string mounted in the pilot’s vision which indicates airflow over the glider, and is called the yaw string.

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Attitude types:

Cruise attitude:

An aircraft is usually designed so that the “horizon/nose sight picture” that the pilot sees in cruising flight is similar to that seen when the aircraft is on the ground. This will also usually coincide with having the interior floor and passenger compartment in a level attitude. In cruise flight, the aircraft maintains a constant airspeed and altitude, which is the result of a constant pitch attitude and aircraft power setting. A particular aircraft will have a design cruise airspeed at which the plane will be in an essentially level attitude.

When a pilot is undergoing flight training, the cruise attitude is usually one of the first things that they will learn. The sight picture associated with cruise flight, will include the horizon and a combination of sky and ground.

Pitch (nose-up) attitude:

To make an aircraft climb, i.e., gain altitude, the pilot will raise the nose higher than it is in the cruise attitude. For many light aircraft, this will correspond to a sight picture where the aircraft nose appears to be on or just slightly above the horizon. The amount of movement will typically not exceed 10-15 degrees.

If the pilot does not adjust the engine power by increasing the throttle setting, the aircraft’s airspeed will decrease. The amount of decrease will depend on the amount the nose was raised compared to the cruise attitude, and what the power setting is. When flying light aircraft, power is usually increased to full for any extended climb.

Even if power is increased, the airspeed will still decrease if the pitch attitude is increased beyond a certain point. The amount that the airspeed decreases with increasing pitch attitude (nose up) is aircraft type dependent, and is usually directly related to how much excess power is available and the power setting used.

Types of climb:

The pilot controls the rate of climb, and the airspeed during the climb by the combination of the pitch attitude and power setting. He will choose the pitch-power settings according to the amount of altitude gain required or how quickly it is desired to climb, or if a constant airspeed is desired. Every aircraft type has limits on the pitch-power settings that can be used for climbing flight. Typically it is the pitch attitude which is the more limiting factor. Somewhat like an automobile, if the “slope” is made too steep, by an excessive increase (nose up) in pitch-attitude, the aircraft will lack sufficient power to climb, and in an extreme nose-up attitude, the airspeed may decrease to the point where the aircraft will stall.

In light aircraft, full power is typically used when climbing. The type of climb is therefore determined by the pitch attitude. The aircraft’s Pilot Operating Handbook (P.O.H.) will list the airspeeds for the various types of climbs. The pilot adjusts the aircraft’s pitch attitude to match the speed quoted in the P.O.H. for that particular type of climb desired. Larger aircraft follow the same principles, the only difference being that full power is not always used, especially at lower altitudes, as the engines are usually powerful enough to create excessive airspeed.

Descent attitude:

To make an aircraft descend (i.e., lose altitude), the pilot will lower the nose lower than it was in the cruise attitude. For many light aircraft, this will correspond to a sight picture where the aircraft nose appears to be slightly below the horizon. The actual amount of down movement usually will not exceed about 10 degrees for most normal descents.

If the pilot does not adjust the engine power by decreasing the throttle setting, the aircraft’s airspeed will increase. The amount of increase will depend on how much the nose was lowered compared to the cruise attitude, and what the previous power setting was. When flying [light aircraft], power usually is decreased to around 2/3 full for a cruise descent.

Even if power is decreased, the airspeed will still increase if the pitch attitude is decreased (nose down) beyond a certain point. The amount that the airspeed increases with decreasing pitch attitude (nose down) is type dependent, and is usually directly related to how aerodynamically clean the aircraft is. If the airspeed is allowed to increase to or past Vne (never-exceed speed) structural damage can occur.

Velocity – Never Exceed (Vne):  

Vne is the speed which should never be exceeded, normally represented by a red line on the airspeed indicator. If flight is attempted above this speed, structural damage or structural failure may result. 

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Section-5

Engine of airplane:

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Propulsion:

Figure below showing balloon with no escape path for the air inside. All forces are balanced.

Propulsion is the net force that results from unequal pressures. Gas (air) under pressure in a sealed container exerts equal pressure on all surfaces of the container; therefore, all the forces are balanced and there are no forces to make the container move.

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Figure below showing balloon with released stem.  Arrow showing forward force has no opposing arrow.

If there is a hole in the container, gas (air) cannot push against that hole and thus the gas escapes.  While the air is escaping and there is still pressure inside the container, the side of the container opposite the hole has pressure against it. Therefore, the net pressures are not balanced and there is a net force available to move the container. This force is called thrust.

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The simplest example of the propulsion principle is an inflated balloon (container) where the stem is not closed off. The pressure of the air inside the balloon exerts forces everywhere inside the balloon. For every force, there is an opposite force, on the other side of the balloon, except on the surface of the balloon opposite the stem. This surface has no opposing force since air is escaping out the stem. This results in a net force that propels the balloon away from the stem. The balloon is propelled by the air pushing on the FRONT of the balloon.

Figure below showing our balloon with machinery in front to keep it full as air escapes out the back for continuous thrust.

The simplest propulsion engine:

The simplest propulsion engine would be a container of air (gas) under pressure that is open at one end.  A diving SCUBA tank would be such an engine if it fell and the valve was knocked off the top.  The practical problem with such an engine is that, as the air escapes out the open end, the pressure inside the container would rapidly drop. This engine would deliver propulsion for only a limited time.

The turbine engine:

A turbine engine is a container with a hole in the back end (tailpipe or nozzle) to let air inside the container escape, and thus provide propulsion. Inside the container is turbomachinery to keep the container full of air under constant pressure. 

Figure below showing turbine engine as a cylinder of turbomachinery with unbalanced forces pushing forward.

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Aircraft engine:

An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many small UAVs have used electric motors. All commercial aircraft designed in the last 40 years (other than aircraft with fewer than a dozen passengers) are powered by gas turbine engines, either turbofan or turboprop.

Piston and gas turbine engines are internal combustion engines and have a similar basic cycle of operation; that is, induction, compression, combustion, expansion, and exhaust. Air is taken in and compressed, and fuel is injected and burned. The hot gases then expand and supply a surplus of power over that required for compression and are finally exhausted. In both piston and jet engines, the efficiency of the cycle is improved by increasing the volume of air taken in and the compression ratio.

An aircraft propeller is an aerodynamic device which converts rotational energy into propulsive force creating thrust which is approximately perpendicular to its plane of rotation. An aircraft propeller, or airscrew, converts rotary motion from an engine or other power source, into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis.

A jet engine is a gas turbine engine. A turbojet is a jet engine, a turboprop is a jet engine with a propeller attached to the front, and a turbofan is a jet engine with a fan attached to the front. A turboprop engine is a turbojet with a propeller. The engine uses the propellers to produce more thrust. This is much different than with piston engines, which also have propellers, but are much different mechanically. A piston engine cannot produce thrust on its own. It provides power to a spinning propeller, which produces thrust by creating a pressure difference between the front and back of the propeller, resulting in a forward force. Exhaust thrust in a turboprop is sacrificed in favour of shaft power, which is obtained by extracting additional power (up to that necessary to drive the compressor) from turbine expansion. Owing to the additional expansion in the turbine system, the residual energy in the exhaust jet is low. Consequently, the exhaust jet produces about 10% of the total thrust. A higher proportion of the thrust comes from the propeller at low speeds and less at higher speeds.

Jets or rocket engines produce thrust by increasing the pressure inside the engine. This increased pressure in the jet or rocket engine exerts more force in the forward direction than the rear direction. The exhaust gases produced by a propeller, jet or rocket, due to Newton’s Third Law, are feeling a force opposite and equal to the thrust, and therefore are moved in the direction opposite to the thrust of the engine. Hence, the exhaust is the effect of thrust. Turbine engines are safer and more reliable than piston engines, which are typically found in smaller aircraft. The key difference between jets and propeller planes is that jets produce thrust through the discharge of gas instead of powering a drive shaft linked to a propeller. This allows jets to fly faster and at higher altitudes. A jet engine develops thrust by accelerating a relatively small mass of air to very high velocity, as opposed to a propeller, which develops thrust by accelerating a much larger mass of air to a much slower velocity.  

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The main blocks of a jet engine:

A conventional jet engine is divided into four large blocks: intake, compression, combustion, and exhaust.

A jet engine is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. While this broad definition can include rocket, water jet, and hybrid propulsion, the term jet engine typically refers to an airbreathing jet engine such as a turboprop, turbofan, ramjet, or pulse jet. In general, jet engines are internal combustion engines.

Airbreathing jet engines typically feature a rotating air compressor powered by a turbine, with the leftover power providing thrust through the propelling nozzle—this process is known as the Brayton thermodynamic cycle. Jet aircraft use such engines for long-distance travel. Early jet aircraft used turboprop engines that were relatively inefficient for subsonic flight. Most modern subsonic jet aircraft use more complex high-bypass turbofan engines. They give higher speed and greater fuel efficiency than piston and propeller aeroengines over long distances. A few air-breathing engines made for high speed applications (ramjets and scramjets) use the ram effect of the vehicle’s speed instead of a mechanical compressor.

The thrust of a typical jetliner engine went from 5,000 lbf (22,000 N) (de Havilland Ghost turbojet) in the 1950s to 115,000 lbf (510,000 N) (General Electric GE90 turbofan) in the 1990s, and their reliability went from 40 in-flight shutdowns per 100,000 engine flight hours to less than 1 per 100,000 in the late 1990s. This, combined with greatly decreased fuel consumption, permitted routine transatlantic flight by twin-engined airliners by the turn of the century, where previously a similar journey would have required multiple fuel stops.

The greater the speed, the greater the engine’s thrust. At this moment, when the temperature of our jet engine reaches (just!) 1500 degrees Celsius, the parts demonstrate their quality in meeting the demands they are subjected to.  The jet of hot air also turns the plane’s turbine, connected to the front of the engine by a shaft. Excess hot air is released at high speed from the back of the engine (exhaust), generating the energy needed for the plane to reach its destination on time. That’s how a plane fly.

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Reaction engines:

Reaction engines, colloquially known as jet engines, generate thrust by expelling reactionary mass. The basic principle behind a reactionary engine is Newton’s Third Law — basically, if you blow something with enough force through the back end of the engine, it will push the front end forward. And jet engines are really good at doing that.

The things we usually refer to as a ‘jet’ engine, the ones strapped to a Boeing passenger plane, are strictly speaking airbreathing jet engines and fall under the turbine-powered class of engines. Ramjet engines, which are usually considered simpler and more reliable as they contain fewer (up to none) moving parts, are also airbreathing jet engines but fall into the ram-powered class. The difference between the two is that ramjets rely on sheer speed to feed air into the engine, whereas turbojets use turbines to draw in and compress air into the combustion chamber. Beyond that, they function largely the same.

In turbojets, air is drawn into the engine chamber and compressed by a rotating turbine. Ramjets draw and compress it by going really fast. Inside the engine, it’s mixed with high-power fuel and ignited. When you concentrate air (and thus oxygen), mix it up with a lot of fuel and detonate it (thus generating exhaust and thermally expanding all the gas), you get a reactionary product that has a huge volume compared to the air drawn in. The only place all this mass of gasses can go through is to the back end of the engine, which it does with extreme force (see figure below). On the way there, it powers the turbine, drawing in more air and sustaining the reaction. And just to add insult to injury, at the back end of the engine there’s a propelling nozzle. This piece of hardware forces all the gas to pass through an even smaller space than it initially came in by — thus further accelerating it into ‘a jet’ of matter. The exhaust exits the engine at incredible speeds, up to three times the speed of sound, pushing the plane forward.

Non-airbreathing jet engines, or rocket engines, function just like jet engines without the front bit — because they don’t need external material to sustain combustion. We can use them in space because they have all the oxidizer they need, packed up in the fuel. 

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Difference in a jet airplane engine and a rocket: 

People generally believe that a rocket must push on air in order to propel the rocket forward, but that is not the case. Briefly stated, a rocket works because of Newton’s third law, which says for every action there is an equal, and opposite reaction. The burning of fuel creates gases at high pressure, which exit from the exhaust nozzle and push the rocket forward. As gases exit the rocket, a reaction force (thrust) pushes on the rocket making it go forward. The faster the gases are expelled from the rocket, the greater the thrust. Think of how a garden hose creates a force pushing back on the hose as water squirts from it.

In fact, jet engines and rockets operate on the same general physics principle. Both eject fuel out the back. The momentum imparted to this exhaust is equal to the momentum gained by the vehicle, thus making the vehicle go forward. One difference between rockets and jets is found in the type of fuel they burn. Jet engines are air breathers. They take in air (which contains oxygen needed for combustion), mix it with fuel, burn it to increase the pressure, and exhaust the spent gases out the back at a high rate of speed. This high-speed ejection of mass propels the plane forward. Rockets do almost the same thing with two exceptions. Unlike jets, they carry their own oxygen along with them and a rocket does not have wings that add lift.

On the space shuttle, you notice an orange tank, which actually contains separate tanks of hydrogen and oxygen. These two ingredients are mixed in the liquid-fuel rocket engine, burned, and expelled out the nozzle. The white, solid-fuel rocket on each side contains a chemical mixture in which the oxidizing agent is part of the fuel. Rocket fuel can burn without external oxygen being present. As a side note, once a solid fuel rocket is ignited, it cannot be turned off. Jet engines must have outside oxygen from the air.

Another difference is that jet planes have wings for lift and rockets do not. The density of air and the speed of the plane affect the lift on the wings. For rockets the lift is provided solely by the expelled gases.

Therefore, a rocket can travel in the vacuum of space void of air, but a jet engine could not. A jet plane has a ceiling limit above which it cannot fly because there is not enough air. The jet engine must be able to ’breathe’ in order to function. Rocket fuel is considerably more efficient than jet fuel and rockets usually are more powerful. However, the rocket generally is heavier because it must carry all of its oxidizer with it.

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Piston (reciprocating) or Turbine Engine?

We all know what piston engines are; we have them in our cars. Piston engines for airplanes are quite common, fairly reliable, and relatively inexpensive to own and operate. There are two key things to consider. One is the power that is produced. Piston engines, even the largest available, are limited to around 300 horsepower each. Turboprops, jet engines coupled to a propeller, generally produce from around 450 horsepower to 2,000 horsepower and more. For an aircraft like a Boeing 777 with two GE 90-115B turbofan engines, each engine produces roughly 30,843 horsepower during cruise flight with a fully loaded aircraft. All conventional twins will lose approximately 80 percent of their ability to climb after an engine failure. Having more power translates not only to greater overall performance, but also to greater overall safety. Federal Aviation Administration studies indicate that piston engines in aircraft have a failure rate, on average, of one every 3,200 flight hours while turbine engines have a failure rate of one per 375,000 flight hours. Accordingly, for every turbine engine experiencing a failure, 117 piston engines will have failed. In other words, turbine engines are more than 11,700 percent more reliable than piston engines.

Although turbine powered aircraft are typically more expensive to buy and to operate than their piston powered counterparts, they do provide an unparalleled degree of performance, productivity, and safety. One additional factor to consider when deciding on the type of powerplant to have in your aircraft is fuel. Piston engines use avgas while turbines use jet fuel. Avgas is currently readily available in the United States, but is increasingly difficult to find in most other parts of the world. Some industry experts claim that avgas will soon become difficult to obtain in the United States as well. Jet fuel, on the other hand, is, and will continue to be, available everywhere in the world.

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Single or Twin Engine?

Generally speaking, twin engine aircraft can go faster, carry more useful load, provide system redundancy, and afford better climb performance than their single engine counterparts. However, twin engine aircraft are also more complex and cost more to operate. One thing that is important to mention here: if you have an engine failure in a single engine aircraft, you will land. In a twin, you may have enough power to continue flight to a suitable landing site such as an airport. However, don’t assume that just because an airplane has two engines it can continue flying. All conventional twins will lose approximately 80 percent of their ability to climb after an engine failure. Despite common assumptions, twins do not have twice the power of a single. They have the required power divided between two engines.

Can a twin-engine plane take off and/or fly on one engine?

Yes it can. A twin-engine aircraft can fly perfectly well on only one engine. In fact, it can even continue the take-off and then safely land with just one engine. Before a certain speed – the so-called decision speed or V1 speed – the takeoff would be aborted and the aircraft would be brought to a stop. If an engine fails after reaching V1 speed, the aircraft will continue its take-off roll and get safely airborne on one engine before returning to the airport. If an engine fails mid-flight, the plane will not be able to maintain its altitude but it will safely continue flying. For example, in 2003, the captain of a United Airlines B777 flying from Auckland, New Zealand, to Los Angeles, USA, was forced to shut down one of the plane’s two engines because the oil pressure dropped dramatically. The Boeing continued to fly for more than 3 hours on one engine over the Pacific Ocean, before landing in Kona, Hawaii. Due to engine failure/shutdown, asymmetric thrust that will be produced. The other engine’s thrust is increased to stop a decay in airspeed. This results in the aircraft wanting to turn away from the working engine and entering a turn. If left unchecked, this will result in loss of control of the aircraft. This usually has to be corrected manually by the pilots through the rudder pedals. Every commercial airplane is able to safely land on one engine. The entire flight crew is trained and regularly checked in the simulator to perform maneuvers such as taking off and landing on one engine. Losing an engine in flight is not usually a particularly serious problem and the pilots are given extensive training to deal with such a situation.

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Is a four-engine 747 safer than a two-engine 777?

No, they are both safe. Having two additional engines is not a guarantee of increased safety. The engine failure rate of the B747 is higher, due to having two more engines and the older technology.

Does having only two engines increase risk when flying over oceans?

No, the reliability of modern jet engines is so good that flying over oceans or remote locations is not risky. One consideration is that having more engines increases the possibility of one of them having a problem. The regulatory authorities have very strict standards for twin-engine overwater operations.

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ETOPS:

ETOPS stands for ‘Extended range Twin-engine Operational Performance Standard’ and applies to twin engine aircraft on routes with a diversion time of more than one hour. It indicates the time that a commercial aircraft is allowed to fly away from the nearest suitable airport, to make sure it can safely land in the unlikely scenario that one of its engines becomes inoperative. The cornerstone of the ETOPS approach is the statistics showing that the turbine assembly of a modern jet engine is an inherently reliable component. There are different levels of ETOPS certification; for example ETOPS 240 means that the airplane can fly as far as up to 240 minutes (even on one engine) from the nearest suitable airport, because it has been reliably proven to do so.

ETOPS certification is a two-step, highly controlled process, where irregularities would immediately lead to a downgrade or suspension of the ETOPS capabilities of an airline:

First, the airframe and engine combination must satisfy the basic ETOPS requirements during its type certification. Such tests may include shutting down an engine and flying on the remaining engine during the complete diversion time. Often such tests are performed in the middle of the ocean. It must be demonstrated that, during the diversion flight, the flight crew is not unduly burdened by extra workload due to the lost engine and that the probability of the remaining engine failing is extremely remote.

Second, an airline who conducts ETOPS flights must satisfy their own country’s aviation regulators about their ability to conduct ETOPS flights, which involves compliance with additional special engineering and flight crew procedures in addition to the normal engineering and flight procedures. Pilots and engineering staff must be qualified and trained for ETOPS.

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Section-6

Physics of flight:

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Flight and flying in animals:

Of the many scientific problems of modern times, there are few possessing a wider or more enduring interest than that of aerial navigation. To fly has always been an object of ambition with man especially when we remember the marvelous freedom enjoyed by volant as compared with non-volant animals. The subject of aviation is admittedly one of extreme difficulty. To tread upon the air (and this is what is really meant) is, at first sight, in the highest degree utopian; and yet there are thousands of living creatures which actually accomplish this feat. These creatures, however varied in form and structure, all fly according to one and the same principle; and this is a significant fact, as it tends to show that the air must be attacked in a particular way to ensure flight. It behoves us then at the outset to scrutinize very carefully the general configuration of flying animals, and in particular the size, shape and movements of their flying organs.

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Flying animals differ entirely from sailing ships and from balloons, with which they are not unfrequently though erroneously compared; and a flying machine constructed upon proper principles can have nothing in common with either of those creations. The ship floats upon water and the balloon upon air; but the ship differs from the balloon, and the ship and the balloon differ from the flying creature and flying machine. The water and air, moreover, have characteristics of their own. The analogies which connect the water with the air, the ship with the balloon, and the ship and the balloon with the flying creature and flying machine are false analogies. A sailing ship is supported by the water and requires merely to be propelled; a flying creature and a flying machine constructed on the living type require to be both supported and propelled. This arises from the fact that water is much denser than air, and because water supports on its surface substances which fall through air. While water and air are both fluid media, they are to be distinguished from each other in the following particulars. Water is comparatively very heavy, inelastic and incompressible; air, on the other hand, is comparatively very light, elastic and compressible. If water be struck with violence, the recoil obtained is great when compared with the recoil obtained from air similarly treated. In water we get a maximum recoil with a minimum of displacement; in air, on the contrary, we obtain a minimum recoil with a maximum of displacement. Water and air when unconfined yield readily to pressure. They thus form movable fulcra to bodies acting upon them. In order to meet these peculiarities the travelling organs of aquatic and flying animals (whether they be feet, fins, flippers or wings) are made not of rigid but of elastic materials. The travelling organs, moreover, increase in size in proportion to the tenuity of the fluid to be acted upon. The difference in size of the travelling organs of animals becomes very marked when the land animals are contrasted with the aquatic, and the aquatic with the aerial.

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To comprehend the biomechanics of flight, a few simple physical principles must be kept in mind. First we have to recognize that air is a fluid, just like water. It is not a liquid, like water, but is a called a fluid because the force needed to deform it depends on how fast it is deformed, not on how much it is deformed (try moving your hand quickly, then slowly through a basin of water for an example). Solids are substances for which the force needed to deform the substance is dependent on the extent of deformation rather than the rate of deformation (so it takes the same amount of force to break a pencil quickly as it does to do it slowly).

Drag is a force exerted on an object moving through a fluid; it is always oriented in the direction of relative fluid flow (try running against a high wind and you’ll feel drag pushing you back in the direction of relative fluid flow). Drag occurs because the fluid and the object exchange momentum when impacting, creating a force opposing the motion of the object. Drag is higher when (1) the surface area of the object exposed to the fluid flow is higher, (2) the object is moving faster (or the relative fluid flow is faster), and (3) the fluid has more momentum, or inertia (the viscosity and density of the fluid are high) — this is generally low for air relative to other fluids such as water. Trying to walk in a strong wind will demonstrate drag for you. A dropped weight falls faster through air than through honey largely because of drag forces.

Lift is another force exerted on an object moving through a fluid; it is generally (but not always) directed upwards (perpendicular to the drag force), opposing the weight of the animal that is pulling it down to Earth. In animals that generate significant lift forces (like true flyers), the angle of the wings against the flow of air creates a resistance that has the net effect of moving the wing (and the animal) upward. The majority of lift in gliders and flyers is produced at the proximal part (base) of the wing, where the wing area is largest. Lift is higher when (1) the area of the bottom of the wing is larger, (2) the animal is moving faster, and (3) again, fluid viscosity and density are higher.

Thrust is the third force. It is only present in true fliers; it is produced by powered flight (wing flapping), especially at the distal (end) of the wing. Thrust is a force induced in the direction of the animal’s flight, opposing the drag force. To fly at a steady speed in a completely horizontal direction, an animal must generate enough thrust to equal the drag forces on it. Thrust is produced by flapping the wings, which creates a vortex wake that has the net effect of pushing the animal forward. Different kinds of wakes are formed in slow flight, fast flight, and bounding (or intermittent) flight, which you can often see in birds such as goldfinches. If the thrust force is greater than the drag force, the animal will accelerate; likewise the animal will decelerate if the drag is greater than the thrust, and when thrust force equals drag force, the animal moves at a constant speed. Thrust is a force basically dependent on the power output of the flight muscles of the animal.

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Bird Flight:

Birds take to the air using the same aerodynamic forces that make it possible for airplanes, helicopters, rockets, and kites to fly. Pressure on top of a bird’s wings compared to below them creates an upward lift. When birds flap their wings, they create thrust to propel them through the air. Some birds glide and soar through the air by holding their wings at a V-shaped angle to control how the wind hits their wings. Birds’ tails also help them control flight elevation and speed. By spreading out their tail feathers, drag occurs, which slows them down for landing.

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Theory of Flight:

Flight is a phenomenon that has long been a part of the natural world. Birds fly not only by flapping their wings, but by gliding with their wings outstretched for long distances. Smoke, which is composed of tiny particles, can rise thousands of feet into the air. Both these types of flight are possible because of the principles of physical science. Likewise, man-made aircraft rely on these principles to overcome the force of gravity and achieve flight.

Lighter-than-air craft, such as the hot air balloon, work on a buoyancy principle. They float on air much like rafts float on water. The density of a raft is less than that of water, so it floats. Although the density of water is constant, the density of air decreases with altitude. The density of hot air inside a balloon is less than that of the air at sea level, so the balloon rises. It will continue to rise until the air outside of the balloon is of the same density as the air inside. Smoke particles rise on a plume of hot air being generated by a fire. When the air cools, the particles fall back to Earth.

Heavier-than-air flight is made possible by a careful balance of four physical forces: lift, drag, weight, and thrust. For flight, an aircraft’s lift must balance its weight, and its thrust must exceed its drag. A plane uses its wings for lift and its engines for thrust. Drag is reduced by a plane’s smooth shape and its weight is controlled by the materials it is constructed of.

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Forces Acting on the Aircraft:

Thrust, drag, lift, and weight are forces that act upon all aircraft in flight. Understanding how these forces work and knowing how to control them with the use of power and flight controls are essential to flight.

The four forces acting on an aircraft in straight-and-level, unaccelerated flight are thrust, drag, lift, and weight. They are defined as follows:

• Thrust—the forward force produced by the powerplant/ propeller or rotor. It opposes or overcomes the force

of drag. As a general rule, it acts parallel to the longitudinal axis. However, this is not always the case, as explained later.

• Drag—a rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other

protruding objects. As a general rule, drag opposes thrust and acts rearward parallel to the relative wind.

• Lift—is a force that is produced by the dynamic effect of the air acting on the airfoil, and acts perpendicular to the flight path through the center of lift (CL) and perpendicular to the lateral axis. In level flight, lift opposes the downward force of weight.
• Weight—the combined load of the aircraft itself, the crew, the fuel, and the cargo or baggage. Weight is a force that pulls the aircraft downward because of the force of gravity. It opposes lift and acts vertically downward through the aircraft’s center of gravity (CG).

In steady flight, the sum of these opposing forces is always zero. It does not mean the four forces are equal. It means the opposing forces are equal to, and thereby cancel, the effects of each other.  The usual explanation states that thrust equals drag and lift equals weight. Although true, this statement can be misleading. The refinement of the old “thrust equals drag; lift equals weight” formula explains that a portion of thrust is directed upward in climbs and slow flight and acts as if it were lift while a portion of weight is directed backward opposite to the direction of flight and acts as if it were drag. In glides, a portion of the weight vector is directed along the forward flight path and, therefore, acts as thrust. In other words, any time the flight path of the aircraft is not horizontal, lift, weight, thrust, and drag vectors must each be broken down into two components.

When the force of the lift exactly balances the weight of the aircraft, the plane will fly level; if the lift exceeds the weight, it will climb; and if weight exceeds lift, it will descend. Lift is proportional to airspeed: the faster a plane travels at a given altitude, the more lift its wings generate. So to make an aircraft climb the pilot increases the engine power; to make it descend, engine power is reduced. The shape of the wing can be altered using flaps (on the rear of the wing) and slats (on the front of the wing), allowing the aircraft to generate more lift at slower speeds, such as at takeoff and landing. These basic principles of physics are what underpin every flight. Unless there is a catastrophic failure of an aircraft’s structure (which is extremely rare indeed), a plane cannot ‘just fall out of the sky’.

Most aircraft, including all airliners (but not helicopters and some military jets), are also inherently stable. The forces acting on them – lift, weight, thrust and drag – tend to balance each other out, meaning the plane will fly straight and level unless the pilot does something to alter that. For instance, if the pilot increases power, the aircraft will climb; but eventually, the speed will reduce, meaning lift will reduce, meaning the plane will level off. Even if the pilot let go of the controls altogether, the plane would eventually reach this straight-and-level equilibrium. There are limits beyond which the plane won’t correct itself automatically. For instance, if an aircraft flies too slowly or climbs too steeply, the wings will not produce enough lift and the aircraft will enter a stall. Stalls are easily recoverable (the pilot points the nose down and increases the engine speed) and are only deliberately created in testing new aircraft and training new pilots. All modern airliners have automatic systems which alert the pilots to these situations well in advance or stop them from happening altogether.

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Wings, aerofoil (airfoil) and angle of attack (AOA):

An airplane is equipped with certain fixed and movable surfaces or airfoil which provide for stability and control during flight. Wings are fixed airfoils. Also, an airfoil (American English) or aerofoil (British English) is the cross-sectional shape of a wing, a body shaped to produce an aerodynamic reaction (lift) perpendicular to its direction of motion, for a small resistance (drag) force in that plane. To help with lift, the wings of a plane have an upward curved surface and a flatter lower surface. This shape is also called aerofoil. So the term airfoil/aerofoil is used both for surfaces attached to fuselage and shape of the surface.

If you take an Aerofoil, the line connecting the leading edge to the trailing edge is what is called the Chord line. The angle that this chord line makes with the incoming air is what is called the Angle of Attack. The chord line is a straight line irrespective of the Curvature of the aerofoil and hence is preferred over the Camber line in determining the angle of attack. The Camber line is not straight.

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Figure below illustrates the terms used in describing an aerofoil surface.

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It might be natural to think that when a wing’s curvature displaces air upward, that air is compressed, resulting in increased pressure atop the wing. However curved upper surface of wing has greater area than flat lower surface, so number of air molecules deflected by upper surface is more than lower surface, more deflected molecules will generated relative paucity of molecules in vicinity of surface resulting in reduced pressure over curved surface compared to flat surface. Also, air is pushed downward by AOA and this downwash of air hitting lower surface of wing pushes on the wing both vertically (producing lift) and horizontally (producing drag). The upward push exists in the form of higher pressure below the wing, and this higher pressure is a result of simple Newtonian action and reaction. The more air that the aerofoil deflects, the greater the lift force.

Remember, due to positive AOA, air is merely flowing over upper surface of wings while pushed hard on the lower surface of wings. This pushed hard hitting air molecules generate lift and drag. Even if the upper surface of wing was not curved but flat, lift and drag will be produced by air molecules hitting lower surface of wings due to AOA. If the AOA of a symmetrical airfoil is zero, there would be no lift no drag. On the other hand, if AOA is zero of cambered airfoil, slight lift will be produced by the curvature of upper surface insufficient to make airplane airborne from ground. That is why wings are typically mounted at a small positive angle with respect to longitudinal axis of the fuselage and that is why airplane is rotated-nose high (increase AOA by using elevator) at Vr speed at takeoff to make airplane airborne.        

During take-off, you will notice that the wings have flaps that extend downwards at different angles. This is to give you that extra lift during take-off. When you’re landing, these will fully extend to manage the lift, and increase drag to slow the plane down effectively.

Aerofoil surface generates lift and drag. The amount of lift and drag generated by an aerofoil depends on its shape (camber), surface area, angle of attack, air density and speed through the air. The objective of aerofoil design is to achieve the best compromise between lift and drag for the flight envelope in which it is intended to operate.

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AOA:

Another important concept to understand is angle of attack (AOA). Since the early days of flight, AOA is fundamental to understanding many aspects of airplane performance, stability, and control. The AOA is defined as the acute angle between the chord line of the airfoil and the direction of the relative wind.

The Angle of Attack is the angle at which relative wind meets an Aerofoil. It is the angle formed by the Chord of the aerofoil and the direction of the relative wind or the vector representing the relative motion between the aircraft and the atmosphere.

The angle of attack can be simply described as the difference between where a wing is pointing and where it is going. An increase in angle of attack results in an increase in both lift and induced drag, up to a point. Too high an angle of attack (usually around 17 degrees) and the airflow across the upper surface of the aerofoil becomes detached, resulting in a loss of lift, otherwise known as a Stall.

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By using the aerodynamic forces of thrust, drag, lift, and weight, pilots can fly a controlled, safe flight. A more detailed discussion of these forces follows.

Thrust:

A fixed-wing aircraft generates forward thrust when air is pushed in the direction opposite to flight. This can be done in several ways including by the spinning blades of a propeller, or a rotating fan pushing air out from the back of a jet engine, or by ejecting hot gases from a rocket engine. The forward thrust is proportional to the mass of the airstream multiplied by the difference in velocity of the airstream. Reverse thrust can be generated to aid braking after landing by reversing the pitch of variable-pitch propeller blades, or using a thrust reverser on a jet engine. Rotary wing aircraft and thrust vectoring V/STOL aircraft use engine thrust to support the weight of the aircraft, and vector sum of this thrust fore and aft to control forward speed.

For an aircraft to start moving, thrust must be exerted and be greater than drag. The aircraft continues to move and gain speed until thrust and drag are equal. In order to maintain a constant airspeed, thrust and drag must remain equal, just as lift and weight must be equal to maintain a constant altitude. If in level flight, the engine power is reduced, the thrust is lessened, and the aircraft slows down. As long as the thrust is less than the drag, the aircraft continues to decelerate. To a point, as the aircraft slows down, the drag force will also decrease. The aircraft will continue to slow down until thrust again equals drag at which point the airspeed will stabilize.

Likewise, if the engine power is increased, thrust becomes greater than drag and the airspeed increases. As long as the thrust continues to be greater than the drag, the aircraft continues to accelerate. When drag equals thrust, the aircraft flies at a constant airspeed.

Straight-and-level flight may be sustained at a wide range of speeds. The pilot coordinates AOA and thrust in all speed regimes if the aircraft is to be held in level flight. An important fact related to the principal of lift (for a given airfoil shape) is that lift varies with the AOA and airspeed. Therefore, a large AOA at low airspeeds produces an equal amount of lift at high airspeeds with a low AOA. The speed regimes of flight can be grouped in three categories: low speed flight, cruising flight, and high-speed flight. When the airspeed is low, the AOA must be relatively high if the balance between lift and weight is to be maintained as seen in the figure below:

Figure above shows Angle of attack at various speeds.

If thrust decreases and airspeed decreases, lift will become less than weight and the aircraft will start to descend. To maintain level flight, the pilot can increase the AOA an amount that generates a lift force again equal to the weight of the aircraft. While the aircraft will be flying more slowly, it will still maintain level flight. The AOA is adjusted to maintain lift equal weight. The airspeed will naturally adjust until drag equals thrust and then maintain that airspeed (assumes the pilot is not trying to hold an exact speed).

In level flight, when thrust is increased, the aircraft speeds up and the lift increases. The aircraft will start to climb unless the AOA is decreased just enough to maintain the relationship between lift and weight. The timing of this decrease in AOA needs to be coordinated with the increase in thrust and airspeed. Otherwise, if the AOA is decreased too fast, the aircraft will descend, and if the AOA is decreased too slowly, the aircraft will climb.

As the airspeed varies due to thrust, the AOA must also vary to maintain level flight. At very high speeds and level flight, it is even possible to have a slightly negative AOA.  As thrust is reduced and airspeed decreases, the AOA must increase in order to maintain altitude. If speed decreases enough, the required AOA will increase to the critical AOA. Any further increase in the AOA will result in the wing stalling. Therefore, extra vigilance is required at reduced thrust settings and low speeds so as not to exceed the critical angle of attack. If the airplane is equipped with an AOA indicator, it should be referenced to help monitor the proximity to the critical AOA.

Some aircraft have the ability to change the direction of the thrust rather than changing the AOA. This is accomplished either by pivoting the engines or by vectoring the exhaust gases.

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Lift:

In the context of an air flow relative to a flying body, the lift force is the component of the aerodynamic force that is perpendicular to the flow direction.  Aerodynamic lift results when the wing causes the surrounding air to be deflected – the air then causes a force on the wing in the opposite direction, in accordance with Newton’s third law of motion. Lift is commonly associated with the wing of an aircraft, although lift is also generated by rotors on rotorcraft (which are effectively rotating wings, performing the same function without requiring that the aircraft move forward through the air). While common meanings of the word “lift” suggest that lift opposes gravity, aerodynamic lift can be in any direction, for example, lift occurs at an angle when climbing, descending or banking.

The pilot can control the lift. Any time the control yoke or stick is moved fore or aft, the AOA is changed. As the AOA increases, lift increases (all other factors being equal). When the aircraft reaches the maximum AOA, lift begins to diminish rapidly. This is the stalling AOA or critical AOA. Examine figure below, noting how the coefficient of lift increases until the critical AOA is reached, then decreases rapidly with any further increase in the AOA.

Figure below shows Coefficient of lift versus the effective angle of attack.

Lift coefficient may also be used as a characteristic of a particular shape (or cross-section) of an airfoil. In this application it is called the section lift coefficient c1. It is common to show, for a particular airfoil section, the relationship between section lift coefficient and angle of attack. Symmetric airfoils necessarily have plots of cl versus angle of attack symmetric about the cl axis, but for any airfoil with positive camber, i.e., asymmetrical, convex from above, there is still a small but positive lift coefficient with angles of attack less than zero. That is, the angle at which cl = 0 is negative. On such airfoils at zero angle of attack the pressures on the upper surface are lower than on the lower surface.

Below is a typical curve showing section lift coefficient versus angle of attack for a cambered airfoil

Typically, the lift begins to decrease at an angle of attack of about 15 degrees. The forces necessary to bend the air to such a steep angle are greater than the viscosity of the air will support, and the air begins to separate from the wing. This separation of the airflow from the top of the wing is a stall. 

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Before proceeding further with the topic of lift and how it can be controlled, velocity must be discussed. The shape of the wing or rotor cannot be effective unless it continually keeps “attacking” new air. If an aircraft is to keep flying, the lift-producing airfoil must keep moving. In a helicopter or gyroplane, this is accomplished by the rotation of the rotor blades. For other types of aircraft, such as airplanes, weight shift control, or gliders, air must be moving across the lifting surface. This is accomplished by the forward speed of the aircraft. Lift is proportional to the square of the aircraft’s velocity. For example, an airplane traveling at 200 knots has four times the lift as the same airplane traveling at 100 knots, if the AOA and other factors remain constant.

The above lift equation exemplifies this mathematically and supports that doubling of the airspeed will result in four times the lift.  As a result, one can see that velocity is an important component to the production of lift, which itself can be affected through varying AOA. When examining above equation, lift (L) is determined through the relationship of the air density (ρ), the airfoil velocity (V), the surface area of the wing (S) and the coefficient of lift (CL) for a given airfoil. In determining the lift of a given airfoil, engineers refer to its lift coefficient.

Taking the equation further, one can see an aircraft could not continue to travel in level flight at a constant altitude and maintain the same AOA if the velocity is increased. The lift would increase and the aircraft would climb as a result of the increased lift force or speed up. Therefore, to keep the aircraft straight and level (not accelerating upward) and in a state of equilibrium, as velocity is increased, lift must be kept constant. This is normally accomplished by reducing the AOA by lowering the nose. Conversely, as the aircraft is slowed, the decreasing velocity requires increasing the AOA to maintain lift sufficient to maintain flight. There is, of course, a limit to how far the AOA can be increased, if a stall is to be avoided.

All other factors being constant, for every AOA there is a corresponding airspeed required to maintain altitude in steady, unaccelerated flight (true only if maintaining level flight). Since an airfoil always stalls at the same AOA, if increasing weight, lift must also be increased. The only method of increasing lift is by increasing velocity if the AOA is held constant just short of the “critical,” or stalling, AOA (assuming no flaps or other high lift devices).

Lift and drag also vary directly with the density of the air. Density is affected by several factors: pressure, temperature, and humidity. At an altitude of 18,000 feet, the density of the air has one-half the density of air at sea level. In order to maintain its lift at a higher altitude, an aircraft must fly at a greater true airspeed for any given AOA.

Warm air is less dense than cool air, and moist air is less dense than dry air. Thus, on a hot humid day, an aircraft must be flown at a greater true airspeed for any given AOA than on a cool, dry day.

If the density factor is decreased and the total lift must equal the total weight to remain in flight, it follows that one of the other factors must be increased. The factor usually increased is the airspeed or the AOA because these are controlled directly by the pilot.

Lift varies directly with the wing area, provided there is no change in the wing’s planform. If the wings have the same proportion and airfoil sections, a wing with a planform area of 200 square feet lifts twice as much at the same AOA as a wing with an area of 100 square feet.

Two major aerodynamic factors from the pilot’s viewpoint are lift and airspeed because they can be controlled readily and accurately. Of course, the pilot can also control density by adjusting the altitude and can control wing area if the aircraft happens to have flaps of the type that enlarge wing area. However, for most situations, the pilot controls lift and airspeed to maneuver an aircraft. For instance, in straight-and-level flight, cruising along at a constant altitude, altitude is maintained by adjusting lift to match the aircraft’s velocity or cruise airspeed, while maintaining a state of equilibrium in which lift equals weight. In an approach to landing, when the pilot wishes to land as slowly as practical, it is necessary to increase AOA near maximum to maintain lift equal to the weight of the aircraft.

Stall speed:

Stall speed is simply the minimum speed needed for an airplane to produce lift. If an airplane drops below its specified stall speed, it will no longer produce lift. Stall speeds vary depending on many factors, some of which include the airplane’s weight, dimensions, altitude, turning and even the weather dimensions. Stalls occur not only at slow airspeed, but at any speed when the wings exceed their critical angle of attack.

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Lift/Drag Ratio:

Aerodynamic lift is created by the motion of an aerodynamic object (wing) through the air, which due to its shape and angle deflects the air. For sustained straight and level flight, lift must be equal and opposite to weight. In general, long narrow wings are able deflect a large amount of air at a slow speed, whereas smaller wings need a higher forward speed to deflect an equivalent amount of air and thus generate an equivalent amount of lift. Large cargo aircraft tend to use longer wings with higher angles of attack, whereas supersonic aircraft tend to have short wings and rely heavily on high forward speed to generate lift. However, this lift (deflection) process inevitably causes a retarding force called drag. Because lift and drag are both aerodynamic forces, the ratio of lift to drag is an indication of the aerodynamic efficiency of the airplane. An airplane has a high L/D ratio if it produces a large amount of lift or a small amount of drag. The lift/drag ratio is determined by dividing the lift coefficient by the drag coefficient, CL/CD.

The lift-to-drag ratio (L/D) is the amount of lift generated by a wing or airfoil compared to its drag. A ratio of L/D indicates airfoil efficiency. Aircraft with higher L/D ratios are more efficient than those with lower L/D ratios. In unaccelerated flight with the lift and drag data steady, the proportions of the coefficient of lift (CL) and coefficient of drag (CD) can be calculated for specific AOA.

Lift-to-drag ratios for practical aircraft vary from about 4:1 for vehicles and birds with relatively short wings, up to 60:1 or more for vehicles with very long wings, such as gliders. A greater angle of attack relative to the forward movement also increases the extent of deflection, and thus generates extra lift. However a greater angle of attack also generates extra drag.

Lift/drag ratio also determines the glide ratio and gliding range. Since the glide ratio is based only on the relationship of the aerodynamics forces acting on the aircraft, aircraft weight will not affect it. The only effect weight has is to vary the time that the aircraft will glide for – a heavier aircraft gliding at a higher airspeed will arrive at the same touchdown point in a shorter time.

Typically at low AOA, the coefficient of drag is low and small changes in AOA create only slight changes in the coefficient of drag. At high AOA, small changes in the AOA cause significant changes in drag. The shape of an airfoil, as well as changes in the AOA, affects the production of lift.

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Drag:

Drag is the force that resists movement of an aircraft through the air. There are two basic types: parasite drag and induced drag. The first is called parasite because it in no way functions to aid flight, while the second, induced drag, is a result of an airfoil developing lift.

-1. Parasite Drag

Parasite drag is comprised of all the forces that work to slow an aircraft’s movement. As the term parasite implies, it is the drag that is not associated with the production of lift. This includes the displacement of the air by the aircraft, turbulence generated in the airstream, or a hindrance of air moving over the surface of the aircraft and airfoil. There are three types of parasite drag: form drag, interference drag, and skin friction.

-Form Drag

Form drag is the portion of parasite drag generated by the aircraft due to its shape and airflow around it. Examples include the engine cowlings, antennas, and the aerodynamic shape of other components. When the air has to separate to move around a moving aircraft and its components, it eventually rejoins after passing the body. How quickly and smoothly it rejoins is representative of the resistance that it creates, which requires additional force to overcome. Form drag is the easiest to reduce when designing an aircraft. The solution is to streamline as many of the parts as possible.

-Interference Drag

Interference drag comes from the intersection of airstreams that creates eddy currents, turbulence, or restricts smooth airflow. For example, the intersection of the wing and the fuselage at the wing root has significant interference drag. Air flowing around the fuselage collides with air flowing over the wing, merging into a current of air different from the two original currents. The most interference drag is observed when two surfaces meet at perpendicular angles. Fairings are used to reduce this tendency. If a jet fighter carries two identical wing tanks, the overall drag is greater than the sum of the individual tanks because both of these create and generate interference drag. Fairings and distance between lifting surfaces and external components (such as radar antennas hung from wings) reduce interference drag.

-Skin Friction Drag

Skin friction drag is the aerodynamic resistance due to the contact of moving air with the surface of an aircraft. Every surface, no matter how apparently smooth, has a rough, ragged surface when viewed under a microscope. The air molecules, which come in direct contact with the surface of the wing, are virtually motionless. Each layer of molecules above the surface moves slightly faster until the molecules are moving at the velocity of the air moving around the aircraft. This speed is called the free-stream velocity. The area between the wing and the free-stream velocity level is about as wide as a playing card and is called the boundary layer. At the top of the boundary layer, the molecules increase velocity and move at the same speed as the molecules outside the boundary layer. The actual speed at which the molecules move depends upon the shape of the wing, the viscosity (stickiness) of the air through which the wing or airfoil is moving, and its compressibility (how much it can be compacted).

The airflow outside of the boundary layer reacts to the shape of the edge of the boundary layer just as it would to the physical surface of an object. The boundary layer gives any object an “effective” shape that is usually slightly different from the physical shape. The boundary layer may also separate from the body, thus creating an effective shape much different from the physical shape of the object. This change in the physical shape of the boundary layer causes a dramatic decrease in lift and an increase in drag. When this happens, the airfoil has stalled.

In order to reduce the effect of skin friction drag, aircraft designers utilize flush mount rivets and remove any irregularities that may protrude above the wing surface. In addition, a smooth and glossy finish aids in transition of air across the surface of the wing. Since dirt on an aircraft disrupts the free flow of air and increases drag, keep the surfaces of an aircraft clean and waxed.

-2. Induced Drag

The second basic type of drag is induced drag. It is an established physical fact that no system that does work in the mechanical sense can be 100 percent efficient. This means that whatever the nature of the system, the required work is obtained at the expense of certain additional work that is dissipated or lost in the system. The more efficient the system, the smaller this loss.

In level flight, the aerodynamic properties of a wing or rotor produce a required lift, but this can be obtained only at the expense of a certain penalty. The name given to this penalty is induced drag. Induced drag is inherent whenever an airfoil is producing lift and, in fact, this type of drag is inseparable from the production of lift. Consequently, it is always present if lift is produced.

An airfoil (wing or rotor blade) produces the lift force by making use of the energy of the free airstream. Whenever an airfoil is producing lift, the pressure on the lower surface of it is greater than that on the upper surface. As a result, the air tends to flow from the high pressure area below the tip upward to the low pressure area on the upper surface. In the vicinity of the tips, there is a tendency for these pressures to equalize, resulting in a lateral flow outward from the underside to the upper surface. This lateral flow imparts a rotational velocity to the air at the tips, creating vortices that trail behind the airfoil.

When the aircraft is viewed from the tail, these vortices circulate counterclockwise about the right tip and clockwise about the left tip. As the air (and vortices) roll off the back of your wing, they angle down, which is known as downwash. In aeronautics, downwash is the change in direction of air deflected by the aerodynamic action of wings as part of the process of producing lift.  

Downwash points the relative wind downward, so the more downwash you have, the more your relative wind points downward. That’s important for one very good reason: lift is always perpendicular to the relative wind. When you have less downwash, your lift vector is more vertical, opposing gravity. And when you have more downwash, your lift vector points back more, causing induced drag. On top of that, it takes energy for your wings to create downwash and vortices, and that energy creates drag.

The greater the size and strength of the vortices and consequent downwash component on the net airflow over the airfoil, the greater the induced drag effect becomes. This downwash over the top of the airfoil at the tip has the same effect as bending the lift vector rearward; therefore, the lift is slightly aft of perpendicular to the relative wind, creating a rearward lift component. This is induced drag.

In order to create a greater negative pressure on the top of an airfoil, the airfoil can be inclined to a higher AOA. If the AOA of a symmetrical airfoil were zero, there would be no pressure differential, and consequently, no downwash component and no induced drag. In any case, as AOA increases, induced drag increases proportionally. To state this another way—the lower the airspeed, the greater the AOA required to produce lift equal to the aircraft’s weight and, therefore, the greater induced drag. The amount of induced drag varies inversely with the square of the airspeed.

Conversely, parasite drag increases as the square of the airspeed. Thus, in steady state, as airspeed decreases to near the stalling speed, the total drag becomes greater, due mainly to the sharp rise in induced drag. Similarly, as the aircraft reaches its never-exceed speed (VNE), the total drag increases rapidly due to the sharp increase of parasite drag. As seen in figure below, at some given airspeed, total drag is at its minimum amount. In figuring the maximum range of aircraft, the thrust required to overcome drag is at a minimum if drag is at a minimum. The minimum power and maximum endurance occur at a different point.

Speed and drag relationships for a typical aircraft is depicted in figure below:

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Formation of Vortices:

The action of the airfoil that gives an aircraft lift also causes induced drag. When an airfoil is flown at a positive AOA, a pressure differential exists between the upper and lower surfaces of the airfoil. The pressure above the wing is less than atmospheric pressure and the pressure below the wing is equal to or greater than atmospheric pressure. Since air always moves from high pressure toward low pressure, and the path of least resistance is toward the airfoil’s tips, there is a spanwise movement of air from the bottom of the airfoil outward from the fuselage around the tips. This flow of air results in “spillage” over the tips, thereby setting up a whirlpool of air called a vortex. 

At the same time, the air on the upper surface has a tendency to flow in toward the fuselage and off the trailing edge. This air current forms a similar vortex at the inboard portion of the trailing edge of the airfoil, but because the fuselage limits the inward flow, the vortex is insignificant. Consequently, the deviation in flow direction is greatest at the outer tips where the unrestricted lateral flow is the strongest.

As the air curls upward around the tip, it combines with the downwash to form a fast-spinning trailing vortex. These vortices increase drag because of energy spent in producing the turbulence. Whenever an airfoil is producing lift, induced drag occurs and wingtip vortices are created. Just as lift increases with an increase in AOA, induced drag also increases. This occurs because as the AOA is increased, there is a greater pressure difference between the top and bottom of the airfoil, and a greater lateral flow of air; consequently, this causes more violent vortices to be set up, resulting in more turbulence and more induced drag.

The intensity or strength of the vortices is directly proportional to the weight of the aircraft and inversely proportional to the wingspan and speed of the aircraft. The heavier and slower the aircraft, the greater the AOA and the stronger the wingtip vortices. Thus, an aircraft will create wingtip vortices with maximum strength occurring during the takeoff, climb, and landing phases of flight. These vortices lead to a particularly dangerous hazard to flight, wake turbulence.

Avoiding Wake Turbulence:

Wingtip vortices are greatest when the generating aircraft is “heavy, clean, and slow.” This condition is most commonly encountered during approaches or departures because an aircraft’s AOA is at the highest to produce the lift necessary to land or take off. To minimize the chances of flying through an aircraft’s wake turbulence:

• Avoid flying through another aircraft’s flight path.
• Rotate prior to the point at which the preceding aircraft rotated when taking off behind another aircraft.
• Avoid following another aircraft on a similar flight path at an altitude within 1,000 feet.
• Approach the runway above a preceding aircraft’s path when landing behind another aircraft and touch down after the point at which the other aircraft wheels contacted the runway.

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Ground Effect:

Ever since the beginning of manned flight, pilots realized that just before touchdown it would suddenly feel like the aircraft did not want to go lower, and it would just want to go on and on. This phenomenon is called ground effect. For fixed-wing aircraft, ground effect is the reduced aerodynamic drag that an aircraft’s wings generate when they are close to a fixed surface.

When an aircraft in flight comes within several feet of the surface, ground or water, a change occurs in the three-dimensional flow pattern around the aircraft because the vertical component of the airflow around the wing is restricted by the surface. This alters the wing’s upwash, downwash, and wingtip vortices. Ground effect, then, is due to the interference of the ground (or water) surface with the airflow patterns about the aircraft in flight. While the aerodynamic characteristics of the tail surfaces and the fuselage are altered by ground effect, the principal effects due to proximity of the ground are the changes in the aerodynamic characteristics of the wing. As the wing encounters ground effect and is maintained at a constant AOA, there is consequent reduction in the upwash, downwash, and wingtip vortices.

Since induced drag predominates at low speeds, the reduction of induced drag due to ground effect will cause a significant reduction of thrust required (parasite plus induced drag) at low speeds. Due to the change in upwash, downwash, and wingtip vortices, there may be a change in position (installation) error of the airspeed system associated with ground effect. In the majority of cases, ground effect causes an increase in the local pressure at the static source and produces a lower indication of airspeed and altitude. Thus, an aircraft may be airborne at an indicated airspeed less than that normally required.

In order for ground effect to be of significant magnitude, the wing must be quite close to the ground. A pilot should not attempt to force an aircraft to become airborne with a deficiency of speed. The manufacturer’s recommended takeoff speed is necessary to provide adequate initial climb performance. It is also important that a definite climb be established before a pilot retracts the landing gear or flaps. Never retract the landing gear or flaps prior to establishing a positive rate of climb and only after achieving a safe altitude.

If, during the landing phase of flight, the aircraft is brought into ground effect with a constant AOA, the aircraft experiences an increase in CL and a reduction in the thrust required, and a “floating” effect may occur. Because of the reduced drag and lack of power-off deceleration in ground effect, any excess speed at the point of flare may incur a considerable “float” distance. As the aircraft nears the point of touchdown, ground effect is most realized at altitudes less than the wingspan. During the final phases of the approach as the aircraft nears the ground, a reduction of power is necessary to offset the increase in lift caused from ground effect otherwise the aircraft will have a tendency to climb above the desired glidepath (GP).

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Weight:

Gravity is the pulling force that tends to draw all bodies to the center of the earth. The CG may be considered as a point at which all the weight of the aircraft is concentrated. If the aircraft were supported at its exact CG, it would balance in any attitude. As the location of the center of gravity affects the stability of the aircraft, it must fall within specified limits that are established by the aircraft manufacturer. Both lateral and longitudinal balance are important, but the primary concern is longitudinal balance; that is, the location of the CG along the longitudinal or lengthwise axis. An airplane in flight can be maneuvered by the pilot using the aerodynamic control surfaces, the elevator, rudder, or ailerons. As the control surfaces change the amount of force that each surface generates, the aircraft will rotate about a point called the center of gravity.

It will be noted that CG is of major importance in an aircraft, for its position has a great bearing upon stability. The allowable location of the CG is determined by the general design of each particular aircraft. The designers determine how far the center of pressure (CP) will travel. It is important to understand that an aircraft’s weight is concentrated at the CG and the aerodynamic forces of lift occur at the CP. When the CG is forward of the CP, there is a natural tendency for the aircraft to want to pitch nose down. If the CP is forward of the CG, a nose up pitching moment is created. Therefore, designers fix the aft limit of the CG forward of the CP for the corresponding flight speed in order to retain flight equilibrium.

Weight has a definite relationship to lift. This relationship is simple, but important in understanding the aerodynamics of flying. Lift is the upward force on the wing acting perpendicular to the relative wind and perpendicular to the aircraft’s lateral axis. Lift is required to counteract the aircraft’s weight. In stabilized level flight, when the lift force is equal to the weight force, the aircraft is in a state of equilibrium and neither accelerates upward or downward. If lift becomes less than weight, the vertical speed will decrease. When lift is greater than weight, the vertical speed will increase.

Thrust to weight ratio:

Thrust-to-weight ratio is, as its name suggests, the ratio of instantaneous thrust to weight (where weight means weight at the Earth’s standard acceleration). It is a dimensionless parameter characteristic of rockets and other jet engines and of vehicles propelled by such engines (typically space launch vehicles and jet aircraft). If the thrust-to-weight ratio is greater than the local gravity strength (expressed in gs), then flight can occur without any forward motion or any aerodynamic lift being required. If the thrust-to-weight ratio times the lift-to-drag ratio is greater than local gravity then takeoff using aerodynamic lift is possible.

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Preparing for Takeoff:

For a plane to take off, enough thrust must be generated to get the plane moving in a forward direction, and enough lift must be created to get the plane off the ground. It’s easy to visualize how thrust might be generated with an engine or a propeller; after all, most people are familiar with how vehicles move on the ground. The harder part is conceptualizing how a plane that weighs tens of thousands of pounds can seem to defy gravity.

Planes do not actually defy gravity, though. Instead, the tilt and area of a plane’s wings manipulate the air particles around the plane, creating a strong enough lift that the force of gravity is overcome by the force of the air beneath the wings. Simply put, airplane wings are designed to create a lift force that’s greater than the weight of the plane.

Takeoff is also a delicate mechanical maneuver for a pilot, as they must understand how to manipulate the speed and shape of the plane to create lift. First, the pilot must start the engine of the plane and travel hundreds of miles per hour down the runway, with the appropriate speed determined by factors like plane weight, air temperature, etc. Once the plane hits “rotation speed” the pilot adjusts a piece at the back of the plane called an elevator, which catches air and forces the plane’s nose upward. Now, the angle of attack is increased, allowing the plane to lift for takeoff. A pilot may also increase wing area by deploying slats at the front of the wing, or flaps at the back of the wing, increasing lift.

Landing the Plane:

Getting a plane into the air isn’t the only important part of a flight – the pilot must return their passengers to the ground safely as well! Unless it’s an emergency, pilots lower the plane slowly so passengers can adjust to changing pressure levels comfortably. Pilots generally operate by the “rule of three,” meaning the plane descends 300 meters (1,000 feet) every three miles. This corresponds to an approximately 3-degree descent angle.

For careful descent, a pilot must reduce a plane’s lift slightly to allow its weight to bring it back to the ground. They do this by decreasing thrust and increasing drag, which decreases the lift.

To achieve this, pilots reduce engine thrust and may pitch the plane nose upward, thereby increasing air friction and creating drag. As the plane gets further along in its descent, a pilot may use flaps and slats to increase drag. When the plane initiates its final descent, landing gear is deployed, the plane touches down on its back wheels and brakes are applied to slow the aircraft.

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Section-7

Flight control:  

A flight control system is used to steer an aircraft during flying. Cockpit controls, hydraulically or electrically operated actuators, computers and sensors, all of these equipment when put together makes the complete aircraft control system. Aircraft flight control surfaces deflects the air during the flight of an aircraft to change attitude, altitude and speed of aircraft.

An airplane is equipped with certain fixed and movable surfaces or airfoil which provide for stability and control during flight. Each of the named airfoil is designed to perform a specific function in the flight of the airplane. The fixed airfoils are the wings, the vertical stabilizer, and the horizontal stabilizer. The movable airfoils called control surfaces, are the ailerons, elevators, rudders and flaps. The ailerons, elevators, and rudders are used to “steer” the airplane in flight to make it go where the pilot wishes it to go. The flaps are normally used only during landings and extends some during takeoff.

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Axes of an Aircraft:

The axes of an aircraft are three imaginary lines that pass through an aircraft’s CG. The axes can be considered as imaginary axles around which the aircraft turns. The three axes pass through the CG at 90° angles to each other. The axis passes through the CG and parallel to a line from nose to tail is the longitudinal axis, the axis that passes parallel to a line from wingtip to wingtip is the lateral axis, and the axis that passes through the CG at right angles to the other two axes is the vertical axis. Whenever an aircraft changes its flight attitude or position in flight, it rotates about one or more of the three axes as seen in the figure below:

The aircraft’s motion about its longitudinal axis resembles the roll of a ship from side to side. In fact, the names used to describe the motion about an aircraft’s three axes were originally nautical terms. They have been adapted to aeronautical terminology due to the similarity of motion of aircraft and seagoing ships. The motion about the aircraft’s longitudinal axis is “roll,” the motion about its lateral axis is “pitch,” and the motion about its vertical axis is “yaw.” Yaw is the left and right movement of the aircraft’s nose.

The three motions of the conventional airplane (roll, pitch, and yaw) are controlled by three control surfaces. Roll is controlled by the ailerons; pitch is controlled by the elevators; yaw is controlled by the rudder.

The pilot is always considered the referenced center of effect as the flight controls are used.

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Flight Control Surfaces:

Aircraft flight control systems consist of primary and secondary systems. The ailerons, elevator (or stabilator), and rudder constitute the primary control system and are required to control an aircraft safely during flight. Wing flaps, leading edge devices, spoilers, and trim systems constitute the secondary control system and improve the performance characteristics of the airplane or relieve the pilot of excessive control forces.

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Use of the Flight Controls:

The airplane flies in an environment that allows it to travel up and down as well as left and right.

Basic flight controls and instrument panel are depicted in figure below:

During flight, it is the pressure pilot exerts on the aileron and elevator controls and rudder pedals that causes the airplane to move about the roll (longitudinal), pitch (lateral), and yaw (vertical) axes. When a control surface is moved out of its streamlined position (even slightly), the air flowing across the surface exerts a force against that surface and it tries to return it to its streamlined position. It is this force that the pilot feels as resistance on the aileron and elevator controls and the rudder pedals.

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Primary Flight Controls:  

Aircraft control systems are carefully designed to provide adequate responsiveness to control inputs while allowing a natural feel. At low airspeeds, the controls usually feel soft and sluggish, and the aircraft responds slowly to control applications. At higher airspeeds, the controls become increasingly firm and aircraft response is more rapid.

Movement of any of the three primary flight control surfaces (ailerons, elevator or stabilator, or rudder), changes the airflow and pressure distribution over and around the airfoil. These changes affect the lift and drag produced by the airfoil/ control surface combination, and allow a pilot to control the aircraft about its three axes of rotation.

Design features limit the amount of deflection of flight control surfaces. For example, control-stop mechanisms may be incorporated into the flight control linkages, or movement of the control column and/or rudder pedals may be limited. The purpose of these design limits is to prevent the pilot from inadvertently overcontrolling and overstressing the aircraft during normal maneuvers.

A properly designed aircraft is stable and easily controlled during normal maneuvering. Control surface inputs cause movement about the three axes of rotation. The types of stability an aircraft exhibits also relate to the three axes of rotation.

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Ailerons:

An aileron (French for “little wing” or “fin”) is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around the aircraft’s longitudinal axis), which normally results in a change in flight path due to the tilting of the lift vector. Movement around this axis is called ‘rolling’ or ‘banking’. 

Figure above shows aircraft ‘rolling’, or ‘banking’, with its ailerons:

The ailerons are used to bank the aircraft; to cause one wing tip to move up and the other wing tip to move down. The banking creates an unbalanced side force component of the large wing lift force which causes the aircraft’s flight path to curve. Airplanes turn because of banking created by the ailerons, not because of a rudder input.

The ailerons work by changing the effective shape of the airfoil of the outer portion of the wing. Changing the angle of deflection at the rear of an airfoil will change the amount of lift generated by the foil. Moving the flight deck control wheel or control stick to the right results in the aileron mounted on the right wing to deflect upward while, at the same time, the aileron on the left wing deflects downward. The upward deflection of the right aileron reduces the camber of the wing resulting in decreased lift on the right wing. Conversely, the downward deflection of the left aileron results in an increase in camber and a corresponding increase in lift on the left wing. The differential lift between the wings results in the aircraft rolling to the right. On some aircraft, ailerons are augmented by roll spoilers mounted on the upper surface of the wing.

Adverse Yaw:

In the example above, the increase in camber of the left-wing results in an increase in lift but this, in turn, also causes an increase in drag. This added drag causes the wing to slow down slightly resulting in rotation, referred to as yaw, around the vertical axis. To overcome this yaw and thereby maintain coordinated flight, rudder input is required while entering and exiting a turn. To minimize the amount of adverse yaw produced during a turn, engineers have developed various aerodynamic and mechanical solutions including differential ailerons and coupled ailerons and rudder.

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Elevator:

Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft’s pitch, and therefore the angle of attack and the lift of the wing. The elevators are usually hinged to the tailplane or horizontal stabilizer. They may be the only pitch control surface present, and are sometimes located at the front of the aircraft (early airplanes) or integrated into a rear “all-moving tailplane”, also called a slab elevator or stabilator.

Figure above shows elevators’ effect on pitch:

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Rudder:

The rudder is a primary flight control surface which controls rotation about the vertical axis of an aircraft. This movement is referred to as “yaw”. The rudder is a movable surface that is mounted on the trailing edge of the vertical stabilizer or fin. Unlike a boat, the rudder is not used to steer the aircraft; rather, it is used to overcome adverse yaw induced by turning or, in the case of a multi-engine aircraft, by engine failure and also allows the aircraft to be intentionally slipped when required.

Figure above shows rudder causing yaw.

Rudder effectiveness increases with speed; therefore, large deflections at low speeds and small deflections at high speeds may be required to provide the desired reaction. In propeller-driven aircraft, any slipstream flowing over the rudder increases its effectiveness.  

The rudder is used to control the position of the nose of the aircraft. Interestingly, it is NOT used to turn the aircraft in flight. Aircraft turns are caused by banking the aircraft to one side using either ailerons or spoilers. The banking creates an unbalanced side force component of the large wing lift force which causes the aircraft’s flight path to curve. The rudder input ensures that the aircraft is properly aligned to the curved flight path during the manoeuvre. Otherwise, the aircraft would encounter additional drag or even a possible adverse yaw condition in which, due to increased drag from the control surfaces, the nose would move farther off the flight path.

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Secondary Flight Controls:

Secondary flight control systems may consist of wing flaps, leading edge devices, spoilers, and trim systems.

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Flaps:

Flaps are the most common high-lift devices used on aircraft. These surfaces, which are attached to the trailing edge of the wing, increase both lift and induced drag for any given AOA. Flaps allow a compromise between high cruising speed and low landing speed because they may be extended when needed and retracted into the wing’s structure when not needed. There are four common types of flaps: plain, split, slotted, and Fowler flaps.

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Flaps during takeoff:

Depending on the aircraft type, flaps may be partially extended for takeoff.  When used during takeoff, flaps trade runway distance for climb rate: using flaps reduces ground roll but also reduces the climb rate. The amount of flap used on takeoff is specific to each type of aircraft, and the manufacturer will suggest limits and may indicate the reduction in climb rate to be expected. The Cessna 172S Pilot Operating Handbook generally recommends 10° of flaps on takeoff, especially when the ground is rough or soft.

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Flaps during landing:

Flap extension during landings provides several advantages by:

• Producing greater lift and permitting lower landing speed.
• Producing greater drag, permitting a steep descent angle without airspeed increase.
• Reducing the length of the landing roll.

Flap extension has a definite effect on the airplane’s pitch behavior. The increased camber from flap deflection produces lift primarily on the rear portion of the wing, producing a nose-down force. This pitch behavior varies on different airplane designs. In general, though:

• Flap deflection of up to 15° primarily produces lift with minimal drag. The airplane has a tendency to balloon up with initial flap deflection because of the lift increase. The nose down pitching moment, however, tends to offset the balloon.
• Flap deflection beyond 15° produces a large increase in drag. In high-wing airplanes, a significant nose up pitching moment can occur because the resulting downwash increases the airflow over the horizontal tail.

When the flaps are lowered, the airspeed will decrease unless the power is increased or the pitch attitude lowered. On final approach, therefore, you must estimate where the airplane will land through discerning judgment of the descent angle. 

If it appears that the airplane is going to overshoot the desired landing spot, use more flaps, reduce power, and lower pitch attitude for a steeper approach.  

If the desired landing spot is being undershot, shallow the approach by increasing power and pitch to readjust the descent angle. Never retract the flaps to correct for an undershoot, since that will suddenly decrease the lift and cause the airplane to sink even more rapidly.

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Figure below shows effect of flaps on the landing point.

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Figure below shows effect of flaps on approach angle.

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Every Pilot should know basic aerodynamic facts about Flaps:

-1) Extending flaps increases the camber, or curvature, of your wing. When you extend the flaps on your plane, you lower your aircraft’s stall speed, and at the same time, increase drag. When your wing has a higher camber, it also has a higher lift coefficient, meaning it can produce more lift at a given angle-of-attack.

-2) Extending flaps reduces your aircraft’s stall speed. Because your wing creates more lift with the flaps down, you don’t need to as much angle-of-attack to balance the four forces of flight. And because you can fly at a lower angle-of-attack with flaps extended, your stall speed will be lower as well.

-3) Extending flaps increases drag. When you produce more lift, you produce more induced drag. But that increase in drag can be very useful, especially when you’re landing.

-4) Aircraft use takeoff flap settings that are usually between 5-15 degrees (most jets use leading edge slats as well). That’s quite a bit different than landing, when aircraft typically use 25-40 degrees of flaps. Why the reduced flap setting in takeoff? By extending the flaps a little bit, your plane benefits from the increase in lift (due to camber), but it doesn’t pay the high drag penalty caused by fully extended flaps.

-5) When you’re landing, you typically extend your flaps close to maximum setting. By putting the flaps out all the way, you maximize the lift and drag that your wing produces. This gives you two distinct advantages:

-You have a slower stall speed, which means you can land slower, and

-You produce more drag, which allows you to fly a steeper descent angle to the runway. 

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Leading Edge Devices:

High-lift devices also can be applied to the leading edge of the airfoil. The most common types are fixed slots, movable slats, leading edge flaps, and cuffs.

Fixed slots direct airflow to the upper wing surface and delay airflow separation at higher angles of attack. The slot does not increase the wing camber, but allows a higher maximum CL because the stall is delayed until the wing reaches a greater AOA.

Movable slats consist of leading-edge segments that move on tracks. At low angles of attack, each slat is held flush against the wing’s leading edge by the high pressure that forms at the wing’s leading edge. As the AOA increases, the high-pressure area moves aft below the lower surface of the wing, allowing the slats to move forward. Some slats, however, are pilot operated and can be deployed at any AOA. Opening a slat allows the air below the wing to flow over the wing’s upper surface, delaying airflow separation.

Leading edge flaps, like trailing edge flaps, are used to increase both CL-MAX and the camber of the wings. This type of leading-edge device is frequently used in conjunction with trailing edge flaps and can reduce the nose-down pitching movement produced by the latter. As is true with trailing edge flaps, a small increment of leading-edge flaps increases lift to a much greater extent than drag. As flaps are extended, drag increases at a greater rate than lift.

Leading edge cuffs, like leading edge flaps and trailing edge flaps are used to increase both CL-MAX and the camber of the wings. Unlike leading edge flaps and trailing edge flaps, leading edge cuffs are fixed aerodynamic devices. In most cases, leading edge cuffs extend the leading edge down and forward. This causes the airflow to attach better to the upper surface of the wing at higher angles of attack, thus lowering an aircraft’s stall speed. The fixed nature of leading edge cuffs extracts a penalty in maximum cruise airspeed, but recent advances in design and technology have reduced this penalty.

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Spoilers:

In aeronautics, a spoiler (sometimes called a lift spoiler or lift dumper) is a device which intentionally reduces the lift component of an airfoil in a controlled way. Most often, spoilers are plates on the top surface of a wing that can be extended upward into the airflow to spoil the streamline flow. By so doing, the spoiler creates a controlled stall over the portion of the wing behind it, greatly reducing the lift of that wing section. Spoilers differ from airbrakes in that airbrakes are designed to increase drag without affecting lift, while spoilers reduce lift as well as increasing drag.

Spoilers fall into two categories: those that are deployed at controlled angles during flight to increase descent rate or control roll, and those that are fully deployed immediately on landing to greatly reduce lift (“lift dumpers”) and increase drag. In modern fly-by-wire aircraft, the same set of control surfaces serve both functions.

Spoilers are often used for roll control, an advantage of which is the elimination of adverse yaw. To turn right, for example, the spoiler on the right wing is raised, destroying some of the lift and creating more drag on the right. The right wing drops, and the aircraft banks and yaws to the right. Deploying spoilers on both wings at the same time allows the aircraft to descend without gaining speed. Spoilers are also deployed to help reduce ground roll after landing. By destroying lift, they transfer weight to the wheels, improving braking effectiveness.

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Trim Systems:

Although an aircraft can be operated throughout a wide range of attitudes, airspeeds, and power settings, it can be designed to fly hands-off within only a very limited combination of these variables. Trim systems are used to relieve the pilot of the need to maintain constant pressure on the flight controls, and usually consist of flight deck controls and small hinged devices attached to the trailing edge of one or more of the primary flight control surfaces. Designed to help minimize a pilot’s workload, trim systems aerodynamically assist movement and position of the flight control surface to which they are attached. Common types of trim systems include trim tabs, balance tabs, antiservo tabs, ground adjustable tabs, and an adjustable stabilizer. In normal flight, the stabilizer is trimmed (on some airplanes, this would be the elevator). This is done frequently, usually by the autopilot, as flight dynamics change. The ailerons and rudder can be trimmed, but such adjustments are not done nearly as often.

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Winglets:

Winglets are one of the most successful examples of a NASA aeronautical innovation being utilized around the world on all types of aircraft. Winglets are vertical extensions of wingtips that improve an aircraft’s fuel efficiency and cruising range. Designed as small airfoils, winglets reduce the aerodynamic drag associated with vortices that develop at the wingtips as the airplane moves through the air.  By reducing wingtip drag, fuel consumption goes down and range is extended. Aircraft of all types and sizes are flying with winglets — from single-seat hang gliders and ultralights to global jumbo jets.  Some aircraft are designed and manufactured with sleek upturned winglets that blend smoothly into the outer wing sections. Add-on winglets are also custom made for many types of aircraft.

Winglets increase an aircraft’s operating efficiency by reducing what is called induced drag at the tips of the wings.  An aircraft’s wing is shaped to generate negative pressure on the upper surface and positive pressure on the lower surface as the aircraft moves forward.  This unequal pressure creates lift across the upper surface and the aircraft is able to leave the ground and fly.

Unequal pressure, however, also causes air at each wingtip to flow outward along the lower surface, around the tip, and inboard along the upper surface producing a whirlwind of air called a wingtip vortex. The effect of these vortices is increased drag and reduced lift that results in less flight efficiency and higher fuel costs. Winglets, which are airfoils operating just like a sailboat tacking upwind, produce a forward thrust inside the circulation field of the vortices and reduce their strength. Weaker vortices mean less drag at the wingtips and lift is restored. Improved wing efficiency translates to more payload, reduced fuel consumption, and a longer cruising range that can allow an air carrier to expand routes and destinations.

Winglets allow the wings to be more efficient at creating lift, which means planes require less power from the engines. That results in greater fuel economy, lower CO2 emissions, and lower costs for airlines. Boeing claims that winglets installed on its 757 and 767 airliners can improve fuel burn by 5% and cut CO2 emissions by up to 5%. An airline that installs winglets on its fleet of 58 Boeing 767 jets is expected to save 500,000 gallons of fuel annually.

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Section-8

Wind and flight:

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Common Types of Wind:

When discussing the ‘wind effect’ it is important to understand the three broad classifications of wind types.

Headwind. A headwind is wind blowing directly towards the front of the aircraft. A headwind increases drag.

Tailwind. A tailwind is wind blowing directly towards the rear of the aircraft. A tailwind assists the aircraft’s propulsion systems.

Crosswind. Winds blowing in any other direction than a headwind or tailwind.

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What are the maximum wind limits for a commercial jet aircraft?

The maximum wind limits for commercial aircraft depend on the aircraft, airport, phase of flight and the direction of the wind compared to the direction of the take-off or landing. A crosswind above about 40mph and tailwind above 10mph can start to cause problems and stop commercial jets taking off and landing. It can sometimes be too windy to take-off or land. The limitations are in place for the safety of the passengers and crew.

There is no headwind limitation for most commercial aircraft for take-off, and therefore is no maximum overall limit for take-off (or landing). If there was a 100mph wind, all of which was a headwind component, in theory the aircraft wouldn’t be restricted from taking off. However, the reality is that there are wind limits for opening and closing the aircraft doors (around 45kts) and no pilots would attempt to taxi and depart in such conditions. The airport would have closed in such circumstances anyway!

Aircraft want to take off and land into a headwind as this reduces the distance they require to get airborne or distance need to bring the aircraft to a stop. If an aircraft is standing still on the runway, and has a headwind component of 20kts, that’s 20kts of air flowing over the wing and therefore giving the aircraft an airspeed of 20kts, even though it’s not moving. If it has a take-off speed of 140kts, the aircraft’s ground speed would only need to be 120kts to get airborne because it already has 20kts of airspeed from the wind.

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Wind is one of the main elements that affect an aircraft’s flight. But how exactly do winds affect flying? Here are a few basic facts.

-1. Headwind is preferred for takeoff and landing

Headwind is wind blowing towards the aircraft. Pilots prefer to land and take off in headwind because it increases the lift. In headwind, a lower ground speed and a shorter run is needed for the plane to become airborne. Landing into the wind has the same advantages: It uses less runway, and ground speed is lower at touchdown.

Crosswinds and tailwinds are more difficult, and therefore aircraft have maximum limits for both, depending on the plane, the airport and the conditions on the runway. If winds exceed those limits, the plane will not attempt takeoff or landing.

-2. Winds are taken into consideration in flight planning

Flight planning is done based on weather conditions and winds are a major factor in picking the most suitable flight plan. During flight, winds have an effect on the plane’s speed, so they must be taken into consideration if the aircraft wants to stay on schedule. For instance, tailwinds make travel faster and save fuel, while headwinds have the opposite effect.

-3. Winds by themselves are rarely the cause of accidents

The most troublesome wind conditions for pilots are gusts of wind that change direction quickly. One of the most dangerous wind phenomena, in fact, is wind shear, where there is a sudden change in headwind or tailwind resulting in changes in the lift to the aircraft. Pilots are, however, especially trained on how to take corrective action to ensure safety in the presence of significant wind shear.

Though difficult wind conditions are mentioned as a factor in half of aviation accidents, strong winds alone do not cause accidents. Other risk factors are involved. The number of wind-related accidents has also declined over the years.

-4. Pilots use a range of instruments to keep track of winds and atmospheric conditions while in-flight. Airspeed Indicators and other instruments are used to give the pilot the information they need in order to compensate for the changes in wind during flight. Altimeters measure air pressure and altitude, Attitude and Heading Indicators are used to show the aircraft’s orientation and direction, and the Vertical Speed Indicator shows the rate of climb or descent.

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In 2008, a German A320 crew nearly lost control just feet above the ground during gusty winds. Here’s a report from the Flight Safety Foundation…

During cruise, the flight crew received a Hamburg automatic terminal information system report of winds from 280 degrees at 23 kt, gusting to 37 kt. They planned for, and later received clearance for, an approach and landing on Runway 23, which is equipped with an instrument landing system (ILS) approach. When the crew reported that they were established on the ILS approach, the airport air traffic controller said that the wind was from 300 degrees at 33 knots, gusting to 47 knots.

A decision to go around would have been reasonable because the controller’s report indicated that the winds exceeded the maximum demonstrated crosswind for landing, which was “33 knots, gusting up to 38 knots” and presented as an operating limitation in the A320 flight crew operating manual.

The captain asked ATC for the current “go-around rate,” and the controller replied, “Fifty percent in the last 10 minutes.” The controller offered to vector the aircraft for a localizer approach to Runway 33, but the captain replied that they would attempt to land on Runway 23 first.

The crew gained visual contact with the runway at the outer marker. The copilot, the pilot flying, disengaged the autopilot and autothrottles about 940 ft above the ground. The copilot used the wings-level, or crabbed, crosswind-correction technique until the aircraft crossed the runway threshold and then applied left rudder and right sidestick to decrab the aircraft, aligning the fuselage with the runway centerline while countering the right crosswind.

The A320 was in a 4-degree left bank when it touched down on the left main landing gear and bounced. Although the copilot applied full-right sidestick and right rudder, the aircraft unexpectedly rolled into a 23-degree left bank. It touched down on the left main landing gear again, striking the left wing tip on the runway, and bounced a second time.

The crew conducted a go-around and landed the aircraft without further incident on Runway 33. The left wing tip, the outboard leading-edge slat and slat rail guides were found to have been slightly damaged during the serious incident, the report said, but the ground contact was not detected by the flight crew.

The A320 crew justified their approach with the knowledge that 50% of the aircraft ahead of them landed successfully. The safer option would have been to take extra time to set up for the localizer approach to Runway 33, which was aligned much more into the wind.

In a nutshell:

Avoid the temptation of using other pilots’ success on landing as an indicator of safety.

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In avoiding the winds of catastrophe, there are several risk management strategies that will keep you from getting blown away:

-1. There must be enough fuel to compensate for reduced groundspeed when flying into a headwind. Many accidents blamed on fuel exhaustion had their genesis in a wind related encounter.

-2. There has to be enough airspeed to maintain controllability during takeoff and landing. When a gust of wind gives us extra lift when we really don’t need it and then abruptly stops. Frequently, the result is a stall, and the cure is adequate airspeed and power to overcome that sudden sinking feeling that is likely to follow.

The pilot’s operating handbook for the Cessna 172N recommends a normal rotation speed of 55 knots under calm conditions. In the expanded description under crosswind takeoffs, the handbook suggests, “With ailerons partially deflected into the wind, the airplane is accelerated to a speed slightly higher than normal, then pulled off abruptly to prevent possible settling back to the runway while drifting.” So how much more speed does “slightly” imply? The rule of thumb is half the wind factor.  If it’s really gusty, add more to be sure that when you pull the airplane off the ground, it will fly even if a gust hits at just the wrong time.

-3. Full-stall landings are a joy to behold in light winds but not the best way to handle a gusty touchdown. The nosewheel still needs to be clear of the runway, but we need higher speeds and lower angles of attack to maintain controllability. Note that there is no such thing as a full stall landing. Your aircraft is not stalled when it touches down. A near stall AOA isn’t always necessary for a smooth touchdown, but usually, it is.

A Mooney pilot with more than 1,000 hours total time and 250 in type and another pilot were preparing to land when suddenly the aircraft was blown into the trees. The effective crosswind component, estimated by the accident investigator, was about 10 knots. The pilot stated that after approach with full flaps, the speed was bled off for an intended full-stall landing. Just prior to touchdown, the pilot reported a gust that shifted 90 degrees to the runway and exceeded the crosswind capability of the aircraft. The pilot added full power, but the aircraft could not fly out of the stall. It drifted to the left side of the runway during the attempted go-around, and when the other pilot attempted to turn right, the left wing struck a tree, and the right wing tip contacted the ground.

While the following quote is again from the 172 handbook, the principles apply to most aircraft: “When landing in a strong crosswind, use the minimum flaps setting required for the field length. The maximum allowable crosswind is dependent upon pilot capability as well as aircraft limitations. With average pilot technique, direct crosswinds of 15 knots can be handled safely.”

-4. Remember that the flight controls should be positioned properly to minimize the effect of wind while taxiing. A wind coming from ahead or from one side can be countered by keeping the elevator neutral and turning the ailerons into the wind. If the wind is from behind, position the controls to “dive away” from it; i.e., elevator down and ailerons opposite to the wind.

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Section-9

How commercial airplane fly:   

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How Airplanes navigate from takeoff to landing:

Commercial passenger aircraft fly on so-called instrument flight rules or IFR (essentially, meaning that they do not fly by sight, but following instrument readings) and according to filed flight plans. This means that the aircraft are under the control of air traffic controllers for the entire duration of the flight, in order to maintain proper separation between them. Aircraft are vertically separated by as little as 1,000 feet. It’s perfectly safe. Aircraft flying above 18,000 feet (in the so-called “flight levels”) are required to use IFR rules and flight plans.

Most flight plans are typically programmed manually. Whether they are loaded manually or uploaded electronically, they are always verified by both pilots. Once the fight plan is inserted correctly into the airplane electronic, flight manuals are loaded to see if the route avoids weather or any other flight restrictions such as military airspace. These so-called “canned” routes are developed with the Federal Aviation Administration—preferred routes that extend from the moment the plane departs to when it reaches its destination. The airline’s dispatchers will work with controllers to find the optimal routes, taking into account weather, winds aloft and the aircraft’s weight and balance.

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Instrument flight rules (IFR) is one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other is visual flight rules (VFR).

Visual flight:

Visual flight or “Visual Attitude Flying” is a method of controlling an aircraft where the aircraft attitude is determined by observing outside visual references. For aircraft the primary visual reference used is usually the relationship between the aircraft’s “nose” or cowling against the natural horizon. The pilot can maintain or change the airspeed, altitude, and direction of flight (heading) as well as the rate of climb or rate of descent and rate of turn (bank angle) through the use of the aircraft flight controls and aircraft engine controls to adjust the “sight picture”. Some reference to flight instruments is usually necessary to determine exact airspeed, altitude, heading, bank angle and rate of climb/descent.

Visual flight rules:

In aviation, visual flight rules (VFR) are a set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minima, i.e., in visual meteorological conditions (VMC), as specified in the rules of the relevant aviation authority. The pilot must be able to operate the aircraft with visual reference to the ground, and by visually avoiding obstructions and other aircraft.

It is possible and fairly straightforward, in relatively clear weather conditions, to fly a plane solely by reference to outside visual cues, such as the horizon to maintain orientation, nearby buildings and terrain features for navigation, and other aircraft to maintain separation. This is known as operating the aircraft under visual flight rules (VFR), and is the most common mode of operation for small aircraft. However, it is safe to fly VFR only when these outside references can be clearly seen from a sufficient distance; when flying through or above clouds, or in fog, rain, dust or similar low-level weather conditions, these references can be obscured. Thus, cloud ceiling and flight visibility are the most important variables for safe operations during all phases of flight. The minimum weather conditions for ceiling and visibility for VFR flights are defined in FAR Part 91.155, and vary depending on the type of airspace in which the aircraft is operating, and on whether the flight is conducted during daytime or nighttime. However, typical daytime VFR minimums for most airspace is 3 statute miles of flight visibility and a distance from clouds of 500 feet below, 1,000 feet above, and 2,000 feet horizontally. Flight conditions reported as equal to or greater than these VFR minimums are referred to as visual meteorological conditions (VMC).

Any aircraft operating under VFR must have the required equipment on board, as described in FAR Part 91.205 (which includes some instruments necessary for IFR flight). VFR pilots may use cockpit instruments as secondary aids to navigation and orientation, but are not required to; the view outside of the aircraft is the primary source for keeping the aircraft straight and level (orientation), flying to the intended destination (navigation), and avoiding obstacles and hazards (separation).

Visual flight rules are generally simpler than instrument flight rules, and require significantly less training and practice. VFR provides a great degree of freedom, allowing pilots to go where they want, when they want, and allows them a much wider latitude in determining how they get there.

If the weather is less than VMC, pilots are required to use instrument flight rules, and operation of the aircraft will primarily be through referencing the instruments rather than visual reference.

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Instrument flight rules:

When operation of an aircraft under VFR is not safe, because the visual cues outside the aircraft are obscured by weather, instrument flight rules must be used instead. IFR permits an aircraft to operate in instrument meteorological conditions (IMC), which is essentially any weather condition less than VMC but in which aircraft can still operate safely. Use of instrument flight rules is also required when flying in “Class A” airspace regardless of weather conditions. Class A airspace extends from 18,000 feet above mean sea level to flight level (FL) 600 (60,000 feet pressure altitude) above the contiguous 48 United States and overlying the waters within 12 miles thereof. Flight in Class A airspace requires pilots and aircraft to be instrument equipped and rated and to be operating under instrument flight rules (IFR). In many countries commercial airliners and their pilots must operate under IFR as the majority of flights enter Class A airspace. Procedures and training are significantly more complex compared to VFR instruction, as a pilot must demonstrate competency in conducting an entire cross-country flight solely by reference to instruments.

Instrument pilots must meticulously evaluate weather, create a detailed flight plan based around specific instrument departure, en route, and arrival procedures, and dispatch the flight. 

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Separation Standards:

If you are a frequent traveller who enjoys a window seat, you might have noticed other aircraft while in air. Flying in the crowded skies over Europe or North America, it is quite common to see other aircraft whizzing past, either above or below. Have you ever wondered how close to each other can aircraft fly?

The distance between two flying commercial aircraft may vary at different flight phases and at a different altitude ─ during a takeoff and landing or at cruise altitude. This vertical and horizontal aircraft separation is under control of the specific aviation regulations and may vary in different regions. There are well-established rules to dictate the space that must exist between two aircraft at all times.

National authorities lay down vertical and horizontal separation standards to facilitate the safe navigation of aircraft in controlled airspace. Observance of these standards ensures safe separation from the ground, from other aircraft and from protected airspace. Separation standards may sometimes serve to reduce exposure to Wake Vortex Turbulence although there are many occurrences of significant wake vortex encounter at separations much greater than prevailing minimum separation.

Vertical Separation:

Vertical separation is achieved by requiring aircraft to use a prescribed altimeter pressure setting within designated airspace, and to operate at different levels expressed in terms of altitude or flight level.

ICAO specify minimum vertical separation for IFR flight as 1000 ft (300 m) below FL290 (29,000 feet) and 2000 ft (600 m) above FL290, except where Reduced Vertical Separation Minima (RVSM) apply. RVSM approval allows aircraft to fly with a vertical separation of 1,000 feet reduced from 2,000 feet between FL290 and FL410 inclusive. Over the ocean, beyond radar coverage, the vertical separation minimum can be a little as 1,000 feet. Most national authorities follow a similar rule, but may specify a different level at which the rule changes.

Horizontal Separation:

Horizontal separation relates to the distance between aircraft in the horizontal plane.

Since aircraft cause wake turbulence that may affect other aircraft flying the same track at the same altitude, horizontal separation is much greater than vertical. In controlled airspace, the required minimum horizontal separation between aircraft flying at the same altitude is five nautical miles, which is just over 9 kilometers. 

When an airplane is departing, Air Traffic Controllers can place aircraft much closer to each other than they do at cruise altitude. Thus, in the terminal area airspace, horizontal separation decreases to three nautical miles.

Horizontal separation may be:

• Longitudinal (aircraft following the same route), where the separation standard is based on time (or distance) along track between aircraft, or
• Lateral.

Longitudinal Separation:

Longitudinal separation is applied so that the spacing between aircraft is never less than a specified amount. For aircraft following the same or diverging tracks, longitudinal separation may be achieved by requiring aircraft to make position reports and comparing the time of their reports and by speed control, ensuring that the speed of the following aircraft does not exceed the speed of the leading aircraft. Reduced separation may apply if the leading aircraft is maintaining a higher speed than the following aircraft.

Lateral Separation:

Lateral separation is achieved by various means, which include the following:

-By position reports which positively indicate the aircraft are over different geographic locations

-By requiring aircraft to fly on specified tracks which are separated by a minimum angle. Both aircraft must be established on radials or tracks which diverge by a specified amount depending on the type of navigation aid in use, and at least one aircraft must be at a distance of 15 NM (nautical mile) or more from the facility.

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Loss of Separation:

Loss of separation between airborne aircraft occurs whenever specified separation minima in controlled airspace are breached. Minimum separation standards for airspace are specified by ATS authorities, based on ICAO standards. Aircraft are considered separated when either the horizontal or the vertical separation minima are met. Conversely, for an event to be classified as a loss of separation, both must have been infringed (i.e., there is neither vertical, nor horizontal separation between the aircraft). An exception to this is the use of composite separation which allows for a combination of partial horizontal and partial vertical separation to be used. Note, however, that this exception is only applicable under specific circumstances and is not used in surveillance environment.

Effects:

Loss of separation is not a hazard on its own in many cases. However, if the situation is not corrected promptly (by restoring the applicable minima), an incident may quickly develop into an accident, e.g.:

-1. Loss of separation from other aircraft may result in collision;

-2. Injury, especially to unsecured cabin crew or passengers, may result from violent maneuvers to avoid collision with other aircraft;

-3. Injury to aircraft occupants may also result from a wake vortex turbulence encounter.

-4. Additionally, a loss of separation may cause high levels of stress for the pilots and controllers involved, and may lead to reduced performance (and possibly, other incidents).

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ACAS:

The Airborne Collision Avoidance System II (ACAS II) was introduced in order to reduce the risk of mid-air collisions or near mid-air collisions between aircraft. It serves as a last-resort safety net irrespective of any separation standards.

ACAS II is an aircraft system based on Secondary Surveillance Radar (SSR) transponder signals. ACAS II interrogates the Mode C and Mode S transponders of nearby aircraft (‘intruders’) and from the replies tracks their altitude and range and issues alerts to the pilots, as appropriate. ACAS II will not detect non-transponder-equipped aircraft and will not issue any resolution advice for traffic without altitude reporting transponder.

ACAS II works independently of the aircraft navigation, flight management systems, and Air Traffic Control (ATC) ground systems. While assessing threats it does not take into account the ATC clearance, pilot’s intentions or Flight Management System inputs. ACAS II is not connected to the autopilot, except the Airbus AP/FD (Auto pilot/flight director) TCAS capability (which provides automated responses to RAs).

Currently, the only commercially available implementations of ICAO standard for ACAS II (Airborne Collision Avoidance System) is TCAS II version 7.1 (Traffic alert and Collision Avoidance System). ICAO Annex 10 vol. IV states that all ACAS II units must be complaint with version 7.1 as of 1 January 2017. In Europe version 7.1 has been mandatory since 1 December 2015. However, in some countries (notably in the United States, where ACAS mandates are different) there is a large population of aircraft still operating versions 6.04a and 7.0.

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Typical flight:

A lot of work goes into ensuring that flights are safe well before aircraft take off, and indeed even before the first tickets go on sale. The aviation industry has a strong safety culture. The routes taken by commercial flights are typically planned by experts who seek to ensure that the flight is as safe and smooth as is possible. Pilots can amend these routes before take-off and during the flight to further improve the comfort and safety of their passengers. The aviation industry is highly regulated in the interests of safety. These regulations cover a very wide range of areas, including aircraft maintenance standards, requiring aircraft to carry more fuel than is required (so they can divert to another airport if needed) and making sure that pilots are well-rested.

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Commercial flights are guided throughout the journey by air traffic controllers on the ground, who ensure aircraft stay on course and remain well separated from each other (usually by several miles). Air traffic controllers also assist pilots with the safest and most comfortable journey from the moment the plane begins taxiing on the runway to the point when it arrives at the gate at which point passengers disembark.

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A commercial aircraft has at least two people on the flight deck: the captain and the first officer. Longer flights will have an additional pilot so that crew can rest in shifts. Like the captain of a ship, an airline captain has ultimate responsibility for the safety of the aircraft and everyone on board. The captain and first officer are both pilots, and both are fully capable of flying the plane. They divide responsibilities between the “pilot flying” who operates the main controls, and the “pilot monitoring” who talks on the radio, reads checklists, and performs support duties. They usually swap after each flight: the captain might be pilot flying on the crew’s first leg, and the first officer would be pilot flying on the next. Due to the way airlines calculate seniority, it’s entirely possible for the first officer to be older or more experienced than the captain, particularly if they flew in the military or another airline. The aircraft will have a number of flight attendants, at a minimum one for every 50 seats, who are responsible for safety in the cabin. The chief flight attendant is commonly known as the purser.

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The following is based on a typical twin-engined jet aircraft, such as the Boeing 737 or the Airbus A320 family (the two most popular commercial aircraft models in service). There may be variations to this typical flight on other aircraft models, but the general sequence of events is the same.

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Pre-flight:

As passengers are boarding the aircraft, the pilots are on the flight deck making last-minute checks on the weather, departure procedures and making sure the aircraft has enough fuel and isn’t overweight. Once the doors are closed, you may hear a small jet engine powering up in the tail of the aircraft. This is the auxiliary power unit (APU), which provides power to the aircraft so the ground supply can be disconnected; it also supplies the compressed air needed to start the main engines. A tug will push the aircraft backwards out of the gate. When the aircraft is clear of the gate and the tug disconnected, the pilot will be given permission to start the main engines.

During pushback, a demonstration will take place to inform passengers of the safety features of the aircraft and their use. This may be given either by the flight attendants or through screening a video. A basic safety demonstration includes the use of the seatbelts, safely stowing luggage, use of the emergency oxygen masks, location and use of life jackets, emergency exit locations, a reminder that the flight is non-smoking, to put electronic devices in flight mode and turn them off for takeoff, and that further safety information can be found on the card in your seat pocket (or printed on the seats) or by asking a flight attendant. If you happen to be sitting in an exit row, you will also receive instructions from the flight attendants on how to operate the exit in case of an emergency evacuation.

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Taxi:

Before an aircraft can take off, it has to taxi (i.e., move on the ground under its own power) from the airport terminal to the runway. Aircraft always take off into a headwind, as a lower ground speed and a shorter run is needed for the plane to become airborne, so the plane will taxi to the downwind end of the runway. At some small airports, this may only take moments, but at larger ones, it can take several minutes. At one extreme, the far end of one runway at Schiphol Airport, Amsterdam is 9 km (5.6 mi) from the terminal and takes 15 to 20 minutes to taxi to and from. Aircraft move slowly on the ground with taxi speeds ranging from 10–40 km/h (6–25 mph).

During taxi, the pilots will deploy flaps and slats on the aircraft wings; the motors moving the flaps and slats make a distinct whining sound. In freezing temperatures, aircraft will need to be “de-iced” before reaching the runway. The plane will be sprayed with an anti-freeze solution to remove built-up snow and ice, as these can disrupt the airflow over the wings and reduce lift. Once in the air, the engines will provide hot air to prevent ice and snow from re-forming on the wings.

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Throttle:

The throttle (or thrust lever) in a gas turbine engine adjusts the thrust produced by controlling the fuel flow to the combustion chamber. Modern jet aircraft technically don’t use throttles; rather they are equipped with thrust levers which are connected to a Fuel Control Unit (FCU). This can come in the form of a mechanical computer in the case of earlier engines or a digital electronic computer called a Fully Authority Digital Engine Controller (FADEC).  Early jet aircraft did use a throttle – literally a cockpit lever connected to a throttleable valve to precisely meter fuel into the combustion chamber(s) of the engine. This could be problematic to operate in flight as the fuel rate has to be changed as altitude – and consequently combustor inlet conditions – changes, making the engine vulnerable to flameouts from excessively rich fuel flow and compressor stalls from abrupt throttle changes. FCUs were developed, specific to each engine to offer simplified control. Most of the modern engines are actually controlled by FADEC- so the signals from the throttle are sent to the computer, which regulates the fuel flow based on various parameters (including engine safety) thereby adjusting thrust. The computer handles the additional components of the engines like the thrust reversers and afterburners.

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A word about radio calls before takeoff:

When the pilot calls ‘ready for departure’, there are several possible answers he could get from Air Traffic Control. He may be asked to hold his position, especially if other aircraft are waiting to take off. He may be asked to ‘line up and wait’, which means he can taxi to the start of the runway, and position the aircraft ready to move down the runway, or commence the ‘takeoff roll’, as it is called. He must not actually commence the takeoff roll until ATC tells him ‘cleared for takeoff’. This is the only phrase ever used which includes the word ‘cleared’. Until that point, the word ‘departure’ is always used. The reason for this is very important, and back to a serious aviation accident which took place at Tenerife, in the Canary Islands, in 1977….

Tenerife airport disaster:

On 27th March 1977, two Boeing 747 jets collided on the runway at Tenerife North Airport, resulting in 583 fatalities. This accident is still considered to be the deadliest in aviation history.

The airport was crowded at the time due to an earlier terrorist incident at Gran Canaria Airport, and therefore airliners were using the runway for taxiing. There were also patches of thick fog on the runway. The accident occurred when one plane initiated its takeoff run before the other plane had taxied clear of the runway. The two aircraft could not see each other due to the fog, and the impact and resulting fire killed almost everyone in both aircraft.

The subsequent investigation found that the primary cause of the accident was that the captain of the departing aircraft mistakenly believed that he had been cleared for takeoff when he heard the word ‘takeoff’ being used in a radio call.

The disaster had a lasting influence on the industry, highlighting in particular the vital importance of using standardized phraseology in radio communications. Since then, the word ‘takeoff’ is only used when the plane is actually ‘cleared for takeoff’. Otherwise, the word ‘departure’ is used.

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Takeoff:

Takeoff is the phase of flight in which airplane leaves the ground and becomes airborne. When cleared for takeoff, the pilot will taxi the aircraft into position at the start of the runway. It’s normal for the pilot to increase engine power to ensure all engines are producing the same amount of power. Finally, the pilot will apply full take-off power; this usually means a rapid acceleration and an increase in engine noise. When the aircraft has reached the correct speed (i.e., when it’s travelling fast enough to generate the lift it needs to fly), the pilot will “rotate” the aircraft by raising the nose, and the plane will lift off from the runway. For most jet aircraft, the takeoff speed is in the region of 250 to 300 km/h (150 to 180 mph). The actual speed required for takeoff depends on the size and weight of the plane and weather conditions at the airport, but these factors are worked out precisely in advance. There is always enough runway left to complete the takeoff.

As the aircraft travels down the runway, you may hear and feel bumps as the aircraft’s undercarriage crosses the runway lights or uneven parts of the runway. Such noises are to be expected and are not a cause for alarm. Equally, when the aircraft lifts off there is often a noticeable bump. This is a normal event caused by the hydraulics in the landing gear reaching their maximum extension as the plane leaves the ground.

On rare occasions, the pilots may decide to reject (abort) a takeoff, usually due to a fault with one of the aircraft’s systems. The maximum speed to safely reject a takeoff, known as “V1”, is precisely calculated before every flight. After an aircraft has passed V1, the pilot must take off or risk running off the end of the runway. If the fault is minor, the pilots may decide to continue the takeoff and come back around to land, since stopping at such high speeds within the remaining runway is very hard on the undercarriage and often results in overheating brakes and blown tires.

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Power settings:

For light aircraft, usually full power is used during takeoff. Large transport category (airliner) aircraft may use a reduced power for takeoff, where less than full power is applied in order to prolong engine life, reduce maintenance costs and reduce noise emissions. In some emergency cases, the power used can then be increased to increase the aircraft’s performance. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems. The aircraft is permitted to accelerate to rotation speed (often referred to as Vr). The term rotation is used because the aircraft pivots around the axis of its main landing gear while still on the ground, usually because of gentle manipulation of the flight controls to make or facilitate this change in aircraft attitude (once proper air displacement occurs under / over the wings, an aircraft will lift off on its own; controls are to ease that in). The nose is raised to a nominal 5°–15° nose up pitch attitude to increase lift from the wings and effect liftoff. For most aircraft, attempting a takeoff without a pitch-up would require cruise speeds while still on the runway.

Fixed-wing aircraft designed for high-speed operation (such as commercial jet aircraft) have difficulty generating enough lift at the low speeds encountered during takeoff. These are therefore fitted with high-lift devices, often including slats and usually flaps, which increase the camber and often area of the wing, making it more effective at low speed, thus creating more lift. These are deployed from the wing before takeoff, and retracted during the climb. They can also be deployed at other times, such as before landing.

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Airliner Takeoff Speeds:

The takeoff speed required varies with aircraft weight and aircraft configuration (flap or slat position, as applicable), and is provided to the flight crew as indicated airspeed.

Whether it is a small double engine Cessna or a Jumbo jet A380, the definition of speed is the same for all types of planes.  These speeds are calculated prior to a take-off in accordance with aircraft weight, environmental factors etc.

Basic information about V1, Vr/Rotate and V2 speeds:

V1 is defined as the speed beyond which the take-off should no longer be aborted. Meaning that in case you experience any trouble with your plane before reaching V1 you would immediately abort your take-off and would apply all the necessary means to bring the aircraft to a halt. If pilots experience any serious aircraft malfunction after V1, otherwise they have to continue the take-off, a take-off board will lead to a runway overrun and could severely damage the plane.

Vr or Rotate is defined as the speed at which the pilot begins to apply control inputs to make the aircraft nose to pitch up, after which it leaves the ground. The term rotation is used because the aircraft pivots around the axis of its main landing gear while still on the ground.  The easiest way to memorize the rotate speed is the point where the nose leaves the ground and vortexes are created at the wing tips which rotate behind the aircraft. Moreover, the point where the main gear leaves the ground is the point where the aircraft has reached the Vlof – lift off speed.

V2 is the speed at which the aircraft may safely be climbed with one engine inoperative. This speed is nicknamed a “take-off safety speed”; it is the speed an aircraft with one engine inoperative must be able to attain in order to leave the runway and get 35 feet off the ground at the end of the runway, maintaining a 200 ft/min climb thereafter. This is the lowest speed at which the aircraft complies with the handling criteria associated with a climb after a take-off, followed by the failure of an engine.

In a single-engine or light twin-engine aircraft, the pilot calculates the length of runway required to take off and clear any obstacles, to ensure sufficient runway to use for takeoff. A safety margin can be added to provide the option to stop on the runway in case of a rejected takeoff. In most such aircraft, any engine failure results in a rejected takeoff as a matter of course, since even overrunning the end of the runway is preferable to lifting off with insufficient power to maintain flight.

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How fast does an average commercial airline plane go when it is taking off from the runway before takeoff?

By “average commercial airline plane,” we are referring to large passenger jetliners such as Boeing and Airbus products. The takeoff speed of such aircraft varies quite a bit, depending on the takeoff weight and the use of high-lift devices like flaps and slats. However, a good average speed range is about 160 mph (260 km/h) to 180 mph (290 km/h). Some typical takeoff speeds for a variety of airliners are provided below.

Aircraft	Takeoff Weight	Takeoff Speed
Boeing 737	100,000 lb 45,360 kg	150 mph 250 km/h 130 kts
Boeing 757	240,000 lb 108,860 kg	160 mph 260 km/h 140 kts
Airbus A320	155,000 lb 70,305 kg	170 mph 275 km/h 150 kts
Airbus A340	571,000 lb 259,000 kg	180 mph 290 km/h 155 kts
Boeing 747	800,000 lb 362,870 kg	180 mph 290 km/h 155 kts
Concorde	400,000 lb 181,435 kg	225 mph 360 km/h 195 kts

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Factors affecting aircraft performance during takeoff:

The takeoff part of a flight is the distance from the brake release point to the point at which the aircraft reaches a defined height over the surface. For any particular takeoff it must be shown that the distance required for takeoff in the prevailing conditions does not exceed the takeoff distance available at the aerodrome. During the takeoff roll, lift is created on the wings to overcome the aircraft weight. This is done by forward acceleration of the aircraft produced by greater thrust force than drag.

The takeoff distance required depends on the interaction of forces:

• The thrust varies during takeoff, in general it decreases as aircraft speeds up;
• The total drag of the aircraft during takeoff results from aerodynamic drag and wheel drag. As the aircraft speeds up the aerodynamic drag will increase. The wheel drag depends on the load and the runway surface resistance. But as the aircraft speeds up the lift force increases, which reduces the load on the wheels and therefore reduces the wheel drag (eventually to zero);
• The lift force increases, as aircraft speeds up;
• The aircraft weight remains constant.

The factors that affect these forces and their interaction are the factors that affect aircraft performance during takeoff:

• aircraft takeoff mass and balance;
• temperature;
• air density;
• wind;
• runway conditions (runway surface, runway slope);
• flap setting and airframe contamination;

The greater the takeoff mass the greater the aircraft weight. This means that greater lift force is required to overcome the weight, therefore greater speed is necessary for takeoff. Thus a longer takeoff distance is required in order to achieve this speed, because the rate of acceleration is reduced (inversely proportional to the mass) and the wheel drag will be greater due to increased load.

The efficiency of the jet engine depends on the temperature of the air surrounding it. The higher the air temperature, the less thrust can be produced by the engine. Because of that the difference between the thrust and the drag during takeoff is smaller. Therefore the rate of acceleration is smaller and the aircraft will need a longer takeoff distance.

Air density affects the thrust, lift and drag forces in the following way:

– low air density gives reduced thrust created by the engines;

– low air density requires higher takeoff speed. The lift is proportional to the air density. So, higher speed is required to produce same lift when the air density is low;

– low air density gives lower aerodynamic drag. However, the effect on the lift and thrust is more dominant since the aerodynamic drag is relatively small;

In general low density requires longer takeoff distance.

Air density is determined by the pressure (elevation), temperature and humidity:

– low atmospheric pressure gives low air density;

– higher the aerodrome is elevated, lower the atmospheric pressure hence lower the air density;

– higher the temperature, lower the air density;

– higher the humidity, lower the air density.

The lift and the drag during takeoff depend on air speed, but the distance required for takeoff depends on the ground speed. A headwind therefore reduces the ground speed at a required takeoff air speed and reduces the takeoff distance. On the other hand, a tailwind increases the ground speed, at a same required takeoff air speed, and increases the takeoff distance. Crosswind component has no effect on the takeoff distance. Pilots are permitted to use only 50% of the reported headwind component (or 150% of the reported tailwind component) when calculating the takeoff distance required. This is to allow for variations in the reported winds during takeoff.

If the runway is sloping, a component of the weight acts along the runway and increases or decreases the acceleration force. A downhill slope increases the accelerating force, and therefore reduces the takeoff distance required, whereas an uphill slope reduces the accelerating force and increases the takeoff distance.

The runway surface condition has effect on the wheel drag. If the runway is contaminated by snow, slush or standing water, the wheel drag will be greater. Thus the accelerating force decreases and the takeoff distance required increases. Further on, if the takeoff is abandoned in such conditions and breaking is required the stopping distance will greatly increase.

Flap setting has an effect on the wing’s lift coefficient and on the aerodynamic drag. Increasing flap angle increases the lift coefficient, and therefore reduces stalling speed and the required takeoff speed (the same lift will be created at smaller air speed due to greater lift coefficient). This reduces the takeoff distance. In the same time increased flap angle increases drag, reduces acceleration, and increases the takeoff distance. The net effect is that takeoff distance will decrease with increase of flap angle initially, but above a certain flap angle the takeoff distance will increase again. An optimum takeoff setting can be determined for each type of aircraft and any deviation from this setting will give an increase in the takeoff distance.

The flap setting also affects the climb gradient. Increasing the flap angle increases the drag, and so reduces the climb gradient for a given aircraft mass. If there are obstacles to be considered in the takeoff flight path, the flap setting that gives the shortest takeoff distance may not give the required climb gradient for obstacle clearance. In addition if the airframe is contaminated by frost, ice or snow during takeoff the aircraft performance will be reduced, and the takeoff distance will be increased.

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Takeoff calculations:

Takeoff calculation is performed before takeoff in order to confirm that the actual weight is below the maximum permissible takeoff weight at particular aerodrome in the conditions prevailing. On modern aircraft this value and the values for the various speeds can be obtained from the Flight Management System (FMS), after feeding in the relevant data for the airfield and conditions.

Following basic conditions are considered in the calculations:

– Airfield elevation

– Runway slope

– Air temperature

– Wind

– Runway length and conditions

– Flap configuration

Using either charts or computer software the maximum permissible takeoff weight is determined and when it is confirmed that the actual weight is within the limits, it is necessary to find the takeoff speeds and thrust setting corresponding to the actual weight.

Following speeds are determined or, on modern aircraft, obtained from the FMS:

• V1 – decision speed, at which in case of engine failure the continued takeoff distance required, will not exceed the takeoff distance available;
• VR – rotation speed, at which aircraft nose is lifted from the ground (rotated) for takeoff;
• V2 – takeoff safety speed with critical engine inoperative, at which the aircraft can take off safely with critical engine inoperative.

Calculating and entering takeoff performance parameters into aircraft systems involves a number of steps that create potential opportunities for errors. In the event the errors are not detected and corrected prior to takeoff, the following adverse consequences may occur:

– tailstrike: when aircraft rotation is initiated at a speed below that required for the aircraft’s weight, lift-off may not be achieved. In response, the pilot may increase the nose-up attitude of the aircraft, which may result in the tail contacting the runway

– reduced takeoff performance: during the takeoff, the crew may observe that the aircraft’s performance is not as expected; the aircraft may appear ‘sluggish’ or ‘heavy’ – degraded handling qualities: after takeoff, there may be a reduced margin between the aircraft’s actual speed and the stall speed until the aircraft accelerates up to the normal climb speed. If the V2 speed is also erroneous, this may not occur until after the aircraft passes through the acceleration height

– rejected takeoff: if the aircraft fails to accelerate or lift-off as expected, the crew may reject the takeoff – runway overrun: if the aircraft fails to stop after a rejected takeoff or the aircraft fails to liftoff, the aircraft rollout may extend beyond the end of the runway resulting in an overrun

– TO/GA (Takeoff/Go around) engine thrust: if the aircraft fails to accelerate or lift-off as expected, the crew may select take-off/go-around (TO/GA) engine thrust (the maximum thrust that the engines will supply)

– increased runway length required: early rotation increases drag and significantly increases the distance from rotation to liftoff

– overweight takeoff: this may occur if an erroneous TOW (Take Off Weight) is used to determine whether a runway is acceptable for the takeoff

– reduced obstacle clearance: if the takeoff is commenced at low speed, the aircraft will not achieve the climb gradient required, and the clearance between any obstacles along the take-off path will be reduced.

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Stall warning at takeoff:

At takeoff, stall warnings are the result of one, or a combination, of the following factors:

• Weather Factors: − Icing conditions − Windshear
• Human Factors: − Insufficient aircraft de-icing in cold weather operations − Incorrect loading (e.g., cargo not positioned in accordance with the load and trim sheet) − Incorrect slats/flaps configuration − Incorrect takeoff speed
• Flight Crew Techniques: − Early rotation below the specified speed, resulting in a higher peak AOA (Angle of Attack) − Maneuvering near the minimum speed at an excessive bank angle − Premature retraction of the flaps
• Aircraft Systems: − Engine failure and subsequent loss of energy − Malfunction of artificial stall warning, leading to spurious stall warnings, caused by a damaged AOA probe, by an AOA probe that is not correctly rigged, or by a computer failure.

A stall warning triggers when the aircraft’s Angle-Of-Attack (AOA) exceeds a predetermined value. This value depends on the slat configuration. The warning indicates the proximity of the aircraft’s AOA compared to the stall’s AOA.

The stall warning is inhibited on ground, until liftoff.

When an aircraft is airborne, stall warning activation can be catastrophic, if the flight crew does not respond correctly and effectively. Worldwide experience records events where flight crews have been misled by a spurious / untimely stall warning activation at liftoff. Some of them have resulted in fatal accidents (e.g.: rejected takeoff after rotation, CFIT).

If a stall warning triggers at a low altitude, the flight crew should consider that there is an immediate flight path threat, and a potential risk of ground contact. In other words, there is no time to differentiate between a real or spurious stall warning, and there is no altitude to convert to speed.

However, when a stall warning triggers (i.e., stick shaker activation), aircraft still have positive climb performance capability.

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Climb:

In aviation, a climb is the operation of increasing the altitude of an aircraft. It is also the logical phase of a typical flight following takeoff and preceding the cruise. During the climb phase there is an increase in altitude to a predetermined level.

Once airborne and climbing, the pilot will raise the landing gear, which makes a bumping sound. Since full power is only needed for takeoff, the pilot will reduce power to the aircraft’s engines and as a result, the noise in the cabin may decrease. The flaps and slats on the wings will also be retracted. It is also normal for planes to climb steeply and to turn, sometimes sharply, shortly after takeoff. These are standard procedures to turn the plane onto its course as soon as possible and to minimize noise for people living near the airport.

Depending on the length of the flight, it may then take 15-20 minutes for the plane to climb to its cruising altitude. The pilot will typically allow the flight attendants to leave their seats once the plane has cleared 10,000 feet (3000 meters) but it is common for the seat-belt light to remain lit for passengers until the plane reaches its cruise altitude. While the climb is often very smooth, occasional jolts (perhaps as the plane climbs through clouds) can still be expected. Most jets climb at 250 knots up to 10,000 feet due to FAA regulations. Above 10,000 feet, 280 to 300 knots with a transition to Mach . 7 around 24,000 feet are average for the 737. During normal flights, the 747-400 & 747-8 has a climb rate ranging from 2000 to 4000 feet per minute.

As the climb progresses, the rate of climb decreases as thrust reduces due to reducing air density. A gradual climb improves forward visibility over the nose of the aircraft.

The opposite of a climb is a descent.

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Factors affecting aircraft performance during climb:

The climb phase of a flight starts after takeoff, when the aircraft reaches a certain height above the ground, and it ends when aircraft levels off at the cruising level. For the first portion of the climb it is more convenient to consider the climb gradient rather than the rate of climb.

Climb gradient is the ratio of height gained to distance traveled, and it is expressed in percentage. All instrument departure procedures have the minimum climb gradient specified in the charts. This climb gradient is required to overfly the obstacles in the departure area at a safe altitude defined as minimum obstacle clearance.

When the obstacles are over flown it is more convenient to consider the rate of climb, since the aircraft would normally require to climb at the maximum rate of climb so as to reach the required altitude in the least possible time. Rate of climb is the vertical component of the aircraft’s velocity.

As a rule of thumb climb gradient may be converted to rate of climb by multiplying the gradient by airspeed in knots (example: climb gradient is 6 %, airspeed is 150 knots therefore rate of climb should be 900 feet per minute).

In steady climb, the weight has a component along the flight path, which adds to the drag force. To maintain a steady speed along the flight path, the opposite forces along the flight path must be equal.

Factors affecting the climb gradient:

The climb gradient by definition is the ratio of height gained to distance traveled. If the angle of climb α is known then the climb gradient is equal to tan (α). For small angles tan (α) = sin (α). Now taking into the consideration the formulas from the drawing above:

Climb gradient = tan (α) = sin (α) = (Thrust – Drag) / Weight

This shows that the climb gradient depends on the difference between the thrust and drag (the excess thrust) and the mass of the aircraft. Factors that affect these forces will have effect on the climb gradient.

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Cruise:

Cruise is a flight phase that occurs when the aircraft levels after a climb to a set altitude and before it begins to descend. Cruising usually consumes the majority of a flight, and it may include changes in heading (direction of flight) at a constant airspeed and altitude.

As it cruises, the plane rides upon an invisible cushion of air that has been pushed down by the shape of the wing. When there are bumps in this ‘cushion’ caused by gusts of wind, the plane may jolt slightly as it follows the shape of the air – this is turbulence. Turbulence may occur in both cloudy and clear skies and is completely normal; aircraft are designed to deal with these bumps and other than fastening your seat belt, there is no action that needs to be taken. Significant turbulence ahead can be detected on the plane’s radar, and if it is the pilot will switch the seat belt sign back on. This may mean a very bumpy ride for a few minutes but there is no cause for alarm. If there is really severe turbulence ahead (for instance in thunder clouds) the pilot will normally divert around it. Some turbulence may cause the plane’s wings to bend or flex a little: this is a deliberate design feature which actually allows the aircraft to withstand turbulence more effectively, just as a tree bends in the wind.

Commercial aircraft don’t fly in a straight line between airports. Instead, they fly via a number of waypoints or intersections, usually along designated airways. Aircraft flying in opposite directions along the same airway are kept apart by flying at alternating altitudes – aircraft in one direction (usually eastbound) fly at odd thousands of feet, while aircraft in the other direction (usually westbound) fly at even thousands of feet. Aircraft flying in the same direction at the same altitude are kept apart by time, typically 5-15 minutes. Air traffic controllers constantly monitor the position of aircraft and can request pilots change their altitude or speed to ensure adequate separation. Modern aircraft are also equipped with traffic collision avoidance systems (TCAS) that automatically detect another aircraft coming too close and initiate evasive action as needed.

During cruise, the autopilot uses programmed instructions to fly the plane. The (human) pilots monitor the autopilot and make corrections to it as required.

For most passenger aircraft, the cruise phase consumes most of the aircraft’s fuel. This lightens the aircraft and raises the optimum altitude for fuel economy. For traffic control reasons it is usually necessary for an aircraft to stay at the cleared flight level. On long-haul flights, the pilot may ask air traffic control to climb from one flight level to a higher one, in a maneuver known as step climb.

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Aircraft generally fly at altitudes of 35,000–40000 feet above mean sea level. At these altitudes, air density is very much low. To maintain the necessary lift to hold the aircraft up in the air, the nose is slightly pitched upwards. Pitching the nose upwards, increases the aircraft’s angle of attack (AOA). Since, lift is directly proportional to the AOA of the aircraft, the airplane flies at slight nose pitch up attitude, even in level flight.

There are some aircrafts which fly with a nose down attitude. A good example is the Boeing B-52 Stratofortress. This is because the relative angle between the wing and the aircraft’s body is very high. Therefore, the wings are already at high angle of attack, even on the ground. If the aircraft would fly straight, without pitching the nose down, the high angle of attack of the wing would cause the aircraft either to stall or to climb. This would prevent the aircraft from maintaining a level flight. Therefore, it flies with a “nose down attitude”, to maintain a level flight.

How cold is it up there?

The higher you get, the colder it gets. If the temperature at ground level was 20C, at 40,000 feet it would be -57C. At 35,000 feet the air temperature is about -54C.

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Cruise speed:

Commercial or passenger aircraft are usually designed for optimum performance at their cruise speed (VC). Combustion engines have an optimum efficiency level for fuel consumption and power output. Generally, gasoline piston engines are most efficient between idle speed and 25% short of full throttle. Diesels are most efficient at their max-torque point, usually around 70%. With aircraft, other factors affecting optimum cruise altitude include payload, center of gravity, air temperature, humidity, and speed. This altitude is usually where the higher ground speeds, the increase in aerodynamic drag power, and the decrease in engine thrust and efficiency at higher altitudes are balanced. The typical cruising airspeed for a long-distance commercial passenger aircraft is approximately 880–926 km/h (475–500 kn; 547–575 mph).

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Descent:

A descent during air travel is any portion where an aircraft decreases altitude, and is the opposite of an ascent or climb.

Descents are part of normal procedures, but also occur during emergencies, such as rapid or explosive decompression, forcing an emergency descent to below 3,000 m (10,000 ft) and preferably below 2,400 m (8,000 ft), respectively the maximum temporary safe altitude for an unpressurized aircraft and the maximum safe altitude for extended duration. An example of explosive decompression is Aloha Airlines Flight 243. Involuntary descent might occur from a decrease in power, decreased lift (wing icing), an increase in drag, or flying in an air mass moving downward, such as a terrain induced downdraft, near a thunderstorm, in a downburst, or microburst.

Normal descents:

Intentional descents might be undertaken to land, avoid other air traffic or poor flight conditions (turbulence, icing conditions, or bad weather), clouds (particularly under visual flight rules), to see something lower, to enter warmer air, or to take advantage of wind direction of a different altitude, particularly with balloons.

Normal descents take place at a constant airspeed and constant angle of descent (3-degree final approach at most airports). The pilot controls the angle of descent by varying engine power and pitch angle (lowering the nose) to keep the airspeed constant. Unpowered descents (such as engine failure) are steeper than powered descents but flown in a similar way as a glider.

Rapid descents:

Rapid descents relate to dramatic changes in cabin air pressure—even pressurized aircraft—and can result in discomfort in the middle ear. Relief is achieved by decreasing relative pressure by equalizing the middle ear with ambient pressure (“popping ears”) through swallowing, yawning, chewing, or the Valsalva maneuver.

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Descent and approach:

As the plane approaches its destination, it will begin to descend. The pilot will reduce engine power, sometimes so that the engines are only idling and barely making any noise. The steepness of this descent varies depending upon the airport and the aircraft. The pilot will typically switch the seat belt sign on as the aircraft begins to descend, although flight attendants won’t typically be seated until the aircraft has descended through 10,000 feet (3000 meters). During the descent, the spoilers on top of the wings may open slightly; the spoilers decrease lift and act as brakes to prevent the aircraft from going too fast.

Aircraft always land into the wind, which helps slow the plane down. So depending on the direction from which you approach the airport, the plane may have to make a series of turns to line up with the runway. These are usually carried out at slow speed and can feel quite sharp as a result.

As the plane begins its initial approach into the airport, the pilots will deploy the flaps and slats on the wings; the flap motors make a distinctive whining sound. The flaps will be deployed in several stages and to a greater extent than at take-off. The pilots will also lower the landing gear; this makes a low thudding noise.

The approach to land can feel unstable. This is because the air near the ground is often more turbulent than it is at altitude. If there is a crosswind, the pilot may also have to bank and turn the aircraft slightly to keep it on course.

In some cases the aircraft will have to land in low cloud or fog, and you may not see the ground until you have almost landed. Most airports have instrument approach systems to help guide aircraft towards the airport and the runway; landings at major international airports with modern airliners can be safely conducted with as little as 50 m (150 ft) of visibility. But again, there are strict rules that pilots must (and do) stick to when landing in bad weather. If the weather is too bad, the pilot may decide to ‘hold’ (fly in circles) and wait for improvement, or divert to another airport where the weather is better. All aircraft must carry at least enough fuel to fly to their destination, hold for up to 30 minutes and then divert to another suitable airport.

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Landing

Just before the aircraft ‘touches down’ on the runway, the pilot flying will idle the engines and flare the aircraft by raising the nose, allowing the main landing gear to touch down first and take the weight of the aircraft before the nose landing gear touches down. The touchdown may be accompanied by a jolt and an audible ‘thud’ as plane’s landing gear touches the ground. If the runway is wet, the pilot often lands deliberately firmly to minimize the risk of skidding. Spoilers on the wings will open to stop the aircraft generating lift and keep it firmly on the runway. To help slow the aircraft down, the pilot will engage reverse thrust: the direction of the engine’s output is changed and the engines will power up again, slowing the plane down rather than pushing it forward. At some airports, the aircraft may slow down very sharply. This is simply to ensure it can turn off the runway at the right point, and/or means that there is another aircraft on the approach which needs to land.

On occasions, you may experience a go-around, which is when the aircraft takes off again shortly before landing. This occurs when the pilots decide to (or air traffic control orders them to) reject landing because of poor visibility, the aircraft not being in line with the runway or getting blown off course, or a runway obstruction. As a result, you will hear the engines power up once more and feel the engines’ thrust to perhaps a greater degree than you did at take-off. The pilot will partially retract the flaps and raise the landing gear to help the aircraft climb. Once at a higher altitude and depending on the circumstances, the aircraft will either be turned around and the landing will be attempted again, or it will be diverted to another airport. Should this happen to you, you should not be alarmed – it is a common procedure and well-practiced by pilots.

Aircraft usually land at an airport on a firm runway or helicopter landing pad, generally constructed of asphalt concrete, concrete, gravel or grass. Aircraft equipped with pontoons (floatplane) or with a boat hull-shaped fuselage (a flying boat) are able to land on water. Aircraft also sometimes use skis to land on snow or ice.

To land, the airspeed and the rate of descent are reduced such that the object descends at a low enough rate to allow for a gentle touch down. Landing is accomplished by slowing down and descending to the runway. This speed reduction is accomplished by reducing thrust and/or inducing a greater amount of drag using flaps, landing gear or speed brakes. When a fixed-wing aircraft approaches the ground, the pilot will move the control column back to execute a flare or round-out. This increases the angle of attack. Progressive movement of the control column back will allow the aircraft to settle onto the runway at minimum speed, landing on its main wheels first in the case of a tricycle gear aircraft or on all three wheels simultaneously in the case of a conventional landing gear-equipped aircraft, commonly referred to as a “taildragger”.

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When configured for landing, the position of the nose is determined by whether there are leading edge slats installed. Airplanes with leading edge slats (movable panels on the front of the wing) approach the runway with the nose up, while airplanes without slats approach with the nose down. Examples of the former include the Boeing 737, while the Bombardier CRJ-200 approaches nose down (later-model CRJs have slats).

In a jet with slats, the nose is slightly above the horizon, and the power is set to give the proper descent rate. When the slats and flaps are extended, the nose being above the horizon does not result in a climb unless the thrust (power) is set to a high setting.

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Landing Flare:

The Landing Flare, in a fixed wing aircraft, is the transition phase between the final approach and the touchdown on the landing surface. This sub-phase of flight normally involves a simultaneous increase in aircraft pitch attitude and a reduction in engine power/thrust, the combination of which results in a decrease in both rate of descent and airspeed.

If executed correctly, the flare will result in the aircraft achieving the appropriate landing attitude with power at or near idle, a reduced rate of descent and a decaying airspeed, all at a height varying from several inches to several feet above the landing surface (dependent upon aircraft type). If not executed correctly, the flare could result in a hard landing, the collapse of the landing gear, a tail strike or in a runway overrun or excursion.

The landing flare is executed during a critical phase of flight and, except for autoland operations, is dependent upon the judgement, skill and experience of the pilot. There are numerous potential threats that can affect the outcome of the maneuver. These include:

-1. Excessive speed during final approach:

B738, Mangalore India, 2010

E145, Nuremberg Germany, 2005

GLF4, Teterboro NJ USA, 2010

-2. Excessive rate of descent during final approach:

MD11, Hong Kong China, 1999

-3. Initiating the flare at a height which is either too high (early flare) or too low (late flare):

 MD11, Riyadh Saudi Arabia, 2010: Late Flare

 B734, Amsterdam Netherlands, 2010 (1): Early Flare

-4. Insufficient flare which could fail to arrest the rate of descent or fail to achieve landing attitude prior to touchdown:

A321, Manchester UK, 2008 (1)

-5. Overly aggressive pitch changes which could result in ballooning (altitude gain)

-6. Inappropriate power/thrust reductions including any one of, or combinations of, too early, too late, too little or too much:

CRJ2, Providence RI USA, 2007: Early

DH8D, London Gatwick UK, 2009: Early

D328, Mannheim Germany, 2008: Too little, late

-7. Excessive hold off:

CRJ7, Kanpur India, 2011

MD11, New York JFK USA, 2003

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Runway length:

A runway of at least 6,000 ft (1,800 m) in length is usually adequate for aircraft weights below approximately 200,000 lb (90,000 kg). Larger aircraft including wide bodies will usually require at least 8,000 ft (2,400 m) at sea level and somewhat more at higher Altitude airports.

Landing Distance:  The horizontal distance traversed by the aeroplane from a point on the approach path at a selected height above the landing surface to the point on the landing surface at which the aeroplane comes to a complete stop.

When discussing landing distance, two categories must be considered:

• Actual landing distance is the distance used in landing and braking to a complete stop (on a dry runway) after crossing the runway threshold at 50 feet; and,
• Required landing distance is the distance derived by applying a factor to the actual landing distance.

Actual landing distances are determined during certification flight tests without the use of thrust reversers.

The required landing distance is used for flight planning purposes (i.e., for selecting the main, alternate aerodromes and aerodromes for emergency landing).

Figure below graphically illustrates the determination of the actual and required landing distances in accordance with JAA/FAA standards.

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The value of the actual landing distance is influenced by the following factors:

• High airport elevation or high-density altitude, resulting in increased groundspeed;
• Runway gradient (i.e., slope);
• Runway condition (dry, wet or contaminated by standing water, slush, snow or ice);
• Wind conditions
• Type of braking (pedal braking or autobrakes, use of thrust reversers);
• Anti-skid system failure;
• Final approach speed;
• Landing technique (e.g., height and airspeed over the threshold, thrust reduction and flare);
• Standard operating procedures (SOPs) deviations (e.g., failure to arm ground spoilers);
• Minimum equipment list (MEL)/dispatch deviation guide (DDG) conditions (e.g., thrust reversers, brake unit, anti-skid or ground spoilers inoperative); and,
• System malfunctions (e.g., increasing final approach speed and/or affecting lift-dumping capability and/or braking capability).

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Landing performance:

The performance data for landing an aircraft can be obtained from the aircraft’s flight manual or pilot’s operating handbook. It will state the distance required to bring the aircraft to a stop under ideal conditions, assuming the aircraft crosses the runway threshold at a height of 50 ft, at the correct speed. The actual landing performance of an aircraft is affected by many variables which must be taken into account.

Factors affecting landing performance:

-1. Weight

The weight of an aircraft is one of the basic factors that determines the landing distance required by an aircraft. An increase in weight increases the stall speed of the aircraft. Stall is a reduction in the lift coefficient generated by a wing as angle of attack increases. Therefore, the minimum approach speed increases as the aircraft’s weight increases. The kinetic energy (1/2 mV2) that has to be overcome to stop an aircraft is a function of the mass of the aircraft and the square of its speed at touchdown. The kinetic energy increases significantly as an aircraft’s weight increases, and the brakes have to absorb this greater energy, increasing the landing roll of the aircraft.

-2. Density altitude

A decrease in density of air results in decrease in both aircraft and engine performance. High elevation airports are characterized by low pressure and high ambient temperatures. The True Airspeed (TAS) will be higher than the Indicated airspeed indicated by the Airspeed indicator to the pilot in air of low density. This increase in TAS leads to greater touchdown speed hence increases the landing roll. More energy has to be absorbed by the brakes thus demanding the need of a longer runway. An increased density altitude means a longer landing distance.

-3. Headwinds and tailwinds

The headwind reduces the landing distance for an aircraft. Landing into a headwind reduces the ground speed (GS) for the same true airspeed (TAS). This is beneficial to pilots as well as Air traffic controllers (ATC). An aircraft landing into a headwind will require less runway and will be able to vacate the runway sooner. If the headwind decreases near the ground, there is a decrease in the airspeed of the aircraft and it will tend to sink and possibly undershoot the aiming point.

Tailwind increases the ground speed of an aircraft for the same TAS and thus a longer runway distance will be required for an aircraft to land. Landing in a tailwind situation could lead to the aircraft overshooting the runway and colliding with objects or terrain.

-4. Runway surface

Runway conditions affect takeoff and landing performance of an aircraft. The runway may be made up of concrete, asphalt, gravel or grass. An important safety concern at airports is the contamination of the runways due to ice, snow, water, rubber deposits etc. The landing distance required by an aircraft is much more in case of low friction runways which do not facilitate effective braking to occur. Aquaplaning is a phenomenon in which directional control is lost because of the presence of film of water between the rubber tires and the runway surface. The construction of grooved surface runways and regular maintenance, especially rubber removal, both help reduce runway slipperiness and facilitate good ground handling and effective braking.

-5. Runway slope

An up-slope runway will allow an aircraft to land in a shorter distance. A down-slope runway will require a greater landing distance. It will take longer for the aeroplane to touch down from 50 ft above the runway threshold, as the runway is falling away beneath the aeroplane. Braking while going downhill is not as effective as on a level or up-slope runway.

-6. Flap settings

Wing flaps are hinged surfaces on the trailing edge of the wings of a fixed-wing aircraft. High flap settings help an aircraft to increase the aerodynamic drag and reduce the stalling speed so that the aircraft can fly at low speeds safely. Flaps also lower the nose of the aircraft and give the pilots a better view of the ground ahead while landing.

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Why does it feel like a plane accelerates just before touching down?

The aircraft flares just before touching down. It descends with a constant velocity, and just before touching down pulls the nose up to reduce the descent. This results in a higher angle of attack, more lift, and a vertical deceleration of the airplane. A passenger perceives this vertical deceleration as a force. Direction of the force is straight down and the aircraft is nose up, you’re leaning back, so there is a component of (gravity + vertical deceleration) that pushes you into the back of your seat.

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Why do planes always land on rear wheels instead of the nose wheels?

Aircraft land on the main wheels. For aircraft with nose wheel, it is the back ones, but for aircraft with tail wheel (also called “tail-draggers”) it is the front ones. In either case the main wheels are very close to center of gravity and carry most of the aircraft’s weight, the nose or tail wheel only carries a small fraction of it. The aircraft must land on wheels that are close to the center of gravity (longitudinally). If they were not, the force on the wheels would create a moment that would violently pitch the aircraft. Actually, tail-draggers tend to bounce on landing a bit because there still is some moment left and in case of tail-draggers it pitches the aircraft up.

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Hard, firm and soft landing:

Sometimes a landing is as smooth as silk. Other times, the landing is quite a bit more bumpy with a solid jolt on touchdown that you feel in your body. Very, very rarely, the landing is so hard that the plane is damaged, sometimes even beyond repair. Hard landing is one kind of typical landing incidents that can cause passenger discomfort, aircraft damage and even loss of life.

The normal sink rate of an aircraft on landing is two to three feet per second (soft landing); when a pilot lands at seven to eight feet per second, it will feel harder than normal. Pilots have been known to report it as a hard landing, even though the landing was within the prescribed limits. It is firm landing.

The technical definition of a hard landing is a peak recorded vertical acceleration that exceeds 2.1G, or a force more than twice your own body weight. Boeing defines a “hard landing” to be any landing that may have resulted in an exceeding of limit load on the airframe or landing gear, with a sink rate of 10 feet per second with zero roll at touchdown. That would be a big drop, much more than seven to eight feet per second.

A hard landing is never ok. A firm landing may be ok.

So, why will pilots land firmly?

First of all, their training manuals for aircraft such as the Boeing 737 specifically state: “Do not allow the airplane to float: fly the airplane onto the runway. Do not extend the flare by increasing pitch attitude in an attempt to achieve a perfectly smooth touchdown.”

There are few good reasons to fly the airplane onto the runway. One is very simple: a runway is a coveted space. You don’t want to hog it when there are dozens of other airplanes that need to get on it quick.

On landing, it’s important to be in the correct place at the correct speed. You don’t want to be 10 or 20 knots too fast, and not set up to land at the right spot on the runway. Pilots need to control the aircraft to an appropriate groundspeed and descent rate before descending to the flare initial point. Then control column and throttle operation in flare maneuver would affect landing performance conjointly.

The other reason to land firm is if the weather is poor with a slippery runway due to “contamination” such as water, slush or snow. On departure, the primary concern is any kind of mechanical issue, itself quite rare. On landing, it’s all related to weather. This kind of weather includes cross-winds, wind shear, microbursts, rain, and slippery runways because of rain or snow. In these instances, the pilots want to put down the plane firmly.

A firm landing allows for the ground spoilers to deploy more quickly, the wheels to spin up and the brakes to be applied. All of this helps with the braking action of the aircraft. Even though the runways are long — there is always the potential for an overrun when conditions are poor.

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Aircraft braking systems include:

-1. Aircraft disc brakes in the landing gear, used to brake the wheels while touching the ground. These brakes are operated hydraulically or pneumatically. In most modern aircraft they are activated by the top section of the rudder pedals (“toe brakes”). In some older aircraft the bottom section is used instead (“heel brakes”). Levers are used in a few aircraft. Most aircraft are capable of differential braking.

-2. Thrust reversers, that allow thrust from the engines to be used to slow the aircraft.

-3. Air brakes, dedicated flight control surfaces that work by increasing drag.

In aeronautics, air brakes or speed brakes are a type of flight control surface used on an aircraft to increase the drag on the aircraft. Air brakes differ from spoilers in that air brakes are designed to increase drag while making little change to lift, whereas spoilers reduce the lift-to-drag ratio and require a higher angle of attack to maintain lift, resulting in a higher stall speed.

-4.  Large drogue parachutes, used by several former and current military and civilian aircraft (examples include the American B-52 and the soviet Tu-134 and Tu-144) and in the Space Shuttle.

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How high do planes actually fly?

One reason that planes cruise above the clouds is so they can fly fast. The higher airplanes climb, the thinner the air gets, and the more efficiently they can fly because of less resistance in the atmosphere. Commercial aircraft typically fly between 31,000 and 38,000 feet — about 5.9 to 7.2 miles — high and usually reach their cruising altitudes in the first 15 minutes of a flight. Planes can fly much higher than this altitude, but that can present safety issues. Flying higher means it would take a longer time to return to a safe altitude in case of an emergency, like rapid decompression. It also isn’t the most efficient use of fuel to fly that high in the first place, since planes can fly at a lower altitude with the assistance of wind. Another reason why planes don’t fly higher is due to the weight of the aircraft. The more you weigh, the harder it is to get to a certain altitude.

And the weight of the plane changes as the aircraft climbs higher into the sky. Jet fuel weighs about 6.7 pounds per gallon, so the more that you burn as you’re flying, you would actually end up losing a lot of fuel weight. This, combined with the thinner atmosphere at this height, creates less resistance.

When the plane gets too high, there is insufficient oxygen to fuel the engines. Most aircraft are limited by engine power. The air is less dense at altitude, so the engine can suck in less and less air per second as it goes higher and at some point the engine can no longer develop sufficient power to climb. Back in 2004, Pinnacle Airlines flight 3701 was destroyed after flying to 41,000 feet, with two members of crew on board at the time. Both engines failed, the crew couldn’t get them restarted, and the aircraft crashed and was destroyed.

Why don’t small private planes fly as high?

In most cases, these planes use a piston-powered engine, which operates similarly to the engine in your car and with power that only allows for shorter flights, according to the National Business Aviation Association. This type of engine prevents these smaller planes from reaching the same altitudes as commercial aircraft. The plane that the average guy can rent and fly, those tend to stay usually below 15,000 feet and that’s just a limit on what the plane can do. Pilots also refrain from flying these types of planes at greater heights because of potential health risks like hypoxia, which is when tissues do not receive enough oxygen. That lack of oxygen can occur at higher altitudes due to a decrease in oxygen pressure. As the plane ascends, the level of oxygen decreases, which can cause rapid decompression for an aircraft that is not pressurized in the same way as a commercial airplane.

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Turning the aircraft:

Unlike turning a boat, changing the direction of an aircraft normally must be done with the ailerons rather than the rudder. The rudder turns (yaws) the aircraft but has little effect on its direction of travel. With aircraft, the change in direction is caused by the horizontal component of lift, acting on the wings. The pilot tilts the lift force, which is perpendicular to the wings, in the direction of the intended turn by rolling the aircraft into the turn. As the bank angle is increased, the lifting force can be split into two components: one acting vertically and one acting horizontally.

If the total lift is kept constant, the vertical component of lift will decrease. As the weight of the aircraft is unchanged, this would result in the aircraft descending if not countered. To maintain level flight requires increased positive (up) elevator to increase the angle of attack, increase the total lift generated and keep the vertical component of lift equal with the weight of the aircraft. This cannot continue indefinitely. The total load factor required to maintain level flight is directly related to the bank angle. This means that for a given airspeed, level flight can only be maintained up to a certain given angle of bank. Beyond this angle of bank, the aircraft will suffer an accelerated stall if the pilot attempts to generate enough lift to maintain level flight.

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Any time the airplane is not in “zero-angle-of-bank” flight, lift created by the wings is not being fully applied against gravity, and more than 1 g will be required for level flight (figure below).

At bank angles greater than 67 degrees, level flight cannot be maintained within flight manual limits for a 2.5 G load factor. In high bank angle increasing airspeed situations, the primary objective is to maneuver the lift of the airplane to directly oppose the force of gravity by rolling to wings level. Applying nose-up elevator at bank angles above 60 degrees causes no appreciable change in pitch attitude and may exceed normal structure load limits as well as the wing angle of attack for stall. A high bank angle is one beyond that necessary for normal flight and bank angle for an upset has been defined as unintentionally more than 45 degrees. Bank angle on a commercial aircraft is limited to 30 degrees under normal conditions resulting in 1.15 G load factor.  At 15 degree the load factor is about 1.03 G.

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Why does Stall Speed increase with Bank Angle?

In physics, G-force is used to describe the acceleration of an object relative to Earth’s gravity. 1G is the acceleration we feel due to the force of gravity. It’s what keeps our feet firmly planted on the ground. Gravity is measured in meters per second squared, or m/s2. On Earth, the acceleration of gravity generally has a value of 9.806 m/s2 or 32.1740 f/s2. A pilot in a steep turn may experience forces of acceleration equivalent to many times the force of gravity. On a normal flight, at take off the G force is around 0.4G. A constant-altitude turn with 45 degrees of bank imposes 1.4 Gs, and a turn with 60 degrees of bank imposes 2 Gs (double the force of gravity). During a coordinated turn with a 70-degree bank, a load factor of approximately 3 Gs is placed on the airplane’s structure. Civil aircraft certification requirements for airliners demand normal operations be possible up to 2.5G for Boeing 747. Beyond that airframe structure may break.

When you bank while maintaining altitude, your stall speed increases. It’s something that you need to be aware of, especially when you’re in the traffic pattern. So why does stall speed increase when you start rolling left or right?

When you’re flying straight and level, the lift that your wings produce points straight up, opposing gravity.

But when you start to bank, that lift vector starts moving too. You now have two components of lift: a vertical component, and a horizontal component. When you combine the two, you get a total (or resultant) lift vector.

The horizontal component of lift is what makes your airplane turn, and the vertical component is what makes your airplane maintain altitude.

Let’s say you enter a 30 degree banked turn and you don’t change the amount of lift your wing is producing. In the banked turn, some of the lift that was keeping your plane at altitude is now working to turn your plane, and you have less vertical component to maintain altitude. So how do you turn and maintain altitude? You need to increase the total amount of lift your wing is producing. And to do that, you need to pull back on the yoke, which increases the angle-of-attack that your wing is flying at. This part is important, because when you increase your angle-of-attack, you get closer to critical angle of attack, which is the point when your wing stalls (regardless of airspeed or attitude).

Another thing that happens in a constant altitude, coordinated turn is load factor. Load factor is measured in Gs. So if your load factor in a turn is 2 Gs, you feel twice as heavy as you really are (and your arms want to flop down to your seat). The same goes for your airplane – it ‘feels’ twice as heavy.

But what does load factor have to do with stall speed? Stall speed increases in proportion to the square root of load factor. For example, if your normal stall speed is 40 knots, and you put a load factor of 4 Gs on your airplane, your plane will stall at 80 knots. Here’s the math on that: the square root of 4 is 2. And 2 X 40 knots = 80 knots.

Now 4 Gs is quite a bit, and it’s beyond the limit load factor for a normal category airplane like a Cessna 172 or a Cirrus SR-22, which is 3.8 Gs. But here’s a real world example that you could experience on your next flight: a 60 degree banked turn produces 2 Gs of load factor. And since the square root of 2 is 1.41, that means that your stall speed will be 41% faster in a 60 degree, constant altitude coordinated turn than it would be in straight and level flight. So if the stall speed in your Cessna 172 is 48 knots, then your stall speed at 60 degrees of bank is 48 knots X 1.41, which equals just over 67 knots.

In a nutshell

When you turn, you need to increase your total lift to maintain altitude. You increase your total lift by increasing your angle of attack, which means you’re closer to stall than you were in wings-level flight. And, your stall speed increases in proportion to the square root of your load factor. So the more you bank, at altitude or in the traffic pattern, the more you need to be aware of an accelerated stall. As long as you understand and have a healthy respect for the relationship between bank angle and stall speed, you’ll keep yourself safe and stall-free.

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Can a pilot turn an airplane using yaw without the ailerons?

A pilot can turn the airplane to the right and the left, the motion we call yaw, without using ailerons, but he/she will quickly lose control. Ailerons help with another important control on the airplane: roll. The yaw can be controlled with the rudder, while the aileron controls the roll of the airplane, or side-to-side movement. When a pilot tries to yaw left or right, the plane starts to roll on its own, so the ailerons are needed to help control the rolling movement.

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There are lot of flights where the plane seems to turn soon after takeoff. Why is this, and is there a minimum altitude the plane must reach before it can turn?

At many airports, there is a departure procedure requiring the pilot to fly a specific heading. This is loaded into the flight management computer. The normal minimum altitude for turns is 400 feet. Some operators have slightly higher minimum altitudes for turns.

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Aircraft Speed:   

Once fueled, an airplane’s minimum flight speed depends on the movement of the air around it. Maximum airspeed, on the other hand, is limited largely by technology. We use the speed of sound as the ultimate measuring stick for airplane velocity, and this is quite simply the rate at which a sound wave moves through a gas.

The exact speed of sound depends on the elasticity and density of the gas medium it’s traveling through — which means varying air pressure and air temperature prevent the existence of a global speed of sound. At 32 degrees Fahrenheit (0 degrees Celsius), the speed of sound in air is 1,087 feet per second (331 meters per second). Raise the temperature to 68 degrees Fahrenheit (20 degrees Celsius), and the speed climbs to 1,127 feet per second (343 meters per second).

Whatever the details of the medium, we refer to the speed of sound as Mach 1, named after physicist Ernst Mach. If an airplane reaches the speed of sound, its speed is Mach 1. If the airplane reaches double the speed of sound, its speed is Mach 2.

Airplanes speeds that are less than Mach 1 are considered subsonic speeds, while those very close to Mach 1 are said to be transonic. Velocities surpassing the speed of sound are divided into high supersonic (Mach 3 through Mach 5) and hypersonic (Mach 5 through Mach 10). Speeds swifter than Mach 10 are considered high hypersonic.

If you’ve ever heard a supersonic aircraft fly overhead, then you’ve probably heard a sonic boom. Once an airplane attains Mach 1, the sound waves emitted by the plane can’t speed ahead of it. Instead, these waves accumulate in a cone of sound behind the plane. When this cone passes overhead, you hear all that accumulated sound at once.

An airplane can slow down and reduce its speed while in flight. The easiest way to do so is to reduce the amount of thrust that the engines are producing. This will produce an almost immediate reduction of the airspeed, especially if the plane is maintaining the same altitude.

There are also devices called air brakes and spoilers that can be further used to reduce speed. These, however, are never used in normal, level flight by passenger aircraft and are normally only used to reduce speed during the descent and landing phases of the aircraft.

If an airplane reduces its speed too much, it will of course stall and start dropping precipitously, at which time the airspeed usually also increases again. The slowest speed an aircraft can maintain at a given altitude without stalling is listed in its flight envelope.

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Here are some facts about airplane speeds, during takeoff, mid-flight and landing.

As a general rule, airplanes can fly from 550 to 580 miles per hour, although this is most common with commercial planes. However, this is only an average because wind and the elements can affect that number. In addition, military aircraft, private jets, and other types of aircraft may have speeds that are higher or lower.

Most commercial planes take off at roughly 160 to 180 MPH.

Commercial airplanes land at approximately 150 to 165 MPH.

As a general rule, airspeed is measured according to the velocity of the plane as it flies through the air. Wind resistance can affect that speed more than anything else, and if takeoff and landing speeds vary it is due to overall weight capacity or runway length, among other factors.

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Jet streams and flight:

Why does it take longer to fly from east to west as compared to west to east on the same route on an airplane?

The reason it took so much longer to fly is the jet stream, a river of fast-moving air high up in the sky. Jet streams are usually about 100 miles wide. They can be thousands of miles long and are found all over the earth. To be called a jet stream, the wind must be moving faster than 60 mph. Jet streams generally blow from the west to the east around the Earth, often following a meandering, curved path just like a river on land. The jet stream over the United States never stays in one place – it tends to move farther south and blow stronger in the winter, and to move farther north and not blow as strong in the summer.

Flying into the wind:  

Airplane pilots measure speed in two different ways. First is airspeed – how fast the wind would feel if you stuck your hand out the window. The second is ground speed – how fast the plane is moving over the ground. When you fly in the jet stream, your airspeed always stays the same, but your ground speed can change a lot because the air around the plane is moving.

Suppose you are flying with an airspeed of 500 mph. But because the jet stream is blowing against your airplane – called a headwind – at 100 mph, you are actually only moving across the ground at 400 mph.

But flying in opposite direction, the jet stream blows from behind the plane and pushes it forward. You are still flying with an airspeed of 500 mph, but the 100 mph tailwind meant that your airplane is moving across the ground at 600 mph. 

‘Jet streams’ were first discovered during the Second World War. Pilots were regularly flying between United Kingdom and the United States of America and they noticed that it was quicker to fly to the UK, reporting tailwinds of over 100 miles per hour. These winds blew in narrow ribbons and were named ‘jet streams’. Jet streams are narrow fast flowing “rivers” of air. They are formed by temperature differences in the upper atmosphere, between the cold polar air and the warm tropical air. This abrupt change in temperature causes a large pressure difference, which forces the air to move. Jet streams move north and south too, following the boundary between warmer and colder air. These boundaries are also where weather fronts generally develop, so when a front passes overhead, bringing wind and rain, it is quite likely that a jet stream is passing undetected too. The wind direction in the jet stream can change from the normal west to east to almost north to south. This is one of the methods that the Earth uses to transport excess heat from the equatorial regions towards the poles, and in turn bring cold polar air southwards.

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Why Planes take curved route and not fly in a straight line on a map?

This is particularly noticeable when flying between Europe and the U.S. when aircraft will fly over Greenland and Northern Canada rather than just simply flying from point A to B as it would visually appear on a map. The reason for this is down to simple mathematics and physics. The circumference of the Earth is a lot further around the equator than it is at higher or lower latitudes towards the poles of the earth, such is the spherical shape of our planet. Flying around the smaller circumference of the Earth is called the “Great Circle Route” and also very noticeable for flights from the U.S. to Asia that will fly far above Alaska and Siberia rather than what would appear to be a straight line. Although there are exceptions, most commercial airlines don’t fly directly over the Pacific Ocean for routes connecting the United States to Asia. Instead, they choose “curved” routes that hug bodies of land. The primary reason airplanes don’t fly over the Pacific Ocean is because curved routes are shorter than straight routes, therefore, offer cost-savings benefits in the form of lower fuel consumption and faster flights. Of course, curved routes connecting the United States to Asia (and vice versa) are also safer than straight routes connecting the same regions as they spend less time over the Pacific Ocean, allowing for emergency landings if needed.

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Can an Airplane fly with One Wing?

Most of us recognize an airplane when we see one. They have a very distinct appearance, a long metal tube pointed at two ends, with two wings and a tail section. Airplanes were modeled after birds. And it is absolutely crucial that they adhere to this appearance in order to take and maintain flight.

So, can an airplane fly with only one wing? No, an airplane cannot fly with only one wing. In order for a plane to stay stable in air, it has to maintain balance. With only one wing, the weight is shifted to one side of the plane. This makes it impossible to balance. There have been instances in history where pilots had to improvise when their planes lost one of their engines. Of course, malfunctioning engines are more common, and it is technically possible for pilots to fly and land a plane with only one running engine. But it is impossible for a plane to fly with just one wing under normal circumstances.

The lift, which is an upward force, is directed upwards from both wings. But the weight of the aircraft, which results in the downward gravitational force, is located in the middle of the plane’s body. So while a plane is in flight, the lift on the two wings balances the weight in the middle. This helps maintain the stability of the plane while it is in flight.

Now imagine a scenario where one of the plane’s wings is broken off. The forces would now be concentrated on two points rather than three. With the lift on the remaining wing directed upwards and the body in the middle being pulled downward, you can guess what happens. The plane starts to rotate and loses all balance. Of course, the pilot may try to maintain balance in some way. Fighter pilots have, in rare instances, managed to land fighter jets that lost a wing while in flight. But fighter planes have a different design compared to regular planes. While most regular planes have to emphasize on symmetry, fighter planes have their weight and lift distributed more asymmetrically. A very important factor in balancing a plane with just one wing is thrust. Depending on how fast the plane is moving forward, it may rotate less and be easier to balance.

Can bad turbulence break a plane’s wing off?

It is almost impossible for a modern airplane to lose a wing to bad turbulence. Most modern planes are built to be extremely resilient to bad weather or turbulence. Their wings can flex up to 10 degrees, which makes it virtually impossible for them to break under normal circumstances. Regulatory bodies such as the FAA make sure that planes can pass harsh conditions before they are approved for active service.

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Can an airplane stay up in the air without moving forward just like helicopter?

No. To stay in the air and sustain its flight, an airplane needs to be moving forward. Since lift is produced when the wing attacks the air to generate downwash, the wings need to be moving through the air above stall speed, to keep producing lift. If the plane stopped flying forward, it could not produce lift, and thus could not stay up, unlike the helicopter which uses a propeller to stay airborne.

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ILS:

In aviation, the instrument landing system (ILS) is a radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. In its original form, it allows an aircraft to approach until it is 200 feet (61 m) over the ground, within a 1⁄2 mile of the runway. At that point the runway should be visible to the pilot; if it is not, they perform a missed approach. Bringing the aircraft this close to the runway dramatically improves the weather conditions in which a safe landing can be made. Later versions of the system, or “categories”, have further reduced the minimum altitudes.

ILS uses two directional radio signals, the localizer (108 to 112 MHz frequency) that provides horizontal guidance, and the glideslope (329.15 to 335 MHz frequency) for vertical. The relationship between the aircraft’s position and these signals is displayed on an aircraft instrument, often additional pointers in the attitude indicator. The pilot attempts to maneuver the aircraft to keep these indicators centered while they approach the runway to the decision height. Optional markers provide distance information as the approach proceeds, including the middle marker placed close to the position of the decision height. ILS may also include high-intensity lighting at the end of the runways. Pilots use ILS to maneuver the airplane laterally and vertically to land on the runway. If an ILS is not available, GPS or other navigation aids are used. A high-quality ILS combined with special equipment onboard can allow pilots to safely land when the visibility is very limited.

Approaches are divided into three categories based on visibility conditions. In good conditions (category 1), the pilot can see the runway lights at 60 meters’ altitude at the latest. In category 2 approaches, the lights can be seen from the altitude of 30 meters, and in category 3 approaches, from 15 meters, which means only a few seconds before touchdown.  The runway navigation facilities (the ILS), runway lighting and approach path must be specially certified for low-visibility landing. Pilots are required to visually see the runway at 200 feet and ½ mile out unless there are special Category I, II or III procedures available.

The main purpose of ILS is to enable Pilots to land the plane when they can’t see the runway. Large airports such as ATL, SEA, ORD, JFK and others have Category III equipment available. Airplanes that are specially equipped and certified with certified crews may land with as little as 300 feet visibility. This totally depends on the instruments available in the Plane and on the Airport.

Limitations:

Due to the complexity of ILS localizer and glide slope systems, there are some limitations. Localizer systems are sensitive to obstructions in the signal broadcast area, such as large buildings or hangars. Glide slope systems are also limited by the terrain in front of the glide slope antennas. If terrain is sloping or uneven, reflections can create an uneven glidepath, causing unwanted needle deflections. Additionally, since the ILS signals are pointed in one direction by the positioning of the arrays, glide slope supports only straight-line approaches with a constant angle of descent. Installation of an ILS can be costly because of siting criteria and the complexity of the antenna system.

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How Pilots fly at night:

Though most passenger flights occur during the daytime, many airplanes get the opportunity to continue to fly at night. The majority of the flights originating in the United States that are outbound to Europe, Africa and the Middle East leave in the late afternoon and fly during the night where they eventually arrive the next morning on the opposite side of the Atlantic Ocean. Cargo companies also take advantage of night flying as they quickly fly packages to sorting facilities that will deliver the next morning.

But is flying at night safe?

As a short answer yes, flying in the dark at night is inherently safe as perfect safety cannot be achieved. That being said, pilots are trained for flying in the dark and use many of the same tools and instruments utilized during daytime operations. With the high level of training required by the FAA, air travel continues to be one of the safest modes of transportation, even in the dark.

Pilots have many tools at their disposal to be able to fly in a safe and efficient manner, even at night. Some of these tools include onboard weather radar systems, glide slope lights, and Ground Proximity Warning System (GPWS) that keep track of the airplane’s proximity to the ground.

After an aircraft pushes back from the gate and begins to taxi, the pilots are able to identify their position on the airport by various colored lights and signs. Taxiway lights are green in the center and blue on the edge. These lights help guide the pilots safely from the taxiway to the runway. The runway is lit with both white and red lights which indicate to the pilot how much runway is remaining for takeoff and landing.

On nights where the moon does not illuminate terrain and weather systems, pilots must utilize their onboard radar and terrain warning systems to navigate safely from airport to airport. These systems are used as well during daytime operations when pilots fly through clouds and are unable to see what is ahead of their flight path.

The Ground Proximity Warning System (GPWS) is designed to notify flight crew when the aircraft is in close proximity to the ground or an obstacle. When activated, the GPWS system triggers lights and sirens to notify the crew that a climb is required to remain clear of what lies below.

Aircraft can also be equipped with Traffic Collision Avoidance System (TCAS). This system notifies pilots when they are too close to another aircraft. When activated, the system will tell both aircraft to climb or descend in opposite directions in order to increase the separation between the two planes.

For weather detection and avoidance, aircraft can be equipped with an on board weather radar. While some aircraft are equipped with a radome that displays real time precipitation returns, recent models have been built to include Automatic Dependent Surveillance Broadcast (ADS-B) weather that allows for a better picture of weather that is not directly in front of the airplane. This tool also allows the pilot to track the aircraft movement in relation to the movement of the storm cell.

During takeoff and landing at night, pilots are able to utilize additional navigation to help guide them from the sky to the runway. During landing, both the autopilot and pilot have the capability to fly an approach to land at an airport. With systems such as Instrument Landing System (ILS) or Global Positioning System (GPS) available for use, aircraft can track these courses.

Though these systems can be used during the day, they are vital to night time operations to ensure the airplane is on the right path to landing when normal day time visual references are not available.

When aircraft do not utilize the navigation systems listed above, pilots can utilize approach and glide-slope lights known as Precision Approach Path Indicator (PAPI) and Visual Approach Slope Indicator (VASI). These lights let the pilots know if they are at the right height above the ground before landing on the runway, and can be seen on approach.

Below is an image showing the light configurations for PAPI and VASI depending on the angle of approach.

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Water landing: 

In aviation, a water landing is, in the broadest sense, an aircraft landing on a body of water. Some aircraft such as floatplanes land on water as a matter of course. The phrase “water landing” is also used as a euphemism for crash-landing into water an aircraft not designed for the purpose, an event formally termed ditching. In this case, the flight crew knowingly make a controlled emergency landing on water. Ditching of commercial aircraft is a rare occurrence.

Aircraft water landings:

By design:

Seaplanes, flying boats, and amphibious aircraft are designed to take off and alight on water. Alighting can be supported by a hull-shaped fuselage and/or pontoons. The availability of a long effective runway was historically important on lifting size restrictions on aircraft, and their freedom from constructed strips remains useful for transportation to lakes and other remote areas. The ability to loiter on water is also important for marine rescue operations and fire fighting. One disadvantage of water alighting is that it is dangerous in the presence of waves. Furthermore, the necessary equipment compromises the craft’s aerodynamic efficiency and speed.

In distress:

While ditching is extremely uncommon in commercial passenger travel, small aircraft tend to ditch slightly more often because they usually have only one engine and their systems have fewer redundancies. According to the National Transportation Safety Board, there are about a dozen ditchings per year.

Commercial aircraft:

The FAA does not require commercial pilots to train to ditch but airline cabin personnel must train on the evacuation process. In addition, the FAA implemented rules under which circumstances (kind of operator, number of passengers, weight, route) an aircraft has to carry emergency equipment including floating devices such as life jackets and life rafts.

Ditching button on the overhead panel of an Airbus A330:

Some aircraft are designed with the possibility of a water landing in mind. Airbus aircraft, for example, feature a “ditching button” which, if pressed, closes valves and openings underneath the aircraft, including the outflow valve, the air inlet for the emergency RAT, the avionics inlet, the extract valve, and the flow control valve. It is meant to slow flooding in a water landing.

Aircraft landing on water for other reasons:

Aircraft also sometimes end up in water by running off the ends of runways, landing in water short of the end of a runway, or even being forcibly flown into the water during suicidal/homicidal events. Twice at LaGuardia Airport, aircraft have rolled into the East River.

Can a plane land on water in case of an emergency?

Yes it can, but it is not designed to do so, and an emergency landing is always better on land at an airport. Of course, everyone knows the famous 2009 accident known as the Hudson miracle, where Captain Chesley Sullenberg ditched his US Airways Airbus A320 in New York City’s Hudson River after both engine flamed out following a strike with a flock of Canada geese. The plane remained intact and all 155 people aboard were rescued, but the river was a calm at the moment of landing, so it would be a totally different scenario when landing on sea, where one has to take into account the height of waves. However, as long as sea conditions are smooth and the ditching is performed in a proper way, an aircraft can land on the sea and remain afloat. One successful example was on October 16, 1956, when a Pan Am flight 6 B377 Stratocruiser ditched en route from Honolulu, Hawaii to San Francisco, about halfway the route, with all 31 aboard being rescued by a nearby Coast Guard Cutter. The only sea landing in the recent modern jet time happened more than 25 years ago, in 1996, when an Ethiopian Airlines Boeing 767 was forced to ditch in the Indian ocean, just off the shores of the Comoros islands, after it was hijacked and ran out of fuel. Unfortunately, it didn’t land smoothly as it slightly banked before touchdown, resulting in a break-up of the plane. Only 50 of the 163 passengers on board survived.

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Why Planes turn lights off for Takeoff and Landing:

Airlines are today required to turn off plane lights during takeoff and landing. The reason this is done is because of the time it takes for our eyes to adjust to the dark. It can take our eyes between 10 to 30 minutes to adjust to darkness. These few minutes can make all the difference when it comes to safely evacuating an airplane during an emergency. Dimming the lights allows your eyes to pre-adjust to darkness, so that you’re not suddenly blinded if something happens and the power goes out, and you’re dashing for the doors in darkness or smoke. The emergency path-lighting and signs are also more clearly visible when airplane lights are dimmed or turned off. There’s another reason why lights are turned off specifically at takeoff and landing – that is when most plane accidents occur. Therefore, airlines today turn off lights during takeoff and landing.

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Section-10

Aviation safety:        

Aviation safety means the state of an aviation system or organization in which risks associated with aviation activities, related to, or in direct support of the operation of aircraft, are reduced and controlled to an acceptable level. It encompasses the theory, practice, investigation, and categorization of flight failures, and the prevention of such failures through regulation, education, and training. It can also be applied in the context of campaigns that inform the public as to the safety of air travel. Runway safety represents 36% of accidents, Ground Safety 18% and Loss of Control in-Flight 16%. The main cause is Pilot in Command error.  Safety has improved from better aircraft design process, engineering and maintenance, the evolution of navigation aids, and safety protocols and procedures. Aviation safety should not be confused with aviation security which includes all of the measures taken to combat intentional malicious acts.

Pilots, airplane technicians and flight traffic controllers are all highly educated and possess a large amount of specialist knowledge. Pilots face a rigorous training program in order to achieve nationally recognized certification. They must also earn thousands of flight hours before they can even begin flying commercial planes. They must also go through regular training and re-certification throughout their careers. Essentially, every person who is involved with flying a plane is very, very good at their job. In addition, backup systems in every plane provide for safety during emergencies that would have been fatal just decades ago.

According to statistics provided by the Federal Aviation Administration (FAA), there are 40,000+ flights with 2.6 million passengers within the US alone, every day. The relatively very small number of major accidents a year is a testament to the airline industry’s dedication to safety.

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Aircraft are maintained to strict and regular schedules. If any essential equipment on an aircraft has even minor problems, the plane is not allowed to take off until it is fixed. However, with all the precautions there is always a chance something may go wrong with the aircraft you are aboard. You should, however, be assured that pilots are trained (and refreshed regularly) on how to respond to common onboard emergencies, and quick reference guides in the cockpit are used to assist in responding to rarer issues. Every commercial aircraft is built with multiple redundancies and ‘fail-safes’, so in the case of one system failing, the aircraft can continue flying safely on the remaining systems. For example, most commercial aircraft today have two or more engines; if one engine fails, the aircraft can continue to fly safely on the remaining engine to a nearby diversion airport. In the very rare case that all engines fail and can’t be restarted, the pilots can glide the aircraft to a suitable landing place. The 1983 “Gimli Glider” (Air Canada flight 143; ran out of fuel due to metric/imperial conversion error) and the 2009 “Miracle on the Hudson” (US Airways flight 1549; engines flamed-out after ingesting a flock of geese) are both testaments that it is possible to do without fatalities or serious injuries.

If any foreseeable conditions arise that might endanger flights, chances are, flights are not even allowed to start or strict rules are put in place to avoid such an occurrence. A particular example of this was the 2010 eruption of the Eyjafjallajökull volcano in Iceland; volcanic ash has been known in the past to clog jet engines but never once caused any actual crash, even still all flights across Europe were grounded as a precaution. Likewise, when the Samsung Galaxy Note 7 smartphone was recalled in October 2016 after faulty batteries caused them to randomly explode, airlines and regulators were quick to ban the phone in any condition aboard aircraft.

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Even with all the fail-safes and extensive flight training, pilot error is still the number one cause of aircraft accidents worldwide. To reduce the chance of errors, pilots use checklists to ensure they have done essential tasks, as well as using quick reference guides to handle onboard issues and emergencies. Pilots and air traffic controllers must have a good knowledge of the English language, and use standard vocabulary to communicate with each other to ensure there are no misunderstandings. A heavy emphasis in pilot training today is put on the soft skills needed to fly a commercial airliner and to effectively handle onboard emergencies. The 1981 introduction of cockpit resource management (CRM), as it is known, was a large contributing factor in driving down the number of fatal airliner accidents, and variants of CRM have since been adopted for other modes of transport, firefighting and emergency healthcare.

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There are extensive measures in place to prevent deliberate acts of sabotage on-board aircraft, such as hijackings and bombings. Metal detectors, X-ray machines and explosive detection dogs are all used to make sure that nothing dangerous can be taken aboard an aircraft. Governments and airlines also have no-fly lists to make sure that dangerous or potentially dangerous passengers cannot buy airline tickets and board an aircraft. Airport and airline staff also take aviation security seriously; all airport police carry firearms (even in countries where regular beat police officers are unarmed) and are not afraid to tackle a person to the ground and drag them away in handcuffs for something as simple as making a joke. Israeli aviation security is particularly thorough and enjoys a reputation for ruthless efficiency even though some question the means by which it is achieved. As a testament to this, Ben Gurion Airport is considered one of the safest in the world and flag carrier El Al has not had a successful hijacking since 1968 despite probably more attempts than at any other airline. Unlike most aviation security, the Israeli doctrine places great emphasis on finding the person who has bad intentions rather than the bomb itself. This makes the line of questioning uncomfortable and somewhat intrusive, but it should assuage your concerns about safety and security.

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Pilot training:

The civil aircraft fleet consists of numerous aircraft capable of high-altitude flight. Certain knowledge elements pertaining to high-altitude flight are essential for the pilots of these aircraft. Pilots who fly in this realm of flight must receive training in the critical factors relating to safe flight operations at high altitudes. These critical factors include knowledge of the special physiological and/or aerodynamic considerations which should be given to high-performance aircraft operating in the high-altitude environment. High-altitude flight has different effects on the human body than those experienced in lower altitude flight. The aircraft’s aerodynamic characteristics in high-altitude flight may differ significantly from those in lower altitude flight.

Pilots who are not familiar with operations in the high altitude and high-speed environment are encouraged to obtain thorough and comprehensive training and a checkout in complex high-performance aircraft before engaging in extensive high-speed flight in such aircraft, particularly at high altitudes. The training should enable the pilot to become thoroughly familiar with aircraft performance charts and aircraft systems and procedures. The more critical elements of high-altitude flight planning and operations should also be reviewed. The aircraft checkout should enable the pilot to demonstrate a comprehensive knowledge of the aircraft performance charts, systems, emergency procedures, and operating limitations, along with a high degree of proficiency in performing all flight maneuvers and in-flight emergency procedures. By attaining such knowledge and skill requirements of high-performance aircraft, the pilot’s preparedness to transition to the operation of aircraft in the high-speed environment and high-altitude flight, should enhance their awareness on safe and efficient operation.

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Overview of aviation safety hazards:

-1. Foreign object debris

Foreign object debris (FOD) includes items left in the aircraft structure during manufacture/repairs, debris on the runway and solids encountered in flight (e.g., hail and dust). Such items can damage engines and other parts of the aircraft. Air France Flight 4590 crashed after hitting a part that had fallen from another aircraft.

-2. Misleading information and lack of information

A pilot misinformed by a printed document (manual, map, etc.), reacting to a faulty instrument or indicator (in the cockpit or on the ground), or following inaccurate instructions or information from flight or ground control can lose spatial orientation, or make another mistake, and consequently lead to accidents or near misses.

-3. Lightning

Boeing studies showed that airliners are struck by lightning twice per year on average; aircraft withstand typical lightning strikes without damage. The effects of typical lightning on traditional metal-covered aircraft are well understood and serious damage from a lightning strike on an airplane is rare. The Boeing 787 Dreamliner of which the exterior is carbon-fiber-reinforced polymer received no damage from a lightning strike during testing.

-4. Ice and snow

Ice and snow can be major factors in airline accidents. In 2005, Southwest Airlines Flight 1248 slid off the end of a runway after landing in heavy snow conditions, killing one child on the ground.

Even a small amount of icing or coarse frost can greatly impair the ability of a wing to develop adequate lift, which is why regulations prohibit ice, snow or even frost on the wings or tail, prior to takeoff. Air Florida Flight 90 crashed on takeoff in 1982, as a result of ice/snow on its wings.

An accumulation of ice during flight can be catastrophic, as evidenced by the loss of control and subsequent crashes of American Eagle Flight 4184 in 1994, and Comair Flight 3272 in 1997. Both aircraft were turboprop airliners, with straight wings, which tend to be more susceptible to inflight ice accumulation, than are swept-wing jet airliners.

Airlines and airports ensure that aircraft are properly de-iced before takeoff whenever the weather involves icing conditions. Modern airliners are designed to prevent ice buildup on wings, engines, and tails (empennage) by either routing heated air from jet engines through the leading edges of the wing, and inlets, or on slower aircraft, by use of inflatable rubber “boots” that expand to break off any accumulated ice.

Airline flight plans require airline dispatch offices to monitor the progress of weather along the routes of their flights, helping the pilots to avoid the worst of inflight icing conditions. Aircraft can also be equipped with an ice detector in order to warn pilots to leave unexpected ice accumulation areas, before the situation becomes critical. Pitot tubes in modern airplanes and helicopters have been provided with the function of “Pitot Heating” to prevent accidents like Air France Flight 447 caused by the pitot tube freezing and giving false readings.

-5. Wind shear or microburst

A wind shear is a change in wind speed and/or direction over a relatively short distance in the atmosphere. A microburst is a localized column of sinking air that drops down in a thunderstorm. Both of these are potential weather threats that may cause an aviation accident. 

Strong outflow from thunderstorms causes rapid changes in the three-dimensional wind velocity just above ground level. Initially, this outflow causes a headwind that increases airspeed, which normally causes a pilot to reduce engine power if they are unaware of the wind shear. As the aircraft passes into the region of the downdraft, the localized headwind diminishes, reducing the aircraft’s airspeed and increasing its sink rate. Then, when the aircraft passes through the other side of the downdraft, the headwind becomes a tailwind, reducing lift generated by the wings, and leaving the aircraft in a low-power, low-speed descent. This can lead to an accident if the aircraft is too low to affect a recovery before ground contact. Between 1964 and 1985, wind shear directly caused or contributed to 26 major civil transport aircraft accidents in the U.S. that led to 620 deaths and 200 injuries.

-6. Engine failure

An engine may fail to function because of fuel starvation (e.g. British Airways Flight 38), fuel exhaustion (e.g. Air Canada Flight 143), foreign object damage (e.g. US Airways Flight 1549), mechanical failure due to metal fatigue (e.g. Kegworth air disaster, El Al Flight 1862, China Airlines Flight 358), mechanical failure due to improper maintenance (e.g. American Airlines Flight 191), mechanical failure caused by an original manufacturing defect in the engine (e.g. Qantas Flight 32, United Airlines Flight 232, Delta Air Lines Flight 1288), and pilot error (e.g. Pinnacle Airlines Flight 3701).

In a multi-engine aircraft, failure of a single engine usually results in a precautionary landing being performed, for example landing at a diversion airport instead of continuing to the intended destination. Failure of a second engine (e.g., US Airways Flight 1549) or damage to other aircraft systems caused by an uncontained engine failure (e.g., United Airlines Flight 232) may, if an emergency landing is not possible, result in the aircraft crashing.

-7. Structural failure of the aircraft

Examples of failure of aircraft structures caused by metal fatigue include the de Havilland Comet accidents (1950s) and Aloha Airlines Flight 243 (1988). Improper repair procedures can also cause structural failures include Japan Airlines Flight 123 (1985) and China Airlines Flight 611 (2002). Now that the subject is better understood, rigorous inspection and nondestructive testing procedures are in place.

Composite materials consist of layers of fibers embedded in a resin matrix. In some cases, especially when subjected to cyclic stress, the layers of the material separate from each other (delaminate) and lose strength. As the failure develops inside the material, nothing is shown on the surface; instrument methods (often ultrasound-based) have to be used to detect such a material failure.

-8. Stalling

Stalling an aircraft (increasing the angle of attack to a point at which the wings fail to produce enough lift) is dangerous and can result in a crash if the pilot fails to make a timely correction.

Devices to warn the pilot when the aircraft’s speed is decreasing close to the stall speed include stall warning horns (now standard on virtually all powered aircraft), stick shakers, and voice warnings. Most stalls are a result of the pilot allowing the airspeed to be too slow for the particular weight and configuration at the time. Stall speed is higher when ice or frost has attached to the wings and/or tail stabilizer. The more severe the icing, the higher the stall speed, not only because smooth airflow over the wings becomes increasingly more difficult, but also because of the added weight of the accumulated ice.

Crashes caused by a full stall of the airfoils include:

British European Airways Flight 548 (1972)

United Airlines Flight 553 (1972)

Aeroflot Flight 7425 (1985)

Arrow Air Flight 1285 (1985)

Northwest Airlines Flight 255 (1987)

The Paul Wellstone crash (2002)

Colgan Air Flight 3407 (2009)

Turkish Airlines Flight 1951 crash (2009)

Air France Flight 447 (2009)

-9. Fire

Fire and its toxic smoke have been the cause of accidents. An electrical fire on Air Canada Flight 797 in 1983 caused the deaths of 23 of the 46 passengers, resulting in the introduction of floor level lighting to assist people to evacuate a smoke-filled aircraft. In 1985, a fire on the runway caused the loss of 55 lives, 48 from the effects of incapacitating and subsequently lethal toxic gas and smoke in the British Airtours Flight 28M accident which raised serious concerns relating to survivability – something that had not been studied in such detail. The swift incursion of the fire into the fuselage and the layout of the aircraft impaired passengers’ ability to evacuate, with areas such as the forward galley area becoming a bottle-neck for escaping passengers, with some dying very close to the exits. Much research into evacuation and cabin and seating layouts was carried out at Cranfield Institute to try to measure what makes a good evacuation route, which led to the seat layout by Overwing exits being changed by mandate and the examination of evacuation requirements relating to the design of galley areas. The use of smoke hoods or misting systems were also examined although both were rejected.

South African Airways Flight 295 was lost in the Indian Ocean in 1987 after an in-flight fire in the cargo hold could not be suppressed by the crew. The cargo holds of most airliners are now equipped with automated halon fire extinguishing systems to combat a fire that might occur in the baggage holds. In May 1996, ValuJet Flight 592 crashed into the Florida Everglades a few minutes after takeoff because of a fire in the forward cargo hold. All 110 people on board were killed.

One possible cause of fires in airplanes is wiring problems that involve intermittent faults, such as wires with breached insulation touching each other, having water dripping on them, or short circuits. Notable was Swissair Flight 111 in 1998 due to an arc in the wiring of IFE which ignite flammable MPET insulation. These are difficult to detect once the aircraft is on the ground. However, there are methods, such as spread-spectrum time-domain reflectometry, that can feasibly test live wires on aircraft during flight.

-10. Bird strike

Bird strike is an aviation term for a collision between a bird and an aircraft. Fatal accidents have been caused by both engine failure following bird ingestion and bird strikes breaking cockpit windshields.

Jet engines have to be designed to withstand the ingestion of birds of a specified weight and number and to not lose more than a specified amount of thrust. The weight and numbers of birds that can be ingested without hazarding the safe flight of the aircraft are related to the engine intake area. The hazards of ingesting birds beyond the “designed-for” limit were shown on US Airways Flight 1549 when the aircraft struck Canada geese.

The outcome of an ingestion event and whether it causes an accident, be it on a small fast plane, such as military jet fighters, or a large transport, depends on the number and weight of birds and where they strike the fan blade span or the nose cone. Core damage usually results with impacts near the blade root or on the nose cone. The highest risk of a bird strike occurs during takeoff and landing in the vicinity of airports, and during low-level flying, for example by military aircraft, crop dusters and helicopters.

-11. Human factors

Human factors, including pilot error, are another potential set of factors, and currently the factor most commonly found in aviation accidents. Much progress in applying human factors analysis to improving aviation safety was made around the time of World War II by such pioneers as Paul Fitts and Alphonse Chapanis. However, there has been progress in safety throughout the history of aviation, such as the development of the pilot’s checklist in 1937.  Crew resource management or cockpit resource management is a set of training procedures for use in environments where human error can have devastating effects. Used primarily for improving aviation safety, CRM focuses on interpersonal communication, leadership, and decision making in the cockpit of an airliner.

Pilot error and improper communication are often factors in the collision of aircraft. This can take place in the air (1978 Pacific Southwest Airlines Flight 182) (TCAS) or on the ground (1977 Tenerife disaster) (RAAS). The barriers to effective communication have internal and external factors. The ability of the flight crew to maintain situation awareness is a critical human factor in air safety. Human factors training is available to general aviation pilots and called single pilot resource management training.

Failure of the pilots to properly monitor the flight instruments caused the crash of Eastern Air Lines Flight 401 in 1972. Controlled flight into terrain (CFIT), and error during take-off and landing can have catastrophic consequences, for example causing the crash of Prinair Flight 191 on landing, also in 1972.

Pilot fatigue:

The International Civil Aviation Organization (ICAO) defines fatigue as “A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload.” The phenomenon places great risk on the crew and passengers of an airplane because it significantly increases the chance of pilot error. Fatigue is particularly prevalent among pilots because of “unpredictable work hours, long duty periods, circadian disruption, and insufficient sleep”.  These factors can occur together to produce a combination of sleep deprivation, circadian rhythm effects, and ‘time-on task’ fatigue. Regulators attempt to mitigate fatigue by limiting the number of hours pilots are allowed to fly over varying periods of time.

Piloting while intoxicated:

Rarely, flight crew members are arrested or subject to disciplinary action for being intoxicated on the job. In 1990, three Northwest Airlines crew members were sentenced to jail for flying while drunk. In 2001, Northwest fired a pilot who failed a breathalyzer test after a flight. In July 2002, both pilots of America West Airlines Flight 556 were arrested just before they were scheduled to fly because they had been drinking alcohol. The pilots were fired and the FAA revoked their pilot licenses. At least one fatal airliner accident involving drunk pilots occurred when Aero Flight 311 crashed at Koivulahti, Finland, killing all 25 on board in 1961.

Pilot suicide and murder:

There have been rare instances of suicide by pilots. Although most air crew are screened for psychological fitness, a very few authorized pilots have flown acts of suicide and even mass murder.

In 1982, Japan Airlines Flight 350 crashed while on approach to the Tokyo Haneda Airport, killing 24 of the 174 on board. The official investigation found the mentally ill captain had attempted suicide by placing the inboard engines into reverse thrust, while the aircraft was close to the runway. The first officer did not have enough time to countermand before the aircraft stalled and crashed.

In the case of EgyptAir Flight 990, it appears that the first officer deliberately crashed into the Atlantic Ocean while the captain was away from his station in 1999 off Nantucket, Massachusetts.

Crew involvement is one of the speculative theories in the disappearance of Malaysia Airlines Flight 370 on 8 March 2014.

In 2015, on March 24, Germanwings Flight 9525 (an Airbus A320-200) crashed 100 kilometers (62 mi) northwest of Nice, in the French Alps, after a constant descent that began one minute after the last routine contact with air traffic control and shortly after the aircraft had reached its assigned cruise altitude. All 144 passengers and six crew members were killed. The crash was intentionally caused by the co-pilot, Andreas Lubitz. Having been declared “unfit to work” without telling his employer, Lubitz reported for duty, and during the flight locked the Captain out of the flight deck. In response to the incident and the circumstances of Lubitz’s involvement, aviation authorities in Canada, New Zealand, Germany and Australia implemented new regulations that require two authorized personnel to be present in the cockpit at all times. Three days after the incident the European Aviation Safety Agency issued a temporary recommendation for airlines to ensure that at least two crew members, including at least one pilot, are in the cockpit at all times of the flight. Several airlines announced they had already adopted similar policies voluntarily.

Deliberate aircrew inaction:

Inaction, omission, failure to act as required, willful disregard of safety procedures, disdain for rules, unjustifiable risk-taking by pilots have also led to accidents and incidents.

Although Smartwings QS-1125 flight of 22 August 2019 successfully made an emergency landing at destination, the captain was censured for failing to follow mandatory procedures, including for not landing at the nearest possible diversion airport after an engine failure.

Human factors of third parties:

Unsafe human factors are not limited to pilot errors. Third party factors include ground crew mishaps, ground vehicle to aircraft collisions and engineering maintenance related problems. For example, failure to properly close a cargo door on Turkish Airlines Flight 981 in 1974 caused the loss of the aircraft. (However, design of the cargo door latch was also a major factor in the accident.) In the case of Japan Airlines Flight 123 in 1985, improper repair of previous damage led to explosive decompression of the cabin, which in turn destroyed the vertical stabilizer and damaged all four hydraulic systems which powered all the flight controls.

-12. Electromagnetic interference

The use of certain electronic equipment is partially or entirely prohibited as it might interfere with aircraft operation, such as causing compass deviations. Use of some types of personal electronic devices is prohibited when an aircraft is below 10,000 feet (3,000 m), taking off, or landing.

Mobile phones on aircraft:

In the U.S., Federal Communications Commission (FCC) regulations prohibit the use of mobile phones aboard aircraft in flight. Contrary to popular misconception, the Federal Aviation Administration (FAA) does not actually prohibit the use of personal electronic devices (including cell phones) on aircraft. Paragraph (b)(5) of 14 CFR 91.21 leaves it up to the airlines to determine if devices can be used in flight, allowing use of “Any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used.”

In Europe, regulations and technology have allowed the limited introduction of the use of passenger mobile phones on some commercial flights, and elsewhere in the world many airlines are moving towards allowing mobile phone use in flight. Many airlines still do not allow the use of mobile phones on aircraft. Those that do often ban the use of mobile phones during take-off and landing.

Many passengers are pressing airlines and their governments to allow and deregulate mobile phone use, while some airlines, under the pressure of competition, are also pushing for deregulation or seeking new technology which could solve the present problems. On the other hand, official aviation agencies and safety boards are resisting any relaxation of the present safety rules unless and until it can be conclusively shown that it would be safe to do so. There are both technical and social factors which make the issues more complex than a simple discussion of safety versus hazard.

Most people think active cell phones could interfere with the plane’s navigation equipment. But that’s not the real reason why your phone has to be in “Airplane Mode.” Airplane mode or flight mode is a setting that lets you suspend the radio-frequency signal transmission of a device. Basically, it turns off the cellular, Bluetooth, and Wi-Fi connections of your phone, tablet, laptop, or other gadgets. Passengers are now allowed to turn on Wi-Fi and Bluetooth while a device is on Airplane mode, but make sure the cellular connection is still inactivated. It’s never been proven that a mobile phone signal has interfered with the navigation performance of the aircraft. But the real reason airlines in the U.S. make you put your phone on “Airplane Mode” is because of the Federal Communications Commission. FCC regulations ban the use of cell phones on planes in order to “protect against radio interference to cell phone networks on the ground.” Meaning at 40,000 feet in the air, active cell phones would be picking up service from multiple cell towers on the ground. This could crowd the networks on the ground and disrupt service.

-13. Ground damage

Various ground support equipment operate in close proximity to the fuselage and wings to service the aircraft and occasionally cause accidental damage in the form of scratches in the paint or small dents in the skin. However, because aircraft structures (including the outer skin) play such a critical role in the safe operation of a flight, all damage is inspected, measured, and possibly tested to ensure that any damage is within safe tolerances.

An example problem was the depressurization incident on Alaska Airlines Flight 536 in 2005. During ground services a baggage handler hit the side of the aircraft with a tug towing a train of baggage carts. This damaged the metal skin of the aircraft. This damage was not reported and the plane departed. Climbing through 26,000 feet (7,900 m) the damaged section of the skin gave way under the difference in pressure between the inside of the aircraft and the outside air. The cabin depressurized explosively necessitating a rapid descent to denser (breathable) air and an emergency landing. Post-landing examination of the fuselage revealed a 12-inch (30 cm) hole on the right side of the airplane.

-14. Effect of natural calamities on aircraft flight

Natural disasters have bad impact on aircraft flights and airport infrastructure. Volcanic eruptions and earthquake are natural calamities that affect the airplanes. Earthquakes are the most destructive disasters for airports, aviation facilities. They can cause more injuries to people and damage to the structures (Smith, 2011). Volcano injects large amounts of very small rock fragments known as volcanic ash. Volcanic ash is an aviation safety hazard. Volcanic ash is composed of a mixture of sharp, angular fragments of rapidly quenched volcanic glass, as well as mineral and rock fragments that range in size from fine powder to fragments up to an eighth of an inch in diameter (Casadevall, 1993). The ash is very hard and small in size; it can scratch and damage airplane body parts (cockpit and forward cabin windows, landing light covers, leading edges of wings and tail rudder, engine cowlings, and the radar nose cone), engine parts and injection of ash cause serious deterioration of engine performance or even engine failure at a very extreme conditions It can also damage aircraft electronic system.

Plumes of volcanic ash near active volcanoes can damage propellers, engines and cockpit windows. In 1982, British Airways Flight 9 flew through an ash cloud and temporarily lost power from all four engines. The plane was badly damaged, with all the leading edges being scratched. The front windscreens had been so badly “sand” blasted by the ash that they could not be used to land the aircraft.

Prior to 2010 the general approach taken by airspace regulators was that if the ash concentration rose above zero, then the airspace was considered unsafe and was consequently closed. Volcanic Ash Advisory Centers enable liaison between meteorologists, volcanologists, and the aviation industry.

-15. Runway safety

Types of runway safety incidents include:

Runway excursion – an incident involving only a single aircraft making an inappropriate exit from the runway.

Runway overrun – a specific type of excursion where the aircraft does not stop before the end of the runway (e.g., Air France Flight 358).

Runway incursion – incorrect presence of a vehicle, person, or another aircraft on the runway (e.g., Tenerife airport disaster).

Runway confusion – crew misidentification the runway for landing or take-off (e.g., Comair Flight 191, Singapore Airlines Flight 6).

The Runway Awareness and Advisory System (RAAS) is one of a number of related software enhancements available on later-model Enhanced Ground Proximity Warning Systems. RAAS is designed to improve flight crew situational awareness, thereby reducing the risks of runway incursion, runway confusion and runway excursions.

-16. Terrorism

Aircrew are normally trained to handle hijack situations. Since the September 11, 2001 attacks, stricter airport and airline security measures are in place to prevent terrorism, such as security checkpoints and locking the cockpit doors during flight.

In the United States, the Federal Flight Deck Officer program is run by the Federal Air Marshal Service, with the aim of training active and licensed airline pilots to carry weapons and defend their aircraft against criminal activity and terrorism. Upon completion of government training, selected pilots enter a covert law enforcement and counter-terrorism service. Their jurisdiction is normally limited to a flight deck or a cabin of a commercial airliner or a cargo aircraft they operate while on duty.

-17. Military action

Passenger planes have rarely been attacked in both peacetime and war. Examples:

In 1955, Bulgaria shot down El Al Flight 402.

In 1973, Israel shot down Libyan Arab Airlines Flight 114.

In 1983, the Soviet Union shot down Korean Air Lines Flight 007.

In 1988, the United States shot down Iran Air Flight 655.

In 2001, the Ukrainian Air Force accidentally shot down Siberia Airlines Flight 1812 during an exercise.

In 2014, a rebel from Ukraine- armed with the Russian Aerospace Defense Forces Buk missile system – shot down Malaysia Airlines Flight 17.

In 2020, Iran shot down Ukraine International Airlines Flight 752. 

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Airworthiness:

An aircraft is airworthy “when it meets its type design and is in a condition for safe operation” [FAA, 1998] and therefore starting a flight in an airworthy aircraft is an important part of the achieving acceptable levels of safety. The regulations require nothing less than this. The effort which goes into delivering airworthy aircraft stems from a huge, complex and highly regulated industry. Like the rest of aviation, it involves human interventions and is subject to human traits.  Airworthiness is the measure of an aircraft’s suitability for safe flight. Certification of airworthiness is conferred by a certificate of airworthiness from the state of aircraft registry national aviation authority, and is maintained by performing the required maintenance actions. Certification is based on standards applied by national aviation authorities. Interoperability is served when national benchmarks adopt standards from international civil and military organizations such as International Civil Aviation Organization (ICAO), European Aviation Safety Agency (EASA), NATO and European Defence Agency (EDA).

In the U.S., Title 14, Code of Federal Regulations, Subchapter F, Part 91.7 states: “a) No person may operate an aircraft unless it is in an airworthy condition. b) The pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight. The pilot in command shall discontinue the flight when unairworthy mechanical, electrical, or structural conditions occur which compromise the airworthiness.”

New Aircraft: 

Newly manufactured aircraft are delivered to customers having been built according to the applicable Type Certificate. This certificate is issued in respect of the defined build standard of the first aircraft of the specific type. Thereafter all subsequent new aircraft of this type must meet the same build standard for the issue of an individual aircraft Certificate of Airworthiness.

The Type Certificate is valid throughout the life of a specific type and only varies in the event of a major change e.g., installation of a freight door. It can also allow what are sometimes referred to as “grandfather rights” to be applied for subsequent newer versions of the original aircraft model. For example, Airbus first produced the A320 aircraft and then subsequently added the A321, A319 and A318 to the same Type Certificate as they were deemed sufficiently similar. A similar process was applied to some versions of the Boeing 737, whilst noting that an Authority may invoke new standards for new derivatives e.g., Boeing 737NG.

New commercial aircraft are designed and tested to operate in conditions far more severe than those encountered on nearly any actual flight. For example, one test involves filling an aircraft with volunteers and testing whether the entire aircraft can be evacuated within 90 seconds with half the exits blocked and only emergency lighting. Only once the aviation regulator, such as the EASA in the European Union and the FAA in the United States, is completely satisfied the aircraft model is safe will they issue a type certificate. If issues are discovered after the aircraft enters revenue service, the regulator can require changes be made through issuing an airworthiness directive. On rare occasions where serious design flaws are discovered, regulators can suspend an aircraft’s type certificate, effectively grounding all aircraft of that model until the issue is fixed and the type certificate reinstated. This happened to the McDonnell-Douglas DC-10 in June 1979 (the certificate was reinstated five weeks later) and the Boeing 737 MAX in March 2019 (certificate reinstated on 30 November 2020). After the Federal Aviation Administration (FAA) in November 2020 cleared the Boeing 737 Max to return to service, other regulators – notably those in Brazil, Canada, Europe and the UK – have done likewise.

Aircraft in Service:

From its very first flight, an aircraft progressively accumulates flying hours, flight cycles (a takeoff to landing is one flight cycle) and naturally elapsed calendar periods.

Daily inspections are carried out covering a small number of important tasks as well as replenishment of lubricants and other fluids. At longer intervals (for example between 750 and 1000 flight hours), an A Check would be carried out, if the schedule is following a Block maintenance format. This involves more extensive checks and would be performed by Line Maintenance personnel. The B Check is no longer used and therefore the next check is a partial C Check. By carefully dividing the requirements of a C Check into a small number of packages, the aircraft will avoid lengthy time out of service. This practice is termed Equalised Maintenance. A typical C Check will be carried out by Base Maintenance personnel using proper accommodation, hangars and access equipment. This check will require the aircraft to be out of service for a number of days.

The final check in the Block check format of maintenance is the D Check. This is a major activity when a very detailed inspection of the whole aircraft is performed. Often such items as landing gear and control surfaces are removed for service and the interior equipment such as seats and galleys are also removed for refurbishment.

The D Check is both costly and time consuming. Many operators sub-contract this work to reduce cost and avoid taking up their hangar space which may be used for smaller work programs. Equally, some operators use the onset of a D Check program to change their fleet to new aircraft thus providing a new owner with a lower cost aircraft after the necessary D check is carried out.

Aircraft in Storage or Out of Service:

When aircraft are out of service and stored for any reason it becomes necessary to apply a preventative maintenance regime. This is laid down in the Aircraft Maintenance Manual (AMM) not the normal Maintenance Program. Specific requirements will vary for such reasons as:

-1. Length of time that the aircraft is not flown.

-2. Environment in which it is stored e.g., in a dry desert environment compared to a moist sea air one.

-3. The degree to which the aircraft is prepared before it is put into storage. For example if engines are removed, this will negate the need to operate them periodically. If the passenger seats and other furnishings are removed that too will reduce the amount of preventive work.

-4. The installation of humidity reduction equipment will have a very positive effect on the aircraft’s internal structure.

Notwithstanding the preparations, the need to provide proper care during storage cannot be overstated. The cost and attendant down time to restore the aircraft to service will be increased considerably if less than rigorous storage procedures are permitted.

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Crashworthiness:

Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of aircraft and vehicles. Depending on the nature of the impact and the vehicle involved, different criteria are used to determine the crashworthiness of the structure. Crashworthiness may be assessed either prospectively, using computer models (e.g., LS-DYNA, PAM-CRASH, MSC Dytran, MADYMO) or experiments, or retrospectively by analyzing crash outcomes. Several criteria are used to assess crashworthiness prospectively, including the deformation patterns of the vehicle structure, the acceleration experienced by the vehicle during an impact, and the probability of injury predicted by human body models. Injury probability is defined using criteria, which are mechanical parameters (e.g., force, acceleration, or deformation) that correlate with injury risk. A common injury criterion is the head impact criterion (HIC). Crashworthiness is assessed retrospectively by analyzing injury risk in real-world crashes, often using regression or other statistical techniques to control for the myriad of confounders that are present in crashes.

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Ejection Seats, Escape Pods and Evacuation Slides:

Airplanes have boasted several ingenious escape features over the years. Let’s walk through some of the ways you might try to exit an aircraft in an emergency.

The evacuation slide: No one wants to abandon an airplane before landing, so if it’s possible, pilots attempt to regain control or at least achieve a crash landing. At this point, you generally want to flee as far from the damaged airplane as possible. This is where the evacuation slide comes in handy. Compressed gas inflates the slide, allowing for speedy deployment. A passenger then slides down and, in some cases, the inflatable slide can be used as a flotation device.

The parachute: The first parachute jump from an airplane took place in 1912, a mere nine years after the Wright brothers’ inaugural flight. It has remained an aviation staple, creating drag to slow down a moving object, person or aircraft. You won’t find a cache of emergency chutes on a commercial airliner, however, as they typically operate at speeds and altitudes that would require additional safety gear. Skydiving also calls for individual training and regular parachute maintenance — to say nothing of the logistics involved in evacuating a plane full of passengers in such a manner.

The ejection seat: This option generally remains the exclusive domain of military and experimental aircraft. While it was possible for the pilots of older, prop-driven aircraft to climb out of a plummeting aircraft, the pilots of high-performance jets require a fast, automated exit from a doomed aircraft. Ejection seats achieve this by simply blasting the pilot’s or passenger’s seat free of the plane. Then a parachute deploys to provide the necessary drag to slow the descent back to the surface.

The escape capsule: In extreme conditions, military or experimental aircraft feature escape capsules for pilots or crew members. The principle is the same as that of an ejection seat, only instead of jettisoning a pilot in a naked seat, it entails the ejection of a pressurized pod. Some aircraft designs even go so far as to eject entire crew cabins as a single, multi-person escape capsule.

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Airline safety ranking:

Flying is less deadly in 2021 than in any year since 1945, but that does not mean all airlines are equally safe. AirlineRatings.com analyzed crash and serious incident histories, fleet ages, and audits of 385 airlines performed by governments and aviation associations. It used that analysis to name the 10 safest airlines for 2021 as:

-1. Qantas

-2. Qatar Airways

-3. Air New Zealand

-4. Singapore Airlines

-5. Emirates

-6. Eva Air

-7. Etihad Airways

-8. Alaska Airlines

-9. Cathay Pacific

-10. British Airways

Qantas, Australia’s flag carrier, was named the world’s safest airline for the third year in a row by the website. Qantas holds the distinction of being the only airline that Dustin Hoffman’s character in the 1988 movie “Rain Man” would fly because it had “never crashed.” The airline suffered fatal crashes of small aircraft prior to 1951, but has had no fatalities in the 70 years since. Last year was extremely difficult for airlines with COVID-19 slashing travel and Airline Ratings editors have looked particularly at the lengths airlines are going to re-train pilots ahead of a return to service. In the case of Qantas, a 737 pilot goes through a six-day course, including a day on well-being. Qantas has been the lead airline in virtually every major operational safety advancement over the past 60 years and has not had a fatality in the pure-jet era. Some of the safety techniques that have set the 100-year-old Qantas apart include its use of a Future Air Navigation System for improved communication between pilots and air traffic controllers; real-time monitoring of engines across its fleet; flight data recorders to monitor plane and crew performance; and implementing technology for precision approaches and automatic landings.

No review of aviation in 2020 can ignore the enormous impact that the COVID-19 crisis has had on the airline industry. But the pandemic was not the only air safety hazard last year. There were five fatal passenger crashes in 2020 with a total of 299 fatalities. Even amid drastically reduced flight schedules, the year’s accident numbers were not far from 2019’s eight fatal crashes and 257 fatalities.

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Zonal Safety Analysis (ZSA):

ZSA is a method of ensuring that the equipment installations within each zone of an aircraft meet adequate safety standards with respect to design and installation standards, interference between systems, and maintenance errors. In those areas of the aeroplane where multiple systems and components are installed in close proximity, it should be ensured that the zonal analysis would identify any failure or malfunction which by itself is considered sustainable but which could have more serious effects when adversely affecting other adjacent systems or components.

Aircraft manufacturers divide the airframe into zones to support airworthiness regulations, the design process, and to plan and facilitate maintenance. The commonly used aviation standard ATA iSpec 2200, which replaced ATA Spec 100, contains guidelines for determining airplane zones and their numbering. Some manufacturers use ASD S1000D for the same purpose. The zones and subzones generally relate to physical barriers in the aircraft. A typical zone map for a small transport aircraft is shown below:

Aircraft zones differ in usage, pressurization, temperature range, exposure to severe weather and lightning strikes, and the hazards contained such as ignition sources, flammable fluids, flammable vapors, or rotating machines. Accordingly, installation rules differ by zone. For example, installation requirements for wiring depends on whether it is installed in a fire zone, rotor burst zone, or cargo area. 

ZSA includes verification that a system’s equipment and interconnecting wires, cables, and hydraulic and pneumatic lines are installed in accordance with defined installation rules and segregation requirements. ZSA evaluates the potential for equipment interference. It also considers failure modes and maintenance errors that could have a cascading effect on systems, such as:

Flailing torque shaft

Oxygen leak

Accumulator burst

Fluid leak

Rotorburst

Loose fastener

Bleed air leak

Overheated wire

Connector keying error

Potential problems are identified and tracked for resolution. For example, if redundant channels of a data bus were routed through an area where rotorburst fragments could result in loss of all channels, at least one channel should be rerouted.

Case Studies:

-1. On July 19, 1989, United Airlines Flight 232, a McDonnell Douglas DC-10 experienced an uncontained failure of its No. 2 engine stage 1 fan rotor disk assembly. The engine fragments severed the No. 1 and No. 3 hydraulic system lines. Forces from the engine failure fractured the No. 2 hydraulic system line. With the loss of all three hydraulic-powered flight control systems, safe landing was impossible. The lack of independence of the three hydraulic systems, although physically isolated, left them vulnerable to a single failure event due to their close proximity to one another. This was a zonal hazard. The aircraft crashed after diversion to Sioux Gateway Airport in Sioux City, Iowa, with 111 fatalities, 47 serious injuries and 125 minor injuries.

-2. On August 12, 1985, Japan Air Lines Flight 123, a Boeing 747-SR100, experienced cabin decompression 12 minutes after takeoff from Haneda Airport in Tokyo, Japan, at 24,000 feet. The decompression was caused by failure of a previously repaired aft pressure bulkhead. Cabin air rushed into the unpressurized fuselage cavity, overpressurizing the area and causing failure of the auxiliary power unit (APU) firewall and the supporting structure for the vertical fin. The vertical fin separated from the airplane. Hydraulic components located in the aft body were also severed, leading to a rapid depletion of all four hydraulic systems. The loss of the vertical fin, coupled with the loss of all four hydraulic systems, left the airplane extremely difficult, if not impossible, to control in all three axes. Lack of independence of four hydraulic systems from a single failure event was a zonal hazard. The aircraft struck a mountain at forty-six minutes after takeoff with 520 fatalities and 4 survivors.

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Aviation Safety: A Whole New World? a 2020 paper:

It has never been safer to fly on commercial airlines, according to a new study by an MIT professor that tracks the continued decrease in passenger fatalities around the globe.

The study finds that between 2008 and 2017, airline passenger fatalities fell significantly compared to the previous decade, as measured per individual passenger boardings — essentially the aggregate number of passengers. Globally, that rate is now one death per 7.9 million passenger boardings, compared to one death per 2.7 million boardings during the period 1998-2007, and one death per 1.3 million boardings during 1988-1997. Going back further, the commercial airline fatality risk was one death per 750,000 boardings during 1978-1987, and one death per 350,000 boardings during 1968-1977.

“The worldwide risk of being killed had been dropping by a factor of two every decade,” says Arnold Barnett, an MIT scholar who has published a new paper summarizing the study’s results. “Not only has that continued in the last decade, the [latest] improvement is closer to a factor of three. The pace of improvement has not slackened at all even as flying has gotten ever safer and further gains become harder to achieve. That is really quite impressive and is important for people to bear in mind.”

The new research also reveals that there is discernible regional variation in airline safety around the world. The study finds that the nations housing the lowest-risk airlines are the U.S., the members of the European Union, China, Japan, Canada, Australia, New Zealand, and Israel. The aggregate fatality risk among those nations was one death per 33.1 million passenger boardings during 2008-2017.

For airlines in a second set of countries, which Barnett terms the “advancing” set with an intermediate risk level, the rate is one death per 7.4 million boardings during 2008-2017. This group — comprising countries that are generally rapidly industrializing and have recently achieved high overall life expectancy and GDP per capita — includes many countries in Asia as well as some countries in South America and the Middle East.

For a third and higher-risk set of developing countries, including some in Asia, Africa, and Latin America, the death risk during 2008-2017 was one per 1.2 million passenger boardings — an improvement from one death per 400,000 passenger boardings during 1998-2007.

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Section-11

Introduction to Plane Crash:  

A plane crash is an accident or sabotage which occurs between the time of boarding and disembarking, ends with a fatality or a serious injury, and ends either with the plane involved having been damaged to some degree or completely destroyed. The aircraft is a machine that can fly in the air carrying passengers and/or goods. The air transport industry is seen as an area of commerce where aircrafts are used to transport people, cargo and mail at the cheapest costs yet with the best safety measures employed. The movement is only complete when there is “safe arrival”. The aviation industry is undoubtedly the safest, fastest and most comfortable mode of transportation. This is because safety and hospitality are great features of the industry (Stephens, 2009). However, for one reason or another air crashes occur once in a while with severe consequences: loss if lives and valuable assets. When measured on a passenger-distance calculation, air travel is the safest form of transportation available.

A 2007 study found that passengers sitting at the back of a plane are 40% more likely to survive a crash than those sitting in the front, although this article also quotes Boeing, the FAA and a website on aircraft safety, all claiming that there is no safest seat. The article studied 20 crashes, not taking in account the developments in safety after those accidents (Noland, 2007). A flight data recorder is usually mounted in the aircraft’s empennage (tail section), where it is more likely to survive a severe crash. Over 95% of people in U.S. plane crashes between 1983 and 2000 survived (Watt, 2007).

The frequency of occurrence of these air crashes is so low when compared with other modes of transport. This is because safety and security are of paramount importance in standard settings for airports, airlines, industry regulators and air users. Worldwide the safety and security of the aviation industry matters so much to governments as the bulk of air travellers is people that contributes greatly to wealth creation and owns the vast majority of world riches. This is particularly true in developing countries (Stephens et al, 2011) where less than five percent of the population uses air transport and these same set of people hold over eighty percent of the wealth in these economies. Stephens (2009) forecasted the growth of the industry in Nigeria to be on a gradual rise as more people in Nigeria are able to afford air tickets due to the deregulation and increased competition. This trend is expected worldwide and this now brings to fore, again, the fear of air crashes as it is expected that developing economies and those emerging and rapidly adopting air transportation a mode of choice to travel (more domestically) as many of these nations may be ill-equipped to hand the expected surge in air travels and its safety measures demand.

The explosive growth in Indonesian air travel initially happened, to a certain extent, at the expense of safety. In the 2000s there were more than a dozen serious incidents and several major disasters. These included Mandala Airlines Flight 91, which in September 2005 crashed into a neighbourhood in Medan, the capital city of North Sumatra, killing 149 people; and Garuda Indonesia Flight 200, which crashed while landing at Yogyakarta, Java in March 2007, killing 20 of the 133 passengers and one crew member. In response, the European Union took the rather drastic step of banning all Indonesian carriers from its airspace in July 2007. (This ban was only fully lifted in June 2018.)  The Sriwijaya Air Flight 182 disaster serves as a warning for aviation safety regulators, not only in Indonesia but worldwide. Four minutes after taking off from Jakarta in heavy rain on January 9, 2021, the Boeing 737-500 nosedived into the ocean, killing all 62 passengers and crew. The Sriwijaya preliminary report found the plane had an imbalance in engine thrust that eventually led it into a sharp roll and then a final dive into the sea. When the plane reached 8,150 feet (2,484 m) after take-off, the left engine throttle lever moved back while the right lever stayed in its original position. One of the pilots was speaking to air traffic control and there is no evidence in the report that they noticed a difference in thrust. At about 10,900 feet, the autopilot disengaged and the plane rolled to the left more than 45 degrees and started its dive, crashing around 25 seconds later, the report said.  The tragedy has naturally raised questions about Indonesia’s air safety standards.

Ability to know the causes of air crashes and disasters will go in a long way to prevent or reduce greatly their occurrence. The knowledge of causes in other countries’ aviation industries is equally important to ascertain if there is any similarity in pattern/causes. 

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Aviation safety experts have realized for some time that aircraft incidents and accidents almost always result from a series of events, each of which is associated with one or more cause factors. Thus, the cause of an accident or incident has many aspects. Some internationally accepted definitions in the context of the investigation of an aircraft accident or incident are listed below (ICAO, 1994):

-1. Causes are actions, omissions, events, conditions, or a combination thereof, that lead to an accident or incident.

-2. Accidents are occurrences associated with the operation of aircraft, from the time any person boards an aircraft with the intention of flight until the time all persons have disembarked, that results in one or more of the following:

-A person is fatally or seriously injured.

-The aircraft sustains damage or structural failure that adversely affects the structural strength, performance, or flight characteristics of the aircraft and would normally require major repair or replacement of the affected component.

-The aircraft is missing or completely inaccessible.

-3. Incidents are occurrences, other than accidents, associated with the operation of aircraft that affect or could affect the safety of operation.

The definition of cause given above takes into account the many events involved in an accident or incident. These events can be viewed as links in a chain. Investigations of some hull loss accidents in the United States have revealed as many as 20 links in the chain; the average is just under 4 links. For example, after an exhaustive technical and legal investigation into one controlled flight into terrain (CFIT) accident, an official commission concluded that at least 10 essential cause factors were involved. If any one of these 10 cause factors had not been present, or if some of the factors had occurred in a different order, the accident would not have happened. The most effective accident prevention strategy must take into account all the links in the chain of events that lead to incidents and accidents.

Subdividing an incident or accident into a chain of events reveals important information. If one more element is added to the chain in an incident, for example, the consequences of the incident might be much more serious, even resulting in an accident. Conversely, removing one link in the accident chain could substantially mitigate the consequences or, possibly, prevent all adverse consequences. In other words, from a safety management viewpoint the only meaningful difference between many incidents and accidents is the consequences.

For example, an aircraft may experience several abnormalities involving equipment malfunction, unexpected adverse weather conditions, and loss of situational awareness by the flight crew. As a result, the aircraft may take longer than expected to slow down after landing. If the aircraft happens to be landing at an airport with runways of the minimum required length with water hazards at the end, there could be a catastrophe. The resulting investigation might lead to a comprehensive review of procedures and systems related to approach and landing. If the same sequence of events happened at an airport with runways of the minimum required length but with a grassy field at the end, the aircraft might run off the end of the runway and experience minor damage and no crew or passenger injuries.

It is important to point out that at air accidents are not only monitored in terms of their direct causes, but also in terms of the phase of flight when they occur. It has been found out that as much as 50 % of all the accidents took place during the approach to landing, which represents only 4 % of the total flight time. Another 27 % of accidents occurred during takeoffs and initial climbs representing only some 2 % of the flight time.  A simple addition of the percentages reveals that more than ¾ of all air accidents occur within a relatively short legs of flight. 

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Major disasters:

The first aircraft incident in which 200 or more people died occurred on March 3, 1974, when 346 died in the crash of Turkish Airlines Flight 981. As of April 2020, there have been 33 aviation incidents in which 200 or more people died. The largest loss of life on board a single-aircraft is the 520 fatalities in the 1985 Japan Airlines Flight 123 incident, the largest loss of life in multiple aircraft in a single incident is the 583 fatalities in the two airplanes that collided in the 1977 Tenerife airport disaster, while the largest loss of life overall in a collective incident is the 2,996 fatalities in the coordinated terrorist destruction of airplanes and occupied buildings in the 2001 September 11 attacks.

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Global Fatal Accident Review 2002 – 2011 © Civil Aviation Authority 2013

This document summarises a study of worldwide fatal accidents to jet and turboprop airplanes above 5,700kg engaged in passenger, cargo and ferry/ positioning flights for the ten-year period 2002 to 2011. The main findings of the study are listed below.

Worldwide Fatal Accident Numbers:

-There were a total of 250 worldwide fatal accidents, which resulted in 7,148 fatalities to passengers and crewmembers onboard the aircraft. The proportion of aircraft occupants killed in these fatal accidents was 70%. 

-There was an overall decreasing trend in the number of fatal accidents, however there was much more fluctuation in the number of fatalities per year.

-The approach, landing and go-around phases accounted for 47% of all fatal accidents and 46% of all onboard fatalities. Take-off and climb accounted for a further 31% of the fatal accidents and 28% of the onboard fatalities.

Worldwide Fatal Accident Rates:

-The overall fatal accident rate for the ten-year period 2002 to 2011 was 0.6 fatal accidents per million flights flown, or 0.4 when expressed as per million hours flown.

-There was a decreasing trend in both the overall rate of fatal accidents and onboard fatalities.

-On average, the fatal accident rate for turboprops was four times that for jets, based on flights flown, and nine times greater when using hours flown as the rate measure.

-On average, the fatal accident rate for cargo flights was eight times greater than for passenger flights, based on flights flown, and seven times greater when using hours flown as the rate of measure.

-The fatal accident rate for African operators was over seven times greater than that for all operators combined. North America had the lowest fatal accident rate of all the regions. North America had more cases of air crashes over other regions but when compared with the volume of traffic in this region one will understand why they had many more crashes than others. They can be adjudged to be safer than some other regions such as Asia and Africa.

Factors and Consequences:

-Over half of all fatal accidents involved an airline related primary causal factor.

-The most frequently identified primary causal factor was “Flight Crew Handling/Skill – Flight handling” which was allocated in 14% of all fatal accidents. “Flight Crew Handling/Skill – Flight handling” was also the joint most commonly assigned causal factor. This generally related to events in which the aircraft was controllable (including single engine failures on twin engine aircraft), however the flight crew’s mishandling of the aircraft or poor manual flying skills led to the catastrophic outcome.

-66% of all fatal accidents involved at least one airline related causal factor. In addition to “Flight handling”, “Omission of action or inappropriate action” was the joint most commonly assigned causal factor.

– “Omission of action or inappropriate action” generally related to flight crew continuing their descent below the decision height or minimum descent/safety heights without visual reference, failing to fly a missed approach or omitting to set the correct aircraft configuration for take-off.

-38% of all fatal accidents involved at least one airworthiness related causal factor, of which “Engine failure/malfunction or loss of thrust” was the most common.

-The most frequently allocated circumstantial factor was “Poor visibility or lack of external visual reference”. In the majority of cases this circumstantial factor was assigned, the accident occurred during a period of thick fog. The second most frequently assigned circumstantial factor “Weather general” mainly referred to accidents which occurred during heavy rain/snow, high winds or icing conditions.

-Nearly 40% of all fatal accidents involved some kind of loss of control, making this the most frequent type of accident. Loss of control events were broken down into four categories – following technical failure, following non-technical failure, following icing, and following unknown reasons. Of these four, non-technical failures (for example flight crew failing to correctly respond to a warning) were the predominant cause of loss of control accidents.

-Roughly half of all fatal accidents in which the pilot(s) lost control following a non-technical failure resulted in a post-crash fire, making this the most common post-crash fire precursor.

-Over a third of all fatal accidents involved a post-crash fire; however this was always in conjunction with, or as a result of another consequence rather than in its own right. Fires in flight were far less common, accounting for 5% of all fatal accidents.

-Mid-air collisions accounted for three out of the 250 fatal accidents (1%).

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Emergency words:

Easy victor:

It’s often used by pilots to warn crew to evacuate the plane without alarming passengers.  Pilots may use the phrase in a sentence to alert crew to begin the evacuation process. However, it won’t be used in an obvious manner over the speaker system. In a “very, very rare event” it would have to be used.

Squawk:

It is the secret code used between pilots and air traffic control to explain that the plane has been hijacked or is at threat of being hijacked.

Mayday:

The most famous word is used when there is a life-threatening emergency on a plane, such as an engine failure or fire. Derived from the French word “m’aidez” meaning “help me”, it is repeated three times at the beginning of the call. Mayday is an emergency procedure word used internationally as a distress signal in voice-procedure radio communications.

Convention requires the word be repeated three times in a row during the initial emergency declaration (“Mayday mayday mayday”) to prevent it being mistaken for some similar-sounding phrase under noisy conditions, and to distinguish an actual mayday call from a message about a mayday call.

If a mayday call cannot be sent because a radio is not available, a variety of other distress signals and calls for help can be used. Additionally, a mayday call can be sent on behalf of one vessel by another; this is known as a mayday relay.

Civilian aircraft making a mayday call in United States airspace are encouraged by the Federal Aviation Administration to use the following format, omitting any portions as necessary for expediency or where they are irrelevant (capitalization as in the original source):

Mayday, Mayday, Mayday; (Name of station addressed); Aircraft call sign and type; Nature of emergency; Weather; Pilot’s intentions and/or requests; Present position and heading, or if lost then last known position and heading and time when aircraft was at that position; Altitude or Flight level; Fuel remaining in minutes; Number of people on board; Any other useful information.

Making a false distress call is a criminal offence in many countries, punishable by a fine, restitution, and possible imprisonment.

Pan-pan:

For less serious emergencies, the phrase comes from the french word “panne”, meaning a “breakdown” and is also repeated three times.

“Pan-pan” indicates an urgent situation, such as a mechanical failure or a medical problem, of a lower order than a “grave and imminent threat requiring immediate assistance”.

A spate of passengers trying to take their bags with them during an evacuation has led to calls for them to be fined. Trying to carry bags through the aisle during an evacuation will slow you down but also damage the inflatable slides. Crew have just 90 seconds to evacuate the entire plane, according to safety regulations. 

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CVR and FDR:

An aircraft’s flight recorders are an invaluable tool for investigators in identifying the factors behind an accident. Recorders usually comprise two individual boxes: the Cockpit Voice Recorder (CVR) and the Flight Data Recorder (FDR). Popularly known as ‘black boxes’, these flight recorders are in fact painted orange to help in their recovery following an accident. The adjective “black” in “black box” means “opaque”. Engineering also uses the phrase “black box testing”, which means tests that are done without access to system internals. Tape CVRs record four channels of audio for 30 minutes, and the DFDR records 25 hours of data. CVRs and FDRs record over the oldest data with the newest data in an endless loop-recording recording pattern.

The two flight recorders are required by international regulation, overseen by the International Civil Aviation Organization, to be capable of surviving the conditions likely to be encountered in a severe aircraft accident. For this reason, they are typically specified to withstand an impact of 3400 G and temperatures of over 1,000 °C (1,830 °F), as required by EUROCAE ED-112. They have been a mandatory requirement in commercial aircraft in the United States since 1967. After the unexplained disappearance of Malaysia Airlines Flight 370 in 2014, commentators have called for live streaming of data to the ground, as well as extending the battery life of the underwater locator beacons.

The recorder is installed in the most crash survivable part of the aircraft, usually the tail section. The data collected in the FDR system can help investigators determine whether an accident was caused by pilot error, by an external event (such as windshear), or by an airplane system problem. Furthermore, these data have contributed to airplane system design improvements and the ability to predict potential difficulties as airplanes age. An example of the latter is using FDR data to monitor the condition of a high-hours engine. Evaluating the data could be useful in making a decision to replace the engine before a failure occurs.

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Flight Data Recorders:

The flight data recorder (FDR) is designed to record the operating data from the plane’s systems. There are sensors wired from various areas on the plane to the flight-data acquisition unit, which is wired to the FDR. So whenever the pilot flips a switch or twiddles a knob, the FDR records each action. In the U.S., the Federal Aviation Administration (FAA) requires that commercial airlines record a minimum of 11 to 29 parameters, depending on the size of the aircraft. Magnetic-tape recorders have the potential to record up to 100 parameters. Solid-state FDRs can record hundreds or even thousands more. On July 17, 1997, the FAA issued a Code of Federal Regulations that requires the recording of at least 88 parameters on aircraft manufactured after Aug. 19, 2002. Here are a few of the parameters recorded by most FDRs:

Time

Pressure altitude

Airspeed

Vertical acceleration

Magnetic heading

Control-column position

Rudder-pedal position

Control-wheel position

Horizontal stabilizer

Fuel flow

Solid-state recorders can track more parameters than magnetic tape because they allow for a faster data flow. Solid-state FDRs can store up to 25 hours of flight data. Each additional parameter recorded by the FDR gives investigators one more clue about the cause of an accident.

Built to Survive:

Airplane crashes are violent affairs. In many such accidents, the only devices that survive are the crash-survivable memory units (CSMUs) of the flight data recorders and cockpit voice recorders. Typically, the rest of the recorders’ chassis and inner components are mangled. The CSMU is a large cylinder that bolts onto the flat portion of the recorder. This device is engineered to withstand extreme heat, jarring crashes and tons of pressure. In older magnetic-tape recorders, the CSMU is inside a rectangular box.

Using three layers of materials, the CSMU in a solid-state black box insulates and protects the stack of memory boards that store the digitized data. These hardened housings are incredibly important. Without adequate protection, all of the flight data would be destroyed. So to make sure that data stays safe, engineers attack their black boxes with full fury to see if their products can withstand extreme abuse.

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Cockpit Voice Recorders:

In almost every commercial aircraft, there are several microphones built into the cockpit that listen to flight crew conversation. These microphones also track any ambient noise in the cockpit, such as switches being thrown or any knocks or thuds. There may be up to four microphones in the plane’s cockpit, each connected to the cockpit voice recorder (CVR). 

Microphones send audio to the CVR, which digitizes and stores the signals. In the cockpit, there is also a device called the associated control unit, which provides pre-amplification for audio going to the CVR. The four microphones are place in the pilot’s headset, co-pilot’s headset, headset of a third crew member (if there is a third crew member) and near the center of the cockpit, to pick up audio alerts and other sounds.

Most magnetic-tape CVRs store the last 30 minutes of sound. They use a continuous loop of tape that completes a cycle every 30 minutes. As new material is recorded, the oldest material is replaced. CVRs that use solid-state storage can record two hours of audio. Similar to the magnetic-tape recorders, solid-state recorders also record over old material.

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Retrieving Information:

After finding the black boxes, investigators take the recorders to a lab where they can download the data from the recorders and attempt to recreate the events of the accident. This process can take weeks or months to complete. In the United States, black box manufacturers supply the National Transportation Safety Board with the readout systems and software needed to do a full analysis of the recorders’ stored data.

If the FDR is not damaged, investigators can simply play it back on the recorder by connecting it to a readout system. With solid-state recorders, investigators can extract stored data in a matter of minutes through USB or Ethernet ports. Very often, recorders retrieved from wreckage are dented or burned. In these cases, the memory boards are removed, cleaned up and have a new memory interface cable installed. Then the memory board is connected to a working recorder. This recorder has special software to facilitate the retrieval of data without the possibility of overwriting any of it.

A team of experts is usually brought in to interpret the recordings stored on a CVR. This group typically includes representatives from the airline and airplane manufacturer, an NTSB transportation-safety specialist and an NTSB air-safety investigator. This group may also include a language specialist from the FBI and, if needed, an interpreter. This board attempts to interpret 30 minutes of words and sounds recorded by the CVR. This can be a painstaking process and may take weeks to complete.

Both the FDR and CVR are invaluable tools for any aircraft investigation. These are often the lone survivors of airplane accidents, and as such provide important clues to the cause that would be impossible to obtain any other way. As technology evolves, black boxes will continue to play a tremendous role in accident investigations.

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The Future of Black Boxes:

There are all sorts of potential improvements on the horizon for black box technology. Most obviously, current systems don’t record any video of cockpit activity. For years, the National Transportation Safety Board has been trying in vain to implement video capabilities into black box systems, but many pilots steadfastly refuse to allow video, saying such systems violate their privacy and that current data capture is sufficient for accident investigators.

The NTSB continues to insist that there’s no such thing as having too much information when investigating plane crashes. At present, video recording is still on hold.

But the technology is more than ready. Airbus, for example, installs a Vision 1000 system in all of its helicopters. The Vision 1000 camera is mounted behind the pilot’s head, where it records video of the pilot’s actions and the cockpit area, as well as the view beyond the windshield, at four frames per second. It weighs about a half a pound and needs only power and a GPS connection for activation.

Video isn’t the only improvement that’s found resistance from the status quo. Since 2002, some legislators have pushed for the Save Aviation and Flight Enhancement Act, which would require not one, but two flight recorders, including one that automatically ejects itself from the plane during an incident. Such self-ejecting recorders are easier to locate are less likely to suffer catastrophic damage. So far, though, the law has not passed Congress.

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Will black box be replaced?

It’s looking increasingly likely that the little black box will be replaced by streaming all essential data directly to a ground-based station. Air-to-ground systems can send flight data to a home base via satellite, which help to eliminate the desperate search for a box, and saving time that might lead to support being provided to a flight in trouble much sooner – possibly averting a crisis.

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Section-12

Causes of plane crash:

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When an official investigator reports the “probable causes” of an accident or incident, consideration should be given to all of the events and cause factors. Cause factors can be grouped into the following categories:

-1.  human factors/personnel error

-2. malfunction or failure of aircraft structures, engines, or other systems

-3. deficient maintenance

-4. hazardous environment involving weather, volcanic ash, birds, etc.

-5.  air traffic management errors

-6. any combination of the above

Identifying the precise cause factors for each event can be complicated, requiring good judgment and accurate interpretation of the facts. There could be more than one cause factor for each event, and some cause factors naturally overlap.

Human factors include mistakes caused by voluntary acts, failure to act, and other factors associated with actions or inaction.

Cause factors associated with aircraft, engines, and systems include deficiencies in the design, manufacture, maintenance, or operation of the aircraft or its systems.

Maintenance-related cause factors include improperly performed maintenance and inadequate maintenance procedures and plans.

Environmental cause factors include hazardous weather, volcanic ash, sand, dust, and birds.

Cause factors associated with air traffic management include deficiencies in weather reporting, regulations, and the air traffic control system (navigational aids; air traffic control directives; and airport facilities, runways, and taxiways).

Combinations of factors and cascading cause-and-effect sequences must be carefully examined to understand all of the cause factors. For example, to prevent accidents caused by system failure, the system that failed could be modified to prevent similar failures in the future. In addition, understanding if the failure was triggered by the failure of some other system, improper maintenance, abnormal operating environment, etc., may suggest additional corrective action.

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Table below shows data resulting from an examination of 2,032 incidents worldwide that were reported over a 10-year period for aircraft built by a particular manufacturer. The aircraft included in this examination accounted for about one-fourth of the world’s large transport airplanes. The reader should keep in mind that manufacturers have a special interest in preventing incidents and accidents associated with system malfunction. Therefore, a jet transport manufacturer’s database may be biased toward incidents in which aircraft system performance is involved. Wherever possible, each incident was broken down into a sequence of events. A total of 1,618 events were identified and categorized by the links in the chain of events and their cause factors. Table below shows the number and percentage of the cause factors associated with each event.  

Causes of Aircraft Incidents:

Cause Factor	Number of Events	Percentage
Personnel (human factors)	800	49.44
Aircraft	547	33.81
Maintenance	214	13.23
Environment	33	2.04
Air traffic management	24	1.48
Totals	1,618	100.00
Source: Boeing.

Accidents and serious incidents almost always have multiple causes, although many analyses and safety records focus on “primary” causes. This narrow focus diverts attention from other cause factors that were essential links in the chain of events and that should also stimulate corrective action to prevent future accidents. With careful analysis, however, a safety management process can identify accident prevention strategies that eliminate factors (“traps”) that recur in many different accidents. Such a process could effectively reduce many different types of accidents by eliminating the cofactors necessary for their occurrence.

Personnel error (human factors) is the most common cause of both incidents and accidents. CFIT and loss-of-control accidents, which almost by definition involve human factors, account for more than half of all fatal accidents. Similarly, inappropriate crew response and fuel exhaustion, which are also essentially human factors problems, are the major contributors to propulsion-related fatal accidents. Although aircraft system malfunctions are involved in a relatively small fraction of aircraft incidents and accidents, improvements in aircraft systems often improve safety by making aircraft more robust—providing flight crews with more accurate information to improve their situational awareness and reducing the likelihood that a human error will result in an incident or accident.

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Situational awareness in aviation:

Situational awareness (SA) means appreciating all you need to know about what is going on when the full scope of your task – flying, controlling or maintaining an aircraft – is taken into account. More specifically and in the context of complex operational environments, SA is concerned with the person’s knowledge of particular task-related events and phenomena.

For a pilot, situational awareness means having a mental picture of the existing inter-relationship of location, flight conditions, configuration and energy state of your aircraft as well as any other factors that could be about to affect its safety such as proximate terrain, obstructions, airspace reservations and weather systems. The potential consequences of inadequate situational awareness include CFIT, loss of control, airspace infringement, loss of separation, or an encounter with wake vortex turbulence, severe air turbulence, heavy icing or unexpectedly strong head winds;

For a controller, situational awareness means acquiring and maintaining a mental picture of the traffic situation being managed and maintaining an appreciation of the potential for unexpected progressions or changes in this scenario.

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Inaccurate situational awareness by the flight crew can arise in several different ways. Some examples are listed below:

-1. The flight crew may not have critical data necessary to adequately define its situation, which may lead to inappropriate decisions and, ultimately, an accident.

-2. The flight crew may have the data it needs but misinterpret the data.

-3. The flight crew may have the data it needs, properly interpret the data, and accurately define the situation, but it may not have the training, skills, or procedures to make proper decisions or to carry them out in the time available.

Automated features of flight control systems can improve situational awareness by reducing crew workload. However, automated actions that compensate for unusual flight conditions or equipment malfunctions can reduce situational awareness if the automated system masks the presence of abnormalities or does not clearly indicate what actions it is taking in response.

Aircraft must be designed so that, for all situations the flight crew can reasonably be expected to encounter, it will have the data it needs in an easily recognizable form that facilitates proper decision making. Furthermore, the aircraft should be designed to help the flight crew carry out necessary tasks, especially in emergencies when things are not as expected and safety depends on quick and correct actions by the flight crew. Except for the time pressure typically associated with in-flight emergencies, the same considerations apply to the actions of maintenance personnel.

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Swiss Cheese Model:

Aircraft accidents never occur due to one particular reason, there are always a multitude of factors which contribute towards an aircraft crash or incident.

An example might be pilot fatigue, coupled with bad weather and a technical problem. If any one of these single factors were not present, the crash wouldn’t have happened. In the industry, this is called the “Swiss Cheese Model”.

If you imagine lots of different slices of Swiss Cheese, from different blocks of cheese, all lined up next to each other, the chances are that you won’t be able to see all the way through one of the holes, as the holes will all be in different places.

Each slice of cheese represents an individual factor such as fatigue, poor weather or poor standard of training. On rare occasions all the holes line up together, that is to say all the factors come together to cause an accident.

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Figure below shows elements for consideration in safety evaluations.

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Most common reasons for airliner disasters:

News of any terrible air accident instantly raises questions about aircraft safety and the threat of terrorism. But until the facts are known, it is unwise to speculate on what might actually have caused a specific crash. What we do know is that there are several causes that are more likely to occur than any other.

-1. Pilot error

As aircraft have become more reliable, the proportion of crashes caused by pilot error has increased and now stands at around 50%. Aircraft are complex machines that require a lot of management. Because pilots actively engage with the aircraft at every stage of a flight, there are numerous opportunities for this to go wrong, from failing to programme the vital flight-management computer (FMC) correctly to miscalculating the required fuel uplift.

An aircraft pilot is responsible for safely transporting his/her passengers to their destination. Even though flying is one of the safest ways to travel, aircraft are piloted by humans who make mistakes. Unfortunately, an error made by a pilot can lead to catastrophic consequences wherein people are severely injured and killed. Pilot error is the cause for nearly half of all aviation accidents and for over two-thirds of all private aircraft accidents.

Pilot error is a decision, action, or inaction by a pilot of an aircraft that’s determined to be a cause or contributing factor in an accident or incident. A few of the most common examples of pilot error include:

• Using aircraft equipment incorrectly
• Making navigational errors
• Incorrectly communicating with air traffic control
• Errors made in the monitoring of speed, altitude and other flight parameters
• Failing to manage fuel levels properly
• Failing to follow set procedures in regards to safety checklists

Examples of Pilot Error:

Tenerife Airport Disaster (1977)

Regarded as the worst accident in aviation history. Due to poor visibility from substantial fog and incorrectly believing he was cleared for takeoff, the pilot of KLM flight collided with a Pan Am flight killing all 583 people aboard both planes.

Adams Air Flight 574 (2007)

There was a problem with the flight’s internal reference system and the plane’s autopilot was disengaged and the plane started to descend. When the pilot tried to gain control of the emergency, he failed at a manoeuvre that led to complete and utter loss of control of the airplane. Adams Air Flight 574 crashed into the ocean and killed 102 passengers on board.

Air France Flight 447 (2009)

When the pilot transferred control of the plane to the co-pilot for a break, mistakes were made and lives were lost. When flight 447 encountered turbulence, the plane disengaged the autopilot function. The co-pilot misjudged the turn to level out the plane, overcompensated for the roll which led to the plane stalling before eventually crashing into the ocean and killing 228 passengers on board.

While such errors are regrettable, it is important to remember that the pilot is the last line of defence when things go catastrophically wrong. In January 2009 an Airbus A320 hit a flock of geese over New York City. With no power, the captain, Chesley Sullenberger, had to weigh up a number of options and act quickly. Using his extensive flying experience and knowledge of the plane’s handling qualities he elected to ditch the aircraft in the Hudson River. The 150 passengers were not saved by computers or any other automated system. They were saved by the two pilots – the very components that techno-enthusiasts claim can be replaced by computers and ground controllers.

-2. Air Traffic Controller Negligence:

The role of air traffic controllers is to monitor and control the flow of air traffic in and around airports. When an air traffic controller makes an error while planes are taking off, in flight or landing, the results can be catastrophic, wherein innocent victims are severely injured or killed. Some of the most commonly made mistakes by air traffic controllers include:

• Working while fatigued or while under the influence of drugs or alcohol which can result in controllers falling asleep on the job
• Allowing two or more planes to fly too closely to each other
• Directing too many aircraft to a runway
• Misinterpretation of radar

-3. Poor Airplane Maintenance:

Maintenance related issues occur when there is a systematic breakdown or organizational mishap that is caused by factors such as time pressure, inadequate skills, stress or even lack of care and laziness. It’s an unfortunate truth that from 1994 to 2004, maintenance problems have contributed to 42% of fatal airline accidents in the United States. Whenever an engine fails, for example, maintenance is the culprit more than 50% of the time.

Examples of Poor Maintenance:

Japan Airlines Flight 123 (1985)

Flight 123 had a damaged rear pressure bulkhead which requires a specific repair process established and approved by Boeing that wasn’t adequately followed in this instance. The improper maintenance led to a crash 32 minutes after takeoff that luckily didn’t fatally harm anyone but did leave its passengers severely injured.

Chalk’s Flight 101 (2005)

The Flight 101 crash occurred off Miami Beach, Florida and killed all 20 passengers on board including 3 infants. The cause of the crash was due to a crack in the plane’s wing that was actually detected earlier but wasn’t properly fixed by the maintenance team. This led to a deeper investigation of Chalk Ocean’s maintenance standards which were ultimately deemed ineffective as numerous planes in their fleet were severely corroded and operating with subpar maintenance practices. If maintenance protocol was sufficiently followed, the Flight 101 crash could have been avoided.

Alaska Airlines Flight 261 (2000)

Planes regularly go through something known as “Preventative Maintenance Schedules.” Part of this procedure entails the lubrication of pieces such as jackscrews that are used to hold together parts such as the airplane pitch control. The screws were in fact not properly lubricated despite the fact that paperwork said otherwise. This led to loss of control and the plane that was flying from Mexico ended up crashing into the Pacific Ocean causing 88 fatalities.

-4. Mechanical failure:

Equipment failures still account for around 20% of aircraft losses, despite improvements in design and manufacturing quality. While engines are significantly more reliable today than they were half a century ago, they still occasionally suffer catastrophic failures.

In 1989, a disintegrating fan blade caused the number one (left-hand) engine of a Belfast-bound British Midland Boeing 737-400 to lose power. Hard-to-read instrumentation contributed to the pilots’ misreading of which engine was losing power. Confused, the pilots shut off the number two (right-hand) engine. With no power, the aircraft crashed short of East Midlands Airport’s Runway 27, killing 47 and injuring many, including the captain and first officer.

More recently, a Qantas A380 carrying 459 passengers and crew suffered an uncontained engine failure over Batam Island, Indonesia. Thanks to the skill of the pilots, the stricken aircraft landed safely.

Sometimes, new technologies introduce new types of failure. In the 1950s, for example, the introduction of high-flying, pressurised jet aircraft introduced an entirely new hazard – metal fatigue brought on by the hull’s pressurisation cycle. Several high-profile disasters caused by this problem led to the withdrawal of the de Havilland Comet aircraft model, pending design changes.

-5. Weather:

Bad weather accounts for around 10% of aircraft losses. Despite a plethora of electronic aids like gyroscopic compasses, satellite navigation and weather data uplinks, aircraft still founder in storms, snow and fog. One of the most notorious bad-weather incidents occurred in February 1958 when a British European Airways twin-engined passenger aircraft crashed while attempting to take off from Munich-Riem Airport. Many of the 23 killed on the aircraft played for Manchester United Football Club. Investigators established that the aircraft had been slowed to such a degree by slush (known to pilots as “runway contamination”), that it failed to achieve take-off speed. Surprisingly, perhaps, lightning is not the threat that many passengers believe (or fear) it to be.

-6. Sabotage:

About 10% of aircraft losses are caused by sabotage. As with lightning strikes, the risk posed by sabotage is much less than many people seem to believe. Nevertheless, there have been numerous spectacular and shocking attacks by saboteurs.

Examples of Airplane Sabotage:

The September 1970 hijacking of three passenger jet aircraft to Dawsons Field in Jordan was a watershed moment in aviation history that prompted a review of security. Hijacked by devotees of the Popular Front for the Liberation of Palestine, the three aircraft were blown up in full view of the world’s press.

September 11. 2001

The most famous and most horrific plane hijacking involved four separate planes being hijacked by 19 individuals. Two of the planes crashed into the twin towers in NYC, the third plane crashed into the pentagon and the fourth and final plane crashed into a field in Pennsylvania killing a total of 2,996 people including the hijackers.

-7. Some other common causes of airplane crashes include the following:

Defects in the landing gear

Design defects

Fuel mismanagement

Improper inspections

Inadequate security

Inadequate training

Instrument failures

Medical emergencies

Metal failures

Mid-air collisions

Poor fuels

Tire failures

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The causes of accidents are broken down into five major categories: Pilot Error, Mechanical, Weather, Sabotage and Other. Some examples of each category can be found in table below. Since most aviation accidents are caused by multiple causes the primary or initiating cause was chosen.   

PILOT ERROR	MECHANICIAL	WEATHER	SABOTAGE	OTHER
Improper procedure	Engine failure	Severe turbulence	Hijacking	ATC error
Flying VFR into IFR conditions	Equipment failure	Windshear	Shot down	Ground crew error
Controlled flight into terrain	Structural failure	Mountain wave	Explosive device aboard	Overloaded
Descending below minima	Design flaw	Poor visibility	Pilot suicide	Improperly loaded cargo
Spatial disorientation		Heavy rain		Bird strike
Premature descent		Severe winds		Fuel contamination
Excessive landing speed		Icing		Pilot incapacitation
Missed runway		Thunderstorms		Obstruction on runway
Fuel starvation		Lightning strike		Mid-air collision caused by other aircraft
Navigation error				Fire/smoke in flight (cabin, cockpit, cargo hold)
Wrong runway takeoff/landing				Maintenance error
Mid-air collision caused by primary pilot

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There is never one single cause attributed to pilot an aircraft crash. For example, if the aircraft suffers a serious technical problem (but one that shouldn’t result in the loss of an aircraft) and it’s subsequently mishandled by the pilots resulting in a crash, does that count as pilot error or mechanical breakdown? The mechanical breakdown on its own shouldn’t have meant the plane crashed, but could have been handled correctly by the pilots. Therefore both are causal factors.

As a result, the statistics made available for the causes of aircraft crashes are not always clear. It is however widely accepted that the following statistics are a reasonable representation:

55% Pilot Error

17% Aircraft Mechanical Error

13% Weather

8% Sabotage

7% Other (ATC, Ground Handling, Unknown)

Examples of Pilot Error include “Loss of Control in Flight” and “CFIT” (Controlled Flight Into Terrain).

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The top 10 leading causes of fatal general aviation accidents:

General aviation refers to any civilian flights except for scheduled passenger or cargo transportation by an airline. Broadly speaking, general aviation applies mostly to smaller aircraft, including those flown by personal aircraft owners and pilots.  According to the FAA, the top 10 leading causes of fatal general aviation accidents from 2001-2016 include:

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-1. Loss of control in-flight (LOC-I):

A pilot’s fundamental responsibility is to prevent a loss of control (LOC). Loss of control in-flight (LOC-I) is the leading cause of fatal general aviation accidents in the U.S. and commercial aviation worldwide. LOC-I is defined as a significant deviation of an aircraft from the intended flightpath and it often results from an airplane upset. Maneuvering is the most common phase of flight for general aviation LOC-I accidents to occur; however, LOC-I accidents occur in all phases of flight.

Loss of control in-flight typically occurs when a plane deviates from its “flight envelope,” i.e., the aerial region within which an aircraft operates safely. This envelope varies per aircraft and defines the safe degrees to which a plane can pitch and bank, as well as the aircraft’s appropriate speed (which can also vary according to weather conditions).

A broad spectrum of issues causes loss of control in-flight, including: stalls, weather conditions, and/or pilot error. In some cases, aspiring pilots may not receive adequate training for how to handle a plane that deviates from its operational envelope. Regardless, LOC-I is the leading cause of general aviation accidents and causes thousands of plane crashes and fatalities worldwide each year. Loss of Control happens in all phases of flight. It can happen anywhere and at any time. There is one fatal accident involving Loss of Control every four days.

Contributing factors may include:

• Poor judgment or aeronautical decision making
• Failure to recognize an aerodynamic stall or spin and execute corrective action
• Intentional failure to comply with regulations
• Failure to maintain airspeed
• Failure to follow procedure
• Pilot inexperience and proficiency
• Use of prohibited or over-the-counter drugs, illegal drugs, or alcohol

Effects:

The effects of loss of control may include:

-Discomfort or injury to the occupants prior to recovery to controlled flight.

-Structural damage to, or total loss of, the aircraft.

-Fatal or serious injury to occupants due to terrain impact and/or post impact fire.

The effects of loss of control depend on the ability of the pilots to recover from the situation. This, in turn, depends on:

-The nature of the upset causing loss of control;

-The experience and ability of the pilots; and,

-The height of the aircraft being adequate.

To prevent LOC-I accidents, it is important for pilots to recognize and maintain a heightened awareness of situations that increase the risk of loss of control. Those situations include: uncoordinated flight, equipment malfunctions, pilot complacency, distraction, turbulence, and poor risk management – like attempting to fly in instrument meteorological conditions (IMC) when the pilot is not qualified or proficient. Sadly, there are also LOC-I accidents resulting from intentional disregard or recklessness. To maintain aircraft control when faced with these or other contributing factors, the pilot must be aware of situations where LOC-I can occur, recognize when an airplane is approaching a stall, has stalled, or is in an upset condition, and understand and execute the correct procedures to recover the aircraft.

Defining an Airplane Upset:

The FAA has defined an upset as an event that unintentionally exceeds the parameters normally experienced in flight or training. These parameters are:

• Pitch attitude greater than 25°, nose up
• Pitch attitude greater than 10°, nose down
• Bank angle greater than 45°
• Within the above parameters, but flying at airspeeds inappropriate for the conditions.

Aerodynamic principles applied to large, swept-wing commercial jet airplanes are similar among all manufacturers, and the recommended techniques for recovering from an upset in an airplane subject to these principles are also compatible. Pilots who understand the conditions of an upset, though such an event is unlikely, will be better prepared to recover from it. The four conditions that generally describe an airplane upset (figure 1 below) are unintentional:

To develop the crucial skills to prevent LOC-I, a pilot must receive upset prevention and recovery training (UPRT), which should include: slow flight, stalls, spins, and unusual attitudes. Upset training has placed more focus on prevention— understanding what can lead to an upset so a pilot does not find himself or herself in such a situation. If an upset does occur, however, upset training also reinforces proper recovery techniques.

In order to avoid an upset, or to recover from one, pilots must understand the following:

• Aerodynamic fundamentals applied to large airplanes.
• Application of aerodynamic fundamentals to airplane upsets.
• Recovery techniques.

Continual crew awareness of airplane attitude, airspeed, flight control position and thrust settings is fundamental for airplane upset prevention and can reduce the effect of startle or surprise caused by rapid unexpected changes.

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-2. Controlled flight into terrain (CFIT):

Second in the FAA’s top causes of general aviation accidents is controlled flight into terrain (CFIT). CFIT occurs when an aircraft unintentionally collides with land, water, or some other obstacle without there being any indication that the pilot lost control. Controlled Flight into Terrain (CFIT) occurs when an airworthy aircraft under the complete control of the pilot is inadvertently flown into terrain, water, or an obstacle. The pilots are generally unaware of the danger until it is too late. Most CFIT accidents occur in the approach and landing phase of flight and are often associated with non-precision approaches. Many CFIT accidents occur because of loss of situational awareness, particularly in the vertical plane, and many crash sites are on the centerline of an approach to an airfield. Lack of familiarity with the approach or misreading of the approach plate are common causal factors, particularly where the approach features steps down in altitude from the initial approach fix to the final approach fix.

CFIT accidents are often caused by issues with visual contact, disorientation, weather conditions, descending below the minimum safe altitude (MSA), and procedural mistakes.

Advances in terrain avoidance and warning systems (TAWS) and ground proximity warning systems (GPWS) are helping to alert pilots and crews of when an aircraft is entering a hazardous situation so that they can act before it’s too late. Another anti-CFIT tool is the Minimum Safe Altitude Warning (MSAW) system which monitors the altitudes transmitted by aircraft transponders and compares that with the system’s defined minimum safe altitudes for a given area. When the system determines the aircraft is lower, or might soon be lower, than the minimum safe altitude, the air traffic controller receives an acoustic and visual warning and then alerts the pilot that the aircraft is too low.

In December 1995, American Airlines Flight 965 tracked off course while approaching Cali, Colombia and hit a mountainside despite a terrain awareness and warning system (TAWS) warning in the cockpit and desperate pilot attempt to gain altitude after the warning. Crew position awareness and monitoring of navigational systems are essential to the prevention of CFIT accidents.

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-3. System component failure – power plant (SCF-PP):

In an aircraft, the power plant refers to the system required to propel the plane and may refer to just an engine or both propellers and an engine. A system component failure – power plant accident occurs when a failure of all or a part of a power plant (pistons, fans, the gearbox, transmission, fans, power plant controls, reversers, propellers, etc.) makes an aircraft impossible to control. SCF-PP accidents can occur in both single and twin-engine planes.

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-4. Fuel-related problems:

Next up on the top causes of general aviation accidents: fuel-related accidents. This type of airplane accident is typically caused by one of several miscalculations: the miscalculation of a plane’s current fuel quantity, a miscalculation of the amount of fuel an aircraft needs, and a misunderstanding of the type of fuel an aircraft needs. A fuel issue can also be the result of a mechanical malfunction or failure of an aircraft component. All of these issues can result in either fuel exhaustion (a total lack of fuel) or fuel starvation (in which fuel is present but cannot reach the engine), both of which can lead to engine failure.

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-5. Unknown or undetermined:

When plane wreckage is difficult to reach (as in underwater or in unsafe terrain) or when damage to the plane wreckage is extensive, it is not always possible to find out information or evidence pertaining to an accident. Under these circumstances, the agencies that investigate the causes of airplane crashes, including the FAA and the NTSB, may be unable to determine the cause of an accident.

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-6. System component failure – non-power plant (SCF-NP):

A system component failure – non-power plant accident occurs when a failure of non-engine parts makes an aircraft impossible to control. Outside of the engine, there are still many areas of an aircraft that can fail. These include:

-Software and database system failures

-Maintenance failures

-The failure of the control system, collective, tail rotor drive, and rotorcraft cyclic

-The separation of parts from the airplane

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-7. Unintended flight in IMC (UIMC):

Instrument meteorological conditions (IMC) refers to weather conditions in which a pilot must refer to instruments in order to navigate. When doing so, the pilot is flying under Instrument Flight Rules (IFR) instead of Visual Flight Rules (VFR). Accidents caused by unintended flight in IMC occur when a pilot who was previously navigating using only Visual Flight Rules (VFR) loses visual references and is either unqualified to fly in IMC and/or is flying an aircraft that’s unequipped to fly IMC.

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-8. Midair collisions (MAC):

Midair collisions are accidents where two aircraft collide while still in-flight. The majority of midair collisions occur near airports, where air traffic is at its heaviest. There are many factors at play when determining the cause of MACs, from the quality of airspace design to pilot management to the use of Traffic Collision Avoidance Systems (TCAS).

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-9. Low-altitude operations (LALT):

LALT accidents occur when a pilot is intentionally operating in close proximity to terrain, water, or other obstacles. These accidents do not include accidents that occur during the takeoff or landing phases of flights. Many of LALT accidents occur during aerial work. They may also be the result of ostentatious maneuverings, sightseeing, or simply needing to fly closely to mountains or canyons. 

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-10. Other:

While the aforementioned 9 types of aircraft accidents make up the majority of fatal crash types. However, there are many other types of airplane accidents, including bird strikes, hijackings, fires, and so on, that make up this final category of top causes of general aviation accidents.

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General Aviation Safety vs. Airlines:

Although most people are informed of plane crashes involving large, multi-passenger commercial flights, the majority of aviation accidents do not occur in commercial flights. Rather, figures from the National Transportation Safety Board indicate that a staggering 97 percent of aviation fatalities occur in general aviation, not in commercial flights. There is an average of five small plane crashes each day, resulting in approximately 500 deaths annually. The term “general aviation” refers to smaller aircraft that are for either private or commercial use. This category encompasses many types of civil aircraft — everything from charter planes and business jets to helicopters, gliders and even hot-air balloons. Statistically speaking, general aviation aircraft are both more common and risky than commercial planes. Commercial airliners have sophisticated safety and navigation technology, and these aircraft fly on planned and carefully controlled air traffic routes. Commercial airline pilots also undergo extensive training and have access to numerous backup systems and failsafe mechanisms that do not exist in most smaller private planes. GA accident rates have always been higher than airline accident rates. People often ask about the reasons for this disparity. There are several:

• Variety of missions – GA pilots conduct a wider range of operations. Some operations, such as aerial application (crop-dusting, in common parlance) and banner towing, have inherent mission-related risks.
• Variability of pilot certificate and experience levels – All airline flights are crewed by at least one ATP (airline transport pilot), the most demanding rating. GA is the training ground for most pilots, and while the GA community has its share of ATPs, the community also includes many new and low-time pilots and a great variety of experience in between.
• Limited cockpit resources and flight support –Usually, a single pilot conducts GA operations, and the pilot typically handles all aspects of the flight, from flight planning to piloting. Amateur pilots technically have more freedom and face fewer restrictions than commercial airline pilots. They do not require as many flight hours to qualify for amateur flight licenses compared to commercial pilots. Inexperience is a commonly cited reason for small plane crashes. Air carrier operations require at least two pilots. Likewise, airlines have dispatchers, mechanics, loadmasters, and others to assist with operations and consult with before and during a flight.
• Greater variety of facilities – GA operations are conducted at about 5,300 public-use and 8,000 private-use airports, while airlines are confined to only about 600 of the larger public-use airports. Many GA-only airports lack the precision approaches, long runways, approach lighting systems, and the advanced services of airline-served airports. Smaller planes can land at various airports, even those with unpaved runways in some cases. However, pilots must have sufficient experience to handle difficult landings.
• More takeoffs and landings – During takeoffs and landings aircraft are close to the ground and in a more vulnerable configuration than in other phases of flight. On a per hour basis, GA conducts many more takeoffs and landings than either air carriers or the military.
• Less weather-tolerant aircraft – Most GA aircraft cannot fly over or around weather the way airliners can, and they often do not have the systems to avoid or cope with hazardous weather conditions, such as ice. Smaller planes are more vulnerable to turbulence and other natural hazards in flight.
• Many small aircraft crashes happen from “controlled flight into terrain,” which means a pilot was in control of the aircraft but allowed it to hit a mountain, water, trees, or other terrain for some reason due to poor visibility or inattention. Losing control of the aircraft is also leading cause of small plane crashes.
• Roughly two aviation accidents in GA occur each week due to losing fuel mid-flight.
• Wildlife can sometimes pose a threat to a smaller plane. For example, some small planes have crashed after birds flew into their engines, causing critical failures mid-flight.

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Phases of flight and plane crash:

Accidents are simply a part of life, and while uncommon, it’s true that they can occur even while flying. Statistically speaking, air travel is perhaps the safest way to travel. But according to a new in-depth analysis by Boeing, if an accident does occur, it’s far more likely to happen during certain parts of a flight than others.

According to an in-depth analysis by Boeing that examined commercial airplane accident from 1959 to 2017, crashes are more likely to happen during takeoff and landing. From 2007 to 2016, nearly 50 percent of all fatal accidents occurred during descent and landing. Takeoff and the initial climb accounted for 13 percent of the fatal crashes. Most accidents and fatalities take place during the departure (take off / climb) and arrival (approach/ landing) stages. During these phases aircraft are close to the ground and in a more vulnerable configuration than during other flight phases as there is less time to recover from a mistake or react to problem: and the crew have to deal with a high workload and reduced manoeuvre margins.

If the aircraft left the gate with undetected faults, these may become apparent during the climb, as the first stage taking place off the ground, and could prove dangerous. If the crew believe the failure requires the aircraft to land as soon as possible, they will decide to perform an IFTB (In-Flight Turn Back). This could turn out to be difficult, however, as the aircraft is flying low and may have already lost some of its capabilities.

Only 10 percent of accidents occur while cruising. This is because this is the longest operational phase, and if an error occurs, there is time and the ability to take corrective action. When accidents do occur at this stage, they’re likely to be more dangerous for passengers. The taxi phase only attributes to 10 percent of accidents.

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Figure below shows distribution of fatal accidents and onboard fatalities, 2007 – 2016, Boeing.

Boeing analyzed worldwide commercial flights from 2007 to 2016, and determined that 48 percent of all fatal accidents occurred during a flight’s final descent and landing. Those airplane accidents were responsible for 46 percent of all onboard fatalities. It’s a rather high number when you consider that the final approach and landing account for just 4 percent of an aircraft’s total journey. After all, only 11 percent of major accidents occurred while cruising from 2007 to 2016, despite this stage taking up 57 percent of flight time. 

Takeoff and the initial climb are the second-most critical parts of a flight, accounting for a combined 13 percent of fatal incidents. (Of those accidents, however, only 6 percent resulted in onboard fatalities.) So really, it’s those first and last few minutes of a flight that are the most dangerous.

In fact, these stages of flight — takeoff, initial climb, final approach, and landing — are known as the “plus three minus eight” rule. Echoing Boeing’s findings, Ben Sherwood, author of The Survivors Club — The Secrets and Science That Could Save Your Life, estimated that 80 percent of all plane crashes happen within the first three minutes of a flight or in the last eight minutes before landing.

And even if you’re in a crash (which is exceedingly unlikely), there are ways to protect yourself. Cheryl Schwartz, a retired United Airlines flight attendant said that it’s always crucial to know where the emergency exits are. The moment you’re seated, she explained, count the number of rows to the nearest exit. Schwartz also said there are different brace positions to use, depending on where you’re seated. If you have a seat in front of you, for example, you can use it for support. If you don’t, bend over your legs and grab behind you knees. Passengers have about 95% chance of surviving an airplane accident, according to the National Transportation Safety Board.

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Approach and Landing Accidents (ALA):

Approach and landing is the highest risk phase of flight, accounting for over 50 percent of all accidents at every level of aviation. Many types of accidents can happen during the approach and landing phase of flight. The most common types of approach and landing accidents are; CFIT (controlled flight into terrain), LOC (loss of control), and runway excursions.

Because of its inherent risk there have been many international efforts addressing the approach and landing phase of flight. These efforts have primarily addressed the highest risk areas such as CFIT and runway excursions. They have addressed all aspects of approach and landing accidents, and in addition they also addressed all the responsible parties involved with reducing the risk of approach and landing accidents. These parties include the aircraft manufacturers, aircraft operators, aircrews, air traffic management, regulators, and airports. Many interventions have been created to assist in reducing the risk of accidents in the approach and landing phase of flight. One of these is stabilized approach criteria, which are designed to assist the crew in flying a safe approach and landing. Another intervention is safe landing criteria, which assist the crew in reducing the risk during the landing phase of flight.

Accidents and Incidents:

On 14 August 2013, a UPS Airbus A300-600 crashed short of the runway at Birmingham Alabama on a night IMC non-precision approach after the crew failed to go around at 1000ft aal (above aerodrome level) when unstabilised and then continued descent below MDA until terrain impact. The Investigation attributed the accident to the individually poor performance of both pilots, to performance deficiencies previously-exhibited in recurrent training by the Captain and to the First Officer’s failure to call in fatigued and unfit to fly after mis-managing her off duty time.

On 19 July 2017, an Airbus A319 crew ignored the prescribed non-precision approach procedure for which they were cleared at Rio de Janeiro Galeão in favour of an unstabilised “dive and drive” technique in which descent was then continued for almost 200 feet below the applicable MDA and led to an EGPWS terrain proximity warning as a go around was finally commenced in IMC with a minimum recorded terrain clearance of 162 feet. The Investigation noted the comprehensive fight crew non-compliance with a series of applicable SOPs and an operational context which was conducive to this although not explicitly causal.

On 5 January 2014, an Airbus A320 was unable to land at Delhi due to visibility below crew minima and during subsequent diversion to Jaipur, visibility there began to deteriorate rapidly. A Cat I ILS approach was continued below minima without any visual reference because there were no other alternates within the then-prevailing fuel endurance. The landing which followed was made in almost zero visibility and the aircraft sustained substantial damage after touching down to the left of the runway. The Investigation found that the other possible alternate on departure from Delhi had materially better weather but had been ignored.

On 23 August 2000, a Gulf Air Airbus A320 flew at speed into the sea during an intended dark night go around at Bahrain and all 143 occupants were killed. It was subsequently concluded that, although a number of factors created the scenario in which the accident could occur, the most plausible explanation for both the descent and the failure to recover from it was the focus on the airspeed indication at the expense of the ADI and the effect of somatogravic illusion on the recently promoted Captain which went unchallenged by his low-experience First Officer.

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Table below shows the most common factors associated with flight incidents during the approach and landing phases.

Factors	% of accidents
Pilots’ incorrect decision	74%
Skipping or improperly performing actions	72%
Ineffective crew interaction, mutual assistance and mutual control	63%
Not adequate understanding of the flight situation in the horizontal and/or vertical plane	52%
Invalid (incomplete or inaccurate) assessment of flight conditions	48%
Slow or late crew action	45%
Difficulty of manual piloting	45%
Wrong or incomplete mutual understanding between the pilot and the controller	33%
Improper use of automated control systems	20%

From the table above it can be seen that the human factor plays a huge role in terms of deteriorating the safety of the final phase of the flight. Roll out is the stage of an aircraft’s landing during which it travels along the runway while losing speed. Roll-outs at landing make up to 20% of the number of incidents during the approach and landing phase. Later or deliberately delayed braking has become a concomitant factor of 45% of such events.

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Airport Runway Accidents:  

Any pilot will tell you that the most critical times of a flight are during takeoff and landing. The margins for errors, in both circumstances, are slim. If anything goes wrong, the likely result is a runway accident, which can have deadly consequences. According to a study published by Boeing Commercial Airplanes, nearly half of all aviation accidents occur during the final approach or landing and 14 percent occur during takeoff or initial climb. The majority of aviation accidents happen on the runway during takeoff or landing, not while the airplane is cruising in the air.

Three reasons why airport runway accidents are the most common of all aviation accidents:

-1. Takeoffs and landings are when planes are closest to the ground. There is often not enough time or altitude for the pilots to take corrective action.

-2. Planes are traveling slower, closer to their stalling speeds, and forced to do more maneuvering during these critical times.

-3. Planes are in closer proximity to one another when taking off or landing at an airport.

When a plane is close to the ground or in the proximity of other aircraft, there is little room for error. As we think of runway accidents, we typically think of a mechanical malfunction, maintenance issues or a number of other problems occurring during takeoff or landing that can lead to catastrophe, but oftentimes the pilots didn’t do everything they were required to do to set up a safe takeoff or landing.

Top causes for runway accidents:

-1. Pilot error – Most runway accidents are the result of pilot error, which can result from tactical errors (such as poor actions, planning or decision making, often caused by lack of experience or fatigue) or operational errors (relating to training or instruction).

-2. Air traffic controller error — Air traffic controllers are often responsible for dozens of planes taking off and landing at the same time. The job is a demanding one; difficult and complex. One small mistake can lead to a mid-air collision or runway incursion (this occurs when another plane or a vehicle is on a runway designated for a plane coming in to land, or starting its takeoff roll).

-3. Mechanical failure or defective design – Either of these causes can result in runway accidents. For example, if a landing gear does not deploy it can force pilots to perform a belly landing.

-4. Maintenance error— Roughly 12 percent of all aviation accident reports cite poor maintenance as a contributing factor. Between the years 1994 to 2004, maintenance issues contributed to 42 percent of fatal airline accidents in the U.S.

-5. Bad weather — Inclement weather can cause runway accidents when a plane is either unable to properly take off due to stormy weather, or unable to land appropriately, often causing the plane to overrun a runway.

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Types of Runway Accidents:

Runway Excursion:

Commonly referred to as a runway overrun, a runway excursion is when an aircraft veers off or overruns the runway surface. Runway excursions occur while an aircraft is taking off or landing and can involve a variety of factors ranging from unstable approaches, to the condition of the runway.

According to a study conducted by the Flight Safety Foundation, roughly 96 percent of all runway accidents and 80 percent of the deaths stemming from runway accidents, are the result of runway excursions. The Flight Safety Foundation study found that runway excursions are the most common type of all runway accidents.

Runway Incursion:

The second most common type of runway accidents, according to the Flight Safety Foundation study, are runway incursions. These occur when an aircraft collides with an unauthorized vehicle, a person on the runway or another plane. Incursion runway accidents are not as common as excursion runway accidents, but they are certainly just as dangerous. In five fatal runway incursions that happened between 1995 and 2007, 129 people lost their lives. The deadliest runway incursion in history killed 583 people in the Canary Islands. Two Boeing 747s collided on March, 27, 1977 at Los Rodeos Airport (now Tenerife North Airport) on the Spanish island of Tenerife.

Runway Confusion:

Runway confusion is when a single plane uses the wrong runway or a taxiway during landing or takeoff. On October 31, 2000, the pilots of Singapore Airlines Flight 006 attempted to takeoff on a closed runway, in the midst of a typhoon. The plane crashed into some construction equipment, killing 83 of the 179 people onboard.

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Cross Wind as a Factor in Runway Excursions:

Investigation of Runway Excursions on landing where the crosswind has been a significant factor usually identify one or more of the following:

-1. Inappropriate flight crew decision to attempt a landing

-2. Inappropriate flight crew aircraft handling

-3. High rates of variation in surface and near-surface wind velocity

-4. Inadequate availability of information about the state of the runway surface

-5. Incomplete understanding by flight crew of the aircraft performance limitations or recommendations in relation to cross wind landings

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Aircraft Alignment for Landing and Touchdown in cross wind:  

For most Operators of transport aircraft, and for most current aircraft types, the required or recommended means of flying the final approach to land is with wings level and applying a drift correction to compensate for any crosswind component. This type of approach is often referred to as a “crabbed approach”. It is possible, although nowadays rarely recommended or permitted in air transport operations, to fly a crosswind final approach by means of a sideslip in which into-wind aileron is ‘balanced’ by opposite rudder input. In this latter case, the slip indicator will show the ball off center.

During the flare to land following a crabbed approach, the aircraft must have its longitudinal axis transitioned to one approximating to the runway centerline whilst an essentially wings-level aircraft attitude is maintained. The rudder is used to make this alignment at an appropriate interval before main gear contact and any consequent tendency to roll is counteracted by aileron. In the case of a crosswind component near to dry runway limits, most aircraft may be landed with residual drift of up to 5 degrees to prevent a difference from wings level of more than 5 degrees occurring. Beyond this amount of departure from the ideal wings-level aircraft attitude, many aircraft with wing mounted engines may be vulnerable to engine nacelle ground contact. Also, whilst touchdown with a small drift angle on a dry runway results in the aircraft regaining the direction of the centerline without difficulty, a touch down with such residual drift on a contaminated runway is likely to lead to the aircraft trajectory on the ground being aligned with the direction of the aircraft axis at touchdown. The initial sideways force on an aircraft landed with residual drift will be aggravated by the effect of thrust reversers (or turboprop reverse pitch) if this is deployed immediately after touchdown but this effect soon decreases with decreasing airspeed or can be temporarily negated by selecting reverse idle thrust (or turboprop ground idle).

The degree of offset of an aircraft axis, from the landing runway centerline during final approach, using a crabbed approach at typical airspeeds can be expected to reduce as wind speed reduces in line with height above the ground. If visual reference becomes available well before the typical Instrument Landing System (ILS) Decision Height, then the amount of drift correction which will have been applied by the Autopilot may be quite considerable and when transitioning to manual flying, pilots must be careful not to inadvertently remove necessary drift correction prematurely. At 3-4 nautical mile, the typical drift correction for a 30 knot surface crosswind component might be in the vicinity of 10 to 12 degrees.

In respect of achieving aircraft longitudinal axis alignment with the runway centerline for a crosswind touchdown, it is also sometimes forgotten that the process is much more difficult in conditions of poor forward visibility, because of the reduced perspective available.

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Runway excursion accidents that feature a significant crosswind component:

On 1 September 2018, a Boeing 737-800, making its second night approach to Sochi beneath a large convective storm with low level windshear reported, floated almost halfway along the wet runway before overrunning it by approximately 400 meters and breaching the perimeter fence before stopping. A small fire did not prevent all occupants from safely evacuating. The Investigation attributed the accident to crew disregard of a number of windshear warnings and a subsequent encounter with horizontal windshear resulting in a late touchdown and noted that the first approach had meant that the crew had been poorly prepared for the second.

On 17 July 2011, an Aer Arann ATR 72-200 made a bounced daylight landing at Shannon in gusty crosswind conditions aggravated by the known effects of a nearby large building. The nose landing gear struck the runway at 2.3g and collapsed with subsequent loss of directional control and departure from the runway. The aircraft was rendered a hull loss but there was no injury to the 25 occupants. The accident was attributed to an excessive approach speed and inadequate control of aircraft pitch during landing. Crew inexperience and incorrect power handling technique whilst landing were also found to have contributed.

On 1 October 2010, a Gulfstream G-IV being operated by General Aviation Flying Service as ‘Meridian Air Charter’ on a corporate flight from Toronto International to Teterboro made a deep landing on 1833m-long runway 06 at destination in normal day visibility and overran the end of the runway at a speed of 40 to 50 knots before coming to a stop 30m into a 122m long EMAS installation. The aircraft suffered only minor damage and none of the 10 occupants were injured.

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Can a plane land on autopilot in case of emergency?

Many autopilot systems are capable of landing the airplane. This is usually the case in very low-visibility conditions. However, it takes a significant amount of training and knowledge to properly program the flight management computer, properly switch the autopilots into the proper modes and then monitor their performance.  Recently, some small airplanes have implemented an emergency system that will automatically land the aircraft on a runway, after advising air traffic control that there is an emergency, evaluating the weather and navigating to the runway. It is very sophisticated using a lot of artificial intelligence. It is highly likely that this technology will expand.

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Section-13

Human factors in plane crash:  

Human factors issues, specifically human errors, contribute to more aircraft incidents and accidents than any other single factor. Human errors include errors by the flight crew, maintenance personnel, air traffic controllers, and others who have a direct impact on flight safety. Human error is defined as a human action with unintended consequences. There is nothing inherently wrong or troublesome with error itself, but when you couple error with aviation maintenance and the negative consequences that it produces, it becomes extremely troublesome. Training, risk assessments, safety inspections, etc., should not be restricted to attempt to avoid errors but rather to make them visible and identify them before they produce damaging and regrettable consequences. Simply put, human error is not avoidable but it is manageable.

Human error causes or contributes to considerably over half of all aviation mishaps. The most common single-aircraft anomalies in flight involve altitude or track deviations. The most common controller errors involve failure to coordinate traffic with other elements of the air traffic control system. Many other incidents involve shortcomings specifically of the human, rather than of the system. Failures of control, failures of decision-making and cockpit resource management are frequent. Boredom, complacency and ennui appear to underlie some failures, while very high workloads are associated with others.

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Human Factors Categories:

The human factors are divided into three parts, physiological, psychological and the others.

Physiological factors are physiological workload influences, that pilots and controllers respond from bearing in aviation environment. It involves age, physical situation, workload, and fatigue.

Psychological factors are variation and influence in mentality arising from different situations or stimuli in environment. It includes attention as resource, distraction, expectation, reaction, decision making, memory limitation, situation awareness, and others.

The others excluding psychological and physiological factors are position/place, nationality, work experience, professional training, education and culture.

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Many aspects of human factors are associated with the operational safety of commercial airplanes, including the following:

-1. design factors associated with aircraft controls, aircraft system controls, warning systems, air traffic control systems, flight deck, passenger seating and egress, etc.

-2. operational factors associated with the selection and training of flight crews, crew assignment policies related to the distribution of experienced personnel and the minimization of flight crew fatigue, checks on crew members’ health, and policies on preflight information

-3. maintenance factors related to training maintenance workers; the clarity of maintenance procedures; and designing aircraft equipment and maintenance tools to make it easier for workers to perform maintenance, avoid errors, and detect abnormal conditions

-4. national and international regulatory factors associated with airworthiness standards, separation standards, and communications standards

Current processes, which are both thorough and complex, have resulted from a large accumulation of flight experience, analytical and computer studies, and reviews of human factors. All of this information represents a complicated web of interrelated factors that makes it difficult to define a clear and simple road map for progress. Complexity, however, is inherent in many human factor issues.

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Common Aviation Human Factors:

The captain, first officer, crew members, and control tower must work together to ensure the safety of the flight and its passengers. Lack of respect, intimidation, distractions, pilot/co-pilot arguments and pride can get in the way and create serious problems that jeopardize lives. The following are examples of human factors that have contributed to some of the worst disasters:

Man-machine interface:  

As many aircraft become increasingly automated, the safety of air travel has improved. With increased automation, however, increased reliance, dependence, and indeed, complacency have become too common. Human factors can contribute to an accident due to incorrect use of, or misunderstanding of, technology, not to mention poorly designed cockpit systems. While operating complicated and often delicate machinery, even small mistakes can lead to devastating consequences. Accidentally pushing the wrong button can be a recipe for disaster in a complex aircraft. China Eastern Airlines Flight 583 accident was caused by human error, when a crew member inadvertently bumped controls, resulting in the plane diving 5,000 feet. This incident occurred while the plane was en route from Shanghai to Los Angeles.

Loss of situational awareness:

When dealing with one emergency issue aboard an aircraft it is easy to forget to maintain awareness of other potential issues. For example, the 1978 United Airlines Flight 173 Portland, Oregon crash occurred when the crew was so distracted while attempting to diagnose an issue with the landing gear that they failed to realize they were running out of fuel. This type of pilot error is also present in many controlled flights into terrain, such as the 1995 American Airlines Flight 965 crash where the crew failed to notice their navigational errors and forgot that they had deployed the air brakes, which led the plane to crash into a mountain in Colombia.

The July 6, 2013 crash of Asiana Airlines Flight 214 at SFO is another prime example. In this case, the pilots failed to properly monitor the landing approach, became fixated on instruments, did not fully understand how the auto-throttle worked (a potential design defect) and did not notice that the auto-throttle was maintaining too-low airspeed and dangerous deviation below the intended glide slope. The crew failed to look out the cockpit windows to see that they could not safely land, all of which led to a catastrophic crash onto the runway.

Crew coordination:

In the aviation industry, this area is usually referred to as crew resource management or CRM. Captains must respect the first officer and acknowledge mistakes or warnings addressed by the first officer (setting aside their own pride). First officers must not be intimidated by the captain and must call attention to problems. When communication between flight crew members breaks down the results are often devastating. One incident that exemplifies this human error is the 1982 Air Florida Flight 90 crash, in which the co-pilot tried three times to warn the pilot of issues regarding ice on the wings and low speeds but was ignored or told he was incorrect each time. The plane crashed into the 14th Street Bridge over the Potomac River, two miles from the White House.

Lack of proper training:

Airlines are responsible for ensuring their pilots and crew have the training needed to properly operate whatever aircraft they are tasked with operating. Yet, many pilots are not necessarily trained on all aspects of a particular plane. This came up as another human factors issue in the crash of Asiana Airlines Flight 214 at SFO. The NTSB determined the probable cause of the crash stemmed, in large part, from the human factors of pilot error and flight crew mismanagement. Asiana’s training was faulted for contributing to the accident since the airline had a policy to always use full automation, discouraging manual flight operations. This led the pilots of Flight 214 to be over-reliant on the automated system and thus unable to properly diagnose or correct the issue when their plane came in for landing too low and slow. Proper training must ingrain efficient and safe CRM principles.

Fatigue:

Fatigue is one of the most commonly reoccurring human factors in aviation. Yet, it is one of the most difficult to combat, because the solutions tend to impact airline profits. Over the years airlines have consistently pushed pilots and flight crew to work longer hours with shorter turnaround time, often forcing the pilots and crew to have the bare minimum of rest hours available to them between flights. Airlines often close their eyes to the difficulties that flight crews experience in the effort to actually get the needed rest. Even though they know crew members are constantly operating on unusual schedules in different cities and time zones each day, and have tight schedules that provide for minimum rest opportunity, airlines often choose to simply believe that every hour off duty means adequate rest. Many plane crashes officially blamed on pilot error are truly caused by pilot fatigue that led to pilot error.

Checklists:

Checklists are made to be followed. Whenever pre-flight and pre-landing checklists are skimmed or skipped entirely in order to make up time or because the flight crew feels it is unnecessary, the risk for a potential accident grows. In the Southwest Airlines Flight 1455 crash mentioned above, rather than reading the full checklist aloud—as required—the first officer visually acknowledged the checklist items.

Air traffic controller error:

Those flying the plane are not the only people who contribute to aviation accidents caused by human factors. If an air traffic controller is distracted from his or her duties, is fatigued or poorly trained, any one of those conditions can easily lead to airport runway accidents, or mid-air collision, or faulty services provided to pilots with aircraft emergencies that unnecessarily leads to loss of life.

Human factors in aviation maintenance:

Human error can play a part in a crash before the plane is even in the air. When aircraft maintenance is done incorrectly an aircraft part can malfunction without warning, causing catastrophe. In the 2003 crash of Air Midwest Flight 5481 at Charlotte/Douglas International Airport, an inexperienced and unsupervised crew of mechanics mis-rigged the elevator control of a Beechcraft 1900D, thus preventing the pilot from having full capability of lowering the nose if a climb was excessive. During the fatal takeoff in a fully loaded airplane, the airplane climbed very steeply, but because of the negligent maintenance of the elevator, the pilots could not stop the climb, and the airplane stalled and crashed, killing all the passengers and crew.

Crew negligence:

While the actions of flight attendants and other onboard crew members may seem less important, their primary responsibility is to keep passengers safe. If they fail to properly close an overhead bin, luggage can fall on passengers and injure them mid-flight. In an emergency situation, if they do not properly follow escape protocol, passengers can be harmed or killed during those critical moments following a plane crash.

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Aviation Human Error Statistics:

According to the Federal Aviation Administration (FAA), human error is the leading cause of both commercial airline crashes and general aircraft accidents. More than 88% of all general aviation accidents are attributed to human error, especially due to loss of control by the pilot during flight. Pilot error may be the most common type of human error in aviation accidents, but they are not solely responsible. Other people involved in aircraft flights, such as flight crew members, air traffic controllers, and mechanics or maintenance staff who work on the airplane.

Flight-crew issues were the primary cause of two-thirds of fatal commercial and business plane crashes worldwide from 1997 through 2006, the United Kingdom’s Civil Aviation reported. A 2006 Federal Aviation Administration study found that from 1990 to 2002, 45 percent of major airline accidents in the United States and 75 percent of commuter-carrier crashes were associated with human error. Many aviation experts to believe that the biggest future safety advancements will come from reductions in human error. But it’s a complex area of research — involving the study of psychology, decision-making, crew member interaction, training, cockpit design and the relationship between humans and sophisticated automated systems — that sometimes takes a back seat to more obvious safety threats.

“Can the accident rate be further reduced substantially? Absolutely yes,” said Robert Dismukes, chief scientist for human factors research and technology at NASA’s Ames Research Center in Moffett Field, Calif. “But this will require better understanding of the underlying causes of human error and better ways of managing human error.” Pilots are concerned that cockpit automation has eroded basic flying skills that may be required in an emergency. “The more automated things get, the more difficult it gets to spend 16 hours at a time in the cockpit and stay engaged, whether it’s one flight or a series of flights over that period of time,” said Paul Rice, an airline captain and a vice president of the Air Line Pilots Association, a union representing 53,000 pilots. “It’s a difficult task. That’s where study of human factors will make gains in the next few years.”  Automation is supposed to relieve an aircraft pilot’s workload and reduce errors. The reality can unfortunately be very different sometimes. When the pilot and the aircraft do not interact as foreseen, automation technology can be the cause of disturbing instability, which has resulted in catastrophic failures.

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Types of Human Error in Aviation Accidents:  

When human errors are factors in an aviation accident, they can usually be broken down into three responsible parties: pilots or flight crew members, air traffic controllers, or maintenance staff.

Pilot or Flight Crew Error:

Pilots make countless decisions and perform a multitude of actions while operating an aircraft, and sometimes they make mistakes. These mistakes are defined as either tactical errors, which are based in decision-making, or operational errors, which are a result of poor training. Flight crew members can also make in-flight errors that result in the injury of airplane passengers.

Examples of errors by pilots or flight crew members include the following:

-Flying under the influence of drugs or alcohol

-Pilots experiencing fatigue

-Confusion when using automated flight systems

-Lack of proper training for pilots or flight crew

-Skimming or skipping pre-flight or pre-landing checklists

-Insufficient of communication between flight crew members

-Negligence of flight crew members

Air Traffic Controller Error:

Air traffic controllers monitor and regulate all aspects of airplanes in the air and on the runway. Their job is to direct air traffic flow and keep planes at a safe distance from one another.

Errors on the part of air traffic controllers include the following:

-Understaffing

-Fatigue

-Inadequate training

-Failure to issue safety alerts or warnings

-Incorrectly guiding pilots

-Poor coordination between air traffic controllers

Aircraft Maintenance Error:

When aircraft maintenance is performed incorrectly, airplane parts can malfunction and cause dangerous flying conditions. There are several potential causes of maintenance errors:

-Fatigue

-Time pressure

-Complexities of required tasks

-Use of outdated manuals

-Improper equipment or part installation

-Incorrectly followed maintenance procedures

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Human Factors Analysis and Classification System (HFACS):

As aircraft have become more reliable, humans have played a progressively more important causal role in aviation accidents. Consequently, a growing number of aviation organizations are tasking their safety personnel with developing accident investigation and other safety programs to address the highly complex and often nebulous issue of human error. Unfortunately, many of today’s aviation safety personnel have little formal education in human factors or aviation psychology. Rather, most are professional pilots with general engineering or other technical backgrounds. Thus, many safety professionals are ill-equipped to perform these new duties and, to their dismay, soon discover that an “off-the-shelf’ or standard approach for investigating and preventing human error in aviation does not exist. This is not surprising, given that human error is a topic that researchers and academicians in the fields of human factors and psychology have been grappling with for decades.

Indeed, recent years have seen a proliferation of human error frameworks and accident investigation schemes to the point where there now appears to be as many human error models as there are people interested in the topic (Senders and Moray, 1991). Even worse, most error models and frameworks tend to be either too “academic” or abstract for practitioners to understand or are too simple and “theoretically void” to get at the underlying causes of human error in aviation operations.

Having been left without adequate guidance to circumnavigate the veritable potpourri of human error frameworks available, many safety professionals have resorted to developing accident investigation and error management programs based on intuition or “pop psychology” concepts, rather than on theory and empirical data. The result has been accident analysis and prevention programs that, on the surface, produce a great deal of activity (e.g., incident reporting, safety seminars and “error awareness” training), but in reality only peck around the edges of the true underlying causes of human error. Demonstrable improvements in safety are therefore hardly ever realized.

Coined the Human Factors Analysis and Classification System (HFACS), its framework is based on James Reason’s (1990) well-known “Swiss cheese” model of accident causation. In essence, HFACS bridges the gap between theory and practice in a way that helps improve both the quantity and quality of information gathered in aviation accidents and incidents.

The HFACS framework was originally developed for, and subsequently adopted by, the U.S. Navy/Marine Corps as an accident investigation and data analysis tool. The U.S. Army, Air Force, and Coast Guard, as well as other military and civilian aviation organizations around the world are also currently using HFACS to supplement their preexisting accident investigation systems. In addition, HFACS has been taught to literally thousands of students and safety professionals through workshops and courses offered at professional meetings and universities. Indeed, HFACS is now relatively well known within many sectors of aviation and an increasing number of organizations worldwide are interested in exploring its usage.

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It is generally accepted that (Wiegmann & Shappell, 2001a, 2003) aviation accidents are typically the result of a chain of events that often culminate with the unsafe acts of operators (aircrew). The aviation industry is not alone in this belief, as the safety community has embraced a sequential theory of accident investigation since Heinrich first published his axioms of industrial safety in 1931 (Heinrich, Peterson, & Roos, 1931). However, it was not until Reason published his “Swiss cheese” model of human error in 1990 that the aviation community truly began to examine human error in a systematic manner.

The HFACS framework is based on Reason’s (1990) model of latent and active failures. Briefly, HFACS encompasses multiple aspects of human error including (1) Unsafe Acts (decision errors, skill-based errors, perceptual errors and violations), (2) Preconditions of Unsafe Acts (adverse mental states, adverse physiological states, physical mental limitations, CRM failures, and personal readiness), (3) Supervisory Failures (inadequate supervision, scheduled inappropriate operations, failure to correct known problems, and supervisory violations) and (4) Organizational Influences (resource management, organizational climate, and organizational process). (see figure below).

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The HFACS framework:

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Several studies using HFACS to examine aircrew errors associated with military, commercial, and general aviation accidents have shown that HFACS can be successfully imposed onto otherwise nebulous databases, allowing unforeseen trends in the types of errors associated with these events to be revealed (Shappell & Wiegmann, 2000). In addition, the application of HFACS to the analysis of ATC operational error reports from the FAA’s internal reporting system (Pounds et al., 2000), suggests that HFACS is a viable tool for analyzing human error within the ATC domain, including perhaps, controller errors associated with aviation accidents and incidents. 

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Human Error and Commercial Aviation Accidents: A Comprehensive, Fine-Grained Analysis Using HFACS, a 2006 study: 

The Human Factors Analysis and Classification System (HFACS) is a theoretically based tool for investigating and analyzing human error associated with accidents and incidents. Previous research has shown that HFACS can be reliably used to identify general trends in the human factors associated with military and general aviation accidents. The aim of this study was to extend previous examinations of aviation accidents to include specific aircrew, environmental, supervisory, and organizational factors associated with 14 CFR Part 121 (Air Carrier) and 14 CFR Part 135 (Commuter) accidents using HFACS.

In the present study, authors examined a variety of human and environmental factors associated with more than 1000 commercial aviation accidents over a 13-year time frame. Given the sheer number of causal factors associated with these accidents, one might believe that there are literally thousands of ways to crash an aircraft. The results of this study, however, demonstrate that accidents appearing to be unique at first glance can be organized based upon underlying situational, demographic, and cognitive mechanisms of accident causation. In this way, previously unidentified trends in the accident record can be exposed.

Generally speaking, nearly 70% of the “commercial” aviation accidents occurring between 1990 and 2002 were associated with some manner of aircrew or supervisory error. However, the percentage varied slightly when air carrier (45%) and commuter (75%) aviation accidents were considered separately. This finding is consistent with results reported elsewhere (Li et al., 2001). However, while other studies typically focused on situational and demographic data, this study employed a human error framework (HFACS) to reveal the specific types of human error associated with commercial aviation accidents.

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Pilot error:   

The term “pilot error” refers to the various types of mistakes that pilots might make at any point during the operation of an aircraft, which can include both tactical errors (mistakes in decision-making) and operational errors (mistakes that result from poor training). Pilot error generally refers to an accident in which an action or decision made by the pilot was the cause or a contributing factor that led to the accident, but also includes the pilot’s failure to make a correct decision or take proper action. Pilots work in complex environments and are routinely exposed to high amounts of situational stress in the workplace which may result in a threat to flight safety. While aircraft accidents are infrequent, they are highly visible and often involve significant numbers of fatalities. For this reason, research on causal factors and methodologies of mitigating risk associated with pilot error is exhaustive. Pilot error results from physiological and psychological limitations inherent in humans. Causes of error include fatigue, workload, and fear as well as cognitive overload, poor interpersonal communications, imperfect information processing, and flawed decision making. Throughout the course of every flight, crews are intrinsically subjected to a variety of external threats and commit a range of errors that have the potential to negatively impact the safety of the aircraft.

Pilots are required to perform many actions and make countless decisions during the course of operating an aircraft, and sometimes they make mistakes that result in a crash, like the case of a 2009 Air France flight from Rio to Paris. Investigators determined that crash was caused by the crew’s “inappropriate response” to a malfunction with the plane’s speed sensors, and noted that the crash could have been avoided had the pilots reacted appropriately.

Operator distraction is a common factor in aircraft accidents, and it can occur even when a pilot is focused on doing his or her job safely. A commercial airline flight nearly crashed at Denver International Airport in 2009, for example, when its pilot became distracted by landing preparations and wound up trying to accelerate the plane while the brakes were in use. Fortunately, the pilot was ultimately able to land safely, but not all risky situations during a flight turn out so well.

Other types of pilot error resulting in aircraft crashes include pilots who fly under the influence of drugs or alcohol. A 2013 Lion Air jet crash in Indonesia, initially thought to have been caused by wind shear, was ultimately found to have occurred due to pilot inebriation.

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Common errors in the performance of straight-and-level flight are:

• Attempting to use improper pitch and bank reference points on the airplane to establish attitude.
• Forgetting the location of preselected reference points on subsequent flights.
• Attempting to establish or correct airplane attitude using flight instruments rather than the natural horizon.
• “Chasing” the flight instruments rather than adhering to the principles of attitude flying.
• Mechanically pushing or pulling on the flight controls rather than exerting accurate and smooth pressure to affect change.
• Not scanning outside the cockpit to look for other aircraft traffic, weather and terrain influences, and not maintaining situational awareness.
• A tight palm grip on the flight controls resulting in a desensitized feeling of the hand and fingers, which results in overcontrolling the airplane.
• Habitually flying with one wing low or maintaining directional control using only the rudder control.
• Failure to make timely and measured control inputs when deviations from straight-and-level flight are detected.
• Inadequate attention to sensory inputs in developing feel for the airplane.

Common errors in level turns are:

• Failure to adequately clear in the direction of turn for aircraft traffic.
• Gaining or losing altitude during the turn.
• Not holding the desired bank angle constant.
• Attempting to execute the turn solely by instrument reference.
• Leaning away from the direction of the turn while seated.
• Insufficient feel for the airplane as evidenced by the inability to detect slips or skids without reference to flight instruments.
• Attempting to maintain a constant bank angle by referencing only the airplane’s nose.
• Making skidding flat turns to avoid banking the airplane.
• Holding excessive rudder in the direction of turn.
• Gaining proficiency in turns in only one direction.
• Failure to coordinate the controls.

Common errors in the performance of climbs and climbing turns are:

• Attempting to establish climb pitch attitude by primarily referencing the airspeed indicator resulting in the pilot chasing the airspeed.
• Applying elevator pressure too aggressively resulting in an excessive climb angle.
• Inadequate or inappropriate rudder pressure during climbing turns.
• Allowing the airplane to yaw during climbs usually due to inadequate right rudder pressure.
• Fixation on the airplane’s nose during straight climbs, resulting in climbing with one wing low.
• Failure to properly initiate a climbing turn with a coordinated use of the flight controls, resulting in no turn but rather a climb with one wing low.
• Improper coordination resulting in a slip that counteracts the rate of climb, resulting in little or no altitude gain.
• Inability to keep pitch and bank attitude constant during climbing turns.
• Attempting to exceed the airplane’s climb capability.
• Applying forward elevator pressure too aggressively during level-off resulting in a loss of altitude or G-force substantially less than one G.

Common errors in the performance of descents and descending turns are:

• Failure to adequately clear for aircraft traffic in the turn direction or descent.
• Inadequate elevator back pressure during glide entry resulting in an overly steep glide.
• Failure to slow the airplane to approximate glide speed prior to lowering pitch attitude.
• Attempting to establish/maintain a normal glide solely by reference to flight instruments.
• Inability to sense changes in airspeed through sound and feel.
• Inability to stabilize the glide (chasing the airspeed indicator).
• Attempting to “stretch” the glide by applying backelevator pressure.
• Skidding or slipping during gliding turns due to inadequate appreciation of the difference in rudder forces as compared to turns with power.
• Failure to lower pitch attitude during gliding turn entry resulting in a decrease in airspeed.
• Excessive rudder pressure during recovery from gliding turns.
• Inadequate pitch control during recovery from straight glide.
• Cross-controlling during gliding turns near the ground.
• Failure to maintain constant bank angle during gliding turns.

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Sterile Cockpit Violations:

One of the contributing factors to accidents that happens during takeoff and landing is distracted or inattentive pilots. When a pilot or member of the flight crew is distracted by conversations or other matters, they’re not focused on what the airplane is doing and what they’re supposed to be doing.

After a number of accidents were found to be caused by distracted flight crews, the Federal Aviation Administration (FAA) implemented the sterile cockpit rule. This regulation requires pilots and all flight crew members to refrain from nonessential activities during critical phases of flight below 10,000 feet. This rule was implemented in 1981. Even with the rule, accident still happen when pilots are distracted from the task at hand while the plane is taking off, climbing, descending or landing.

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Plane crashes due to pilot error:

Adam Air Flight 574 (2007)

When the crew of this aircraft were preoccupied with trying to correct a malfunctioning internal reference system, the autopilot of the aircraft was disabled on its own and the plane began to descend.  The pilot tried to correct a slow right roll. But, it turned out to be a failure when the complete control was lost. All 102 passengers and crew aboard died when the plane crashed terrifyingly into the ocean. Following the crash, large-scale reforms to Indonesia’s transportation industry were formed. 

Air France Flight 447 (2009) 

As per a standard procedure in France for flights that cruise for more than three hours, the pilot of Air France 447 had put one of his co-pilots at the helm before heading to the rest cabin for a break. The aircraft hit turbulence and in a short span of time, the autopilot turned off and the plane started rolling to the right slightly. The co-pilot overcompensated for this and his action eventually led to the increase in the plane’s angle of attack to a great extent. This action also made the plane stall 3 times and later it started falling out of the sky. It eventually plummeted into ocean and led to the death of all 228 people on board.

Transasia Flight 235 (2015)

Very few minutes after the TransAsia 235 took off, one of the engines had suffered from flameout. Normally, this phenomenon would not cause a catastrophe as modern aircraft are manufactured after ensuring that they can run on one engine if necessary. But in this case, the pilot pre-assumed the perfect engine for the defective one and shut it down. Hence, the plane was flying without thrust when the pilots tried to save the people who were on the ground in a very populated city. One of the wings hit a bridge and caused the plane to crash into a nearby river. 

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Risk assessment:

According to National Transportation Safety Board (NTSB) statistics, in the last 20 years, approximately 85 percent of aviation accidents have been caused by “pilot error” in general aviation. Many of these accidents are the result of the tendency to focus flight training on the physical aspects of flying the aircraft by teaching the student pilot enough aeronautical knowledge and skill to pass the written and practical tests. Risk management is ignored, with sometimes fatal results. The certificated flight instructor (CFI) who integrates risk management into flight training teaches aspiring pilots how to be more aware of potential risks in flying, how to clearly identify those risks, and how to manage them successfully.

The risks involved with flying are quite different from those experienced in daily activities. Managing these risks requires a conscious effort and established standards (or a maximum risk threshold). Pilots who practice effective risk management have predetermined personal standards and have formed habit patterns and checklists to incorporate them. The goal is to reduce the general aviation accident rate involving poor risk management. Pilots who make a habit of using risk management tools will find their flights considerably more enjoyable and less stressful for themselves and their passengers. In addition, some aircraft insurance companies reduce insurance rates after a pilot completes a formal risk management course.

Figure below is sample risk assessment matrix a pilot can use to differentiate between low-risk and high-risk flights.

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Is there an accident-prone pilot?

A study in 1951 published by Elizabeth Mechem Fuller and Helen B. Baune of the University of Minnesota determined there were injury-prone children. The study was comprised of two separate groups of second grade students. Fifty-five students were considered accident repeaters and 48 students had no accidents. Both groups were from the same school of 600 and their family demographics were similar.

The accident-free group showed a superior knowledge of safety and were considered industrious and cooperative with others but were not considered physically inclined. The accident-repeater group had better gymnastic skills, were considered aggressive and impulsive, demonstrated rebellious behavior when under stress, were poor losers, and liked to be the center of attention.

Fifty-five years after Fuller-Baune study, Dr. Patrick R. Veillette debated the possibility of an accident prone pilot in his 2006 article “Accident-Prone Pilots,” published in Business and Commercial Aviation.

According to human behavior studies, there is a direct correlation between disdain for rules and aircraft accidents as seen in the figure below:

In an attempt to discover what makes a pilot accident prone, the Federal Aviation Administration (FAA) oversaw an extensive research study on the similarities and dissimilarities of pilots who were accident free and those who were not. The project surveyed over 4,000 pilots, half of whom had “clean” records while the other half had been involved in an accident.

Five traits were discovered in pilots prone to having accidents: 

-1. Disdain toward rules

-2. High correlation between accidents in their flying records and safety violations in their driving records

-3. Frequently falling into the personality category of “thrill and adventure seeking”

-4. Impulsive rather than methodical and disciplined in information gathering and in the speed and selection of actions taken

-5. Disregard for or underutilization of outside sources of information, including copilots, flight attendants, flight service personnel, flight instructors, and air traffic controllers

In contrast, the successful pilot possesses the ability to concentrate, manage workloads, monitor, and perform several simultaneous tasks. Some of the latest psychological screenings used in aviation test applicants for their ability to multitask, measuring both accuracy and the individual’s ability to focus attention on several subjects simultaneously.

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Comparative Analysis of Accident and Non-Accident Pilots, a 2015 study:

The purpose of this study was to investigate potential differences between two pilot groups; the first was a sample of individuals who have not been involved in an accident and the second was a sample of pilots from the National Transportation Safety Board (NTSB) accident database. Factors investigated included flight time, pilot flight review status, pilot certification, employment as a professional pilot, gender, and age.

This study sought to identify potential differences between accident and non-accident pilots as well as associations of various factors on the incidence of accidents. Initial reflection on the survey sample is that it contained a more experienced group (e.g., higher certifications, higher flight time, higher ages) than was found among accident pilots. It is unclear if this is a valid indicator of differences between non-accident and accident pilots, although these findings do align with various previous studies on the subject. It also logical that younger, less experienced pilots may be more inclined to make mistakes or mishandle situations that may lead to an accident. The nature of the relationship between age and experience, in terms of both flight time and certification, also reinforces the findings of this and previous studies, specifically that younger pilots tend to have less experience.

In sum, it appears that pilot experience based on several measures (e.g., age, flight time, certification, currency, and profession) is related to accident occurrence. Increased levels of capability do seem to provide a protective effect. Conversely, with increased experience comes elevated accident exposure risk. These two facts are supported by this study and the findings in previous studies. As is the case in this current study, the factors of age, flight time, and certification are the most positive potential defenses against accident occurrence. One can surmise that maturity, experience, practice, and currency (currently frequently flying) all play a role in why this apparently is true.

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TFH and accidents:

Is there a range of pilot flight hours over which general aviation (GA) pilots are at greatest risk?

More broadly, can we predict accident rates, given a pilot’s total flight hours (TFH)?

Many GA research studies implicitly assume that accident rates are a linear function of TFH when, in fact, that relation appears nonlinear.  

Total flight hours has long been considered one of the risk factors in aviation, and is often used to represent either pilot flight experience or cumulative risk exposure (e.g., Dionne, Gagné & Vanasse, 1992; Guohua, Baker, Grabowski, Qiang, McCarthy & Rebok, 2011; Mills, 2005; Sherman, 1997). TFH has served as both an independent variable in its own right, as well as a statistical covariate, to control for the effects of experience or risk.

Many aviation research studies implicitly assume a straight-line relation between accident rates and TFH. They merely assume that risk decreases as pilots get more experienced. In fact, that relation appears markedly nonlinear. Investigators have often unwittingly assumed a linear relation between TFH and accident frequency and/or rate. However, evidence is emerging that such relations are actually nonlinear. For instance, Bazargan & Guzhva (2007) reported that the logarithmic transform log (TFH) significantly predicted GA fatalities in a logistic regression model. More recently, Knecht & Smith (2012) reported that a risk covariate starting with log (TFH), followed by a gamma transform, significantly predicted GA fatalities in a log-linear model.

In his 2001 book, The Killing Zone, Paul Craig presented early evidence that GA pilot fatalities might relate nonlinearly to TFH. Craig showed that fatalities occur most frequently at a middle range of TFH (≈50-350), and hypothesized that this band of time may be one in which pilots are at greatest risk due to overconfidence at having mastered flying the aircraft, combined with lack of actual experience and skill in dealing with rare, challenging events. He supported this hypothesis with histograms of GA accident frequencies, although not with a formal model. In group after group, a similar pattern emerged in his data, one of a “skewed camel hump” with a long tail at higher TFH. Recent data suggest that the “killing zone” proposed by Craig may be wider than originally believed. Due to the nature of the data, it may be advisable to place the greatest prediction confidence in a middle range of TFH, perhaps from 50-5,000. Fortunately, that is also the range that captures the vast majority of all GA pilots.   

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Pilot’s age and accident:

The effects of aging on cognitive functions and piloting skills have been studied extensively. Research on pilots indicates that age-related declines are largely limited to domain-independent cognitive functions such as memory capacity and psychomotor skills. Domain-dependent cognitive functions that are directly related to flight tasks, such as decision making, tracking, takeoff, and landing, are less sensitive to aging effects. Among the few flight-related tasks that are found to decline with advancing age are abilities to respond to verbal communication and time-sharing efficiency. Older pilots tend to perform worse than younger pilots in executing long and rapidly spoken air traffic control commands and in multitasking under conditions of increased attentional demands.

The findings from flight simulator based experimental studies of older pilots have not been well corroborated by epidemiologic evidence. It is unclear whether the prevalence and characteristics of pilot error differ with pilot age, though it is conceivable that pilots at different stages of cognitive aging may have different error propensity and make different types of error. Pilot error has been identified as a contributing factor in 85% of general aviation crashes and 68% of commercial aviation crashes. However, relatively little is known about age-related variations in pilot error. In a study of commuter and air-taxi pilots, Li et al reported that the prevalence and patterns of pilot error showed little change as pilots aged from the 40s into their 50s. However, that study was limited by its modest sample size (N = 165 crashes) and truncated age range (40–60 years) which may have reduced the likelihood of finding significant age effects. In a recent study of pilot error in air carrier crashes involving Part 121 operations, Li et al. found that the prevalence and patterns of pilot error in air-carrier crashes do not appear to change with pilot age. However, the low prevalence rate of pilot error in air carrier crashes makes it difficult to fully assess age-related variation.

The International Civil Aviation Authority (ICAO) sets the maximum retirement age at 65, which the FAA has adopted. However, some local civil aviation authorities have extended that age to address a shortage of pilots in their markets. Japan’s civil aviation authority raised the mandatory retirement age to 67 in 2015, and the Civil Aviation Administration of China, which currently sets the maximum retirement age at 60, is considering extending that age, too.

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Pilot’s sleep and accident:

Pilots would only normally sleep on long haul flights, although sleep on short haul flights is permitted to avoid the effects of fatigue.

Pilot rest can be separated into two categories; ‘Controlled Rest’ where the pilot sleeps whilst in the cockpit at the controls or ‘Bunk Rest’ where sleep or rest is taken either in the passenger cabin (in a seat reserved for the pilots) or in the dedicated pilot bunks available on long haul aircraft.

This is standard practice throughout the industry as it is proven to improve flight safety by ensuring the flight crew are well rested for the approach and landing. Needless to say, at least one pilot must be awake and at the controls at all times. Controlled or bunk rest is more common on long haul flights that are scheduled to operate overnight.

Some long haul flights require there to be 3 or 4 pilots due to the length of the flight and to allow a suitable sleep/rest opportunity for the pilots. The same two pilots are at the controls for take-off and landing whilst the other pilot(s) will take control for other segments of the flight to given the other pilots an opportunity to sleep. The extra pilots (i.e., the ones not at the controls for take-off and landing) are often referred to as ‘Heavy’ crew.

Most long haul aircraft have bunk beds available for both the Pilots and Cabin Crew. These are generally hidden out of view from passengers. If no bunks are available, commercial passenger seats in business or first class are set aside for the pilots to ensure a good standard of rest can be achieved. Shortly after take-off, the first pilot(s) will head to the bunks to sleep for a set period of time, before rotating with the other pilots. The rest is typically distributed evenly amongst the crew, before all the pilots return to the flight deck approximately 1 hour before landing.

Controlled Rest:

Controlled rest allows one pilot at a time to get up to 45 minutes of sleep during periods of low workload (in the cruise). This is to promote a higher level of alertness levels during periods of high workload, for example the descent, approach and landing. The principle of controlled rest is to allow the pilots to boost alertness and energy. It’s the equivalent of a “power nap”. Ideally controlled rest should be between around 10 – 20 minutes as this limits you to the lighter stages of non-rapid eye movement (NREM) sleep. Sleeps between 30 and 60 minutes can result in sleep inertia when you wake up, which will leave you feeling groggy similar to a hangover.

In 2011, an Air Canada pilot woke up from his mid-flight nap. Dazed from his nap, he confused the planet Venus for another aircraft and, thinking they were going to collide, put the jet into a nosedive. The passengers were thrown from their seats, several of them seriously injured.

A dozing pilot was to blame for a plane crash in 2010 May in southern India which killed 158 people, an official investigation has reportedly found. The Air India Express plane approached Mangalore at the wrong height and angle. The Serbian pilot, Zlatko Glusica, was “disorientated” having been asleep for much of the three-hour flight. The data recorders captured the sound of snoring. Glusica is said to have been affected by “sleep inertia” after his nap. Co-pilot H S Ahluwalia was reportedly heard making repeated warnings to the Serb to abort landing and try again. Seconds before the plane erupted into a fireball, voice recordings picked up the co-pilot saying: “We don’t have runway left.”

In a survey by the British Airline Pilots’ Association, 43% of the 500 participants said they had involuntarily fallen asleep in the cockpit and of those 31% said that they woke to also find the other pilot asleep. (BBC, 2012)

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Pilot fatigue and accident:

Flight operations often take place at night, which can disrupt the circadian rhythms responsible for monitoring sleep and wake cycles.

The International Civil Aviation Organization (ICAO) defines fatigue as “A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload.”  The phenomenon places great risk on the crew and passengers of an airplane because it significantly increases the chance of pilot error.  Fatigue is particularly prevalent among pilots because of “unpredictable work hours, long duty periods, circadian disruption, and insufficient sleep”.  These factors can occur together to produce a combination of sleep deprivation, circadian rhythm effects, and ‘time-on task’ fatigue. Regulators attempt to mitigate fatigue by limiting the number of hours pilots are allowed to fly over varying periods of time.

It has been estimated that 4-7% of civil aviation incidents and accidents can be attributed to fatigued pilots. Symptoms associated with fatigue include slower reaction times, difficulty concentrating on tasks resulting in procedural mistakes, lapses in attention, inability to anticipate events, higher toleration for risk, forgetfulness, and reduced decision-making ability. The magnitude of these effects are correlated to the circadian rhythm and length of time awake. Performance is affected the most, when there is a combination of extended wakefulness and circadian influences.

A Federal Aviation Administration (FAA) study of 55 human-factor aviation accidents from 1978 to 1999 concluded that number accidents increased proportionally to the amount of time the captain had been on duty. The accident proportion relative to exposure proportion rose from 0.79 (1–3 hours on duty) to 5.62 (more than 13 hours on duty). According to the study, 5.62% of human-factors accidents occurred to pilots who had been on duty for 13 or more hours, which make up only 1% of total pilot duty hours.

In-flight strategies:

Cockpit napping:  A forty-minute nap after a long period of wakefulness can be extremely beneficial. As demonstrated in the Rosekind study, pilots who took a forty-minute nap were much more alert during the last 90 minutes of the flight and they also responded better on the psychomotor vigilance test (PVT) showing faster response rates and fewer lapses. The control group who had not taken a nap showed lapses during the approach and landing phases of the flight. In-seat cockpit napping is a risk-management tool for controlling fatigue. The FAA still has not adopted the cockpit napping strategy, however it is being utilized by Airlines such as British Airways, Air Canada, Emirates, Air New Zealand, Qantas.

Activity breaks are another measure found to be most beneficial when a pilot is experiencing partial sleep loss or high levels of fatigue. Bunk sleeping is another effective in-flight strategy. Based on the time zone pilots take-off from, they can determine which times during the flight they will feel inadvertently drowsy. Humans usually feel drowsier mid-morning and then mid-afternoon. In-flight rostering involves assigning the crew to specific tasks at specific times during the flight so that other members of the crew have time for activity breaks and bunk sleep. This allows well-rested crew members to be used during the critical phases of flight.

Accidents and incidents related to pilot fatigue:

American International Airways Flight 808 was a McDonnell Douglas DC-8 that crashed short of the runway at NAS Guantanamo Bay, Cuba on August 18, 1993. This is the first accident in history for which pilot fatigue was cited as the primary cause.

Korean Airlines Flight 801 was a Boeing 747 en route to Antonio Won Pat Airport which crashed into a hill three miles away from the runway. The accident killed 228 out of the 254 people on board, including the flight crew. The captain failed to brief the first officer on the approach procedure and descended below the minimum safe altitude. The captain’s fatigue “…degraded his performance and contributed to his failure to properly execute the approach.”

On American Airlines Flight 1420 fatigue was found to be a contributing factor. Eleven people were killed when the McDonnell Douglas MD-82 crashed in Little Rock, Arkansas in 1999.

Corporate Airlines Flight 5966 crashed short of the runway on approach to Kirksville Regional Airport in 2004 after its fatigued pilots had been on their sixth consecutive day of flight and on duty for 14 hours that day. The NTSB found the accident was caused by the pilots’ failure to follow established safety procedures, while conducting a non-precision approach in IMC and that “…their fatigue likely contributed to their degraded performance.”

Pilots operating Go! Airlines Flight 1002 in October 2008, a thirty-six-minute leg from Honolulu to Hilo, fell asleep and overshot their destination by 30 nautical miles. Subsequently, they woke up and landed the airplane safely. The day the incident occurred was the third consecutive day pilots started duty at 5:40 AM. Colgan Air Flight 3407 crashed in the US in 2009, killing 50 people (all 49 on board and one person on the ground). The NTSB concluded that the flight crew were experiencing fatigue, but was unable to determine how much it degraded their performance.

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ATC error:

Figure above shows airport control tower with a jet taking off in the background.

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Air Traffic Controllers can be termed as the guardians of the sky. They ensure the safe, orderly and expeditious flow of air traffic. With the increase in air traffic, the work of air traffic controller has become very demanding and stressful which can produce errors. Such errors can break the well-woven safety nets, ending in a fatal accident. In general, it is not possible that a single error can cause an accident as there are multiple safety nets or layers that are when all infringed cause a disaster. It can be better understood with Swiss Cheese Model.

Human error has been cited as a major factor in the majority of aviation accidents and incidents (Shappell & Wiegmann, 1996). To date, however, the causal role of aircrew errors has received the bulk of the attention by both air safety investigators and human factors researchers. Nevertheless, there is a growing concern within the aviation community over safety issues that arise outside the cockpit and an increasing number of aviation safety professionals are being called upon to address these issues. One particular area of growing concern is that of air traffic control.

During the early years of aviation, aircrew avoided becoming lost by using simple cockpit instruments and visual landmarks on the ground. However, both military and commercial demands gradually required pilots to fly in poor visibility conditions and at night. The job of air traffic control was subsequently established to help maintain safe separation between aircraft and to ensure that pilots would not fly their planes into the ground or other obstacles (Hopkin, 1995). Still, as the number of aircraft and demands on air-traffic control services has increased over the decades, so too has the number of accidents, incidents, and runway incursions (loss of safe separation among aircraft and other ground vehicles). As with most aviation accidents today, many of these occurrences have not been due to faulty control equipment, but rather to human error, including mistakes made by air traffic controllers (FAA, 2000).

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An air traffic controller monitors the skies:

Durin­g peak air travel times in the United States, there are about 5,000 airplanes in the sky every hour. This translates to approximately 50,000 aircraft operating in skies each day. How do these aircraft keep from colliding with each other? How does air traffic move into and out of an airport or across the country?

The task of ensuring safe operations of commercial and private aircraft falls on air traffic controllers. They must coordinate the movements of thousands of aircraft, keep them at ­safe distances from each other, direct them during takeoff and landing from airports, direct them around bad weather and ensure that traffic flows smoothly with minimal delays.

The movement of aircraft through the various airspace divisions is much like players moving through a “zone” defense that a basketball or football team might use. As an aircraft travels through a given airspace division, it is monitored by the one or more air traffic controllers responsible for that division. The controllers monitor this plane and give instructions to the pilot. As the plane leaves that airspace division and enters another, the air traffic controller passes it off to the controllers responsible for the new airspace division.

Some pilots of small aircraft fly by vision only (visual flight rules, or VFR). These pilots are not required by the FAA to file flight plans and, except for FSS and local towers, are not serviced by the mainstream air traffic control system. Pilots of large commercial flights use instruments to fly (instrument flight rules, or IFR), so they can fly in all sorts of weather. They must file flight plans and are serviced by the mainstream air traffic control system. 

Avionics entails all of an aircraft’s electronic flight control systems: communications gear, navigation system, collision avoidance and meteorological systems. An overarching aerospace and air traffic control system ensures the safety of commercial and private aircraft as they take off, land and traverse vast distances without incident. Through the use of radar, computerized flight plans and steady communication, air traffic controllers ensure planes operate at safe distances from each other and redirect them around bad weather.

Needless to say, global air traffic control is a colossal task. It essentially involves governance of the skies, so we tackle that operation similarly to how we would on the ground: We divide things up. U.S. airspace, for example, breaks down into 21 air route traffic control centers (ARTCCs), each a designated territory that spans whole states and more. Internationally, you’ll also hear these airspaces called area control centers (ACCs). Depending on a country’s size, they may employ one or several ACCs.

If a flight takes a plane across several countries, it passes through various ACCs, each monitored by different air traffic controllers who give instructions to the pilot as needed. If a flight takes a plane into international airspace (the air above international waters), the crew will still depend on the assistance of an ACC, though the ground controllers may have to forgo the use of radar and depend on pilot reports and computer models.

ATC do not control all flights. The majority of VFR (Visual Flight Rules) flights in North America are not required to contact ATC (unless they are passing through a busy terminal area or using a major airport), and in many areas, such as northern Canada and low altitude in northern Scotland, Air traffic control services are not available even for IFR flights at lower altitudes.

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Figure above shows the pivotal role of the air traffic controller in information transfer.  The interfaces shown are those that bear directly on aircraft management in the airspace system.

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According to the Boeing Company, it turned out that of the commercial aircraft accidents for the past 10 years, 55% were caused by pilot error, 17% by aircraft defect, 13% by weather condition, 5% by airport and ATC, 3% by maintenance and 7% by miscellaneous matters. Although ATC accounted for only 5% of commercial aircraft accidents, which is comparatively lower than other factors, it should not be overlooked that the 55% portion for which pilot error accounts, either directly or indirectly involves ATC because the cooperation be- tween a pilot and an air traffic controller composes a significant part of aircraft operation.

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Air Traffic Controller Errors:

Responsible for overseeing nearly every aspect of the flight plans within their airspace, air traffic controllers play a critical role in the safety on and above an airport. With that in mind, any lapse in judgment may have a whole range of devastating consequences for everyone aboard the affected aircraft. Some of the most commonly cited errors air traffic controllers make include:

-1. Routing two flight plans too closely each other

-2. Over capacitating the runway

-3. Misreading the radar

In many instances, air traffic controllers who commit errors are found to be exceedingly tired or under the influence of drugs or alcohol at the time of the incident.

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Structure of ATC Error Elements:

ATC errors are categorized into three categories; communication error, procedure error, and instruction error. The definition of each error category is as follows:

-Communication error refers to errors during radio communication. Communication error in ATC is divided into the two categories of errors that occur between a pilot and an air traffic controller, and the errors that occur between air traffic controllers. For instance, there are errors such as not challenging incorrect readback, using wrong call-signs, using non-standard phraseology, and missing and clipping the call sign. 

-Procedure error involves incompliance with ATC procedures; for instance, failure to respond to an unanswered call, not responding to alarm, not identifying aircraft, failure to terminate radar services, not issuing approach clearance, not giving reasons for vectoring information, failure to deliver information to aircraft, etc. 

-Instruction error occurs while conducting control procedures and communications. Specifically, there are errors such as delivery of incorrect information, issuing descent instruction late, issuing flight phase change instruction late, direction instruction error, clearance instruction error, etc.

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To follow ATC or TCAS? Überlingen Mid-air Collision (2002):

Let’s first understand what TCAS is. Basically TCAS is on-board Traffic Collision Avoidance System that alerts pilots of Aircraft on collision course to take necessary actions to avoid the collision.

That day, DHL Flight 611 was flying from Milano to Brussels while Bashkirian Airlines flight 2937 was flying from Moscow to Barcelona, Spain. At the time of accident, both aircraft were flying in the airspace managed by Skyguide Company’s Air Traffic Controllers. It was a busy day for the concerned controller as he was managing two sectors simultaneously. Because of this he was unable to recognize that two aircraft were on collision course.

When he realized the apparent collision, although too late, he instructed Russian Aircraft flying at Flight level 360 to descent to flight level 350 immediately as DLH was also on the same altitude (flight level 360). This was to be done to ensure to have a minimum specified vertical separation of 1000 feet between two aircraft. By the time Russian aircraft started descend, TCAS came into role and advised it to climb while TCAS advised DLH flight to descent. It was a confusing state for Russian pilots as there was contradiction between ATC instruction and TCAS advisory. Russian aircraft again confirmed from ATC whether to descend or not. ATC once again instructed it to descend considering that DHL aircraft was maintaining flight level 360. As ATC thought that he has sorted out the situation and was handling heavy traffic he did not check whether DHL was maintaining the level 360 or not. Russian crew disregarded TCAS advisory and continued to descent but DLH aircraft that did not get any ATC instruction, followed TCAS advisory and started descend to avoid collision. Now both aircraft were descending and at an altitude of 34890, both aircraft collided.

After this accident, it was adopted by ICAO that in such situations when there is contradiction between ATC and TCAS instructions; TCAS Advisory is to be followed by both aircraft irrespective of ATC instruction.

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Miscommunication between pilots and ATC:

Many incidents and accidents in civil aviation have been attributed to human factors and the most prominent of these factors is miscommunication. Majority of times it is because of the language problem but sometimes it is due to complacency, overconfidence of person and other factors such as poor knowledge of procedures and phraseology etc. It may seem ridiculous, but many aviation injuries occur simply because airline staff members cannot work together. While this includes conflicts between flight crew members, it can also be a disconnect between those in the air and workers on the ground. Pilots receive most of their instructions through auditory communication from air traffic controllers, and these verbal messages can be forgotten, misinterpreted, or even never heard at all. According to one study, communication failures have contributed to the deaths of more than 2,000 people in plane crashes since the mid-1970s. While airlines are responsible for ensuring that their pilots and crews are adequately trained, many have made simple mistakes that can lead to passenger injuries.

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Since this segment examines miscommunication in aviation discourse, an understanding of the term is necessary. To Bremer (1996), a misunderstanding in a conversation refers to any instances during the communication when the listener achieves an interpretation which makes sense to him/her but is not the message intended by the speaker. Mauranen (2006, p. 128) defines misunderstanding simply as “a potential breakdown point in conversation”. She further adds that misunderstanding can occur even without a conversational breakdown. It could be any “communicative turbulence”. According to Simmons (1974), miscommunication in the aviation context refers specifically to any misinterpretation of the instruction by the pilot or controller that is indicated by the absence of readback, or incomplete instruction or readback. Miscommunication is also defined as any indication of a misunderstanding in a conversation due to a misinterpretation or non-understanding of the message. This is indicated by verbal or non-verbal clues (such as inappropriate response, request for repeat, absent, wrong or incomplete readback, hesitation and silence) by the responder.

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“Don’t talk to him too much”, the captain advised the first officer of the air traffic controller.  “He’s trying to get us to admit we made a big mistake coming through here”.

 —cockpit voice recorder transcript, Lockheed 188A Electra crash near Dawson, Texas, 1968. 

(Gero, 1996)

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The collision between the Pan Am and KLM Boeing 747’s at Tenerife in March 1977, which killed 583 people, was a defining event in aviation safety.  While there were many predisposing human factors involved, the accident was a tragic lesson in miscommunications.  KLM pilot Jacob van Zanten was eager to leave. Van Zanten and his crew had almost reached the legal limit of their on-duty time and would have to stay in Tenerife overnight unless they got going soon. This may have contributed to the pilot’s fatal mistake when he received the communication “you are clear” from the air traffic control tower.

A second clearance was required before van Zaten could take off, but instead he began to accelerate down the runway. In the meantime, the Pan Am flight, which was attempting to find its assigned taxiway in the heavy fog, was directly in the KLM airplane’s path. The resulting collision obliterated the Dutch plane, sending it some 100 feet into the air before it came crashing down and exploded in a ball of fire. The Pan Am flight was sliced into pieces and also went up in flames.

The accident demonstrated that, in the aviation industry, “information transmitted by radio communication can be understood in a different way to that intended, as a result of ambiguous terminology and/or the obliteration of key words or phrases” and that “the oral transmission of essential information, via single and vulnerable radio contacts, carries with it great potential dangers” (Job, 1994:180).  Nine months after this accident, the Air Navigation Committee of the International Civil Aviation Organisation (ICAO) took action, issuing three reports and implementing radiotelephony changes in 1984. Yet miscommunication still caused aircraft accidents. In September 1997, confusion between the pilot and air traffic controller is considered the most likely cause of the Garuda A300 Airbus crash at Medan, Sumatra, which claimed 234 lives (Thomas, 1998).  

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English was formally endorsed by The International Civil of Aviation Organization (ICAO), a United Nations agency that regulates the development of international air transport, as the default language of aviation in 1944. This means that English would be used as the language of communication between pilots and ground staff in all countries. Even before its formal endorsement, English was already used quite widely when pilots communicated with aircontrollers internationally, regardless of their nationality and language background (Mitsutomi & O’Brien 2003). In 2008, ICAO further decreed that pilots and controllers have to be proficient in English to improve pilot-controller communication (Krasnicka 2016). English is the preferred language for communication in the aviation industry. Pilots and air traffic controllers of different nationalities and proficiency levels interact with each other using a specialized form of English termed aviation English that comprises of aviation phraseology and “plain English”. Here, miscommunication could have disastrous consequences.

According to Breul (2013), English is most often used as a lingua franca among members of an international cockpit crew whereas a semi-artificial sublanguage based on English serves as the standard means of verbal communication between pilots and air traffic controllers. As English language is widely used within the international aviation industry, therefore there is a variety of Englishes that are spoken and at diverse levels of proficiency (Ragan 1997, Tajima 2004).  Given the lingua franca context in which English is used, it is inevitable that there would be instances of miscommunication in pilot-controller communication. These miscommunications have been found to be due to inadequacy in English proficiency amongst non-native speaker (NNS) pilots and controllers (e.g., Prinzo et al. 2010, Estival & Molesworth 2009, Tajima 2004, Cookson 2009). Nevertheless, studies by researchers such as Trippe and Baese-Berk (2019), Boschen and Jones (2004), Burki-Cohen (1995a & 1995b) and Douglas (2014) have found that even amongst native speakers, pilot-controller communication is challenging.  

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Types of miscommunication:

Ambiguous phrasing.

The recent International Air Transport Association (IATA) Phraseology Study found the use of non-standard and/or ambiguous phraseology by ATC was the biggest communication issue for 2,070 airline pilots surveyed. Ambiguous messages consist of words, phrases or sentences with more than one meaning. Simple misunderstandings can have dire consequences at 25,000 feet. One miscommunication incident involved a flight attendant asking the flight deck to “turn around” because the cabin door was open and needed closing. However, the captain interpreted these two words to mean the plane was in jeopardy and turned the airplane back toward the departure airport.

Language barriers.

The words and inflection used between pilots and flight controllers are critical in communicating potential problems. English speakers in the aviation industry are particularly likely to cause misunderstandings when speaking to non-native English speaking pilots, crew, or air traffic control. For example, a pilot mentioning that the plane is “running low on fuel” without using an international distress signal may be interpreted as a mere concern and not an emergency situation.

Incorrect terminology.

The misuse of standardized phrases and terms can not only cause confusion, but it can also cause fatal injuries. For instance, replacing “inbound” with “outbound,” using “no” instead of “negative” or “yes” instead of “affirmative” can start a chain reaction that leads to runway incursions or near-misses.

Number confusion.

Numbers are particularly vexing, especially homophones (words that sound the same as other words), such as “two” (“to”) and “four” (“for”). Ambiguous usage or interpretation of these four words — cited as the second biggest communication problem identified by pilots in the Phraseology Study — was responsible for a fatal CFIT accident involving a Boeing 747 on final approach to Subang Airport, in Kuala Lumpur, Malaysia, in February 1989. The crew misperceived ATC’s clearance of “descend two four zero” (descend to 2,400 ft) as “to four zero” (descend to 400 ft).

Since numbers can refer to a variety of parameters in flight — headings, altitudes, airspeeds, etc. — even non-homophonic numbers can be confusing. For example, after clearing a Learjet to “climb and maintain 14,000 feet,” the controller issued instructions to “fly heading two zero zero.” The pilot read it back as “two zero zero” then proceeded to climb to 20,000 ft.

Failure to confirm.

Accidents often occur when a pilot incorrectly reads back instructions, and the controller doesn’t hear the error. A controller’s transmission of “two-two-four” may become garbled or have static at either end of the message—and could be heard as “to two-four.” Controllers may also be too busy to acknowledge a pilot’s readback, leaving pilots to misinterpret this silence as confirmation.

Untimely transmissions.

Controllers who fail to catch and correct mistakes early may have to make last-minute adjustments to an altitude or flight path. Unfortunately, vital messages may be relayed too late for pilots to take proper evasive action.

Equipment and technology problems.

While some advances have allowed text transmission between planes and ground crews, radio remains the primary means of communication between air traffic controllers and pilots. Any problems with electrical systems, power sources, microphones, and speakers, or digital communication programs can block effective communication.

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Pilots should practice countermeasures designed to minimize miscommunication errors, some of which are listed below:

-1. Incorporate the highest possible intelligibility in each transmission by enunciating each word clearly and distinctly at a constant volume and in a normal conversational tone, maintaining an even rate of speech not exceeding 100 words per minute (controllers should use a slower rate when a message needs to be written down by flight crews), and pausing slightly before and after numerals to reduce confusion.

-2. Use standard phraseology at all times.

-3. When using numbers, include key words describing what they refer to (e.g., “heading two four zero;” “climb to Flight Level two seven zero;” “maintain one eight zero knots,” etc.).

-4. To avoid call sign confusion, use the aircraft’s full phonetic call sign. Controllers should inform pilots of similar call signs operating on the same frequency.

-5. Employ effective listening strategies to avoid succumbing to expectation bias. Pay attention to conversations between ATC and other aircraft, especially near an airport.

-6. If the pilot monitoring (PM) is handling radio communications with ATC, the pilot flying (PF) should still monitor the PM’s communications.

-7. Read back ATC clearances and instructions in the same sequence as they are given. If a readback is unacknowledged by ATC, ask for confirmation of acceptance. Using “Roger” in lieu of a full readback is unacceptable.

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Miscommunication, culture and plane crash:

Gladwell (2008) cited several cases where plane crashes were a result of poor communication between the pilot and copilot or between the pilots and air traffic control. Copilots may often use what Gladwell referred to as “mitigated speech”, a term borrowed from linguists. Mitigated speech is a form of communication that is watered down to take the edge taken off so as to avoid conflict with another individual. Rather than commanding another person to take an action, a polite request is made in its place which may be interpreted as a request that does not require immediate attention. This could lead to serious consequences in the case of a copilot communicating with the pilot or air traffic control.  

Why is it that some pilots and copilots have had difficulty in communicating between themselves and air traffic control?

Gladwell suggested that it has something to do with culture. Geert Hofstede, a Dutch psychologist, sociologist, and anthropologist, and his colleagues came up with several dimensions of culture which have been used by researchers worldwide (Wu, 2006). These dimensions include power distance, uncertainty avoidance, individualism, and masculinity. If a country ranks high in power distance, the order of inequality and hierarchy is well defined and one’s place in society is known and accepted. In such a society individuals are deferential to their leaders and have a high regard for them. If a country ranks high in individualism, there is a greater emphasis in that society on individual achievement and rewards and less of an emphasis on team decisions and achievements. If a nation ranks high in uncertainty avoidance, society prefers formal rules and structure while change is not readily accepted. If a nation ranks high in masculinity, that society is generally more competitive and assertive in nature. Gladwell noted that in many cases involving plane accidents, the flight crew was from a high power distance country. In such cases, he found that the copilot spoke using culturally-accepted mitigated speech in order to show deference and respect to authority. Herein lays the problem. When faced with a crisis in the cockpit, what is needed is strong and direct communication between the pilot, copilot, and air traffic control. The mitigated language and deference to one’s elders typically found in high power distance societies do not sufficiently convey enough correct information about the urgency of the problem at hand. Many studies have established that there is a strong correlation between culture and plane crashes. Culture remains important even when aviation infrastructure and weather are accounted for in regression models.

Aviation infrastructure represented by per-capita GDP is also important in determining plane accidents.  In all regression models, nations with higher levels of per-capita GDP tended to have fewer plane accidents. The U.S. has by far, the largest number of plane accidents of any country. It also has the most flights giving it a low plane accident rate (4.47 accidents per million flights from 1970 to 2012). The U.S. is also a leader in aviation infrastructure (high per capita GDP) and it ranks the highest in individualism and very low in power distance. By way of contrast, Nigeria has a relatively high plane accident rate (75.6 accidents per million flights from 1970 to 2012).

In addition to improving aviation infrastructure, major airlines have been training pilots and copilots in communication to overcome cultural barriers. Gladwell cites examples of where pilots remind their copilots that the pilots need help in flying a sophisticated aircraft when malfunctions occur. It is only when the entire crew are working together as equals, will the chance of success be greatest. The kinds of errors that cause plane crashes are invariably errors of teamwork and communication. One pilot knows something important and somehow doesn’t tell the other pilot. One pilot does something wrong, and the other pilot doesn’t catch the error. A tricky situation needs to be resolved through a complex series of steps – and somehow the pilots fail to coordinate and miss one of them.

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Miscommunication Disasters:

In the technological world of modern air travel, there’s a certain irony in the fact that the majority of aviation disasters are caused by human error. And one of the most common forms of error is miscommunication. Even if just one person makes a mistake, the repercussions can be catastrophic.

Avianca Flight 52 (1990)

On January 25, 1990, Avianca Flight 52 was carrying 149 passengers from Bogotá, Colombia to New York. However, because of bad weather conditions and air traffic congestion, the Boeing 707 was forced into a holding pattern off the coast near New York. And after circling for nearly an hour and a half, the aircraft was running low on fuel. When Flight 52 arrived at Kennedy Airport, due to the fog and wind, only one runway was open for the 33 planes that were attempting to land every hour. What’s more, the flight was delayed again as the aircraft ahead of them failed to touch down. Flight 52’s fuel situation soon became desperate. Two crucial pieces of miscommunication led to the disaster that was to follow. When the aircraft was passed from regional to local air traffic controllers, the local controllers were not informed that the aircraft had too little fuel to reach its alternative airport. Compounding the problem, crucially the aircraft’s crew did not explicitly declare that there was “fuel emergency” to the local controllers, which would have indicated that the plane was actually in danger of crashing. As a result, after missing its first attempt to land, the airplane was given a landing pattern that it had too little fuel to execute. While the crew attempted to maneuver the plane, its engines flamed out in quick succession. The Boeing 707 slammed into the village of Cove Neck, Long Island, killing 65 of its 149 passengers and eight out of nine of its crew.

Air Florida Flight 90 (1982)

On January 13, 1982, Air Florida Flight 90 was due to travel from Washington National Airport in Virginia to Hollywood International Airport in Fort Lauderdale, FL, with a layover in Tampa.

Conditions were snowy, and the aircraft had been de-iced improperly. Neither did it have its engine anti-icing system activated. This caused instruments to freeze and fail to register the correct readings. So, while the cabin crew thought that they had throttled up sufficiently for takeoff, in actual fact they didn’t have enough power. The Boeing 737’s run-up took almost half a mile (800m) longer than it should have done. Even as they set off down the runway, the first officer noticed that something was wrong with the plane’s instruments and that it wasn’t capable of getting airborne. However, his attempts to communicate this were brushed off by the captain, who ordered the takeoff to continue. The plane crashed into the 14th Street Bridge, killing 78 people, including four motorists. Later, reports showed that there was sufficient space for the aircraft’s takeoff to have been aborted – if only the flight crew had been communicating better.

Linate Airport Disaster (2001)

On October 8, 2001, miscommunication played a role in a major collision at Linate Airport in Milan, Italy. The runway was obscured by thick fog, effectively reducing visibility to around 656 feet (200 meters), which may also have contributed to the tragedy, together with factors such as high traffic volume. A Cessna Citation CJ2 business jet was given clearance to taxi to its takeoff point on a route that would avoid the main runway. However, due partly to poor use of radio communications and lack of proper markings and signs, the Cessna misinterpreted the message and turned in the wrong direction, crossing the main runway. Its route led it into the path of Scandinavian Airlines Flight 686, a McDonnell Douglas MD-87 airliner. The two planes collided, with Flight 686 traveling at about 170 mph (270 kph). The Cessna went up in flames, while the right engine of the MD-87 was destroyed. The pilot of Flight 686, Joakim Gustafsson, managed to get the plane airborne for a brief period. And in an attempt to regain control, he hit the thrust reverser and brakes – noted as a particularly skillful maneuver. Even so, Gustafsson lost control of the plane, and it smashed into a luggage hangar at the end of the runway. In total, 118 people were killed in the disaster.

Dan Air Flight 1008 (1980)

This disaster was caused by a single misheard word. Dan Air Flight 1008 departed from Manchester, England, on the morning of April 25, 1980, en route to Tenerife, one of Spain’s Canary Islands. At 1:21 pm, the plane ploughed into the side of the island’s mount La Esperanza, killing all 146 people on board. The cause of the disaster was a misinterpretation made by the Boeing 727’s flight crew. The plane was instructed by the control tower to take an unpublished, not officially approved, and potentially dangerous holding pattern above Los Rodeos Airport. But the pilot also seems to have mistaken the word “inbound” for “outbound” in the instructions he received, flying in the opposite direction to which he was supposed to. This turn in the wrong direction took the plane through an area of exceptionally high ground. And due to the airport’s lack of ground radar, the air traffic controllers were unable to tell the flight crew that the plane was off course. Heavy clouds obscured the crew’s vision, likely preventing them from seeing the looming threat of the mountain. The first sign they had of any impending danger was when the plane’s ground proximity warning device was triggered. The crew attempted a steep climb, but the aircraft slammed into the mountainside, killing everyone on board instantly.

Charkhi Dadri Mid-Air Collision (1996)

The Charkhi Dadri mid-air collision occurred on November 12, 1996 is the worst mid-air crash in the history of aviation. Kazakhstan Airlines Flight 1907 collided with Saudi Arabian Airlines Flight 763 at an altitude of almost 14,000 feet (4,300 meters), killing all 349 people on board both planes. The cause of the disaster can be traced back to communications difficulties in the Kazakhstani plane. None of the Kazakhstani flight crew, except the radio operator, understood English, so they were completely reliant on him to communicate with air traffic control. The radio operator also lacked his own set of instruments and had to look over the shoulders of the pilots in order to find out information, such as the aircraft’s height. The result of this was that Flight 1907 descended more than 1,000 feet (300 m) below its assigned altitude of 15,000 feet (4,600 meters), while struggling with turbulence inside a bank of cloud. The radio operator noticed the descent and told the crew to bring the aircraft back up, unfortunately placing them square in the path of the Saudi Arabian Boeing 747. The resulting collision destroyed the left wing and stabilizer of Saudi Arabian aircraft, sending it spiraling towards Earth, disintegrating as it fell. Flight 1907, meanwhile, crashed into a field. Four survivors were recovered from the wreckage of the Kazakhstani plane, but all of them died soon afterwards.

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Section-14

Weather and plane crash:  

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A pilot, his wife, and daughter fortunately survived the accident below.

In August of 2005, the pilot had received his private pilot certificate on a Tuesday, and this accident occurred the following Saturday. It was his first cross-country flight, travelling with his family, from Fort Mill, NC, to Myrtle Beach, SC, to enjoy the beach. While en route, he had seen an area of weather along the route and diverted to Lumberton, NC. In Lumberton, he was checking the automated weather terminal at the fixed base operator (FBO) when an instrument rated (IR) pilot and a flight instructor offered assistance. They suggested that he take his family to lunch while the thunderstorms passed, and the trip could likely be completed as planned after lunch. Instead, he elected to depart immediately and return home, attempting to do so before the weather reached the Lumberton airport. As he taxied out for departure, the approaching weather was now visible; however the winds were calm. As he began his takeoff, the storm winds began to impact the runway area. The plane became airborne, and the pilot was in the process of retracting the landing gear when the gusts and downdrafts struck, driving the aircraft into the ground and literally breaking it into pieces. Remarkably, no one was injured. As bystanders arrived on the accident scene to offer assistance, they heard the pilot say, “Why didn’t somebody tell me it could be this bad?”

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Since the beginning of manned flight, low-altitude encounters with atmospheric turbulence and gusts have been among the most challenging safety issues facing aircraft operators, air traffic controllers, and the aerospace engineering community. The prediction, detection, and avoidance of potentially hazardous wind conditions have been a high priority technical target internationally. Major wind-induced accidents caused by the inability of the pilots to maintain aircraft performance and control have historically plagued the entire spectrum of civil aircraft types, including large commercial transports, regional airliners, business jets, and small personal-owner general aviation vehicles.

Commercial pilots are trained to fly in many different weather conditions.  Airplanes often fly in extreme weather, but passengers may not realize how much preparation goes into each flight. Some major airlines have meteorology centers with full-time employees who work to predict the weather. The FAA also helps pilots and airports determine if conditions are safe. Airlines will cancel flights if the weather makes for truly dangerous flight conditions. In most major airlines, pilots have thousands of hours of flying experience and training for flying in a variety of weather conditions, including snow and thunderstorms.

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The weather has always been an important factor in aviation safety since the dawn of the air transport industry. To mitigate the safety risks associated with weather hazards in the different phases of flight, state‐of‐the‐art aircraft incorporate a variety of systems and sensors, including de‐icing systems and weather radars. These airborne systems, in combination with other systems (e.g., global navigation satellite systems, instrument landing systems) and services (e.g., the provision of frequently updated, accurate weather forecasts), have allowed a significant and continued reduction in the ratio of accidents and incidents per number of aircraft operations. Thanks to this, according to the International Civil Aviation Organization (ICAO) (2009), aviation has become the first ultra‐safe system in transport history.

Despite all the safety improvements, the weather is still today a major cause of aviation accidents and incidents. Namely, according to statistics from the US Federal Aviation Administration (FAA), the weather was the primary cause of 23% of all aviation accidents in the United States in 2012. In addition, the weather has been responsible for an increasing percentage of flight delays over the last decades, up to, for instance, approximately 70% of the delays in the US National Airspace System (NAS) in 2012. Moreover, the total economic impact of the weather in 2013 was estimated in US$3 billion, including the costs of property damage, injuries to people, delays and associated increases in aircraft operating costs (FAA, 2013).

Low visibility is the main contributing factor to weather‐caused accidents in all flight phases except cruise and descent, where it is the second major factor after turbulence. Rain is the second major contributing factor in the take‐off, approach and landing phases. In the take‐off phase, rain (storms) causes 3% of the weather‐caused accidents, while in the landing phase it causes 6%. This suggests that more often take‐off is conveniently delayed due to rain and/or storms, thus preventing the aircraft from being exposed to a high level of risk, while conversely landing under rain and/or storms is unfortunately attempted more than it should due to, for example, low fuel level.

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Effect of weather on aircraft flight:

Weather is one of the major cause and explicit factor of aviation accidents and incidents. Aviation is highly weather dependent. Weather factor contribute to accident to occur and enhance the probability and effects of other factors such as heavy weather and poor visibility may increase the possibility of pilot errors and collision with terrain or with other aircraft. Weather-induced rough flights, capable of causing serious discomfort and even injury are a matter of common experience by many passengers (Mahapatra and Zrnic, 1991). In unsuitable weather conditions it is very difficult for a pilot to take decision. Weather phenomenon may also increase the delay of flight.

There are various significant atmospheric factors that have serious air disasters as well as frequent flight schedule disruptions. The major atmospheric hazards are thunderstorms, lightning, hail, icing, wind shear, heavy precipitation, heavy rain, low cloud etc. The cause of large number of accident and incident is thunderstorm. Thunderstorms are dynamic phenomena with well-defined life cycles that are initiated in environments where a deep unstable atmospheric layer exists from the ground upward (Battan, 1961; Magono, 1980). Hail is more hazardous for aircraft engines and structures because it is solid nature and high-water content and in extreme case it cause engine to flame out (Guégan et.al, 2011). Kulesa stated that icing is very dangerous during flight because structural icing on wings and control surfaces increases aircraft weight, degrades lift, generates false instrument readings, and compromises control of the aircraft. The presence of ice and snow on the runway reduces the available tire– pavement friction needed for retardation and directional control of aircraft (Pasteet.al, Impact of Environmental Factors on Aviation Safety 2012). Rain causes visibility problems and one of the major problems of heavy rain is the combustion of aircraft engines. Wind shear defined as spatial as well as temporal rates of variation of wind speed and/or direction. Wind shear causes rough flights, problem in controlling the aircraft sometimes irrecoverable loss of control lead to an accident.

It is very difficult and costly for an aircraft to operate on plateaus which have low pressure, complex climate and rough topography (Shanhua and Xueqing, 2007). Weather change in mountains is very quickly. Flight conditions in mountains will be better in the morning and in afternoon more cloud can build-up and stronger winds. It is very important for pilot to understand the major airflow patterns while flying at mountainous areas. During pre-flight planning charts should be carefully read by the pilot to know the steepness of glaciers and mountainsides. The accident of aircraft also involve due to collision with terrain i.e. hills or mountains. For the prevention of CFIT (controlled flight into terrain) accidents crew position awareness and monitoring of navigational systems are very essential. 

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Turbulence:

Everyone has a story about hitting a rough patch of air, those hair-raising moments when suddenly more than the plane is flying. Bellies drop, drinks slop, and people caught in the aisle lurch against seats. In rare cases, it can even mean more than bumps or bruises. In air travel, turbulence is a certainty and a major source of flight anxiety for flyers of all stripes.

The definition of turbulence is fairly straightforward: chaotic and capricious eddies of air, disturbed from a calmer state by various forces. Rough air happens everywhere, from ground level to far above cruising altitude. But the most common turbulence experienced by flyers has three common causes: mountains, jet streams, and storms. Though weather forecasts and pilot reports are helpful for avoiding bumpy zones, they are relatively blunt tools. Weather models can’t predict turbulence at airplane-sized scales, and pilots frequently misreport turbulent locations by many dozens of miles.

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Turbulence comes in various forms, and various degrees of intensity;

-1. Light – Still able to walk around, but can feel slight movement. Seatbelt signs may not be switched on in this case.

-2. Moderate – Harder to walk around. Seatbelt signs will usually be switched on. Flight Attendants will normally continue with their work.

-3. Severe – Flight Attendants will be instructed to put their seatbelts on.

Clear-Air Turbulence (CAT):

When you are cruising at 38,000ft with not a cloud in sight, and it starts to get bumpy, you are experiencing Clear Air Turbulence. This form of turbulence is often found in mountainous areas and near jet streams.

Convective Turbulence:

Convective turbulence is sometimes encountered in warm climates, during sunlight. Air is warmed by the sun and rises as a result, before cooling and falling. This process continues on a constant basis, so air is rising and falling continuously. When we fly through this it can cause turbulence as the air is moving in different directions.

What is the best thing to do during turbulence?

Do as pilots do – always wear your seat belt. Whenever you return from the toilet and sit back in your seat, strap in. Turbulence injuries are often caused because people aren’t wearing their belt.

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Lightning:

Standard commercial airplanes are designed to take lightning strikes. When lightning hits an aircraft, it arcs through the fuselage, from the wings and nose, and exits through the tail. All wires onboard are grounded or isolated away from the body, and the electric current passes through the conductive outer shell of the aircraft. The only thing you should hear is a boom and perhaps a light shake. The rule of thumb is the smaller the aircraft, the less likely it is to be hit by a rogue bolt. The bigger aircraft, conversely, are so big that they can shrug off just about anything.

Sometimes, while flying at night you will see lightning, but just remember that the light passes through the cloud, which makes it look much closer than it is. The majority of lightning strikes that occur are during the early and latter stages of flight. In fact, an aircraft can sometimes cause lightning by flying close to an electrically charged cloud. The aircraft simply acts as a huge, floating, lightning conductor.

Back in 1967, an aircraft exploded after being hit by lightning on the fuel tank. Wires allowed electricity to arc and ignite the fuel vapors, causing the fuel to explode. Because of this disaster, plane manufacturers have taken great care to ensure that their aircraft can easily shrug off a lightning blow. Everything from flight computers to fuel lines to even the entertainment screens are isolated and protected from lightning.

Lightning never affects passengers onboard (or other critical components) is due to the fact that the current passes through the body of the aircraft. However, with more aircraft using a composite structure to save weight (such as the 777x and A350), it means that the overall conductivity is now lower than before. As such, the electric current might choose to flow through something else… like airline fuel. As a workaround, aerospace manufacturers are deliberately laying conductive wires in the fuselage which are not connected to anything, but are attractive for electrical current to pass through. Additionally, airline fuel has been better engineered to be less flammable and not spark under stormy conditions (even if the sparks can get through thick insulation that covers every inch of a jet’s fuel system).

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Thunderstorms and Cumulonimbus:

Thunderstorm, a violent short-lived weather disturbance that is almost always associated with lightning, thunder, dense clouds, heavy rain or hail, and strong gusty winds. Thunderstorms arise when layers of warm, moist air rise in a large, swift updraft to cooler regions of the atmosphere. Cumulonimbus clouds are a type of cumulus cloud associated with thunder storms and heavy precipitation.

Thunderstorms produce the most severe weather you can find in aviation. And you don’t need to be in a thunderstorm to be in trouble. Thunderstorms can launch hail out of themselves up to 20 miles away. Strong downdrafts and microbursts can form underneath them. And severe turbulence is always a possibility near convective clouds. Storms (including lightning and heavy winds) have a rather testimonial impact in the take‐off and cruise phases: only 3 and 0.5% of the weather‐caused accidents are attributed to storms in these phases respectively. On the other hand, the percentage of weather‐caused accidents associated with storms is roughly uniform for the other flight phases (between 5 and 7%). An explanation might be that severe storms are often associated with cumulonimbus, which can be found practically in any layer of the troposphere, and consequently aircraft are exposed to this hazard in all flight phases. In general, the contributions of storms to weather‐caused accidents are low, probably because storms are reported by weather forecasting services and other affected aircraft, and can be detected by airborne weather radars. Thus, aircraft can often dodge storms. Another reason is that aircraft respond generally very well to lightning impacts, which most of the time do not cause high‐severity damage on the airframe or the avionics. The particularly low contribution of storms to weather‐caused accidents in the landing phase is likely thanks to the fact that aircraft are diverted to alternative airports if a severe storm is affecting the destination airport. The even lower impact of storms in the take‐off phase is probably because flight departure is often conveniently delayed if a potentially dangerous storm is affecting the aerodrome of origin.

Numerous accidents have occurred in the vicinity of thunderstorms. It is often said that the turbulence can be extreme enough inside a cumulonimbus to tear an aircraft into pieces. However, this kind of accident is relatively rare. Moreover, the turbulence under a thunderstorm can be non-existent and is usually no more than moderate. Most thunderstorm-related crashes occur due to a stall close to the ground when the pilot gets caught by surprise by a thunderstorm-induced wind shift. Moreover, aircraft damage caused by thunderstorms is rarely in the form of structural failure due to turbulence but is typically less severe and the consequence of secondary effects of thunderstorms (e.g., denting by hail or paint removal by high-speed flight in torrential rain).

Thus, cumulonimbus are known to be extremely dangerous to air traffic, and it is recommended to avoid them as much as possible. Cumulonimbus can be extremely insidious, and an inattentive pilot can end up in a very dangerous situation while flying in apparently very calm air.

While there is a gradation with respect to thunderstorm severity, there is little quantitative difference between a significant shower generated by a cumulus congestus and a small thunderstorm with a few thunderclaps associated with a small cumulonimbus. For this reason, a glider pilot could exploit the rising air under a thunderstorm without recognising the situation – thinking instead that the rising air was due to a more benign variety of cumulus. However, forecasting thunderstorm severity is an inexact science; in numerous occasions, pilots got trapped by underestimating the severity of a thunderstorm that suddenly strengthened. 

General hazards to aircraft:

Even large airliners avoid crossing the path of a cumulonimbus. Two dangerous effects of cumulonimbus have been put forward to explain the crash of flight AF447 that sank into the sea on 31 May 2009 about 600 kilometers (370 mi) northeast of Brazil. It encountered a mesoscale convective system in the intertropical convergence zone (known by sailors as the “doldrums”), where cumulonimbus rise to more than 15 kilometers (49,000 ft) in altitude. However, the aircraft did not disintegrate in flight. A different hypothesis was put forward and later confirmed: accumulation of ice on the aircraft’s pitot tubes. The inconsistency between the airspeeds measured by the different sensors is one of the causes of the accident according to the final report.

The US FAA recommends that aircraft (including gliders) stay at least 20 nautical miles away from a severe thunderstorm, while a glider pilot could be tempted to use the updraughts below and inside the cloud. There are two sorts of danger for this type of aircraft. One is related to the shear effects between updraughts and downdraughts inside the cloud – effects that can smash the glider. This shear creates a Kelvin-Helmholtz instability that can generate extremely violent sub-vortices. The second danger is more insidious: the strong updraughts below a supercell cumulonimbus can cover a large area and contain little or no turbulence as explained below. In this case, the glider can be sucked into the cloud, where the pilot can quickly lose visual reference to the ground, causing conditions to quickly become IMC. In these conditions, the aircraft (if not equipped for IMC flight and flown by a pilot experienced in IMC flight) is likely to enter a graveyard spiral and eventually break up by exceeding the wing load limit. In this situation, the cause of the disintegration of the aircraft is not atmospheric turbulence but is the inability of the pilot to control the aircraft following the loss of visual reference to the ground. In the case of an instrument flight, cumulonimbus can catch a pilot by surprise when embedded in a more benign cloud mass. For example, nimbostratus can originate from the spreading of a cumulonimbus (nimbostratus cumulonimbogenitus), making the presence of active convective cells likely. Small private airplanes are generally not equipped with on-board weather radars; and during an IFR approach, they can be sent accidentally by air traffic control to non-obvious active cells.

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Rain:

It appears that the main concern with regards to flying in rain is the take-off and landing on a wet runway. It may look as though the runway is as flat as your average road, and therefore susceptible to surface water. As this possibility enters your mind, you find yourself instantly thinking the runway is slippery and unsafe. Thoughts of aquaplaning aircraft and impending doom fill your mind. What you can’t see is that runways are designed to ensure surface water drains off via a grooved surface, therefore improving grip during take-off and landing. Further to this, constant improvements in runway design ensure safety standards are increased year by year.

In poor weather conditions (rain, snow and/or ice) Air Traffic Control receives information from pilots regarding the braking action on the runway. Normally the runway is ‘split’ into three parts, and a pilot would report braking action for each individual part – i.e., poor, average, poor.

This information is then passed on to pilots on final approach to the runway to enable them to be better prepared for poor conditions. It’s important to note that a ‘poor, poor, poor’ braking action report does not mean the runway is unsafe, but simply ensures pilots are prepared. This may simply mean that reverse thrust is used to aid braking and slow the aircraft down quicker.

Another important note: Just as always, if at any time the runway is deemed to be unsafe it WILL NOT BE USED.

With regards to flying through rain clouds, it is not a problem. In normal circumstances these clouds are not turbulent and feel no different to flying through a standard cloud. In more severe storms the clouds may cause a few bumps, but are by no means anything to worry about.

Finally, in case you were not aware, planes are equipped with wipers allowing pilots to still see where they are going. However, due to the speed at take-off, rain usually moves off the windscreen of its own accord, just like driving a car at 100mph forces the water to move upwards and to the side.

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The wings and engines of today’s aircraft work together to produce “lift,” which moves the plane upward off the ground by changing the direction and pressure of the air. In general, rain does not impede this process. This is true both when it comes to take-off, as well as when a plane is at cruising altitude (usually around 35,000 feet), since the majority of rain occurs at lowers levels of the atmosphere. This is why skies outside an airplane are typically clean, even if the weather on the ground is rainy or overcast.

Technically speaking, lift can occur irrespective of how heavy rain is. Within this paradigm, two main issues come up: Visibility and auxiliary weather conditions.

If rain is too heavy, the pilot’s visibility can be impaired, which can make it unsafe to take off, thereby preventing his or her aircraft from flying. In rare circumstances, heavy rain can also cause a plane’s engine’s to “flameout,” though pilots can usually re-ignite them.

Rain that falls at high altitudes (where temperatures are much colder than at ground level) can in extremely rare instances freeze on a plane’s wings. This presents the remote possibility of a stall, a reduction in lift that can cause the plane to fall from the sky if pilots are not able to regain lift. Thankfully, they almost always are!

Likewise heavy winds, lightning and other adverse conditions often accompany heavy rain, and these are often enough to prevent a plane from flying. If temperatures are below freezing, on the other hand, rain can freeze when it hits the ground, which can create slick runway conditions that are unsuitable for take-off. Freezing rain can also adhere to the aircraft itself, which requires de-icing before flight in this case.

Rain can affect an aircraft’s ability to land much in the same way it affects its ability to take-off. Namely, that if rain on the ground is too heavy, the pilot cannot see well enough to land the aircraft; or accompanying weather conditions can make an unsafe landing impossible.

Historical Air Accidents caused by Rain:

Although weather accounts for up to a quarter of air accidents worldwide, rain alone has almost never brought an airplane down. One notable exception was Garuda Indonesia flight 421, which suffered a flameout over the island of Java in 2002. Pilots couldn’t restart the engines and had to land the plane in a river, which was successful, though one flight attendant died due to aircraft damage.

Several notable air incidents have occurred due to stalling, which as noted can sometimes happen as a result of frozen rain on an aircraft wing. However, other conditions besides rain contributed to the crashes of flights such as Air France 447 in 2009 and Air Asia 8501 in 2014, to name just a couple of relatively recent examples.

In a nutshell

-Heavy rain can impair pilot visibility

-Other weather (winds, lightning, etc.) can accompany heavy rain

 – “Flameouts” can occur, require pilots to re-ignite engines

 -High-altitude rain can freeze and cause a plane to “stall”

 -Freezing rain at ground level can present additional dangers

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Low visibility (caused by fog, heavy rain or snowfall) is a major factor in weather‐caused accidents, especially in those flight phases for which the terrain is much closer to the aircraft, or the aircraft flies in more congested air spaces such as the vicinity of aerodromes. In particular, low visibility is majorly responsible for around 67, 53, 52, 21 and 46% of the weather‐caused accidents in the take‐off, climb, approach, descent and landing phases respectively. Rain is also more likely to affect aircraft flying at low levels of the troposphere. In particular, it is the second major cause of weather‐caused accidents in the landing phase, with around 34%, while for the take‐off, climb, approach and descent phases the influence drops to around 16, 12, 17, 11 and 5% respectively. As regards weather‐caused accidents in the cruise phase, the influence of rain is minimal (only around 3%).

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Fog:

Fog conditions often reduce aircraft arrival/departure flow rates and can become dense enough to close an airfield. Flying in fog is quite challenging, even for the most experienced of pilots. For pilots that are not as skilled, fog is an extremely dangerous and potentially deadly hazard. The biggest problem that fog poses is lack of visibility. This is generally not a problem in modern times due to the advancement of autopilot and GPS technology, pilots are able to fly effortlessly through the clouds without being able to see where they are going. This however does not mean that they land the plane completely blind. Pilots are required to attain what is called an Instrument Flight Rules rating (IFR). This gives the pilots the training and skills necessary to safely fly a plane in IMC (instrument meteorological conditions).

While in IMC conditions, your eyes and your mind can play tricks on you. While you may feel like you are banking one direction, you may actually be flying completely level or climbing/descending in another direction. This is why pilots must train to fly solely off of their instruments, since they cannot trust their “seat of the pants” sensations. These instruments and autopilot systems can fly an aircraft from right after take off all the way to just before touchdown, when the pilots are required to take over controls and land the airplane safely.

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Icing:

For years, airframe icing has been recognized as a significant aviation hazard. Icing encounters can lead to increased aerodynamic drag and weight, along with a reduction in lift and thrust. Together, these factors result in a higher stall speed and degradation in overall aircraft performance. To maintain altitude and counter the effects of drag during flight in icing conditions, the angle of attack is generally increased and power is applied to the engine(s). This can further expose unprotected regions of the aircraft to ice accretions. If exposure is prolonged, the aircraft will lose the ability to continue stable flight. 

Of equal importance is ice that accumulates on aircraft surfaces prior to takeoff. One of the first jet air transport category accidents linked to airframe icing occurred on December 27, 1968. A Douglas DC-9, operated by Ozark Air Lines, Inc., crashed shortly after takeoff. In this case, the aircraft suffered substantial performance penalties when it was subjected to freezing drizzle before takeoff.

Considerable progress has been made in understanding the meteorological conditions associated with airframe icing (Sand et al. 1984; Cober et al. 1995; Bernstein and McDonough 2000; Politovich and Bernstein 2001). A substantial amount of interest and research into icing, with attention to supercooled large droplets (SLD), was generated when an ATR-72 was destroyed after it experienced an uncommanded departure from controlled flight and crashed near Roselawn, Indiana (1994).  A ridge of ice that accreted behind the deice boots contributed to an unanticipated aileron hinge moment reversal and an abrupt loss of control. The accident raised awareness about the hazards of operating in SLD conditions, which are not accounted for in 14 Code of Federal Regulations (CFR) Part 25, Appendix C.  Because supercooled large droplets can run back and freeze on surfaces behind an airplane’s deicing boots, it is extremely hazardous.

In recent years, icing research has translated into applied technologies aimed at diagnosing and forecasting icing hazards for both ground and in-flight aviation operations (McDonough and Bernstein 1999; Rasmussen et al. 2001; McDonough et al. 2004). Continued development and improvement of such technologies, along with training initiatives, will aid in reducing the number of icing related accidents.

Although airframe icing accidents only accounted for a small percentage of the total aviation accidents, they resulted in 583 accidents and more than 800 fatalities during the 19-year period from 1982 to 2000. Most accidents took place when the aircraft was in the cruise portion of flight. Takeoff accidents also accounted for a large fraction of icing related accidents. These findings suggest that flight crews need to be more vigilant about ensuring airplanes are free of ice prior to departure. Even small amounts of frost on a wing can reduce its ability to generate lift.  Every effort should also be made to monitor the aircraft for signs of icing while in flight.  Pilots should have an understanding of how ice accretions will impact their aircraft’s performance, keeping in mind that different aircraft will perform differently in identical icing conditions. Airframe icing continues to be a serious aviation hazard, but following certain precautions and procedures can considerably reduce the probability of having an icing related mishap. Pilots should develop a comprehensive understanding of icing (type, environments, signs, etc.) and the impacts it can have on the performance of their aircraft. They should obtain current information regarding icing location, type, and severity along their route of flight just before departure, always make certain that frost/ice is removed prior to takeoff, and have an exit strategy in place in the event an unexpected icing encounter does occur.

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Wind shear and microburst:

In the 1970s and 1980s, an alarming number of fatal accidents in the United States and abroad were attributed to the phenomenon known as wind shear, defined as any rapid change in wind direction or velocity. Severe wind shear is a rapid change in wind direction or velocity and causes horizontal velocity changes of at least 15 m/sec over distances of 1 to 4 km, or vertical speed changes greater than 500 ft/min. About 540 fatalities and numerous injuries resulted from wind-shear crashes involving 27 civil aircraft between 1964 and 1994. Wind shear also caused numerous near accidents in which the aircraft recovered just before ground contact.

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Fujita, who developed the tornado severity scale that bears his name, had conducted extensive studies on airline crashes. A key causal factor in his analysis was the generation and effects of a rapidly descending vertical column of air formed when air at high altitudes quickly cools due to the evaporation of ice, rain, or snow. Fujita submitted that a concentrated, strong three-dimensional outflow associated with the ground impact of the downdraft was the real fatal hazard in aircraft encounters. Although not totally technically correct in details, a layman’s interpretation of this physical phenomenon is the flow from a water-hose nozzle directed straight at a driveway, producing a spray of water in all directions. In this simplified model, the impact pressure field causes the downflow component to decelerate as air approaches the surface, and the horizontal component of the wind to accelerate outward from the impact center. But Fujita’s theory of a critical vertical “downdraft” in the mid-1970s was highly controversial at the time. Subsequently, photographic evidence of the phenomenon was obtained, and Fujita coined the name “microburst” for it. Fujita defined a microburst as a relatively small downburst whose outward, damaging winds extend no more than 4 km (2.2 nmi) over the surface. Radar meteorologists have redefined a microburst as a divergent low-level wind field with a velocity change of at least 15 knots over a distance between 1 and 4 km. The microburst exhibits severe, low-altitude wind-shear gradients that are experienced by a landing aircraft as rapid changes in the relative wind vector, sometimes to an extent that the performance capabilities of the airplane are exceeded, which results in ground impact. Roughly half of microbursts, as defined by radar meteorologists, are truly hazardous to aircraft.

Another characteristic feature of the microburst is air circulation in the form of a vortex ring surrounding the downdraft core. This vortex ring contains strong outflow winds that contribute to the larger hazards caused by horizontal shears and vertical winds over scales between 1 and 4 km. Most microbursts last for a few minutes, and generally less than 10 min. Microbursts can occur anywhere convective weather conditions (thunderstorms, rain showers, or virga) occur. Virga is rain that evaporates before it reaches the ground and is associated with a “dry” microburst. The terms “microburst” and “wind shear” are often used interchangeably because the vast majority of dangerous wind shears result from microbursts.

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An aircraft flying through a microburst may experience extremely hazardous airspeed fluctuations. As the aircraft enters the edge of the downburst outdraft, it initially encounters an increased head wind. This head wind increases the lift of the aircraft and, therefore, the altitude of the aircraft. If the pilots are unaware that this speed increase is caused by wind shear, they are likely to react to correct the aircraft approach angle by reducing engine power. The aircraft then passes into the vertically descending microburst core, where it encounters an abrupt change from head winds to downflow winds, which results in a loss of lift and altitude. Immediately thereafter, the aircraft crosses into a region of tail winds. This wind change reduces the relative airspeed of the aircraft and further decreases lift, which causes the aircraft to lose more altitude. Because the aircraft is now flying on reduced power, it is vulnerable to sudden losses of airspeed and altitude. The pilots may be able to escape the microburst by adding power to the engines, but if the engine response time is not rapid or if the shear is strong enough, the aircraft may crash.

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Obviously, technology that permits the detection and avoidance of severe wind-shear conditions is a key element in the national air transportation system. Working with industry, academia, and the FAA, researchers provided key concepts and the validation of advanced airborne detection systems that have been implemented by airlines in the 1990s. As a result of these breakthrough efforts, wind-shear accidents have been virtually eliminated for large commercial transports.

Comparison of different accident causes for the periods 1960–1999 (left) and 2000–2015:

The figure above compares the share of fatal and hull loss accidents resulting from environmental hazards for the periods 1960–1999 and 2000–2015. To compensate for the different length of the compared periods, the shares and not absolute numbers of accidents are provided. Over the last few decades, technological improvements and additional safety equipment have been introduced to reduce the number of windshear and turbulence related accidents. The effect of these measures, especially on turbulence-related accidents, is visible in figure above. On the other hand, the shares of serious accidents due to bird strike, lightning strike and thunderstorm increased.

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Wind shear refers to the variation of wind over either horizontal or vertical distances. Airplane pilots generally regard significant wind shear to be a horizontal change in airspeed of 30 knots (15 m/s) for light aircraft, and near 45 knots (23 m/s) for airliners at flight altitude. Vertical speed changes greater than 4.9 knots (2.5 m/s) also qualify as significant wind shear for aircraft. Low-level wind shear can affect aircraft airspeed during takeoff and landing in disastrous ways, and airliner pilots are trained to avoid all microburst wind shear (headwind loss in excess of 30 knots [15 m/s]). The rationale for this additional caution includes: 

-1. microburst intensity can double in a minute or less,

-2. the winds can shift to excessive crosswinds,

-3. 40–50 knots (21–26 m/s) is the threshold for survivability at some stages of low-altitude operations, and

-4. several of the historical wind shear accidents involved 35–45 knots (18–23 m/s) microbursts.

Wind shear is also a key factor in the creation of severe thunderstorms. The additional hazard of turbulence is often associated with wind shear.

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Wake Turbulence:

Every aircraft produces some amount of wake turbulence. Remember the saying “heavy, clean, and slow.” That’s where the strongest wingtip vortices form. If you’re taking off behind a larger aircraft, wait at least 3 minutes for the vortices to dissipate. And if you’re landing behind a larger aircraft, fly a higher glide path, and land beyond their touchdown point to avoid flying through their vortices.

IMC:

Inadvertent flight into IMC is one of the deadliest mistakes you can make in general aviation. According to the Nall Report, VFR flight into IMC accounts for over 25% of all fatalities in GA flying. If the weather starts deteriorating on your flight, start looking for diversion airports, and don’t delay your decision to divert. If weather conditions start falling apart quickly, consider a 180 degree turn, and fly back to better weather.

It can take up to 60 seconds for experienced IFR pilots to orient themselves in the clouds. If you’re a VFR pilot, or you’re an instrument rated pilot that isn’t proficient, you may be getting yourself into something you can’t handle (not to mention, it’s not legal).

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Plane crashes due to weather:

199 fatalities: TAM Airlines Flight #3054 in Sao Paulo, Brazil on July 17, 2007

TAM Airlines (a Brazilian carrier) was making a domestic flight from Porto Alegre, Brazil to Sao Paulo when it hydroplaned upon landing and overshot the runway plowing into a warehouse and gas station. The wet runway was determined to be the cause of the accident since mechanical or pilot error were discounted during the post-crash investigation. There were no survivors on the plane and 12 on the ground were killed.

176 fatalities: Chartered aircraft landing in Kano, Nigeria on January 22, 1973

This Boeing 707 was on a chartered flight (Jordanian owned) carrying Muslim pilgrims from Jeddah, Saudi Arabia to Lagos, Nigeria when it was diverted by bad weather to Kano. High winds at the Kano Airport reportedly caused the airliner to skid off the runway while landing. There were 26 survivors. At the time it was the deadliest aviation accident on record.

171 fatalities: Cubano de Aviacion Flight #9646 near Havana, Cuba on September 3, 1989

This Russian-built Ilyushin 11-62M was taking off from Jose Marti Airport in Havana on its way to Cologne Bonn Airport, Germany in heavy rain and high winds gusting to 50 mph (80 km/h) when, at an altitude of just 175 feet a downburst forced it to the ground. It struck a navigation facility before careening into a residential neighborhood. There were no survivors on the aircraft (126 crew and passengers) and 45 residents of the neighborhood died. It remains Cuba’s worst aviation accident on record.

United Nations Bombardier Crj-100 (2011)

Georgian Airways Canadair Regional Jet (CRJ 100 ER), crashed during Go Around at Kinshasa Airport. At the time when the aircraft landed, the airport was experiencing an intense thunderstorm. The aircraft had touched the ground about 170 meters (560 ft) to the left of the desired orientation. At the time of impact, aircraft was heading at 220 degrees and its speed was 330 km/h. After the intense impact, the aircraft had started breaking up and also skid along the ground. It eventually rolled over before it halted. The consequence of the catastrophe was that whole aircraft had disintegrated completely and all parts sheared off. A total of 32 people died and a Congolese journalist was the only survivor. 

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Weather related queries:

-1. What happens when en route flights encounter thunderstorms?

Jet aircraft can safely fly over thunderstorms only if their flight altitude is well above the turbulent cloud tops. The most intense and turbulent storms are often the tallest storms, so en route flights always seek to go around them. If a busy jet route becomes blocked by intense thunderstorms, traffic will reroute into the neighboring airspace, which can become overcrowded if the flow is not managed.  

-2. What happens if thunderstorms prevent landing at an airport?

As the arriving aircraft approaches its destination airport, the pilot will usually be asked to slow down or enter a holding pattern until the thunderstorms in and around the airport have cleared. As more planes arrive and holding continues, over-crowded airspace and running out of fuel can become serious issues. Landing these arrivals safely becomes the top priority. Controllers can opt to use more of the available terminal routes for arrivals and fewer for departures. With fewer planes departing, remain occupied and airport grid lock can occur.

If thunderstorms persist, holding aircraft will divert to alternate airports, wait out the bad weather, refuel, and fly again later to the original destination. Diversions are undesirable because of the magnitude of passenger delay and cost to the airlines. Once the storms began to dissipate and move away, regular flow of traffic resumed.

-3. How far in advance do traffic flow planners need weather predictions?

Unforeseen weather impacts on en route and terminal airspace can lead to long delays and ultimately be costly to the airlines and traveling public. If weather impacts are either short-lived or local, they can be mitigated by effectively using available airspace. All airborne and scheduled flights can be handled with only minor reroutes.

However, as the weather impacts become longer lived, affect larger regions of the country, or both, management of the demand must be planned strategically. In weather events requiring moderate to aggressive management, many scheduled flights will require new flight plans that do not intersect the weather impacted areas. Some flights through the impacted airspace may originate at nearby airports, with only short intervals from departure to arrival, whereas other flights may cross the country and be airborne for hours. A severe long-lived weather impact will require management of short- and long-haul flights in order to effectively control the demand.

-4. Why don’t aircraft fly through storms?

All commercial airline planes are designed to fly through storms and have to comply with safety regulations. A rainstorm is unlikely to cause damage to the aircraft. The only danger of flying through a rainstorm is the risk of freezing rain, but in this case, your plane will most likely be delayed until the storm passes. Even though aircraft are built to withstand heavy rain and strong winds, and pilots are trained to navigate through these conditions, flying through a storm can be a safety hazard. Besides safety issue, thunder clouds are bumpy. All airlines will aim to give you the most comfortable ride possible. Therefore, they will fly around thunderstorms to ensure that you remain comfortable and safe. Thunderstorms can be very dangerous for small aircraft. They often involve severe turbulence, which can cause structural damage. In the event of a particularly violent storm, a pilot will choose to avoid taking off or landing as an extra safety precaution.

-5. How difficult is it to read your instruments during turbulence?

Reading the instruments during turbulence is a skill that pilots learn. General information is often all that is required, such as altitude within 100 feet or airspeed within 10 knots. The airplane manufacturers are very careful to produce instruments that are easy to read in all flight conditions. Modern airplanes display information much better than older ones, making it easier to get the necessary information during turbulence.

-6. Can severe turbulence tear the wing off a jetliner?

From a practical point, no, a modern airliner will not lose a wing due to turbulence. Modern airlines are very tough and designed to withstand extreme turbulence.

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Section-15  

Bird strike:

When you go on an airplane, you generally expect to have a safe, uneventful plane ride with an experienced cabin crew. However, accidents can occur while flying, with one of the most common being bird strikes. These airplane accidents happen when the plane collides with a bird, leading to sometimes devastating consequences. Thousands of airplane bird strikes occur in the skies each year, but many airlines have developed techniques to avoid these incidents. While incidents of bird-strikes are rare, they’re not as rare as one would hope.

Most would not assume a 2 kg pigeon could do much damage to a plane weighing over 40,000 kg, but birds pose serious risks to aircraft of all types – and the record shows it. The most frequent time collisions occur are during a plane’s takeoff due to the birds flying at a lower altitude. Around 90 per cent of these incidents happen around airports, according to the International Civil Aviation Organization.

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A bird strike accident occurs when a bird strikes the aircraft while in flight. These impacts usually occur on the airplane’s windshield or into one or both of its engines. In most cases, these bird strikes lead to damage to the aircraft. However, some bird strike accidents have resulted in fatalities and serious accidents.

Both large birds and flocks of birds can cause damage to planes. They can harm the windscreen and be sucked into the engines. These occurrences lead to unsafe flying conditions and critical damage, often leading the airplane to make an emergency landing.

According to Bird Strike Committee USA, bird strikes are very common and can lead to devastating consequences.

-Since 1988, over 219 people died as a result of bird strikes while traveling by airplane.

-In 2010 alone, the United States Air Force reported 5,000 bird strike incidents. Civil aircraft reported 9,000 bird and wildlife strikes in the United States the same year.

-Between 1990 and 2009, bird strike accidents led to about $650 million in damages to civil aviation in the United States.

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In fact, ever since the invention of the airplane, birds and planes have shared the skies in an uneasy coexistence. Although it seems like there’s no limit to the space in the skies, birds and airplanes still manage to get in each other’s way frequently. As you can probably guess, airplane and bird interactions usually don’t end well for either the bird or the plane. These bird-plane collisions, known as bird strikes, occur thousands of times each year. Nearly all of these are fatal for the birds involved. Fortunately, most bird strikes don’t result in significant damage to airplanes or their passengers. Occasionally, though, large birds can get sucked into airplane engines, causing significant damage and sometimes even causing a crash. As a result of the danger involved with bird strikes, airports have developed a number of safety and conservation measures to minimize bird strikes upon takeoff and landing.

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With the noise of airplanes coming and going, you might think that airports wouldn’t attract birds. Unfortunately, airports tend to attract large flocks of birds of all different types. Birds seem to be attracted to the large, undeveloped tracts of land that surround most airports as noise and safety barriers. The hustle and bustle of airports does tend to drive away larger predators. As a result, the lands surrounding airports can be like a sanctuary for birds, especially if they also contain wetlands or drainage ponds.

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Conflicts between birds and aircraft have increased dramatically in the resent years because the world has become a global village through technological advancement in communication and significant improvement in aircraft design (Faster and Quieter). Globally, the bird strikes have resulted in loss of more than 219 people and 200 aircraft since 1988 (ICAO, 2006). Several factors contribute to this increasing threat. Many populations of bird species commonly involved in strikes have increased markedly in the last few decades. In addition, air traffic has also increased substantially since 1980. Collisions with birds and other wildlife have negatively impacted the airline industry, and ultimately the flying public. In addition to the economic losses, some collisions have resulted in loss of human life. Although the economic costs of bird strikes are extreme, the cost in human lives lost when aircraft crash as a result of strikes best illustrates the need for management of the wildlife strike problem.

Historically, the first powered flight by the Wright Brothers occurred in December 1903, and the wildlife strike problem began shortly thereafter. The first reported bird strike occurred on 7 September 1905 as recorded by Oliver Wright in his diary, when his aircraft hit a red-winged blackbird as he flew over a cornfield near Dayton Ohio. On 3 April 1912 Calbraith Rodgers, the first person to fly across the continental USA, was also the first to die as a result of bird strike when his aircraft struck a gull along the coast of Southern California (Cleary and Dolbeer, 2005). Since those first bird strikes, aircraft designs and performance have changed radically, and bird populations and air traffic have also increased (Dolbeer and Seubert, 2009). As a result, at least 122 civil aircraft have been destroyed and over 255 civilian lives have been lost worldwide due to bird strikes from 1960 to 2004. During this same period, bird strikes have resulted in at least 333 military aircraft destroyed and over 150 military personnel killed (Shobakin, 2009).

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Figure below shows Jet Engine blade damaged by Bird Strike: 

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While collisions between birds and aircraft usually result in lethal consequences for the bird, aircraft damage is rare. Two to eight percent of all recorded bird strikes result in actual aircraft damage in civil aviation. Regarding operational impacts, between six and seven percent of all reports indicate a negative operational effect on the flight. It is estimated that bird strikes cause annual costs of at least one billion US $ to the worldwide commercial aviation industry. Due to incomplete reporting, these figures have to be interpreted as conservative estimates. As accidents have demonstrated, collisions between birds and aircraft also bear the potential for catastrophic outcome for the involved aircraft. As of 11 November 2019, bird strikes were determined to have caused 618 hull losses and 534 fatalities since the beginning of aviation.

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Why do Birds collide with Aircraft?

Airfields can provide good resources (e.g., foraging and nesting sites) for some bird species (e.g., Kershner and Bollinger 1998). However, they can be hazardous habitats due to the danger of getting hit by an aircraft. The ability to avoid an aircraft may involve learning to judge the threat and flying in a manner to evade it successfully. As bird strikes typically occur four to six times per 10,000 aircraft movements, it is possible that most individual birds succeed in evading an aircraft. However, it is critical to understand why evasive behavior does not always work. Birds should typically be good at sound and color signal detection. Those abilities, however, can vary with species and individuals. How nutritional stress, parental duties, disease, and ecotoxins (e.g. neurotoxins) affect a bird’s ability to evade an aircraft remains poorly understood (Kelly et al. 2000).

It is also possible that due to a lack of previous near-fatal encounters, most birds do not perceive an aircraft as a threat or potential predator. Limited evidence suggests that the amount of air traffic affects birds’ evading abilities. The chance of bird strikes increases with the reduction of air traffic on a runway (Burger 1985). Birds probably get acclimatized to the lack of traffic and become less vigilant. Therefore, airport mangers must take specific action (e.g., disperse birds before resuming aircraft activity) when a runway has been inactive for several hours.

Recent design improvements might have made aircraft more vulnerable to bird collisions. Due to public and economic pressure, quieter, larger, and faster aircraft have been developed. Faster and wider-bodied aircraft are struck more often by birds than are the older, narrower-bodied jets (Burger 1983). For example, birds strike 737 passenger jets less frequently than the larger 767 jets (Chilvers et al. 1997). With the wider bodied aircraft, birds have to fly twice as far to escape than they do for the older small-bodied aircraft. Perhaps birds are also unable to hear the newer, larger- bodied quieter aircraft. Engine recording playbacks have shown that the escape distance from third generation quieter jet engines is much less than older, noisier engines (Solman 1981). At least for some species, aircraft noise may have little effect on daily activities (Conomy et al. 1998a). Furthermore, it may be hard for birds to distinguish aircraft noise from background noise at airports.

Species respond differently to aircraft characteristics (e.g., visual and auditory cues; Conomy et al. 1998b), suggesting that some bird species might be better at learning to avoid aircraft, but the evidence remains anecdotal. For example, American Crows (Corvus brachyrhynchos), Northern Harriers (Circus cyaneus), and American Kestrels (Falco sparverius) were not reported to strike aircraft, despite being common at the John F. Kennedy International Airport in New York City (Burger 1985).

Numerous questions remain unanswered as to why some birds do not or cannot perceive the aircraft as threat. Modifications to the newer aircraft might have made them less detectable and difficult to evade.

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Which Birds are hitting Aircraft?

Around the world, gulls (Larus spp.) account for a majority of strikes on civilian as well as military aircraft (e.g., Van Tets 1969, de Jong 1970, Solman 1978, Burger 1985, Smith 1986, Dolbeer et al. 2000). At the Lihue Airport in Kauai, Hawaii, the body mass of birds that hit the aircraft ranges from 13 to 1,300 g (Linnell et al. 1996). Individuals of heavier bird species are more hazardous to aircraft (Dolbeer et al. 2000). The average body mass of the bird species that caused fatalities or injuries to aircraft occupants is 5.1 kg (Neubauer 1990).

Several authors have suggested that disproportionately more immature individuals may be involved in aircraft strikes. Significantly more young than adult individuals of Herring (L. argentatus), Ring-billed (L. delawarensis), and Laughing (L. atricilla) gulls strike aircraft at the John F. Kennedy International Airport (Burger 1985). However, such is not the case for the Great Black-backed Gull (L. marinus). The reason for these species differences is not clear, but young individuals are probably either less capable of perceiving an approaching aircraft as a threat or less successful at evading it.

All things being equal, a solitary individual will cause less damage to an aircraft than will a flock. The number of birds that strike aircraft varies with species. Usually, ducks, geese, herons, owls, and doves collide with aircraft as individuals. However, shorebirds and starlings usually hit aircraft in flocks.

The probability of bird strikes is determined by many parameters such as altitude, time of day, environmental conditions, geographical location, season and the aircraft itself.

The largest numbers of strikes happen during the spring and fall migrations. Bird strikes above 500 feet (150 m) altitude are about 7 times more common at night than during the day during the bird migration season.

For the U.S. Air Force aircraft, 61% of bird strikes occur during clear weather, when both birds and aircraft are more active (Neubauer 1990). To save energy, migratory birds usually use tail wind to fly. However, wind speed does not significantly affect bird strikes (Manktelow 2000).

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Altitude and bird strike:

The highest probability of bird-aircraft collisions is at low altitudes. According to Dolbeer et al. 88% of the bird strikes in the USA over the past 27 years have occurred below 2500 ft (71% below 500 ft). A European study concluded that even 95% of all strikes occur below 2500 ft (70% below 200 ft), when considering worldwide traffic. The probability decreases with increasing altitude, as figure below visualizes. This corresponds to the flight phases for which most bird strikes are reported: takeoff, initial climb, landing and approach. However, the share of damaging bird strikes increases with increasing altitude. Contributing factors are a higher kinetic energy due to increasing bird size and rising aircraft velocity. Furthermore, while mitigation measures at airports have been shown to be successful in reducing the number and consequences of bird strikes, outside the airport boundaries, the options for counteracting measures are limited.

Figure above shows distribution of bird strikes by altitude band that occurred between 1990 and 2018 in the USA, where the altitude was known.

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Effect on Flight:  

Depending on the magnitude of the damage, there is a direct operational effect on the flight. In addition to the aircraft involved, airport operations and other airspace users may also be impaired. Table below provides an overview of operational impacts for various countries and continents.

Reported operational effects in Europe, Canada, the USA as well as world-wide in percentages.

Operational Impact	Europe (2008–2018)	Canada (2008–2018)	USA (1990–2018)	Worldwide (2008–2015)
None, unknown	95•	69 21	56 38	83 12
precautionary landing	1	5	3	1
aborted take-off	1	2	1	1
engine shut-down	<1	<1	<1	<1
other	3	3	1	3

• Europe groups none and unknown into one category.

Independent of their impact on a flight, an examination to ensure the airworthiness of the aircraft involved has to be performed before the next departure. Therefore, not only damaging but all recognized bird strikes affect operations and consequently result in costs. Furthermore, airport operations might be impaired—for example due to temporary runway closure to remove bird remains.

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Some deadly bird-strike incidents:

Louisiana, 2009.

A red-tailed hawk blasted through the windscreen of a Sikorsky S-76 helicopter. The impact of the bird shattered the windscreen, activated the engine fire suppression controls, delaying the helicopter’s throttles and forcing the engines to lose power. The subsequent crash left eight out of nine passengers dead.

Paris, 1995.

During its takeoff, a Dassault Falcon 20 sucked in multiple lapwings through its engines which severed its fuel lines, causing one of its engines to fail. A fire ignited near the rear of the cabin and the pilots lost control while attempting to make an emergency landing. All 10 passengers were killed.

Alaska, 1995.

A U.S. Air Force Boeing E-3 Sentry ingested multiple Canadian Geese into both of its engines on the same wing during takeoff. The engines started to dump fuel and lost power which caused the plane to lose altitude. The plane crashed into a wooded area and exploded killing all 24 crew members.

Bahir Dar, 1988.

A flock of speckled pigeons were pulled into the engines of a Boeing 737 passenger airplane as it took off from the runway. One of its engines lost thrust instantly. The other engine failed shortly after during an emergency landing. The 737 crash landed and caught fire, killing 35 of 98 passengers.

Boston, 1960.

A Lockheed L-188 Electra flew through a large flock of 120 starlings shortly after takeoff causing all four engine to fail before it crashed into Boston harbour. The time from the takeoff to hitting the water was under a minute. Sixty-two out of the 72 passengers died in the greatest loss of life from a bird-strike on record.

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Prevention of bird strike accidents:

Because bird strikes lead to such dangerous situations, airports have developed certain strategies to minimize their occurrence. Generally, airports and air controllers use three methods to prevent bird strike accidents: modifying aircraft behavior, modifying the habitat of the birds, and modifying the behavior of the birds.

Airports study the birds in their area to understand their behaviors. Using this data, these authorities can modify flight paths and schedules to reduce the occurrence of bird strikes. For example, some airports can use spotters to warn planes of birds or use radar equipment to track bird movement and density. Airports can also readjust their flight times to stop flying during times of high bird activity.

Airports can also take steps to control the birds to minimize strikes. They can modify the environment around the airport so that birds do not roost or feed there. Airports can eliminate bird food sources by removing plants or using pesticides. They can cover ponds with netting and remove brush and trees to reduce nesting and landing sites. In addition, airports can mow grass short to reduce bird shelters in the area.

In addition, airports can modify bird behavior and keep the population out of the area.

The following strategies can help keep the birds out of the region without harming the birds.

-Training dogs to track through bird habitats, increasing the bird’s awareness of predators

-Using recordings and noise generators, such as predator calls and sonic cannons

-Flying Falcons over roosting areas to disrupt other birds

-Using lasers to scare birds from the area, mimicking predators

Speed Limitations:

Aircraft speed is a major factor in crashes due to bird strikes (Niering 1990). That is because the kinetic energy that is dissipated during a bird strike increases with the aircraft speed. A further reason why only a small number of all bird strikes lead to aircraft damage results from regulations for maximum aircraft speeds of 250 kts (Knots-Indicated Airspeed (KIAS)) below 10,000 ft as a matter of Air Traffic Control (ATC) airspace organization. Among others, the limitation of speed should reduce the kinetic impact of bird strikes in the areas where bird strikes mostly occur. Many countries such as Canada, Mexico, the USA and Germany have applied such a regulation.

Improvements to Aircraft Design:

There is probably no jet engine in the world that can ingest as large a bird as a Canada Goose and still fly (Eschenfelder 1990). Based on bird-strike data, efforts are underway to improve aircraft so that they can withstand a greater impact (Niering 1990). Those efforts include new material designs for aircraft engine compressor blades, stronger windshield design, and more damage-resistant wings. For military aircraft, windshields need further strengthening modifications, and some of the older aircraft are probably still vulnerable during bird strikes (Neubauer 1990). Previous lessons are sometimes taken into account when making recommendations to improve aircraft design. When a DC10 remained in the air for 10 min after two of its three engines were hit by birds in 1973, the Bird Strike Committee of Europe recommended that European airbuses should have three engines instead of two (Solman 1978).

Most large commercial jet engines include design features that ensure they can shut-down after “ingesting” a bird weighing up to 1.8 kg (4.0 lb). The engine does not have to survive the ingestion, just be safely shut down. This is a ‘stand-alone’ requirement, i.e., the engine, not the aircraft, must pass the test. Multiple strikes (from hitting a bird flock) on twin-engine jet aircraft are very serious events because they can disable multiple aircraft systems, requiring emergency action to land the aircraft, as in the January 15, 2009 forced ditching of US Airways Flight 1549.

Modern jet aircraft structures must be able to withstand one 1.8 kg (4.0 lb) collision; the empennage (tail) must withstand one 3.6 kg (7.9 lb) bird collision. Cockpit windows on jet aircraft must be able to withstand one 1.8 kg (4.0 lb) bird collision without yielding or spalling.

Flight path:

Pilots should not take off or land in the presence of wildlife and should avoid migratory routes, wildlife reserves, estuaries and other sites where birds may congregate. When operating in the presence of bird flocks, pilots should seek to climb above 3,000 feet (910 m) as rapidly as possible as most bird strikes occur below 3,000 feet (910 m). Additionally, pilots should slow down their aircraft when confronted with birds. The energy that must be dissipated in the collision is approximately the relative kinetic energy E of the bird, defined by the equation E = ½ mv^2 where m is the mass of the bird and v is the relative velocity (the difference of the velocities of the bird and the plane, resulting in a lower absolute value if they are flying in the same direction and higher absolute value if they are flying in opposite directions). Therefore, the speed of the aircraft is much more important than the size of the bird when it comes to reducing energy transfer in a collision. The same can be said for jet engines: the slower the rotation of the engine, the less energy which will be imparted onto the engine at collision.

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Section-16

Mechanical failure:   

There are several common causes of aviation accidents in the United States and around the world. Human error, mechanical failure, or a combination of both are the most common causes of commercial aircraft accidents. The Federal Aviation Administration maintains that a full 50 percent of commercial aircraft accidents arise from human error. 13 to 15 percent of aviation accidents are the result of a mechanical breakdown. In addition, mechanical failure and human error combine to result in catastrophic aviation accidents.

Mechanical failure includes engine failures, control system problems, landing gear failures, etc. The largest chunk of mechanical failures are “powerplant failures”, which account for 38% of the mechanical failures, or a bit under 5% of total accidents. Mechanical failures can be described quite specifically (e.g., engine failure in hover, oil pump failure, tail rotor control failure, fuel starvation, etc.).

Underlying causes of Mechanical Failures that result in Aviation Accidents:

There exists a number of different types of mechanical failures that result in catastrophic aviation accidents that result in serious injuries and fatalities. The underlying causes of aviation accidents caused by mechanical failures include:

-Manufacturing defect (of aircraft or component part)

-Design defect (of aircraft or component part)

-Failure to appropriately inspect aircraft

-Failure to properly maintain aircraft

-Failure to timely replace component parts

-Metal fatigue

Many people do not fully appreciate that a myriad of mechanical failures on and around aircrafts do not result on horrific crashes. Rather, every year a significant number of commercial airline passengers are injured as the result of mechanical breakdowns that don’t result in fatal crashes.

A recurring mechanical failure on commercial planes that result in what prove to be serious injuries is a breakdown associated with the beverage cart. Time and again, the brake of beverage carts fail to engage properly because of some type of defect associated with the device. When that occurs, a beverage cart can suddenly roll free down the cabin aisle, injuring a passenger or passengers.

Another relatively common type of mechanical breakdown that results in injuries but not a catastrophic crash involves sudden cabin decompression. Other mechanical issues associated with commercial aircraft that can result in injuries but not a major crash include seat belt malfunction, turbulence warning system failure, and malfunctions associated with Jetway leading to the aircraft. Jetway is a portable bridge put against an aircraft door to allow passengers to embark or disembark.

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Airplane Engine failure:

An aircraft engine is one of the most complex engineering systems that have been developed. To properly investigate and evaluate the failure of an aircraft engine requires a strong working knowledge of proper aircraft maintenance practices, mechanical engineering, and metallurgical and material sciences. Failures of aircraft engines can be caused by a variety and combination of reasons. Statistically the failure starts with a human error. The challenge to the investigator is to be able to understand and interpret the remains of the physical evidence, and correlate that to the earliest link in the error chain.

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Every pilot flying twins remembers the mantra driven into them during their initial training: Maintain Control, Mixture Up, Pitch Up, Power Up, Gear Up, Flap Up, Dead Leg—Dead Engine, Confirm, Identify and Feather. A plan for the worst, which if executed, should allow you to lumber away to a safe altitude. It’s a clear set of actions rehearsed not only in training but also during the day to day of flying.

Yet when we think about flying singles, we often don’t have the same rigid plan for responding to a power loss after take-off. Pilots are taught to push and hold the nose forward and trim for best glide, but then what? You’ve got 30 seconds until impact. Do you try trouble checks or do you configure the aircraft for the imminent landing? How does this change between airports, aircraft and pilots? This indecision characterizes how we place less emphasis on planning for engine failure in singles, despite arguably greater consequences.

Statistically, engine failure is rare. The ATSB’s 2014 investigation into failure rates in piston engine powerplants showed that the traditional Continental and Textron/Lycoming engines had a failure rate of about 13 failures per 100,000 flight hours, with Rotax coming in at a slightly higher 15 per 100,000 flight hours. Move to turbo-prop types and these rates drop further—in 2016, the Pratt & Whitney PT6 family posted a remarkable in-flight shut-down rate of 0.15 per 100,000 flight hours.

Fatal accident rates also support single engine aircraft being safe and reliable. Reviewing general aviation in the US fleet between 1984 and 2006 (from NTSB annual reviews), the average fatal accident rate of single piston engine aircraft sits at 1.63 fatal accidents per 100,000 flight hours, compared with 1.88 fatal accidents per 100,000 flight hours in their multi piston engine cousins.

Given the comforting statistics for engine failure rates, it’s easy to see how engine failure in singles can be pushed to the very back of one’s mind. However, these statistics bely the consequences of engine failure in singles. Engine failure at any stage of flight exposes the occupants of a single engine aircraft to a subsequent forced landing, with the very real possibilities of serious injury or death. Pilots may be limited in their ability to prevent engine failure, but they have a defining influence on whether that failure leads to a safe landing or a fatal accident.

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The failure rate of aircraft engines has reached an all-time low. This means that many flight crews will never face an engine failure during their career, other than those in the flight simulator. However, simulators are not fully representative of engine failures because accelerations (e.g., due to a failed engine), noise (e.g., caused by an engine stall), or vibrations (e.g., in the event of a blade rupture) are hard to simulate.  Consequently, flight crews are not always able to identify and understand engine malfunctions. Incorrect crew understanding of engine malfunctions can lead to unnecessary engine shutdowns, but also to incidents and accidents.

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When the jet engine was introduced in civil aviation in the 1950s (de Havilland Comet, Sud-Aviation Caravelle), the available thrust was less than 10,000 lbs. In 1998 high by-pass ratio engines produce up to 115,000 lbs of thrust.

 During the same time, the rate of In-Flight Shut Downs (IFSD) has decreased as follows:

	IFSD (per 100,000 engine FH)
1960s	40
1998	Less than 1

(Source: AIA/AECMA Project Report on Propulsion System Malfunction + Inappropriate Crew Response, November 1998) 

This improvement in the rate of IFSD has allowed the introduction of ETOPS (Extended Twin Operations) in 1985. Among other criteria, to be approved for ETOPS 180, the rate of IFSD must be less than 2 per 100 000 engine flight hours.

This also means that pilots that start their career today will probably never experience an IFSD due to an engine malfunction.

However, despite the significant improvement in engine reliability, the number of accidents (per aircraft departure) due to an incorrect crew response following an engine malfunction has remained constant for many years. This prompted a study with all major industry actors involved (aircraft and engine manufacturers, authorities, accident investigation agencies, pilot organizations).

Among the results were:

• The vast majority of engine malfunctions are identified and handled correctly. However, some malfunctions are harder to identify
• Most crews have little or no experience of real (i.e., not simulated) engine malfunctions
• Simulators are not fully representative of all malfunctions
• Training does not sufficiently address the characteristics of engine malfunctions.

The following crew undue actions, caused by engine malfunctions, have been observed:

• Loss of control (trajectory not adapted to the engine failure)
• Rejected takeoff above V1
• Shutdown of the wrong engine
• Unnecessary engine shutdown
• Application of the wrong procedure / Deviation from the published procedure.

Recently FAA said that turbine engines have a failure rate of one per 375,000 flight hours compared to one every 3,200 flight hours for piston engines. This means jet engines are 117 times less likely to quit than reciprocating ones. The General Electric GE90 has an in-flight shutdown rate (IFSD) of one per million engine flight-hours. The Pratt & Whitney Canada PT6 is known for its reliability with an in-flight shutdown rate of one per 333 thousand hours from 1963 to 2016, lowering to one per 651 thousand hours over 12 months in 2016. According to the NTSB, there are somewhere between 150 and 200 accidents per year that are caused by power loss.

For piston twins and experimental aircraft, the accident rate is higher. There were over 4,000 accidents attributable to engine failure during a recent five-year period; that’s about two per day in general aviation. But the actual engine failure number is likely double or triple that rate when you consider the number of engine failures that resulted in a successful landing with no damage i.e., not an “accident”. If you have more than 5,000 hours in GA and have not yet had one, statistically speaking, the odds say yes.

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Contained and uncontained engine failure:

Most gas turbine engine failures are “contained” which means that although the components might separate inside the engine, they either remain within the engine case or exit it via the tail pipe. This is a standard design feature of all turbine engines and generally means that the failure of a single engine on a multi engine aircraft will not present an immediate risk to the safety of the flight. Sizeable pieces of ejected debris may, though, present a hazard to persons on the ground.

However, an “uncontained” engine failure is likely to be a violent one, and can be much more serious because engine debris exits it at high speeds in other directions, posing potential danger to the pressurized aircraft structure, adjacent engines, the integrity of the flight control system and, possibly, directly to the aircraft occupants.

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Uncontained Engine Failure Events:

A388, en-route Batam Island Indonesia, 2010:

On 4 November 2010, an Airbus A380-800 being operated by Qantas on a flight in day VMC from Changi Airport, Singapore to Sydney, Australia was passing 7,000 ft in the climb when the No 2 engine suddenly suffered an uncontained failure and a return to Singapore followed.

A320, Toronto Canada, 2000:

On 13 September, an Airbus A320-200 being operated by Canadian airline Skyservice on a domestic passenger charter flight from Toronto to Edmonton was departing in day VMC when, after a “loud bang and shudder” during rotation, evidence of left engine malfunction occurred during initial climb and the flight crew declared an emergency and returned for an immediate overweight landing on the departure runway which necessitated navigation around several pieces of debris, later confirmed as the fan cowlings of the left engine. There were no injuries to the occupants.

B737, Manchester UK, 1985:

On 22nd August 1985, a B737-200 operated by British Airtours, a wholly-owned subsidiary of British Airways, suffered an uncontained engine failure, with fire spreading to the fuselage during the rejected take off, causing rapid destruction of the aircraft before many of the occupants had evacuated.

B757, Las Vegas NV USA, 2008:

On 22 December 2008, a Boeing 757-200 departing Las Vegas for New York JFK experienced sudden failure of the right engine as takeoff thrust was set and the aircraft was stopped on the runway for fire services inspection. Fire service personnel observed a hole in the bottom of the right engine nacelle and saw a glow inside so they discharged a fire bottle into the nacelle through the open pressure relief doors. The failed engine was found to have experienced an uncontained release of high pressure turbine material.

B777, engine failure at Denver, Feb 21, 2021:

Metal fatigue in the fan blades may have been behind the engine failure of a Boeing jet in Denver, the US National Transportation Safety Board has said. The Pratt & Whitney engine caught fire shortly after take-off on a United Airlines Boeing 777-200, during a flight from Denver to Honolulu, with 231 passengers and 10 crew onboard. The pilots declared an emergency, turned the plane around and landed back in Denver 20 minutes later. Parts of the shell containing the engine disintegrated and fell to the ground, with some pieces landing in front yards and a soccer field. The next day, dozens of 777 planes were grounded after Boeing said those with Pratt & Whitney PW4000 engines should not be used until full inspections could be carried out. In another incident on the same engine type on a Japan Airlines 777 in December 2020, Japan’s Transport Safety Board reported it found two damaged fan blades, one with a metal fatigue crack.

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Common causes of engine failure and their prevention:

All pilots are taught to abide by a basic aviation rule regardless of the severity of any airborne event. This is summarized by the acronym; Aviate, Navigate, Communicate. The crux of this is to ensure the flight crew prioritize flying the aircraft first, ensuring that it is fully under control before verifying or correcting its navigational path and making sure it is flying where the pilots want it to fly, i.e., not heading towards a high mountain. This is followed by communicating the relevant information to all the appropriate parties, starting with Air Traffic Control.

Generally, the reasons aeroplane engines stop can be traced to the lack of one of the following components.

-1. Carburettor ice

In conditions of high humidity, carburettor ice can form during taxiing and may be hard to detect at low power settings. Being aware of the temperature and moisture content of the air will alert you to the possibility of ice forming. There may be clues in the way the engine is running on the ground.

Selecting carburettor heat HOT is the first action, other than flying the aeroplane, to be taken in the event of any engine failure, and if carburettor icing is the cause of an engine failure it should re-establish smooth engine running. Selecting carburettor heat to HOT also provides an immediate alternate source of air to the carburettor, should the air filter have become blocked during take-off.

The risk of carburettor ice causing an engine failure is minimised by carrying out the preflight engine run-up. In conditions of suspected carburettor icing, after prolonged idling, it is advisable to cycle the carburettor heat just before take-off. Be aware of the ground surface when applying carburettor heat. Bypassing the filter can introduce dust and grass seeds into the carburettor, another possible cause of engine failure.

Always ensure that carburettor heat is selected to COLD before opening the throttle for take-off.

-2. Air blockage

Another possible cause of the air supply being obstructed is a blockage in the carburettor air filter. In this situation, the carburettor heat, which bypasses the air filter, will provide an alternate source of air to the carburettor. The risk of filter blockage is minimised by carefully examining the air intake during the preflight inspection.

-3. Fuel contamination

The most probable cause of engine failure is fuel contamination, i.e., something in the fuel – most commonly water. Mechanical failure is not the most common cause. The risk of fuel contamination is minimised by inspecting a fuel sample during the preflight and after-refuelling checks – looking for foreign objects, colour and smell, as well as carrying out the pre-take-off engine run-up. Be aware that immediately after refuelling some water, if present, will still be in suspension, and a fuel check done too soon after refuelling may not discover this. Be aware that if the aeroplane is not on level ground, a fuel sample check may not be capturing any water or contamination present.

-4. Fuel starvation

Fuel starvation occurs when there is fuel on board but it’s not getting to the engine. The most common cause of fuel starvation is the pilot selecting the wrong fuel tank or placing the fuel selector in the OFF position by mistake. Other less common but possible causes are either engine-driven fuel pump failure or blocked fuel lines, injectors or fuel vents. To help avoid fuel starvation, the pilot must be familiar with the aeroplane’s systems, carry out the engine run-up before take-off, and apply sound fuel planning and management procedures.

-5. Fuel exhaustion

Fuel exhaustion occurs when there is no useable fuel on board, and is less likely to be a factor of EFATO (engine failure after takeoff) than fuel starvation. The most common cause of fuel exhaustion is poor in-flight decision making – simply running out of fuel. Another cause is leaving the fuel caps off, this allows fuel to be sucked out by the low-pressure area over the wing surface. Fuel exhaustion is avoided by careful preflight planning, a thorough preflight inspection and being aware of how much fuel there is on board at all times.

-6. Spark

During take-off the engine is working at its hardest and, although mechanical failure is still the least likely cause, the risk of mechanical failure is increased. Statistically, the first reduction in power after take-off is the most common time for a mechanical failure to occur. Therefore, if a reduced power setting is to be used for the climb, full power should be maintained to a safe height, and the aeroplane cleaned up and established in the climb before power is reduced.

A thorough preflight inspection and engine run-up should be completed to check for any signs of impending mechanical failure.

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Implications of an engine failure:

Asymmetric Thrust / Controllability.

The first implication is the asymmetric thrust that will be produced. If an engine fails and is shutdown, the other engine’s thrust is increased to stop a decay in airspeed. This results in the aircraft wanting to turn away from the working engine and entering a turn. If left unchecked, this will result in loss of control of the aircraft. This usually has to be corrected manually by the pilots through the rudder pedals. Any time there is an adjustment in speed, thrust or altitude, the pilots will need to ensure the aircraft remains balanced and in control.

Altitude.

With 50% of the aircraft’s power no longer available it will not be able to maintain its cruise altitude. If the aircraft is in the cruise at the time of the failure (which is statistically most likely), a descent will need to be quickly initiated to an intermediate altitude which can be maintained by the remaining engine (typically between 15,000ft – 25,000ft for most aircraft, depending on weight).

System Redundancy.

Many of the aircraft’s systems are powered by its engines. These usually include the Hydraulics, Pneumatics (which provide cabin air) and Electrics. Whilst these systems have a level of redundancy (in part through the other engine), some parts of the system may no longer be available which could affect aircraft handling and performance.

Landing Performance.

Losing an engine often requires a different flap configuration for landing, in part due to the performance that must be achieved were the aircraft to abort the approach/landing and conduct a ‘go-around’. Landing with a lower flap configuration increases the landing distance required and therefore the pilots must carefully consider which airport they elect to land at. Airport weather, runway length and aircraft weight all play a part in these considerations.

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What is the most dangerous phase of flight to have an engine failure?

For a pilot, the most testing place to have an engine failure is during the take-off phase, i.e., the start of the ground roll until the aircraft passes around 1,500ft. However extensive training is provided for this scenario and the pilots are tested on their reactions to such an event every six-months in the simulator. They must safely deal with such a scenario to a high standard or they will not be allowed to continue to fly until adequate performance is demonstrated.

During the take-off, the pilots use a carefully pre-calculated speed called V1 (pronounced “Vee One”) to determine their actions were an engine to fail. During the take-off roll, if an engine failure occurs before the V1 speed, the pilots must abort the take-off, which is known in the industry as a ‘Rejected Take-Off’ or RTO for short. If they elected to continue, the aircraft would not gain enough speed to take-off with the remaining engine power available on the runway length remaining.

If a failure occurs after V1, the pilots must continue the take-off and get airborne. If the pilots tried to abort the take-off at this speed, there would not be enough runway left to safely bring the aircraft to a stop.

Once the aircraft is in the air, the pilots will just concentrate on flying and controlling the aircraft until approximately 400ft. At this altitude, they will review what has occurred and carry out any ‘Memory Actions’ if required.

What happens if you lose an engine on an aircraft with more than two engines?

A four-engine aircraft losing a single engine is even less of an issue. A few years ago, a four-engine Virgin Atlantic Boeing 747-400 (a jumbo jet) had an engine failure over the United States en-route to the UK. The aircraft continued all the way over the Atlantic Ocean back to the UK without any further problems. If a four-engine aircraft lost more than one engine, it can still potentially fly at a lower altitude and will perform better at lower weights.

What happens if all engines fail? Can a plane fly if all its engines have failed?

A passenger aircraft will glide perfectly well even if all its engines have failed, it won’t simply fall out the sky. Aircraft are designed in a way that allows them to glide through the air even with no engine thrust. In fact, the chances are that if you’ve flown in a plane, you’ve seen it effectively glide at some point during the descent to land.

Aircraft are able to fly through the movement of air passing over the wings and as long as this process continues the aircraft will continue to fly. If both engines fail, the aeroplane is no longer being pushed forwards through thrust, therefore in order to keep the air flowing over the wings, the aircraft must exchange energy through losing altitude in order to maintain forward airspeed.

The aircraft doesn’t have to lose altitude particularly rapidly to keep flying and therefore it both engines were to fail a high altitude, the aircraft may have as much as 20 – 30 minutes of airborne time to find somewhere to land.

How far can a Jet travel with all its engines failed?

A passenger jet could glide for up to about 60 miles if it suffers a total engine failure at its cruising altitude. Here’s an example. A typical commercial aircraft has a lift to drag ratio of around 10:1. This means that for every 10 miles it travels forward it loses 1 mile in altitude. If an aircraft is at a typical cruise altitude of 36,000 (which is 6 miles up) and loses both engines, it can therefore travel a forward distance of 60 miles before reaching the ground. Therefore, if such an incident occurs within 60 miles of a runway, the aircraft could potentially be landed safely.

US Airways Flight 1459

We all know about the story of US Airways flight 1459 landing in the Hudson River in New York after both its engines were destroyed by birds, but that really was exceptional – and everyone survived thanks to the quick actions of the actions of the pilots Captain Chesley Sullenberger (‘Sully’) and First Officer Jeffrey Skiles.

Air Transat Flight 236

The plane had a fuel leak causing both engines to fail at approximately 65 nautical miles from Lajes Air Base in the Azores. With an average descent rate of 2,000 fpm, the aircraft glided without power to the airbase where the crew carried out a successful landing about 17 minutes after the last engine failed.

Gliding Every Flight

The lower the engine power, the less fuel the engines burn. On most flights pilots try and burn as little fuel as possible and part of this process involves descending the aircraft towards the destination airport at idle (minimum) thrust. When the thrust is at its minimum setting, it isn’t really producing any meaningful thrust at all so the aircraft is effectively gliding. Therefore you will have experience the aircraft gliding on almost every flight you have been on!

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Section-17

Poor maintenance and plane crash:

Numerous studies indicate that three-quarters of accidents are the fault of the pilot. The remaining one-quarter are machine-caused, and those are just about evenly divided between ones caused by aircraft design flaws and ones caused by maintenance induced failures (MIFs). That suggests one-eighth of accidents are maintenance-induced, a significant number. The lion’s share of MIFs are errors of omission. These include fasteners left uninstalled or untightened, inspection panels left loose, fuel and oil caps left off, things left disconnected (e.g., static lines), and other reassembly tasks left undone.

Distractions play a big part in many of these omissions. A mechanic installs some fasteners finger-tight, then gets a phone call or goes on lunch break and forgets to finish the job by torqueing the fasteners; and several fatal accidents are caused by such omissions.

In a detailed analysis of 93 major world-wide accidents which occurred between 1959 and 1983, it was revealed that maintenance and inspection were factors in 12% of the accidents. In some accidents, where the error was attributed to maintenance and inspection, the error itself was a primary causal factor of the accident whereas, in other cases, the maintenance discrepancy was just one link in a chain of events that led to the accident.

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There are many examples of crashes due to failed aircraft maintenance:

Japan Airlines Flight 123, which took off without a vertical stabilizer in 1985. It crashed 32 minutes after takeoff.

Chalk’s Flight 101 in December 2005. The plane crashed shortly after takeoff, killing everyone on board. The cause was traced back to metal fatigue—and a crack in the plane’s wing that was discovered but never properly fixed.

Alaska Airlines Flight 261, which nose-dived into the Pacific Ocean during a flight from Mexico to Seattle in 2000. Everyone aboard the McDonnell Douglas MD-83 was killed, and investigators later determined the cause to be insufficient lubrication of a jackscrew assembly by airline employees during preventive maintenance.

Surprisingly, ignoring aircraft maintenance wasn’t always an anomaly—it used to be a generally accepted industry practice. It wasn’t until a huge section of Aloha Airlines Flight 243’s fuselage blew off in 1988 that the National Transportation Safety Board tightened its maintenance requirements. The Boeing 737 was at 24,000 feet and climbing when the plane started ripping apart, sweeping a flight attendant to her death. Investigators later determined that the plane, which was 19-years-old, had succumbed to corrosion and widespread fatigue. It may have been prevented, investigators said, if strict inspection and maintenance procedures for high-use aircraft had been in place.

Today, aviation experts have learned a lot from past tragedies, and strict standards are placed on the inspection and maintenance of aircrafts. It can’t always prevent tragedy from striking at 34,000 feet, but it can serve as a line of defense in the effort to avert death and keep people safe—and aircraft mechanics are on the front lines.

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Human Errors in Aviation Maintenance:

The aviation maintenance personnel work in highly sophisticated aircrafts with complex inbuilt systems. Hence they need to be trained on upgraded technologies and new systems in order to provide an error free maintenance. The maintenance personnel should be trained in a way they must be able to repair, analyze and certify the systems in accordance to the standards of the Aircraft manufacturers and the Aviation authorities. Rapid improvements in technology and complexity of the systems have been helpful in maintenance operations but they also present new possibilities of human errors.

According to Pratt & Whitney in their survey in 1992, the major causes for the 120 inflight engine shutdowns on Boeing 747 aircrafts were mainly due to:

Incomplete installation (33%)

Damaged on installation (14.5%)

Improper installation (11%)

Equipment not installed or missing (11%)

Foreign object damage (6.5%)

Improper fault isolation, inspection (6%)

Equipment not activated or deactivated (4%)

Some of the other related causes are:

Complex maintenance related tasks

Time pressure for delivering the aircraft

Fatigue of the maintenance personnel

Maintenance procedures not followed accordingly

Usage of outdated maintenance manuals

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The United Kingdom Civil Aviation Authority (UK CAA) has published a listing of frequently recurring maintenance discrepancies. According to this listing, the leading maintenance problems in order of occurrence are:

incorrect installation of components

fitting of wrong parts

electrical wiring discrepancies (including cross-connections)

loose objects (tools, etc.) left in aircraft

inadequate lubrication

cowlings, access panels and fairings not secured

landing gear ground lock pins not removed before departure.

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Causes and Trends in Maintenance-Related Accidents in FAA Certified Single Engine Piston Aircraft, a 2015 study:

The accident rate for general aviation remains high. While most general aviation accident studies have been pilot-focused, there is little research on the involvement of aircraft maintenance errors. Authors undertook a study to answer this question.

The Microsoft Access database was queried for accidents occurring between 1989 and 2013 involving single engine piston airplanes operating under 14CFR Part 91. Pearson Chi-Square, Fisher’s Exact Test, and Poisson probability were used in statistical analyses.

The rate of maintenance-related general aviation accidents was 4.3 per million flight hours for the 1989–1993 period and remained unchanged for the most recent period (2009–2013). Maintenance errors were no more likely to cause a fatal accident than accidents unrelated to a maintenance deficiency. Inadequate/improper maintenance (e.g., undertorquing/non-safetied nuts) represented the largest category causal for, or a factor in, accidents. Maintenance errors involving the powerplant caused, or contributed to, most accidents, but did not carry a disproportionate fraction of fatal accidents. Noncertified airframe and powerplant (A&P) aircraft maintenance technicians (AMTs) performed maintenance on 13 out of 280 aircraft involved in maintenance-related accidents. While there is current concern as to the safety of the aging general aviation fleet, the fraction of fatal accidents for aircraft manufactured prior to 1950 was not higher than those manufactured more recently.

Authors conclude that the general aviation accident rate related to maintenance deficiency, while low, is static. Increased emphasis should be placed on tasks involving torquing and improper rigging as well as maintenance related to installation/assembly/reassembly. Whether a maintenance error decision aid plan, shown to reduce maintenance errors at airline facilities, would benefit general aviation deserves consideration.

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Section-18

Software failure:  

Software systems are actively used today in safety-critical areas such as aeronautics, astronautics, medicine, nuclear power generation and nuclear research, transportation, etc. When employed in such systems, software is often responsible for controlling the behavior of electromechanical components and monitoring their interactions in addition to other tasks such as user interface management, computer administration, and others. Since most accidents arise in the interfaces and interactions among the components, software plays a direct and important role in system safety. Consequently, an important issue that comes up is that of software safety – which means that the software should execute within a system context without contributing to hazards. However, should the software operation directly or indirectly lead to a hazard in the case of a safety-critical system, then the consequences of the hazard realization could be catastrophic. By catastrophic it is implied that the damage is not just restricted to financial losses, or losses in terms of time or property, but rather may also include the loss of life.

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Software contributions to aircraft adverse events: Case studies and analyses of recurrent accident patterns and failure mechanisms, a 2013 study:

Software is central to aircraft flight operation, and by the same token it is playing an increasing role in aircraft incidents and accidents. Software related errors have distinctive failure mechanisms, and their contributions to aircraft accident sequences are not properly understood or captured by traditional risk analysis techniques. To better understand these mechanisms, authors analyze in this work five recent aircraft accidents and incidents involving software. For each case, authors identify the role of software and analyze its contributions to the sequence of events leading to the accident. They adopt a visualization tool based on the Sequential Timed Event Plotting (STEP) methodology to highlight the software’s interaction with sensors and other aircraft subsystems, and its contributions to the incident/accident. The case studies enable an in-depth analysis of recurrent failure mechanisms and provide insight into the causal chain and patterns through which software contributes to adverse events. For example, the case studies illustrate how software related failures can be context- or situation-dependent, situations that may have been overlooked during software verification and validation or testing. The case studies also identify the critical role of flawed sensor inputs as a key determinant or trigger of “dormant” software defects. In some cases, authors find that software features put in place to address certain risks under nominal operating conditions are the ones that lead or contribute to accidents under off-nominal or unconsidered conditions. The case studies also demonstrate that the software may be complying with its requirements but still place the aircraft in a hazardous state or contribute to an adverse event. This result challenges the traditional notion, articulated in most standards, of software failure as non-compliance with requirements, and it invites a careful re-thinking of this and related concepts. Authors provide a careful review of these terms (software error, fault, failure), propose a synthesis of recurrent patterns of software contributions to adverse events and their triggering mechanisms, and conclude with some preliminary recommendations for tackling them.

Highlights:

-Software contributions to aircraft adverse events (incidents, accidents) are analyzed.

-Triggers of software dormant defects are identified and examined.

-Critical role of flawed sensor inputs in software is highlighted.

-Robustness of software to off-nominal scenarios and sensor malfunctions is advocated.

-Careful rethinking of the concept of software failure and related standards is recommended.

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Everything you need to know about the Boeing 737 Max airplane crashes:

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The first sign of trouble appeared just after takeoff. Inside the cockpit of PK-LQP, a brand-new Boeing 737 Max belonging to Lion Air, the stick shaker on the captain’s side began to vibrate. Stick shakers are designed to warn pilots of an impending stall, which can cause a dangerous loss of control. They’re unmistakably loud for that reason. But the airplane was flying normally, nowhere near a stall. The captain ignored it. About 30 seconds later, he noticed an alert on his flight display — IAS DISAGREE — which meant that the flight computer had detected a sensor malfunction. This required a bit more attention.

 

A modern-day passenger airplane is less like a racecar and more like a temperamental printer: you spend more time monitoring and checking systems than you do actually driving the thing. So the captain passed control of the aircraft to the first officer and began the troubleshooting process from memory.

Like all commercial aircraft, the Boeing 737 Max has multiple levels of redundancy for its important systems. In the cockpit, there are three flight computers and digital instrument panels operating in parallel: two primary systems and one backup. Each system is fed by an independent set of sensors. In this case, the captain checked both instrument panels against the backup, and he found that the instruments on his side — the left side — were getting bad data. So with the turn of a dial, the captain switched the primary displays to only use data from the working sensors on the right side of the airplane. Easy. All of this took under a minute, and everything appeared to be back to normal.

At 1,500 feet of altitude, the takeoff portion of the flight was officially complete, and the first officer began the initial climb. He adjusted the throttle, set the aircraft on its optimal climb slope, and retracted the flaps. Except the airplane didn’t climb. It lurched downward, its nose pointed toward the ground. The first officer reacted instinctively. He flicked a switch on his control column to counteract the dive. The airplane responded right away, pitching its nose back up. Five seconds later, it dove once again. The first officer brought the airplane’s nose up a third time. It pitched back down.

There was no memorized checklist that seemed to apply to this situation, so the captain reached for the airplane’s Quick Reference Handbook (QRH). The QRH is a series of simple checklists that are designed to help pilots rapidly assess and manage “non-normal” situations. The idea is that Boeing has thought of every conceivable thing that might happen to one of its airplanes, and it has included all of them in the QRH. Basically, it’s more troubleshooting. But nothing in the QRH seemed to apply, either.

Over the next six minutes, as the first officer struggled to control the airplane and the captain searched for the right checklist, PK-LQP climbed and dove over a dozen times. At one point, the airplane pulled out of a 900-foot dive at an airspeed of almost 375 mph, which is uncomfortably close to the 737’s “redline” of 390 mph. The flight crew had to figure something out fast before they lost control of the airplane.

Then the third person in the cockpit, who was technically off-duty, “dead-heading” to his next assignment, reportedly spoke up.

What about the runaway stabilizer checklist?

It was a shot in the dark, another checklist. “Runaway trim” occurs when some kind of failure causes an airplane’s horizontal stabilizer to move — or “trim” — when it shouldn’t be moving at all. Usually, this creates a constant up or downforce that the flight crew has to try to counteract for the remainder of the flight. It’s kind of like trying to drive when your wheels are out of alignment.

PK-LQP’s problem was a little different. It was intermittent, temporarily reversible, and it wasn’t even clear if the horizontal stabilizer was causing the problem. But they were running out of options. They followed the checklist and flipped the STAB TRIM switches to CUT OUT on the center console.

The airplane stopped pitching down. Five seconds passed. Then five minutes. Once again, PK-LQP was under their control and out of danger.

An hour later, Lion Air flight 043 landed in Jakarta, Indonesia, only a few minutes delayed. Following standard procedure, the captain reported the episode to the airline, and the airline’s maintenance team checked for serious equipment failures, finding none.

The following morning, PK-LQP, operating as Lion Air flight 610, took off at 6:20AM local time on its way to Pangkal Pinang, Indonesia. Its stick shaker activated just after takeoff. It threw multiple errors on the flight display. It dove just after the flight crew retracted the flaps. And it relentlessly activated its automatic pitch trim in the nose-down direction 28 times over the course of eight minutes.

This time, there was no third pilot to help the flight crew.

PK-LQP may have reached 600 mph, faster than a Tomahawk missile, as it plunged into the water. It was the first 737 Max accident in its 18 months of service. 

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Lion Air Flight 610 took off from Jakarta, Indonesia on Monday, October 29th, 2018, at 6:20AM local time. Its destination was Pangkal Pinang, the largest city of Indonesia’s Bangka Belitung Islands. Twelve minutes after takeoff, the plane crashed into the Java Sea, killing all 189 passengers and crew.

Nearly five months later, Ethiopian Airlines Flight 302 took off from Addis Ababa, Ethiopia on Sunday, March 10th, 2019, at 8:38AM local time. Its destination was Nairobi, Kenya. Six minutes after takeoff, the plane crashed near the town of Bishoftu, Ethiopia, killing all 157 people aboard.

In both cases, the planes kept pushing their noses down despite the pilots’ efforts to correct it.

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Investigation indicated that Lion Air 610 crashed because a faulty sensor erroneously reported that the airplane was stalling. The false report triggered an automated system known as the Maneuvering Characteristics Augmentation System, or MCAS. This system tried to point the aircraft’s nose down so that it could gain enough speed to fly safely. The aircraft maintenance records indicated that the AOA Sensor was just replaced before the accident flight.

MCAS takes readings from two sensors that determine how much the plane’s nose is pointing up or down relative to oncoming airflow. When MCAS detects that the plane is pointing up at a dangerous angle, it can automatically push down the nose of the plane in an effort to prevent the plane from stalling.

Investigators have found strong similarities in the angle of attack data from both flights. A piece of a stabilizer in the wreckage of the Ethiopian jet with the trim set in an unusual position was similar to that of the Lion Air plane.

The biggest failing of MCAS was that it relied on only one angle-of-attack sensor located on either side of the plane, not both. Those sensors fail all the time when they get hit by a bird or freeze, and engineers decided to use only one of them, which is mind-boggling. In the Ethiopian Airlines crash in March 2019, a faulty angle of attack sensor went from 12 degrees to 70 degrees in less than a second, but MCAS trusted that reading in making a pitch adjustment instead of comparing the reading with the other angle of attack sensor on the other side of the aircraft. The MCAS software didn’t have any basic sanity checks to confirm the data was bad.

Boeing says the decision to include MCAS to the flight control operations wasn’t arbitrary. When the company designed the Max jets, it made the engines larger to increase fuel efficiency, and positioned them slightly forward and higher up on the plane’s wings. These tweaks changed how the jet handled in certain situations. The relocated engines caused the jet’s nose to pitch skyward. To compensate, Boeing added a computerized system called MCAS to prevent the plane’s nose from getting too high and causing a stall. MCAS is unique to the Max jets, and isn’t present in other Boeing 737s.

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Indonesian officials cited nine factors in the Lion Air crash of 2018. They largely blamed MCAS, noting it was “not a failsafe design and did not include redundancy.” According to the Indonesian findings, MCAS relied on only one sensor, which had a fault, and the flight crews hadn’t been well trained in how to use it. Also they said: There was also no cockpit warning light; the Lion Air pilots were unable to determine their true airspeed and altitude as the plane oscillated for nearly 10 minutes; and every time the pilots pulled up from a dive, MCAS pushed the nose down again, horribly.

MCAS is activated without the pilot’s input, which has led to some frustration among pilots of the 737 Max jet. At least half a dozen pilots have reported being caught off guard by sudden descents in the aircraft. One pilot said it was “unconscionable that a manufacturer, the FAA, and the airlines would have pilots flying an airplane without adequately training, or even providing available resources and sufficient documentation to understand the highly complex systems that differentiate this aircraft from prior models,” according to an incident report filed with a NASA database.

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Were pilots given adequate training?

Short answer: no. When the Max jet was under development, regulators determined that pilots could fly the planes without extensive retraining because they were essentially the same as previous generations. This saved Boeing a lot of money on extra training, which aided the company in its competition with Airbus to introduce newer, more fuel-efficient airplanes. The FAA didn’t change those rules after Lion Air 610 crashed. So rather than hours-long training sessions in giant, multimillion-dollar simulators, many pilots instead learned about the 737’s new features on an iPad. Pilots at United Airlines put together a 13-page guide to the 737 Max, which did not mention the MCAS. The doomed Lion Air cockpit voice recorder revealed how pilots scoured a manual in a losing battle to figure out why they were hurtling down to sea.

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Boeing’s response:

With regards to MCAS, Boeing is testing an updated MCAS in-flight and had conducted it in 1,157 flights, totaling 2,175 hours as of Feb. 24,2020, a Boeing spokesman said. He said additional layers of protection have been added, including that MCAS now compares data from both angle of attack sensors before activating and will only respond if data from both sensors agree. MCAS also will activate a single time only and never provide more input than the pilot can counteract using the control column alone. Boeing also has posted on its website a discussion of how it has handled its own investigations into the MAX’s angle of attack indicator and its AOA Disagree alert, which notes its AOA Disagree alert will be implemented as a standard, standalone feature before the MAX plane returns to service. AOA Disagree is a software-based information feature designed to alert flight crews when data from the left and right angle of attack sensors disagree, but it had not been standard originally.

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Lessons learned:

There are lessons from the case of the 737 MAX that can help other organizations designing complex systems avoid making similar mistakes in the future:

-1. Keep software and systems in complex machines as simple as possible, but not too simple.  Engineers call this the Goldilocks approach, when things are “just right.”

-2. Don’t impose software on an intractable hardware problem. MCAS didn’t fundamentally change the way the 737 MAX would fly. Keeping the engines further back on the wing would have.

-3. Remember redundancy. Do not rely on data readings from just one angle of attack sensor or any single data input.

-4. Pilot is not a computer engineer or scientist. Pilots must be trained to use software correctly, detect software malfunction and override software function if necessary.

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The beleaguered aircraft was grounded worldwide on March 13, 2019, after two crashes, one in Indonesia in 2018 and the other in Ethiopia in 2019, that killed a combined total of 346 people. Apart from the human tragedy, it was a huge blow to Boeing’s business, since the company has thousands of 737 Max orders on its books. In addition to the flight control system at the center of both investigations, other reports identified concerns with the airliner’s flight control computer, wiring and engines.

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Section-19

Stall and spin:

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Despite the emphasis on stall recognition and recovery throughout primary training and on checkrides and flight reviews, unintended stalls continue to be among the most common triggers of fatal accidents in light airplanes. In the 15 years from 2000 through 2014, stalls were implicated in 10 percent of all non-commercial accidents but almost 24 percent of fatal accidents. Nearly half of all stall accidents proved fatal compared to just 17 percent of those not involving stalls. On commercial flights—on-demand charter and cargo transport under Part 135 and aerial application flights under Part 137—30 percent of stall accidents caused fatalities compared to 13 percent of those without stalls. Stalls led to seven percent of all commercial accidents and 15 percent of those with fatalities. The increased lethality is a direct reflection of crash dynamics: Striking the ground in a steep nose-down descent produces much more rapid deceleration and correspondingly higher G-forces than deceleration over even 100 feet in a more normal landing attitude.

The number involving spins can’t be pinned down with precision; most light airplanes are not equipped with data loggers or other recording devices, and in the absence of eyewitness accounts, the limitations of forensic examination often make it impossible to determine the aircraft’s flight condition prior to impact. Awareness and prevention are key to avoiding spin accidents: A NASA study conducted in the 1970s confirmed that recovering from an intentional spin typically required about 1,200 feet of altitude, making a spin initiated at or below pattern altitude unrecoverable even with perfect technique. While it can be a valuable addition to a pilot’s education, the chief virtue of spin training for low-altitude flight lies in instilling awareness of the conditions and control inputs that provoke a spin.

The Air Safety Institute analyzed 2,015 accidents involving stalls over a 15-year period.  Nearly 95 percent of them (1,901) occurred on non-commercial flights, including 911 of the 945 fatal accidents (96 percent). While a reduction in their frequency in recent years has contributed to an overall improvement in general aviation accident rates, they still led to almost 200 fatal accidents between 2010 and 2014.

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Stall vs descent:

A wing generates lift by encouraging attached flow of the air around its surface. Attached flow is the tendency of an airstream to “stick” to a surface as it passes it. Air traveling above and below the wing follow the contour of the wing, and because the contour of the wing guides the air downward, an equal and opposite upward force is created, and you have Newtonian lift.

The angle between the wing and the oncoming air is called the angle of attack. If it’s zero, the wing is meeting the oncoming air head-on, and no lift is being created (because the air is not being deflected at all). If it’s a (small) positive number, the air is being deflected slightly downward, creating the upward lift needed to fly.

As angle of attack increases, so does lift. This is why pitching up (increasing the angle of the wings) causes the aircraft to climb. However, attached flow will only exist up to a certain point, called the critical angle of attack. Beyond this, the curve the wing asks of the air is too great, and the air separates from the wing. In the wake of this separation, the air forms turbulent eddies that destroy the lift of the wing. This is a stall.

When a wing is stalled, it begins to generate significantly less lift. While it’s true that reduced airspeed can lead to a stall, this is only because a reduction in airspeed requires a corresponding increase in angle of attack in order to maintain the same altitude. If you reduce speed too far while trying to maintain altitude, eventually you will exceed the critical angle of attack and stall your wing.

This is also important because it demonstrates that a stall is not a direct function of airspeed. A wing can stall at any airspeed; all that is required is exceeding the critical angle of attack.

Yes, as the airplane slows, lift decreases if angle of attack is not increased. However, all this results in is a descent. This is merely the condition of descent, not a stall.

Stall speed is the speed at which the best angle is the only angle that can keep the plane level. Not sure what “best angle” is, but the definition of stall speed is the speed at which the angle of attack required to generate sufficient lift for level flight is the critical angle of attack. In other words, any further reduction of speed would require an increase in angle of attack beyond the critical angle of attack, therefore creating a stall. Any slower and the plane will stall no matter what the angle of the wings. An airplane whose nose is pointed straight down (or nearly so) will not stall at a speed below stall speed. Because the airplane is falling, if the nose is pointed down, the angle of attack is small, and therefore the airplane is not stalled. This is why stall recovery involves lowering the nose.

Have you ever thrown a paper airplane into the air, watched it zoom upward, pause, then pitch down and glide back to Earth? If so, you’ve seen an airplane stall. And if you were really paying attention, you also learned a lesson about stalls and airplane stability. Whether it’s a general aviation trainer or the paper airplane, a stall is a transient condition; given enough altitude, a properly designed airplane will recover.

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In aerodynamics a ‘Stall’ occurs when a ‘wing’ (wing, rudder, propeller blade, compressor blade, etc.) reaches the critical angle of attack. Up to the critical angle of attack, lift increases broadly linearly with increased angle of attack and induced drag increases broadly with the square of angle of attack. At the critical angle of attack, this relationship breaks down and the lift decreases with further increase in angle of attack and induced drag continues to increase. This is normally accompanied by a pronounced separation of the airflow and associated turbulent flow. The experience for the pilot is a sudden increase in descent rate, buffeting of the wing and sometimes loss of aileron effectiveness due to the turbulent airflow.

When you learn to fly one of the first things that you learn is that recovering from a stall at low altitude is rarely successful. So we go up to at least 1,500 ft Above Ground Level (agl) and we practice putting the airplane into a position just before it stalls—the stall warning light goes on and the wing begins to buffet. Then we use appropriate power, ailerons, and rudder to recover from the stall. Every pilot is tested on this before they receive their pilot’s license. Commercial pilots and air transport pilots are tested again with higher standards than private pilots. The idea is that you know the conditions that result in stalls and avoid getting into that situation. If for some reason you do stall the airplane, your training should kick in and you should be able to recover.

Unfortunately, many general aviation pilots get distracted on final approach and there are frequent stall-spin accidents in light airplanes. They are extremely rare in the airlines. The one that comes to mind is the Colgan Air accident in 2009 where the plane iced up and the pilot flying ignored the stall warnings and pulled up on the stick instead of pushing the nose down and adding power.

We are taught that a stall can occur at any airspeed if the airplane exceeds the critical angle of attack. There are lots of ways you can do that but the two most common are banking and icing up the wing. The Colgan Air crash is an example of the later. When the wings are iced up they do not provide as much lift as when they are clean. In order to keep the plane level you need to increase the pitch. This increases the angle of attack and at some point the wing exceeds the critical angle of attack and the plane stalls.

A model airplane may be used to show that airplanes do not fly at an angle of attack of 90 degrees to the relative airflow. Therefore, somewhere between straight and level and 90 degrees, a limit is reached at which the air can no longer flow smoothly over the aerofoil.

For the average aerofoil used on general aviation airplanes, this limit is reached at an angle of attack of about 15 degrees. It should be emphasized that no matter what speed the aeroplane is flying at, when this angle is exceeded, the aeroplane will stall because of the breakdown of the smooth airflow.

One way to do this would be, from straight and level, to close the throttle to idle and attempt to continue flying level. In straight and level flight the angle of attack is about 4 degrees (see Figure 1a below).

As lift is primarily controlled through angle of attack and airspeed, and lift must equal the airplane’s weight to maintain level flight. As the airspeed decreases, the angle of attack must be increased to maintain lift equal to weight.

L = angle of attack x airspeed (oversimplified equation)  

As the angle of attack increases, the airflow finds it more and more difficult to follow the contoured upper surface of the wing (aerofoil) smoothly, and the point at which the airflow breaks away from the wing, the separation point, moves forward from the trailing edge. At the same time, the point through which lift acts, the center of pressure (CP), also moves forward along the chord line; this movement is unstable because it reduces the moment of the lift/weight couple (see Figure 1b below).

Eventually, the stalling (or critical) angle of attack is reached (Figure 1c), and the inability of the air to flow smoothly over the top surface of the wing results in a decrease in lift and a large increase in drag.

Figure 1a Straight and level flight

Figure 1b Increased angle of attack

Figure 1c Stalling or critical angle of attack

The result is that the airplane sinks. At the same time, the center of pressure moves rapidly rearward. The rearward movement of the center of pressure increases the moment provided by the lift/weight couple, causing the nose to pitch down – a stable movement.

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Stall Definition:

Stall is defined as a sudden reduction in the lift generated by an aerofoil when the critical angle of attack is reached or exceeded. Engine stall and airplane stall are very different.

A stalled wing may be accompanied by one or more of the following:

Buffet (vibration caused by separated airflow)

Poor pitch authority.

Poor roll control.

An inability to arrest descent.

On all transport aircraft, some form of stall protection system is a certification requirement. Such a system is likely to incorporate stall warning based on the continuous direct measurement of angle of attack moderated by wing configuration in order to enable recovery from an incipient or approaching stall. For aircraft with a conventional control column, this usually includes a stick shaker which provides tactile as well as aural alerting. At the onset of a full stall, most stall protection systems activate a stick pusher to ensure that aircraft pitch attitude is automatically reduced as an essential component of recovery to safe flight.

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Stall Recognition:

A pilot must recognize the flight conditions that are conducive to stalls and know how to apply the necessary corrective action. This level of proficiency requires learning to recognize an impending stall by sight, sound, and feel.

Stalls are usually accompanied by a continuous stall warning for airplanes equipped with stall warning devices. These devices may include an aural alert, lights, or a stick shaker all which alert the pilot when approaching the critical AOA. Certification standards permit manufacturers to provide the required stall warning either through the inherent aerodynamic qualities of the airplane or through a stall warning device that gives a clear indication of the impending stall. However, most vintage airplanes, and many types of light sport and experimental airplanes, do not have stall warning devices installed.

Other sensory cues for the pilot include:

• Feel—the pilot will feel control pressures change as speed is reduced. With progressively less resistance on the control surfaces, the pilot must use larger control movements to get the desired airplane response. The pilot will notice the airplane’s reaction time to control movement increases. Just before the stall occurs, buffeting, uncommanded rolling, or vibrations may begin to occur.
• Vision—since the airplane can be stalled in any attitude, vision is not a foolproof indicator of an impending stall. However, maintaining pitch awareness is important.
• Hearing—as speed decreases, the pilot should notice a change in sound made by the air flowing along the airplane structure.
• Kinesthesia—the physical sensation (sometimes referred to as “seat of the pants” sensations) of changes in direction or speed is an important indicator to the trained and experienced pilot in visual flight. If this sensitivity is properly developed, it can warn the pilot of an impending stall.

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Fundamentals of Stall Recovery:

Depending on the complexity of the airplane, stall recovery could consist of as many as six steps. Even so, the pilot should remember the most important action to an impending stall or a full stall is to reduce the AOA. There have been numerous situations where pilots did not first reduce AOA, and instead prioritized power and maintaining altitude, which resulted in a loss of control. A pilot should always follow the aircraft-specific manufacturer’s recommended procedures if published and current.

The recovery actions should be made in a procedural manner; they can be summarized below in six steps:

-1. Disconnect the wing leveler or autopilot (if equipped). Manual control is essential to recovery in all situations. Disconnecting this equipment should be done immediately and allow the pilot to move to the next crucial step quickly. Leaving the wing leveler or autopilot connected may result in inadvertent changes or adjustments to the flight controls or trim that may not be easily recognized or appropriate, especially during high workload situations.

-2. a) Pitch nose-down control. Reducing the AOA is crucial for all stall recoveries. Push forward on the flight controls to reduce the AOA below the critical AOA until the impending stall indications are eliminated before proceeding to the next step.  b) Trim nose-down pitch. If the elevator does not provide the needed response, pitch trim may be necessary. However, excessive use of pitch trim may aggravate the condition, or may result in loss of control or high structural loads.

-3. Roll wings level. This orients the lift vector properly for an effective recovery. It is important not to be tempted to control the bank angle prior to reducing AOA. Both roll stability and roll control will improve considerably after getting the wings flying again. It is also imperative for the pilot to proactively cancel yaw with proper use of the rudder to prevent a stall from progressing into a spin.

-4. Add thrust/power. Power should be added as needed, as stalls can occur at high power or low power settings, or at high airspeeds or low airspeeds. Advance the throttle promptly, but smoothly, as needed while using rudder and elevator controls to stop any yawing motion and prevent any undesirable pitching motion. Adding power typically reduces the loss of altitude during a stall recovery, but it does not eliminate a stall. The reduction in AOA is imperative. For propeller driven airplanes, power application increases the airflow around the wing, assisting in stall recovery.

-5. Retract speed brakes/spoilers (if equipped). This will improve lift and the stall margin.

-6. Return to the desired flightpath. Apply smooth and coordinated flight control movements to return the airplane to the desired flightpath being careful to avoid a secondary stall. The pilot should, however, be situationally aware of the proximity to terrain during the recovery and take the necessary flight control action to avoid contact with it.  

The above procedure can be adapted for the type of aircraft flown. For example, a single-engine training airplane without an autopilot would likely only use four of the six steps. The first step is not needed therefore reduction of the AOA until the stall warning is eliminated is first. Use of pitch trim is less of a concern because most pilots can overpower the trim in these airplanes and any mistrim can be corrected when returning to the desired flightpath. The next step is rolling the wings level followed by the addition of power as needed all while maintaining coordinated flight. The airplane is not equipped with speed brakes or spoilers therefore this step can be skipped and the recovery will conclude with returning to the desired flightpath.

Similarly, a glider pilot does not have an autopilot therefore the first step is the reduction of AOA until the stall warning is eliminated. The pilot would then roll wings level while maintaining coordinated flight. There is no power to add therefore this step would not apply. Retracting speed brakes or spoilers would be the next step for a glider pilot followed by returning to the desired flightpath.

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Spin:

A spin is a yaw aggravated stall which results in rotation about the spin axis. The aircraft follows a steep, “corkscrew” like, downward path.

Spin—an aggravated stall and autorotation as seen in the figure below:

A spin is an aggravated stall that typically occurs from a full stall occurring with the airplane in a yawed state and results in the airplane following a downward corkscrew path. As the airplane rotates around a vertical axis, the outboard wing is less stalled than the inboard wing, which creates a rolling, yawing, and pitching motion. The airplane is basically descending due to gravity, rolling, yawing, and pitching in a spiral path. The rotation results from an unequal AOA on the airplane’s wings. The less-stalled rising wing has a decreasing AOA, where the relative lift increases and the drag decreases. Meanwhile, the descending wing has an increasing AOA, which results in decreasing relative lift and increasing drag. The aircraft will descend rapidly in a corkscrew motion. According to the Jeppesen Private Pilot Manual, a small airplane will descend about 500 feet for each turn in a spin, so there’s not much altitude or time available for a recovery in many cases. Considering stalls and spins often occur at low altitudes to begin with, it’s clear why the fatality rate is higher for these accidents.

Stages of a Spin:

The FAA has outlined three stages for spins in light aircraft: incipient, fully developed and recovery.

Incipient: The incipient phase of a spin is the stall and spin entry, up to about 2 turns in the spin.

Fully Developed: When the airspeed and rotation stabilize, the spin is considered fully developed.

Recovery: Recovery occurs when the pilot applies rudder and aileron inputs to counter the spin and the aircraft regains lift and control function. Once the inputs are initiated to stop the spin, the aircraft can usually recover in less than one spin.

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Spin recovery:

To accomplish spin recovery, always follow the manufacturer’s recommended procedures. In the absence of the manufacturer’s recommended spin recovery procedures and techniques, use the spin recovery procedures as described below. If the flaps and/or retractable landing gear are extended prior to the spin, they should be retracted as soon as practicable after spin entry.

The following discussion explains each of the six steps of spin recovery:

-1. Reduce the Power (Throttle) to Idle. Power aggravates spin characteristics. It can result in a flatter spin attitude and usually increases the rate of rotation.

-2. Position the Ailerons to Neutral. Ailerons may have an adverse effect on spin recovery. Aileron control in the direction of the spin may accelerate the rate of rotation, steepen the spin attitude and delay the recovery. Aileron control opposite the direction of the spin may cause flattening of the spin attitude and delayed recovery; or may even be responsible for causing an unrecoverable spin. The best procedure is to ensure that the ailerons are neutral.

-3. Apply Full Opposite Rudder against the Rotation. Apply and hold full opposite rudder until rotation stops. Rudder tends to be the most important control for recovery in typical, single-engine airplanes, and its application should be brisk and full opposite to the direction of rotation. Avoid slow and overly cautious opposite rudder movement during spin recovery, which can allow the airplane to spin indefinitely, even with anti-spin inputs. A brisk and positive technique results in a more positive spin recovery.

-4. Apply Positive, Brisk, and Straight Forward Elevator (Forward of Neutral). This step should be taken immediately after full rudder application. Do not wait for the rotation to stop before performing this step. The forceful movement of the elevator decreases the AOA and drives the airplane toward unstalled flight. In some cases, full forward elevator may be required for recovery. Hold the controls firmly in these positions until the spinning stops. (Note: If the airspeed is increasing, the airplane is no longer in a spin. In a spin, the airplane is stalled, and the indicated airspeed should therefore be relatively low and constant and not be accelerating.)

-5. Neutralize the Rudder After Spin Rotation Stops. Failure to neutralize the rudder at this time, when airspeed is increasing, causes a yawing or sideslipping effect.

-6. Apply Back Elevator Pressure to Return to Level Flight. Be careful not to apply excessive back elevator pressure after the rotation stops and the rudder has been neutralized. Excessive back elevator pressure can cause a secondary stall and may result in another spin. The pilot must also avoid exceeding the G-load limits and airspeed limitations during the pull out.

Again, it is important to remember that the spin recovery procedures and techniques described above are recommended for use only in the absence of the manufacturer’s procedures. The pilot must always be familiar with the manufacturer’s procedures for spin recovery.

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Prevention of stall:

Regulatory changes in recent years have greatly simplified the installation of electronic or electromechanical angle-of-attack (AOA) indicators, and manufacturers have responded with new and progressively less expensive systems that qualify as minor rather than major alterations, requiring only a logbook entry from an airframe and powerplant mechanic. In addition to warning against unintended stalls at low altitude, AOA indicators can help improve the precision of short- and soft-field operations by enabling the pilot to fly the exact angle of attack that maximizes lift at minimum airspeed. One potential drawback, however, is that most AOA indicators are based on a single probe on one wing—making it possible to stall the other wing before AOA on the monitored wing reaches its critical value.

While AOA indicators are useful, pilots have flown safely without them for more than a century. A few simple rules, if followed consistently, will minimize the risk of an unintended stall:

• Avoid abrupt changes of pitch or bank below 1,000 feet agl. Remember that these can provoke accelerated stalls at airspeeds much higher than the wings-level VS0 and VS1 specified in the POH.
• Maintain an altitude that will keep you safely above towers, power lines, and other obstructions.
• Keep all low-altitude turns coordinated with a maximum bank angle of 30 degrees.
• Don’t attempt to salvage an unstable landing approach, and don’t attempt to correct for an overshoot with inside rudder. If normal, coordinated maneuvering at a maximum 30 degrees of bank won’t re-establish the airplane on a stable approach no less than 500 feet agl, go around!
• Don’t follow other aircraft too closely in the traffic pattern, and be conservative about attempting S-turns or 360s for spacing.
• Regularly practice stall recognition and prevention at a safe altitude, preferably under the supervision of an instructor. Learning to recognize the cues of an impending stall and correct by promptly reducing the angle of attack is more important than practicing recovery from fully developed stalls. (One school of thought holds that practicing stalls to full break may perversely reinforce the tendency to keep pulling back as the airframe begins to buffet and stall warning sounds, exactly the wrong response at low altitude!)
• Consider seeking spin training from an experienced instructor in an airplane certified for intentional spins to learn to recognize the attitudes and control inputs that can trigger a spin before it actually develops.

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Is it dangerous for passengers when an aircraft stall?

We only need to look at Air France flight 447 in 2009 to see what happens when a commercial aircraft (Airbus A330) encounters stall condition. The plane was en route to Paris, France from Rio De Janeiro, Brazil, when ice crystals clouded the airspeed sensors and disabled auto-pilot systems. Pilots then mistakenly increased the angle of attack of the aircraft, causing stall conditions, and plunging the plane into the ocean. All passengers and crew on board perished.

The aviation industry learned several lessons from this event:

-Warning messages failed to alert the crew or provided incorrect feedback. The angle of attack was so extreme that alarms disregarded the readings as false. When pilots lowered the nose, alarms kicked back in as the angle of attack data was now more ‘reasonable.’

-A lack of training for pilots flying at a high altitude and losing airspeed indicators

-False readings told the pilots that their aircraft was moving slowly and thus in a stall. In retrospect, had the pilots not taken any action when the auto-pilot disabled, or lowered the nose back to level when stalling, the airspeed would have increased with a lower angle of attack, and the aircraft would have remained in the air.

Since the event, Airbus has told airlines to switch at least half of the sensors onboard the A330 and A340 to a different supplier to ensure they cannot be iced over.

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Section-20

Mid-air collision: [please read ‘loss of separation’ segment vide supra]    

In aviation, a mid-air collision is an accident in which two or more aircraft come into unplanned contact during flight.  Owing to the relatively high velocities involved and the likelihood of subsequent impact with the ground or sea, very severe damage or the total destruction of at least one of the aircraft usually results. The potential for a mid-air collision is increased by miscommunication, mistrust, error in navigation, deviations from flight plans, lack of situational awareness, and the lack of collision-avoidance systems. Although a rare occurrence in general due to the vastness of open space available, collisions often happen near or at airports, where large volumes of aircraft are spaced more closely than in general flight.

Events where aircraft collide on the runway or while one is on the ground and the other in the air close to the ground are covered under Runway Incursion.

Events where aircraft collide during taxi or push-back (including collisions with parked aircraft) are covered under Ground Operations.

Events where aircraft collide with obstacles (e.g., terrain, buildings, masts, trees etc.) while in flight are covered under CFIT.

A collision of two or more aircraft should be analyzed and reported statistically as one accident.

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Efforts to prevent mid-air collisions include:

-Airspace design, including the classification of airspace, the route structure, flight levels and the SIDs and STARs around airports.

-Air traffic flow and capacity management (ATFCM), including capacity planning, flexible use of airspace and flow management.

-Traffic synchronisation, including sector planning, multi-sector planning and arrival/departure sequencing.

-ATC conflict management, in which ATCOs provide separation between aircraft.

-Pilot conflict management, in which pilots are responsible for avoiding other aircraft, sometimes with the assistance of information from ATC.

-Airborne collision avoidance, including: Airborne collision avoidance system (ACAS) and Visual airborne collision avoidance (See and Avoid).

-Providence (i.e., the chance separation of the two aircraft trajectories in time or space) can also be considered a barrier against mis-air collision. It explains why a loss of separation does not necessarily lead to a collision, even if all the managed collision avoidance barriers are unsuccessful.

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TCAS:

Almost all modern large aircraft are fitted with a traffic collision avoidance system (TCAS), which is designed to try to prevent mid-air collisions. The system, based on the signals from aircraft transponders, alerts pilots if a potential collision with another aircraft is imminent. Despite its limitations, it is believed to have greatly reduced mid-air collisions.

A traffic collision avoidance system or traffic alert and collision avoidance system (both abbreviated as TCAS) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of mid-air collision (MAC). It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5,700 kg (12,600 lb) or authorized to carry more than 19 passengers. CFR 14, Ch I, part 135 requires that TCAS I be installed for aircraft with 10-30 passengers and TCAS II for aircraft with more than 30 passengers. ACAS/TCAS is based on secondary surveillance radar (SSR) transponder signals, but operates independently of ground-based equipment to provide advice to the pilot on potentially conflicting aircraft.

The term ACAS II is typically used when referring to the standard or concept and TCAS II when referring to the implementation.

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Section-21

Cabin Decompression (Depressurization):

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Inside an airplane cabin when it is cruising at 33,000 feet: 

The first thing to understand is that people dressed in normal clothing definitely cannot survive at 33,000. This altitude is roughly the equivalent to standing at the summit of Mount Everest. If there were some way you could stick your arm out the window at 33,000 feet, the first thing you would notice is that it is incredibly cold – minus 50 degrees C. The second problem is incredibly low air pressure. The pressure is so low that people would pass out very quickly from lack of oxygen. The air at that altitude and temperature is also extremely dry.

So how are we able to sit in an airplane’s comfy chairs at 33,000 feet feeling like we are sitting in someone’s living room?

The first thing that has to happen is pressurization. The air at sea level is about 14.7 PSI (pounds per square inch). The pressure at 33,000 feet (roughly 6 miles up) is approximately 4 PSI. Something has to be done to increase the pressure, or people would quickly pass out from lack of oxygen at 4 PSI. Fortunately, the jet engines on the aircraft act like big air compressors.

If you take apart a jet engine and look at it, it has four main sections. At the front, where the air is coming in, there is the compressor stage. Blades suck in air and compress it. The fuel is injected into the compressed air and ignited in the combustion stage. The air expands greatly from the heat of combustion, and flows through another set of blades, turning them as it passes through. And then the exhaust gases flow out of the engine to create thrust to keep the airplane in the air. By creating an opening in the engine between the compression stage and the combustion stage, high pressure air can bleed out of the engine and feed into the cabin to pressurize it. Because this air has just been pressurized, it is hot. Therefore, the ventilation system on the plane will first cool it down (using the extremely cold outside air that is readily available) to a comfortable temperature. The air pressure inside the plane is not sea level pressure but about altitude of 7000 ft.

Now we have a cabin that is pressurized and warm. But because the outside air is so incredibly dry, some consideration has to be given to humidity. Fortunately the plane is full of humidifiers. People give off moisture every time they exhale, and also through perspiration. So the dry air from outside is mixed with the air already in the cabin and recirculated. The ratio of new air and existing air is typically 50/50. The recirculated air passes through filters that remove any airborne particulates. The air in the cabin is still dry, but not nearly as dry as it could be.

What happens if cabin pressurization fails?

Depressurization (decompression) of the aircraft cabin occurs a result of structural failure, pressurization system malfunction, explosion, or an inadvertent crew action. Depressurization can occur if the airplane’s skin ruptures or a window breaks. When that happens, the masks overhead will deploy and the pilot will immediately start descending down to a safe altitude like 8,000 feet. The masks get their oxygen not from pressurized tanks of oxygen (they would be too heavy) but instead from a chemical reaction involving something like potassium chlorate. When heated, potassium chlorate gives off lots of oxygen and a chemical oxygen canister like this is very light, relatively speaking.

The next time you board an airplane, take a moment to marvel at what is happening. You will be sitting in a comfortable chair at 33,000 feet, just like you might sit in your living room. An amazing amount of technology makes that possible.

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Need for cabin pressurization:

Sure, humans evolved to thrive in Earth’s atmosphere, but it’s important to realize that we only evolved to thrive in a thin layer of the planet’s gaseous outer layer. Air pressure changes depending on altitude. In the same way that the water pressure in the ocean is greater on the seafloor than it is just below the surface, air pressure decreases the higher you ascend through the atmosphere. When humans breathe thinner, high-altitude air, they have a harder time taking in enough oxygen. And when we hang out at heights higher than 9,800 feet (3,000 meters), our bodies become susceptible to a host of unpleasant or even deadly illnesses.

Pressurization becomes increasingly necessary at altitudes above 10,000 feet (3,000 m) above sea level to protect crew and passengers from the risk of a number of physiological problems caused by the low outside air pressure above that altitude. For private aircraft operating in the US, crew members are required to use oxygen masks if the cabin altitude (a representation of the air pressure) stays above 12,500 ft for more than 30 minutes, or if the cabin altitude reaches 14,000 ft at any time. At altitudes above 15,000 ft, passengers are required to be provided oxygen masks as well. On commercial aircraft, the cabin altitude must be maintained at 8,000 feet (2,400 m) or less. Pressurization of the cargo hold is also required to prevent damage to pressure-sensitive goods that might leak, expand, burst or be crushed on re-pressurization.

The principal physiological problems of depressurization (decompression) are listed below.

Hypoxia:

The lower partial pressure of oxygen at high altitude reduces the alveolar oxygen tension in the lungs and subsequently in the brain, leading to sluggish thinking, dimmed vision, loss of consciousness, and ultimately death. In some individuals, particularly those with heart or lung disease, symptoms may begin as low as 5,000 feet (1,500 m), although most passengers can tolerate altitudes of 8,000 feet (2,400 m) without ill effect. At this altitude, there is about 25% less oxygen than there is at sea level.

Hypoxia may be addressed by the administration of supplemental oxygen, either through an oxygen mask or through a nasal cannula. Without pressurization, sufficient oxygen can be delivered up to an altitude of about 40,000 feet (12,000 m). This is because a person who is used to living at sea level needs about 0.20 bar partial oxygen pressure to function normally and that pressure can be maintained up to about 40,000 feet (12,000 m) by increasing the mole fraction of oxygen in the air that is being breathed. At 40,000 feet (12,000 m), the ambient air pressure falls to about 0.2 bar, at which maintaining a minimum partial pressure of oxygen of 0.2 bar requires breathing 100% oxygen using an oxygen mask.

Emergency oxygen supply masks in the passenger compartment of airliners do not need to be pressure-demand masks because most flights stay below 40,000 feet (12,000 m). Above that altitude the partial pressure of oxygen will fall below 0.2 bar even at 100% oxygen and some degree of cabin pressurization or rapid descent will be essential to avoid the risk of hypoxia.

Altitude sickness:

Hyperventilation, the body’s most common response to hypoxia, does help to partially restore the partial pressure of oxygen in the blood, but it also causes carbon dioxide (CO2) to wash out, raising the blood pH and inducing alkalosis. Passengers may experience fatigue, nausea, headaches, sleeplessness, and (on extended flights) even pulmonary oedema. These are the same symptoms that mountain climbers experience, but the limited duration of powered flight makes the development of pulmonary oedema unlikely. Altitude sickness may be controlled by a full pressure suit with helmet and faceplate, which completely envelops the body in a pressurized environment; however, this is impractical for commercial passengers.

Decompression sickness:

The low partial pressure of gases, principally nitrogen (N2) but including all other gases, may cause dissolved gases in the bloodstream to precipitate out, resulting in gas embolism, or bubbles in the bloodstream. The mechanism is the same as that of compressed-air divers on ascent from depth. Symptoms may include the early symptoms of “the bends”—tiredness, forgetfulness, headache, stroke, thrombosis, and subcutaneous itching—but rarely the full symptoms thereof. Decompression sickness may also be controlled by a full-pressure suit as for altitude sickness.

Barotrauma:

As the aircraft climbs or descends, passengers may experience discomfort or acute pain as gases trapped within their bodies expand or contract. The most common problems occur with air trapped in the middle ear (aerotitis) or paranasal sinuses by a blocked Eustachian tube or sinuses. Pain may also be experienced in the gastrointestinal tract or even the teeth (barodontalgia). Usually these are not severe enough to cause actual trauma but can result in soreness in the ear that persists after the flight and can exacerbate or precipitate pre-existing medical conditions, such as pneumothorax.

Pressurized cabins enable pilots, crew and passengers to avoid these pitfalls of flying at high altitude. While the air outside the cabin thins out the higher a plane climbs, compressed air inside the cabin maintains more surface-level air pressure and oxygen-rich air. In the event of accidental loss of cabin pressure, emergency oxygen masks provide the necessary air quality. Pressurized flight suits achieve the same effect as pressurized cabins, only on an individual basis. Characterized by enclosed helmets, these suits typically see use in military and high-performance aircraft.

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Cabin altitude:

The pressure inside the cabin is technically referred to as the equivalent effective cabin altitude or more commonly as the cabin altitude. This is defined as the equivalent altitude above mean sea level having the same atmospheric pressure according to a standard atmospheric model such as the International Standard Atmosphere. Thus a cabin altitude of zero would have the pressure found at mean sea level, which is taken to be 101.325 kilopascals (14.696 psi).

In airliners, cabin altitude during flight is kept above sea level in order to reduce stress on the pressurized part of the fuselage; this stress is proportional to the difference in pressure inside and outside the cabin. In a typical commercial passenger flight, the cabin altitude is programmed to rise gradually from the altitude of the airport of origin to a regulatory maximum of 8,000 ft (2,400 m). This cabin altitude is maintained while the aircraft is cruising at its maximum altitude and then reduced gradually during descent until the cabin pressure matches the ambient air pressure at the destination.

Keeping the cabin altitude below 8,000 ft (2,400 m) generally prevents significant hypoxia, altitude sickness, decompression sickness, and barotrauma. Federal Aviation Administration (FAA) regulations in the U.S. mandate that under normal operating conditions, the cabin altitude may not exceed this limit at the maximum operating altitude of the aircraft. This mandatory maximum cabin altitude does not eliminate all physiological problems; passengers with conditions such as pneumothorax are advised not to fly until fully healed, and people suffering from a cold or other infection may still experience pain in the ears and sinuses. The rate of change of cabin altitude strongly affects comfort as humans are sensitive to pressure changes in the inner ear and sinuses and this has to be managed carefully.

The regulations stipulate that the maximum cabin altitude should not exceed 8000 feet during normal operations, and, in fact, at usual cruising altitude the cabin altitude rarely exceeds 6000 or 7000 feet in a modern jet airliner.

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Cabin Decompression and Hypoxia:

At the hypobaric chamber at the RAAF base in Edinburgh several hundred air force pilots each year get to check out their reactions to depressurization and the effects of hypoxia. The chamber is set to an altitude of 25,000 feet, which gives a time of useful consciousness of around three to five minutes. Up to ten pilots at a time sit in the chamber tensely-waiting for the depressurization, which starts at 8,000 feet and moves to 25,000 feet in just 10 seconds. Each clutches a checklist of tasks they are to perform. Each is determined to remain conscious and capable for as long as possible. After about two minutes one of the subjects is asked to repeat back a number. Inevitably the subject is unable to do so. In fact, most don’t remember being asked. Trying to go through the checklist the pilots tend to exhibit one of two kinds of behaviour; they are either “page flickers” or “fixators”. The page flickers will just sit there mindlessly flipping through the checklists while the fixators will just stare at one page. They are “passengers in their own bodies”. These two quite different behavioural responses to rapid depressurization hint at the variation in individual responses to lack of oxygen, or hypoxia.

Hypoxia is a threat to safety for all pilots operating pressurised aircraft and for unpressurised aircraft that fly at an altitude of 10,000 feet or above — the legal ceiling above which oxygen must be used by flight crew members in unpressurised aircraft. Some individuals with reduced lung function will become hypoxic well below this level. This includes people with emphysema, industrial lung disease, certain forms of anaemia, ischaemic heart disease and even mild degrees of heart failure.

If you smoke, you may have already reduced your oxygen intake by a significant factor. Avoid smoking before and during flight.

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The term hypoxia translates from the Latin to mean below normal (hypo) oxygen (oxia). It is a physiological state in which tissues are deprived of adequate oxygen, and organs such as the brain, eyes, ears, lungs and heart are adversely affected.

When an aircraft undergoes rapid decompression above around 35,000 feet, the time of useful consciousness for crew may be 30 seconds or less, depending on the altitude (see table below).

Time of Useful Consciousness (TUC) is the amount of time in which a person is able to effectively or adequately perform flight duties with an insufficient supply of oxygen. TUC decreases with altitude, until eventually coinciding with the time it takes for blood to circulate from the lungs to the head usually at an altitude above 35,000 feet. Other factors that determine TUC are physical activities, and day-to-day factors such as physical fitness, diet, rest, prescription drugs, smoking, and illness. Altitude chamber experiments found a significantly longer TUC for nonsmoker pilots who exercise and watch their diet than for pilots who smoke and are not physically fit.

Time of Useful Consciousness
Altitude (feet)		Consciousness
15,000 18,000 22,000 25,000 28,000 30,000 35,000 40,000 45,000 50,000		30 minutes or more 20-30 minutes 5-10 minutes 3-5 minutes 2.5-3 minutes 1-3 minutes 30-60 seconds 15-20 seconds 9-15 seconds 6-9 seconds
Pressure and Altitude
Altitude (feet)	Pressure    hpa          lb/in2		Temperature oC
0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000	1013.25 843.1 696.8 571.8 465.6 376.0 300.9 238.4 147.5	14.70 12.23 10.11 8.29 6.75 5.45 4.36 3.46 2.72	+15.0 +5.1 -4.8 -14.7 -24.6 -34.5 -44.4 -54.2 -56.5

A US Federal Aviation Administration chart showed that at 43,000 feet crew members are able to perform flight duties with an insufficient supply of oxygen for a mere five seconds, Hardly long enough to don an oxygen mask. But at 22,000 feet, passengers and crew would have five minutes of “useful consciousness” after rapid decompression.

At lower altitudes the time of useful consciousness maybe longer, but subtle effects may still impair your functioning. The more rapid the decompression, the faster the symptoms of hypoxia will appear.

Crew surprise and perhaps lack of familiarity with decompression can contribute to dangerous delays in appropriate response. Research by the US Air Force shows 80 per cent of pilots with no experience of decompression wait as long as 15 seconds to respond correctly to a loss of cabin pressure.

Because of the insidious effects of hypoxia on judgement and reasoning, the correct response to loss of cabin pressure is always to don the oxygen mask – immediately. That’s the only way you can be sure that you will make the right choices.

Another problem with a large hole could be a drop in cabin temperature from 21 degrees Celsius to -50C. With temperatures that low, it is only a matter of seconds before hypothermia sets in and everyone begins to freeze to death.

Recovery Procedures:

Don your oxygen mask immediately, select 100 percent oxygen if you have differential settings, then descend to 10,000 feet or below, terrain permitting. You may find that you feel worse immediately after putting your oxygen mask on. Do not take it off. This is called the oxygen paradox and you will feel better after about one minute. Breathe at a normal rate and depth. Declare an emergency, and land as soon as possible. After recovery from an episode of hypoxia, some symptoms may persist. These include headache, fatigue and lethargy.

Note that if you have been in an aircraft which has been decompressed, you should not fly again the same day because you will increase your risk of decompression illness. Decompression illness (or the bends) can be incapacitating, particularly if nitrogen bubbles enter the brain.

You should also use oxygen if you detect fumes or smoke. Again, set the oxygen at 100 per cent in order to prevent any toxins from the fumes or smoke entering the system.

Prevention:

The key to prevention is twofold. First, you need to follow your flight manual prompts to accurately set and monitor cabin pressure. As soon as the cabin pressure drops below recommended levels you should take preventative action.

If warning systems indicate problems with cabin pressure, you must immediately don your oxygen mask and descend if terrain permits. It pays to know your equipment, because it can take some time to put the oxygen mask on. Make sure you know how to use the masks, practice using them, and time yourself in putting them on.

There are traps with checklists which you must guard against. You should understand your pressurization and oxygen systems, and fill in the gaps in your checklists so that you are sure of what to do in an emergency. For example, if you are over ocean and have an uncontained engine failure which leads to depressurization, you will want 20,000 feet or so to retain range. But do you have enough oxygen? Do you know how to calculate that?

Sixty per cent of corporate jet depressurizations are caused by uncontained engine failures. Most others are caused by doors or windows departing the aeroplane. Even if you set up and use checklists properly, things can still go wrong.

A checklist is a skill based action which means it is a stored pattern of preprogrammed activity. The greater the skill level, the greater the chance of “strong, but wrong” error. All it takes is a change to a well practised routine and a missed attentional check. The intention may be correct, but the action may be wrong.

You could get it wrong through inattention, jisti action or preoccupation. That’s why checklists need to be monitored carefully as they are the last line of defence.

If you are halfway through a checklist, and are interrupted, go back to the beginning and start again. Be sure, however, not to introduce new errors by operating things like switches which have already been activated correctly.

The one thing that you should not do first is to start working out what’s gone wrong. That is, you should not be problem solving and planning on line. This is hard to do. If you know the aircraft well and you have a pressurization warning going off, but the cabin pressure indicator seems OK, you should not be trying to work out which is correct. You must immediately put on the oxygen mask, descend and then look to problem solving.

The reason you should not work the problem early is that hypoxia interferes with your ability to solve problems and limits your time of useful consciousness. Get the oxygen right first, then ponder your situation. If you go into problem solving mode you will lose valuable time. You should take the course of least regret.

From a human factors point of view, once you notice a pressurization warning, you need to quickly don your oxygen mask. So your well-practised rule should always be:

Pressurization warning.

Don mask.

Descend (terrain permitting).

Solve the problem.

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How can someone get sucked out of airplane?

If a plane window breaks, a door opens, or a hole emerges in the fuselage mid-flight, it is possible for something — or someone — to get sucked out. And that’s because of the big difference in pressure between the air inside a plane and the air outside it. Plane cabins are kept at an air pressure that’s roughly similar to about 6000 to 8000 feet above sea level. When the plane is at cruising altitude, at around 30,000 feet, the pressure outside the plane is a lot lower — about two-and-a-half times lower. This means that when a hole forms, the rush to equalize causes a strong tunnel of wind capable of rapidly blowing things out through the hole — including people. Experts said the impact would vary depending on the size of the hole — the bigger the hole, the bigger the danger.

It would take about 100 seconds for pressure to equalize through a roughly 30cm hole in the fuselage of a Boeing 747. Anyone sitting next to that hole would have half a ton of force pulling them in the direction of it.

The force of the wind rushing through the hole could also make it bigger. Seatbelts could save people, though — anyone wearing their seatbelt are unlikely to be drawn through a hole, provided their seats remained attached to the cabin floor.

Holes in planes don’t always mean catastrophes, and they’re not common. But explosive decompression has caused a number of midair deaths.

-1. In 1989, a United Airlines Boeing 747 from Los Angeles to Sydney was flying between scheduled stops in Honolulu and Auckland when a cargo door failure struck, causing nine passengers, who were strapped to their seats, to be blown out of the aircraft. Inside the cabin there were pieces of debris flying all over.

-2. In another incident, on an Aloha Airlines flight between Hilo and Honolulu in 1988, a massive hole ripped open on the ceiling above first class and a flight attendant was sucked out of the jet with the escaping air. The hole was blamed on metal fatigue and maintenance error.

-3. Eight people died in 2000 when the Beechcraft Kir Air 200 they were flying in lost cabin oxygen on a flight from Perth destined for Leonora in Western Australia. The plane kept going for about five hours before crashing when fuel ran out. The Australian Transport Safety Bureau report found the pilot and passengers were probably overcome by hypoxia, or oxygen starvation, after the plane’s pressurization system failed. The accident was similar to the 1999 crash that killed US Open golf champion Payne Stewart and companions. Sudden high-altitude decompression after a blow out in the Learjet 35 was one theory put forward to explain the crash.

-4. In 2005 Alaska Airlines flight 536 was forced to turn back to Seattle 20 minutes after takeoff when a crease in the side of the aircraft became a 30-by-15-centimeter hole, causing the cabin to lose pressure. Fortunately the MD-80 plane was quickly stabilized and landed safely. An investigation found the crease had been caused by baggage handlers who had bumped the fuselage with loading equipment.  

-5. In 2009, a Southwest Airlines flight was forced to make an emergency landing in West Virginia after metal fatigue caused a crack and football-sized hole in the fuselage of the Boeing 737, causing rapid decompression. There were no fatalities or major injuries, but a similar incident happened to another Southwest Airlines aircraft two years later. 

-6. Sichuan Airlines Flight 8633 was a flight from Chongqing Jiangbei International Airport to Lhasa Gonggar Airport on 14 May 2018, which was forced to make an emergency landing at Chengdu Shuangliu International Airport after the cockpit windshield failed. The aircraft involved was an Airbus A319-100. The incident has been adapted into the 2019 film The Captain.

Approximately 40 minutes after departure while over Xiaojin County, Sichuan at 30,000 feet, the right front segment of the windshield separated from the aircraft followed by an uncontrolled decompression. As a result of the sudden decompression, the flight control unit was damaged, and the loud external noise made spoken communications impossible. The co-pilot however, was able to use the transponder to squawk 7700, alerting Chengdu Shuangliu International Airport control about their situation. Because the flight was within a mountainous region, the pilots were unable to descend to the required 8,000 ft (2,400 m) to compensate for the loss of cabin pressure. About 35 minutes later, the jetliner made an emergency landing at 7:42 CST (23:42 UTC) at Chengdu Shuangliu International Airport. The aircraft was overweight on landing. As a result, the plane took a longer distance to come to a stop and the tires burst.

Airplanes are designed to remain safe if a windshield or cabin window cracks. While this does happen occasionally, it is infrequent. Pilots will descend to reduce the pressure and plan on a diversion if necessary.

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Can a bullet cause decompression?

Professional pilot and international aviation training consultant David Lombardo made a point in his book Advanced Aircraft Systems. “A bullet hole in a cabin wall would have no perceived effect on cabin pressure…. A bullet hole is far smaller than the opening of the outflow valve. In fact, such a hole would account for less air leakage than what is normally lost around door and window seals.”

TV series Mythbusters also did an episode showing nothing much happened when a bullet was fired through the fuselage of a pressurized aircraft. Obviously the plane was on the ground at the time.

Airline pilot, blogger and author Patrick Smith wrote in a column in Salon in 2006, that large scale structural failures, which could be disastrous, were “extremely rare”. With a small breach, once cabin pressure had escaped, it could be reasonably assumed a plane would stay in one solid piece and fly fine.

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Section-22

Spatial Disorientation:   

Spatial Orientation is our natural ability to maintain our body orientation and/or posture in relation to the surrounding environment (physical space) at rest and during motion.

Genetically speaking, humans are designed to maintain spatial orientation on the ground. The three-dimensional environment of flight is unfamiliar to the human body, creating sensory conflicts and illusions that make spatial orientation difficult, and sometimes impossible to achieve. Statistics show that between 5 to 10% of all general aviation accidents can be attributed to spatial disorientation, 90% of which are fatal.

Spatial orientation in flight is difficult to achieve because numerous sensory stimuli (visual, vestibular, and proprioceptive) vary in magnitude, direction, and frequency. Any differences or discrepancies between visual, vestibular, and proprioceptive sensory inputs result in a sensory mismatch that can produce illusions and lead to spatial disorientation. Good spatial orientation relies on the effective perception, integration and interpretation of visual, vestibular (organs of equilibrium located in the inner ear) and proprioceptive (receptors located in the skin, muscles, tendons, and joints) sensory information.

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Spatial disorientation is defined as: A state characterized by an erroneous sense of one’s position and motion relative to the plane of the earth’s surface. Spatial disorientation is caused by the senses of the body misrepresenting the pilot’s position in space; these senses are vision (eyes), vestibular (inner ear), proprioceptors (muscle/tendon senses… “seat of the pants”).

The eyes, the most important source of information, send pictures to the brain about the aircraft’s position, velocity, and attitude relative to the ground. This works great on clear days in VFR (visual flight rules) conditions with a well-defined horizon; but in poor visibility, night flying, or IFR (instrument flight rules), a pilot can experience visual illusions (runway and approach illusions). A note of caution is that even on a clear VFR day, the eyes can play tricks, since up to 90 percent of orientation is provided by visual cues.

The part of the vestibular system are the semicircular canals in the inner ear. These canals are filled with fluid that indicates rotation on the yaw, pitch, and roll axis. They are actually accelerometers that sense changes in velocity.  After 10 to 20 seconds of constant angular acceleration of the inner ear’s fluid, the sensation of motion transmitted to the brain can be false. The pilot can be in a turn and not know it. In addition, there is a fixed acceleration threshold, below which the semicircular canals cannot sense any rotation at all. This threshold is approximately 2 degrees per second; if the rotation is gradual enough, the pilot won’t sense any change and will develop “the leans.” 

In all cases of spatial disorientation, the pilot must rely on the flight instruments when making control inputs – and must be patient until the false sensations dissipate.

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Disorientation in the Clouds:

Your eyes are your primary sensory input when you’re flying. You look outside, you see which way the sky is pointing, and you adjust your airplane. But all of that falls apart when you’re in the clouds. That’s because the sensory input of your eyes and ears start to disagree in the clouds. Your ears have three fluid-filled canals that help you determine which way is up, and they start taking over, for better or worse, when you can’t see beyond your propeller. So what’s the problem with your ears telling you which way is up? They aren’t as instant, or accurate, as your eyes. Because of friction between the fluid and the canals, it can take 15-20 seconds for your ears to reach equilibrium when you turn, climb or descend. That actually works out pretty well when you start manoeuvring your plane in the clouds, but the benefit doesn’t last long. For example, if you enter a constant-rate turn to the left, the friction of fluid sloshing around in your ear canals tells your brain that you’re turning left. The problem is, if you stay in that constant rate turn long enough, the fluid eventually stops moving. When that happens, your brain thinks the turn has stopped, and that’s not a good thing, because you’re still in the turn.

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Sensory illusions in aviation:

Human senses are not naturally geared for the inflight environment. Pilots may experience disorientation and loss of perspective, creating illusions that range from false horizons to sensory conflict with instrument readings or the misjudging of altitude over water.

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-1. Vestibular system

The vestibular system, which is responsible for the sense of balance in humans, consists of the otolith organs and the semicircular canals. Illusions in aviation are caused when the brain cannot reconcile inputs from the vestibular system and visual system. The three semicircular canals, which recognize accelerations in pitch, yaw, and roll, are stimulated by angular accelerations; while the otolith organs, the saccule and utricle, are stimulated by linear accelerations. Stimulation of the semicircular canals occurs when the movement of the endolymph inside the canals causes movement of the crista ampullaris and the hair cells within them. Stimulation of the otolith organs occurs when gravitational forces or linear accelerations cause movement of the otolith membrane, the otoliths, or the hair cells of the macula.

Somatogyral illusions occur as a result of angular accelerations stimulating the semicircular canals. Somatogravic illusions, on the other hand, occur as a result of linear accelerations stimulating the otolith organs.

-somatogyral illusions

Illusions involving the semicircular and somatogyral canals of the vestibular system of the ear occur primarily under conditions of unreliable or unavailable external visual references and result in false sensations of rotation. These include the leans, the graveyard spin and spiral, and the Coriolis illusion.

The leans

This is the most common illusion during flight, and can be caused by a sudden return to wings-level flight following a gradual entry and prolonged application of bank that had gone unnoticed by the pilot. The reason a pilot can be unaware of such an attitude change in the first place is that human exposure to a rotational acceleration of ~2 degrees per second or lower is below the detection threshold of the semicircular canals. Rolling wings-level from such an attitude may cause an illusion that the aircraft is banking in the opposite direction. In response to such an illusion, a pilot will tend to roll back in the direction of the original bank in a corrective attempt to regain the perception of a level attitude.

Graveyard spin

The graveyard spin is an illusion that can occur to a pilot who enters into a spin and is characterized by the pilot becoming less aware of the sense of rotation induced by the spin as the spin continues. As the pilot becomes less aware of the spin, any correction of the spin may cause the pilot to sense that he or she is spinning in the opposite direction.  As an example, if the airplane is spinning to the right but goes unnoticed for a period of time sufficient for the pilot to become desensitized to the magnitude of the spin, a small adjustment to the left rudder may leave the pilot with a sensation of spinning to the left. As a result, the pilot will apply right rudder and unknowingly re-enter the original right spin. Cross-checking the airplane’s flight instruments would show that the airplane is still in a turn, which causes sensory conflict for the pilot. If the pilot does not correct the spin, the airplane will continue to lose altitude until contact with the terrain occurs.

Graveyard spiral

The graveyard spiral is characterized by the pilot mistakenly believing he or she is in wings-level flight when the aircraft is in fact engaged in a banking turn, and notices the altimeter indicating an ongoing drop in altitude. The sensory disorientation of returning from a prolonged banking turn to wings-level flight can cause the pilot to re-enter the banking turn, as in the graveyard spin illusion. While the plane continues in the turn and begins to indicate a loss of altitude, the pilot will try to correct the loss of altitude by “pulling up” on the plane’s controls.  Attempting to adjust the controls in this way will have the effect of tightening the radius of the turn and eventually quickening the rate of descent until the pilot is visually cued to the nature of the error or contact with the terrain occurs. One of the most famous cases of an aircraft mishap from this form of spatial disorientation was the crash that killed John F. Kennedy Jr. over Martha’s Vineyard in 1999.

Coriolis illusion

This involves the simultaneous stimulation of two semicircular canals and is associated with a sudden tilting (forward or backwards) of the pilot’s head while the aircraft is turning. This can occur when tilting the head down (to look at an approach chart or to write on the knee pad), up (to look at an overhead instrument or switch), or sideways. This can produce an overpowering sensation that the aircraft is rolling, pitching, and yawing all at the same time, which can be compared with the sensation of rolling down a hillside. This illusion can make the pilot quickly become disoriented and lose control of the aircraft.

-somatogravic illusion

Somatogravic illusions are caused by linear accelerations. These illusions involving the utricle and the saccule of the vestibular system are most likely under conditions with unreliable or unavailable external visual references.

Inversion

An abrupt change from climb to straight-and-level flight can stimulate the otolith organs enough to create the illusion of tumbling backwards, or inversion illusion. The disoriented pilot may push the aircraft abruptly into a nose-low attitude, possibly intensifying this illusion.

Head-up

The head-up illusion involves a sudden forward linear acceleration during level flight where the pilot perceives the illusion that the nose of the aircraft is pitching up. The pilot’s response to this illusion would be to push the yoke or the stick forward to pitch the nose of the aircraft down. A night take-off from a well-lit airport into a totally dark sky (black hole) or a catapult take-off from an aircraft carrier can also lead to this illusion, and could result in a crash.

Head-down

The head-down illusion involves a sudden linear deceleration (air braking, lowering flaps, decreasing engine power) during level flight where the pilot perceives the illusion that the nose of the aircraft is pitching down. The pilot’s response to this illusion would be to pitch the nose of the aircraft up. If this illusion occurs during a low-speed final approach, the pilot could stall the aircraft.

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-2. Visual

Visual illusions are familiar to most of us. Even under conditions of good visibility, one can experience visual illusions.

-Linear perspective

This illusion may make a pilot change (increase or decrease) the slope of their final approach. They are caused by runways with different widths, upsloping or downsloping runways, and upsloping or downsloping final approach terrain. Pilots learn to recognize a normal final approach by developing and recalling a mental image of the expected relationship between the length and the width of an average runway. An example would be a pilot used to small general aviation fields visiting a large international airport. The much wider runway would give the pilot the mental picture of the point where they would usually begin the flare, when they are much higher than they should be. A pilot flying an aircraft where the cockpit height relative to the ground is vastly higher or lower than they are used to can cause a similar illusion in the last part of the approach.

-Upsloping terrain or narrow or long runway

A final approach over an upsloping terrain with a flat runway, or to an unusually narrow or long runway may produce the visual illusion of being too high on final approach. The pilot may then increase their rate of descent, positioning the aircraft unusually low on the approach path.

-Downsloping terrain or wide runway

A final approach over a downsloping terrain with a flat runway, or to an unusually wide runway may produce the visual illusion of being too low on final approach. The pilot may then pitch the aircraft’s nose up to increase the altitude, which can result in a low-altitude stall or a missed approach.

-Black-hole approach

A black-hole approach illusion can happen during a final approach at night (with no stars or moonlight) over water or unlit terrain to a lighted runway, in which the horizon is not visible. As the name suggests, it involves an approach to landing during the night where there is nothing to see between the aircraft and the intended runway, there is just a visual “black-hole”. Pilots too often confidently proceed with a visual approach instead of relying on instruments during nighttime landings. As a result, this can lead to the pilot experiencing glide path overestimation (GPO) because of the lack of peripheral visual cues, especially, below the aircraft. In addition, with no peripheral visual cues allowing for an orientation relative to the earth there can be an illusion of the pilot being upright and the runway being tilted and sloping. As a result, they initiate an aggressive descent and wrongly adjust to an unsafe glide path below the desired three-degree glide path.

-Autokinesis

The autokinetic illusion occurs at night or in conditions with poor visual cues. This illusion gives the pilot the impression that a stationary object is moving in front of the airplane’s path; it is caused by staring at a fixed single point of light (ground light or a star) in a totally dark and featureless background. The reason why this visual illusion occurs is because of very small movements of the eyes. In conditions with poor visual cues accompanied by a single source of light, these eye movements are interpreted by the brain as movement of the object being viewed. This illusion can cause a misperception that such a light is on a collision course with the aircraft.

Planets or stars in the night sky can often cause the illusion to occur. Often these bright stars or planets have been mistaken for landing lights of oncoming aircraft, satellites, or even UFOs. An example of a star that commonly causes this illusion is Sirius, which is the brightest star in the northern hemisphere and in winter appears over the entire continental United States at one to three fist-widths above the horizon. At dusk, the planet Venus can cause this illusion to occur and many pilots have mistaken it as lights coming from other aircraft.

-False visual reference

False visual reference illusions may cause the pilot to orient the aircraft in relation to a false horizon; these illusions can be caused by flying over a banked cloud, night flying over featureless terrain with ground lights that are indistinguishable from a dark sky with stars, or night flying over a featureless terrain with a clearly defined pattern of ground lights and a dark, starless sky.

-Glassy water landings in seaplanes

Calm glassy water poses a hazard to pilots of seaplanes because the absence of waves hinders accurate judgment of the aircraft’s altitude above the water surface on landing. If the pilot overestimates the aircraft’s altitude and fails to flare, the tips of the floats may be driven into the water, flipping the seaplane; similarly, if the pilot underestimates the aircraft’s altitude, flares too high and stalls, the aircraft will pitch down with the same potential result. Glassy water may also result in an unusually clear view of the lake or sea floor and abnormally brilliant reflections of clouds or shore features; these extraneous visual cues may further disorient the pilot. These hazards may be mitigated by flying the final approach over land or parallel to a nearby shoreline, allowing the pilot to use the land as a visual reference; however, the pilot must take care that the presumably shallow landing zone is free of obstructions. In the absence of a suitable landing area near shore, the recommended procedure is to make a long and shallow approach at a slow and steady descent rate and not to attempt to flare; however, the pilot should account for the increased glide and landing distance when using this technique.

-Vection

This is when the brain perceives peripheral motion, without sufficient other cues, as applying to itself. Consider the example of being in a car in lanes of traffic, when cars in the adjacent lane start creeping slowly forward. This can produce the perception of actually moving backwards, particularly if the wheels of the other cars are not visible. A similar illusion can happen while taxiing an aircraft.

-Repeating pattern

This is when an aircraft is moving at very low altitude over a surface that has a regular repeating pattern, for example ripples on water. The pilot’s eyes can misinterpret the altitude if each eye lines up different parts of the pattern rather than both eyes lining up on the same part. This leads to a large error in altitude perception, and any descent can result in impact with the surface. This illusion is of particular danger to helicopter pilots operating at a few meters altitude over calm water. 

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Prevention of Spatial Disorientation:

• Take the opportunity to personally experience sensory illusions in a Barany chair, a Vertigon, a GYRO, or a Virtual Reality Spatial Disorientation Demonstrator (VRSDD). By experiencing sensory illusions first-hand (on the ground), pilots are better prepared to recognize a sensory illusion when it happens during flight and to take immediate and appropriate action. The Aerospace Medical Education Division of the FAA Civil Aerospace Medical Institute offers spatial disorientation demonstrations with the GYRO and the VRSDD in Oklahoma City and at all of the major airshows in the continental U.S.
• Obtain training and maintain your proficiency in aircraft control by reference to instruments.
• When flying at night or in reduced visibility, use and rely on your flight instruments.
• Study and become familiar with unique geographical conditions where flight is intended.
• Do not attempt visual flight when there is a possibility of being trapped in deteriorating weather.
• If you experience a visual illusion during flight (most pilots do at one time or another), have confidence in your instruments and ignore all conflicting signals your body gives you. Accidents usually happen as a result of a pilot’s indecision to rely on the instruments.
• If you are one of two pilots in an aircraft and you begin to experience a visual illusion, transfer control of the aircraft to the other pilot, since pilots seldom experience visual illusions at the same time.
• By being knowledgeable, relying on experience, and trusting your instruments, you will be contributing to keeping the skies safe for everyone.

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Spatial Disorientation and Airsickness:

It is important to know the difference between spatial disorientation and airsickness. Airsickness is a normal response of healthy individuals when exposed to a flight environment characterized by unfamiliar motion and orientation clues. Common signs and symptoms of airsickness include: vertigo, loss of appetite, increased salivation and swallowing, burping, stomach awareness, nausea, retching, vomiting, increased need for bowel movements, cold sweating, skin pallor, sensation of fullness of the head, difficulty concentrating, mental confusion, apathy, drowsiness, difficulty focusing, visual flashbacks, eye strain, blurred vision, increased yawning, headache, dizziness, postural instability, and increased fatigue.

The symptoms are usually progressive. First, the desire for food is lost. Then, as saliva collects in the mouth, the person begins to perspire freely, the head aches, and the airsick person may eventually become nauseated and vomit. Severe airsickness may cause a pilot to become completely incapacitated.

Although airsickness is uncommon among experienced pilots, it does occur occasionally (especially among student pilots). Some people are more susceptible to airsickness than others. Fatigue, alcohol, drugs, medications, stress, illnesses, anxiety, fear, and insecurity are some factors that can increase individual susceptibility to motion sickness of any type. Women have been shown to be more susceptible to motion sickness than men of any age. In addition, reduced mental activity (low mental workload) during exposure to an unfamiliar motion has been implicated as a predisposing factor for airsickness.

A pilot who concentrates on the mental tasks required to fly an aircraft will be less likely to become airsick because his/ her attention is occupied. This explains why sometimes a student pilot who is at the controls of an aircraft does not get airsick, but the experienced instructor who is only monitoring the student unexpectedly becomes airsick.

A pilot who has been the victim of airsickness knows how uncomfortable and impairing it can be. Most importantly, it jeopardizes the pilot’s flying proficiency and safety, particularly under conditions that require peak piloting skills and performance (equipment malfunctions, instrument flight conditions, bad weather, final approach, and landing).

Pilots who are susceptible to airsickness should not take anti-motion sickness medications (prescription or over-the- counter). These medications can make one drowsy or affect brain functions in other ways. Research has shown that most anti-motion sickness medications cause a temporary deterioration of navigational skills or other tasks demanding keen judgment.

An effective method to increase pilot resistance to airsickness consists of repetitive exposure to the flying conditions that initially resulted in airsickness. In other words, repeated exposure to the flight environment decreases an individual’s susceptibility to subsequent airsickness.

If you become airsick while piloting an aircraft, open the air vents, loosen your clothing, use supplemental oxygen, keep your eyes on a point outside the aircraft, place your head against the seat’s headrest, and avoid unnecessary head movements. Then, cancel the flight, and land as soon as possible.

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Laser Interference in Aviation:

In recent years there has been a proliferation in the use of lasers outdoors for legitimate purposes such as laser shows and tests. More worryingly, there has also been an increase in the deliberate (and illegitimate) use of laser pointers to illuminate aircraft and sometimes air traffic control facilities.

The potentially hazardous visual effects of lasers are generally only visible during night time. The lasers produce an intense, coherent directional beam of light with wave lengths covering the visual spectrum of 400-700nm.

The main visual effects are:

Distraction and Startle: This occurs when an unexpected laser (or other bright light) can distract a pilot during a night time take-off or approach/landing.

Glare and Disruption: This occurs as the intensity of the laser light increases such that it starts to interfere with vision; night vision starts to deteriorate.

Temporary Flash blindness: This effect is similar to that experienced when looking at a bright camera flash. There is no injury, but a portion of the visual field is temporarily knocked out. Sometimes there are ‘afterimages’.

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Factors affecting Laser interference in Aviation:

Weather,

Time of day,

Power of the laser,

Colour of the laser,

Distance and relative angle of the laser and aircraft,

Speed of the aircraft and,

Exposure time.

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Reducing the Hazard:

There are several means employed to try to reduce hazards associated with lasers in navigable airspace:

Laser Light Hazard Reduction –

Concentrates on preventing and keeping the laser light from being directed into navigable airspace especially that used by aircraft around airports and on known flight paths. In the US automated detection/avoidance systems are used to terminate or reduce the power of the lasers in certain circumstances; airspace observers or ‘spotters’ are also used to help keep the lasers away from in-flight aircraft.

Regulatory Reductions –

Include national measures to restrict the sale, carriage and use of lasers as well as amending existing laws and statutes. Educating the public in the safe use of pointers is also important as is providing warning labels on the laser devices (especially those above 5mW) about the dangers of shining lasers at aircraft. Some laser manufacturers are also actively engaged in strengthening the regulatory process in some countries.

Pilot Defences –

Consist of pilots being trained in laser illumination recovery techniques (e.g., look away from the beam and do not try to find the source of the laser, engage autopilot, turn up cockpit lighting). Pilots should also check NOTAMs for notified laser activity along their flight plan route. Finally, pilots should report all laser illuminations to air traffic control and complete an Air Safety Report in accordance with company/national policies.

Air Traffic Control Defences –

Consist of air traffic controllers recognising a laser illumination (of the visual control room facility) and reacting accordingly. They should not try to identify the light source and should inform aircraft under their control about the laser illumination. As with pilots, air traffic controllers should report laser illuminations to their company/CAA in accordance with company and national policies.

Physical Defences –

Could include the wearing of laser safety goggles to shield pilots’ eyes although their use is generally considered impracticable in most circumstances. Glare shields may also offer limited protection but again their use and effectiveness is questionable.

Regulations and Control –

In the US, the FAA has established airspace zones around airports which limits the power of lasers used inside the zones.

-The airspace zones consist of:

Laser Free Zones around the immediate environs of the airport;

Critical Flight Zones covering 10nm around airports (light intensity < 5 microwatts per square centimeter (µW/cm²));

and Sensitive Flight Zones (optional) where the FAA has specified that light intensity must be less than 100µW/cm².

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Laser incidents:

On March 28, 2008, a coordinated attack took place using four green laser pointers aimed at six aircraft landing at Sydney airport in New South Wales, Australia. As a result of this attack plus others, a law was proposed in mid-April 2008 in New South Wales to ban possession of handheld lasers, including low-power classroom pointers.

On February 22, 2009, a dozen planes were targeted with green laser beams at Seattle-Tacoma International Airport. An FAA spokeswoman said there were 148 laser attacks on aircraft in the U.S. from January 1, 2009 to February 23, 2009.

During the July 2013 protests against the presidency of Mohamed Morsi in Egypt and later celebration of his removal, thousands of protesters and revelers aimed laser pointers at government helicopters.

On February 2016 a Virgin Atlantic flight from Heathrow to New York JFK Airport was forced to turn back when a laser beam was shone into the cockpit. The incident led the British Airline Pilots’ Association to call for lasers to be classified as offensive weapons.

In the first seven months of 2018, United States Armed Forces pilots were targeted with laser points in multiple regions, but particularly in the Middle East.

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Section-23

Plane crash injuries:  

As with any accident, victims of an aviation disaster could sustain any number of injuries—some of which may be fatal.

Traumatic Brain Injuries:

Traumatic brain injuries (TBIs) can be caused, for example, by blunt force trauma during a plane crash. Injuries to the brain require extensive healthcare treatment, and the long-term effects of TBIs are numerous and can include ongoing medical costs as well as changes in decision-making skills, personality, mood, or work prospects.

Spinal Cord and Back Injuries:

When an aircraft hits the ground or collides with another plane, passengers are susceptible to spinal cord and other back injuries. These injuries can affect a person’s ability to move or feel physical sensations. With severe spinal cord injuries, a victim could become partially or fully paralyzed.

Broken Bones and Fractures:

It’s common for aviation accident victims to suffer from multiple bone fractures or breaks to both their lower and upper body. Factors such as the altitude of the plane when it began its descent and how fast the aircraft impacted the ground can affect the quantity and severity of bone injuries.

Burns:

Runway accidents and aircraft collisions can cause a fire due to the extreme friction at play or the combustibility of fuel. Passengers on the airplane as well as personnel on the ground can suffer from severe burns, leaving victims to suffer from an extreme amount of pain or endure cosmetic surgery.

Emotional Trauma:

Survivors of aviation accidents can suffer from post-traumatic stress disorder (PTSD), anxiety, and other types of emotional trauma. This type of injury usually requires therapy and psychological treatment to help victims heal. Additionally, if a loved one is killed in an aviation accident, surviving family members suffer from loss of consortium.

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Aviation Injury Statistics:

A 2009 study analyzed the injuries sustained by victims of aviation accidents. During the six-year study period (2000–2005), more than 6000 patients were admitted to short-term hospitals in the United States due to aviation-related injuries. Researchers broke down the data as follows.

Commercial aircraft accident injuries:

Head injury, 7.5%

Internal injury, 2.6%

Burns, 2.7%

Injury to joint/muscle, 8.1%

Lower-limb fracture, 28.4%

Open wound, 7.4%

Upper-limb fracture, 11.2%

Other injury, 31.1%

Noncommercial aircraft accident injuries:

Head injury, 12.9%

Internal injury, 10.8%

Burns, 4.4%

Injury to joint/muscle, 3.1%

Lower-limb fracture, 17.2%

Open wound, 15.6%

Upper-limb fracture, 10.0%

Other injury, 26.0%

In both cases, lower-limb fractures were the most common injuries.

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A critical analysis of the fatal injuries resulting from the Continental flight 1713 airline disaster: evidence in favor of improved passenger restraint systems, a 1994 study:

Data synthesis:

There were 28 fatalities: nine died of mechanical asphyxiation, one of a penetrating cranial injury, and 18 of blunt trauma. The blunt injuries were remarkably similar to the deceleration injuries seen in high-speed motor vehicle crashes. Head trauma was the most common fatal blunt injury, followed by injuries to the chest and the abdomen. Thirty-six percent of the head injuries and 27% of the chest injuries had associated cervical and thoracic spine fractures, respectively. Analysis revealed a marked similarity in injury pattern sustained by seatmates, with a high incidence of fatal and serious injuries suffered by those passengers sitting in the front half of the airplane.

Conclusions:

Fatal blunt injury secondary to deceleration forces was the most common cause of death seen in this analysis. The use of a lap belt restraint system alone is not adequate to protect passengers against these forces as shown convincingly in the automotive industry literature. What impact a better passenger restraint system may have had on survival in this disaster is unknown, however, at a minimum, it would have significantly improved survival for 6 of 28 passengers dying of isolated blunt head trauma. Minor alterations in aircraft design (secure bolting of passenger seats to the airplane superstructure) and passenger restraints (3-point lap and shoulder harness system) are proposed to positively influence survival during an airplane crash at negligible increased airline expense or passenger inconvenience.

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Injury patterns in aviation-related fatalities. Implications for preventive strategies, October 1997 study:

This study examines the injury patterns for persons who died in aviation crashes in the United States and the implications for preventive strategies. Death certificate data for all aviation-related fatalities for the years 1980 (n = 1,543) and 1990 (n = 1,011) were obtained from the National Center for Health Statistics. The immediate cause of death and all injury diagnoses recorded on the death certificates were analyzed in relation to year of injury, crash category, and type of victim. Despite a 34% reduction in the number of aviation-related fatalities between 1980 and 1990, injury patterns were fairly stable. Multiple injuries were listed as the immediate cause of death in 42% of the fatalities, followed by head injury (22%); internal injury of thorax, abdomen, or pelvis (12%); burns (4%); and drowning (3%). Head injuries were most common among children. The majority (86%) died at the scene or were dead on arrival at the hospital. Eighteen percent of the victims were reported to have sustained a single injury, with head injury being the cause of death in nearly a third of these fatalities. Blunt injuries resulting from deceleration forces, in particular head injury, are still the most important hazard threatening occupants’ survival in aviation crashes. To further reduce aviation-related fatalities requires more effective restraint systems and other improvements in aircraft design.

The predominance of decelerative injuries, in particular, head injury, in aviation-related fatalities calls for more effective restraint systems, such as shoulder harnesses for all occupants or improved seat design. Restraint failure or inadequacy of restraint has long been recognized as one of the principal sources of mechanical injury in aviation crashes.

The currently used lap belt is insufficient in protecting passengers from decelerative injuries in aviation crashes. To prevent serious head injuries, more effective restraint systems as well as crashworthy seats, airframes, and superstructures must be considered. Current models of light aircraft incorporate integrated shoulder harnesses, an improvement not available to the occupants of the far more numerous older aircraft.

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Sturdier Seats:

Congress’s Airport and Airway Safety Act of 1987 called for regulators to improve what is called the “crash-worthiness standard” of seats — in effect, the likelihood that they will crumple and crush passengers at impact. It took 17 years to accomplish the task, as the Federal Aviation Administration tussled with aircraft manufacturers and airlines that balked at paying for the upgraded seats. The FAA produced evidence that sturdier seats could have prevented 45 fatalities between 1984 and 1998. A deal was reached. In 2005, the FAA mandated that all U.S. aircraft built after October 2009 meet the “16g rule” — seats must be built to withstand crash forces equivalent to 16 times the force of gravity (older seats were 9g compliant). Ironically, the long negotiation period and concerns among the airlines that the FAA would make requirements retroactive means that almost all major airlines in operation today already have 16g-compatible seats. 

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Analysis of injuries among pilots involved in fatal general aviation airplane accidents, a 2003 study:

The purpose of this study was to analyze patterns of injuries sustained by pilots involved in fatal general aviation (GA) airplane accidents. Detailed information on the pattern and nature of injuries was retrieved from the Federal Aviation Administration’s autopsy database for pilots involved in fatal GA airplane accidents from 1996 to 1999. A review of 559 autopsies revealed that blunt trauma was the primary cause of death in 86.0% (N=481) of the autopsies. The most commonly occurring bony injuries were fracture of the ribs (72.3%), skull (55.1%), facial bones (49.4%), tibia (37.9%) and pelvis (36.0%). Common organ injuries included laceration of the liver (48.1%), lung (37.6%) heart (35.6%), and spleen (30.1%), and hemorrhage of the brain (33.3%) and lung (32.9%). A fractured larynx was observed in 14.7% of the cases, a finding that has not been reported in literature until now. It was observed that individuals who sustained brain hemorrhage were also more likely to have fractures of the facial bones rather than skull fractures.

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Why do planes always explode in flames in a collision or crash?

It’s a combination of a lot more fuel, a much larger fuel tank, much higher speeds, and a constantly present ignition source.

The typical passenger airliner carries massive amounts of fuel. A widebody heavy jet can carry over 40,000 gallons of fuel… well over 100 gallons for every person on board. Even if the fuel tanks were almost empty, the volume of the fuel tanks, the remaining fuel, and the fuel vapors can still lead to a massive fireball.  Almost the entire interior volume of the wing (plus the tail, on some designs) is fuel tank. This greatly increases the chance of the fuel tank rupturing in a crash; it’s extremely difficult to crash an airplane and not have the fuel tank open up.

Then there is speed…a normal airliner at its slowest is going faster than the top speed of most cars. Typical landing speeds are about 150 mph. This means there is a lot more energy, and a lot more damage, in an airliner crash, so the fuel tank is more likely to break and spray fuel around.

Finally, there’s the ignition source. In a car, the burning fuel and igniters are very well contained inside the cylinders…it would take an incredible crash to tear open an engine block. A jet engine is running continuously and isn’t “sealed”…the only thing keeping the fire inside the engine is the fans at the front and the turbines at the back. Those components are running very close to their limits in normal operation, in a crash they’re going to stop spinning very quickly and “let the fire out”. They are also far hotter than anything in a car engine and located right below the wings (where the fuel is), so spilled fuel often ends up very close to a very hot and running jet engine, where it ignites.

Jet fuel is actually much safer than gasoline in terms of ability to ignite but, in an airplane, there are just too many ignition sources around.

Jet fuel is not as volatile as and doesn’t vaporize as well as automobile gasoline. Still, under crash conditions a fire is very likely. Usually, due to the low volatility of the fuel, there’s not an explosion as much as a “fireball.” Jet fuel fires tend to be dense and intense, with lots of smoke.

Catastrophic crashes (not including emergency landings) do tend to result in a fire. In fact, in airline crashes overall, more people die in the post-crash fire (burns and smoke inhalation) than die in the actual crash. 68% of deaths are due to fire, according to historical NTSB data.

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Aircraft fires, smoke toxicity, and survival, a 1996 study:

In-flight fires in modern aircraft are rare, but post-crash fires do occur. Cabin occupants frequently survive initial forces of such crashes but are incapacitated from smoke inhalation. According to an international study, there were 95 fire-related civil passenger aircraft accidents worldwide over a 26-yr period, claiming approximately 2400 lives. Between 1985 and 1991, about 16% (32 accidents) of all U.S. transport aircraft accidents involved fire and 22% (140 fatalities) of the deaths in these accidents resulted from fire/smoke toxicity. The laboratory analyses of post-mortem blood samples (1967-93) indicate that 360 individuals in 134 fatal fire-related civil aircraft (air carrier and general aviation) accidents had carboxyhemoglobin saturation levels (> or = 20%), with or without blood cyanide, high enough to impair performance.

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Section-24

Plane Crash Survival:

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The most amazing survival story ever in commercial aviation history was that of the 17-year-old German passenger Juliane Koepke who fell 10,000 feet strapped into her seat into the Amazonian jungle of Peru after a lightning bolt struck and ignited the right-wing fuel tank on a commercial flight from Lima to Pulcappa, Peru on Christmas Eve December 24, 1971. All 91 passengers and crew aboard perished, except for Juliane. Her three-seat segment in the aircraft ‘helicoptered’ 10,000 feet through the atmosphere and into the dense Amazonian forest (she described the forest canopy as looking like broccoli as she fell towards it). She landed on the forest floor (jungle canopy breaking her descent) with a broken collar bone and popped eyeball (a result of the decompression during her fall). After 10 days wandering through the jungle and swimming down a river she happened upon a lumbermen shack where she was eventually rescued. Many documentaries have been produced about this incredible story including a film by Werner Herzog who was booked on the same flight while researching locations for his cult classic film ‘Aguire; The Wrath of God’.

Air travel, however, is a lot safer than one would think from watching the news and all of its wild airplane stories. The National Transportation and Safety Board — the U.S. federal agency that investigates civil aviation accidents — did a study of aviation statistics from 1983 through 2000, and found that a total of 53,487 people were involved in such accidents. The study found that 95.7 percent, or 51,207 people, survived. Not only are the odds of being in a plane crash just one in 11 million, but the odds of not surviving a crash are even lower: one in 29.4 million. That’s a far lower risk than death from a car accident, which has a rate of one in 5,000.

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Survival rate of passengers on aircraft involved in fatal accidents carrying 19+ passengers:

Decade	% surviving
1940s	4.8
1950s	8.1
1960s	8.2
1970s	10.8
1980s	14.6
1990s	12.8
2000s	12.8
2010s	5.8

Source: PlaneCrashInfo.com accident database

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Experience of Weightlessness:

In a crash where your plane nosedives or hits a sharp turn, unconsciousness is an eventuality. Because of that, you might not actually feel what it’s like to go into freefall in your seat, but your body will experience it. When the plane goes into a dive, your body and the plane will eventually be falling at the same rate and it will appear that you are weightless within the plane. Your body will rise from your seat, your limbs will float, and objects around you will hover, as if you are in space.

One survivor, Robert Young Pelton, remembers this specific feeling right before the crash well:

 “You get thrown up in the air, everything goes weightless and everything inside the plane starts floating around.”

What’s interesting is that your body is not actually weightless – it’s just a sensation. Instead, you are just falling in such a way that you appear weightless in relation to the plane. It won’t be like being in space or on a zero G simulator, and it may only happen for a brief instant. However, just because heavy objects in the cabin are able to move about as if weightless does not mean that they are. If those objects float into you, their weight will feel very real and very painful.

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Accident survivability:

Earlier tragedies investigations and improved engineering has allowed many safety improvements that have allowed an increasing safer aviation.

Airport design:

Airport design and location can have a large impact on aviation safety, especially since some airports such as Chicago Midway International Airport were originally built for propeller planes and many airports are in congested areas where it is difficult to meet newer safety standards. For instance, the FAA issued rules in 1999 calling for a runway safety area, usually extending 500 feet (150 m) to each side and 1,000 feet (300 m) beyond the end of a runway. This is intended to cover ninety percent of the cases of an aircraft leaving the runway by providing a buffer space free of obstacles. Many older airports do not meet this standard. One method of substituting for the 1,000 feet (300 m) at the end of a runway for airports in congested areas is to install an engineered materials arrestor system (EMAS). EMAS or arrester bed is a bed of engineered materials built at the end of a runway to reduce the severity of the consequences of a runway excursion. These systems are usually made of a lightweight, crushable concrete that absorbs the energy of the aircraft to bring it to a rapid stop. A standard EMAS can stop an aircraft from overrunning the runway at approximately 80 miles per hour. The FAA lists at least 15 incidents in the US where EMAS systems have safely stopped overrunning aircraft, carrying 406 crew and passengers, aboard those flights.

Emergency airplane evacuations:

According to a 2000 report by the National Transportation Safety Board, emergency aircraft evacuations happen about once every 11 days in the U.S. While some situations are extremely dire, such as when the plane is on fire, in many cases the greatest challenge for passengers can be the use of the evacuation slide. When a new supersized Airbus A380 underwent mandatory evacuation tests in 2006, thirty-three of the 873 evacuating volunteers got hurt. While the evacuation was considered a success, one volunteer suffered a broken leg, while the remaining 32 received slide burns. Such accidents are common. Passengers must go through tips on how to make it down the airplane slide without injury.  Another improvement to airplane evacuations is the requirement by the Federal Aviation Administration for planes to demonstrate an evacuation time of 90 seconds with half the emergency exits blocked for each type of airplane in their fleet. According to studies, 90 seconds is the time needed to evacuate before the plane starts burning, before there can be a very large fire or explosions, or before fumes fill the cabin.

Aircraft materials and design:

Changes such as using new materials for seat fabric and insulation has given between 40 and 60 additional seconds to people on board to evacuate before the cabin gets filled with fire and potential deadly fumes. Other improvements through the years include the use of properly rated seatbelts, impact resistant seat frames, and airplane wings and engines designed to shear off to absorb impact forces.

Radar and wind shear detection systems:

As the result of the accidents due to wind shear and other weather disturbances, most notably the 1985 crash of Delta Air Lines Flight 191, the U.S. Federal Aviation Administration mandated that all commercial aircraft have on-board wind shear detection systems by 1993.  Since 1995, the number of major civil aircraft accidents caused by wind shear has dropped to approximately one every ten years, due to the mandated on-board detection as well as the addition of Doppler weather radar units on the ground (NEXRAD). The installation of high-resolution Terminal Doppler Weather Radar stations at many U.S. airports that are commonly affected by wind shear has further aided the ability of pilots and ground controllers to avoid wind shear conditions.

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Tips for plane crash survival:

-1. Take a nonstop flight, if possible. Most accidents happen in the takeoff and landing phases of flight; the fewer stops you make, the less chance of an accident.

-2. Fly in bigger planes if possible. If you have the choice between flying in a puddle jumper or a 737, choose the 737. According to FAA investigations, larger planes have more energy absorption in a crash which means you’re subjected to less deadly force, and that may equate to a better survival rate. Also avoid regional carriers if possible — they have an accidents and incidents rate double that of national carriers and their pilots are often less experienced and overworked. Note that national airlines frequently use a regional carrier for some of the routes that fly under their name.  

-3. Watch the skies. Many accidents involve severe weather. As takeoff time approaches, check the weather along the route, particularly in places where you will land. Consider delaying your flight if the weather could be severe.

-4. Wear long-sleeved shirts and long pants made of natural fibers. Radiant heat and flash burns can be avoided if you put a barrier between you and the heat. Avoid easy-care polyester and nylon: most synthetic materials that aren’t specifically treated to be fire resistant will melt at relatively low temperatures (300 to 400 degrees Fahrenheit). Synthetic fabrics will usually shrink before they melt, and if they are in contact with skin when this happens, they will make the burn – and its treatment – much more serious. Wear closed-toe, hard soled shoes; you might have to walk through twisted, torn metal or flames. In many cases, people survive the crash, but are killed or injured by post-impact fire and its by-products, like smoke and toxic gases.

-5. Select a seat on the aisle, somewhere in the rear half of the cabin. The odds of surviving a crash are higher in the middle-to-rear section compared to the middle-to-front section of the cabin. An aisle seat offers the easiest escape route access, unless you are sitting right next to an emergency exit: If you can get a window seat right next to an emergency exit, this is a better choice.

-6. Listen to the safety briefing and locate your nearest exits. Most airplane accident survivors had listened to the briefing and knew how to get out of the plane. Pick an exit to use in case of emergency, and an alternate in case the first one is not available.

-7. Count the seats between you and the exits in case smoke fills the plane and you cannot see them. Make sure you understand how the exit doors work and how to operate them.

-8. Practice opening your seat belt a few times. Many people mistakenly try to push the center of the buckle rather than pull up on it.

-9. Plus Three, Minus Eight: According to David Palmerton, a US Federal Aviation Administration (FAA) expert on plane crashes, these are the crucial 11 minutes when you need to be alert on an airplane. The three minutes during takeoff and final 8 minutes before landing are when 80% of plane crashes occur. Stay sober, hold off on your nap, and don’t bury your face in a book and follow the plus three, minus eight rule.

Here are some suggestions from The Survivor’s Club on what to do and not do during Plus 3/Minus 8:

Don’t sleep.

Make sure your shoes are on and secured.

Don’t drink before getting on a plane. You want to be fully present in the event of a crash.

Make sure your seatbelt is securely fastened — low and tight.

You don’t need to be paranoid during this time, just vigilantly relaxed.

-10. Be ready to part with your Carry On. Most people who survive the initial impact of a plane crash, yet still lose their lives, do so because they try to take their carry-on luggage with them. Anything that’s really important to you sentimentally or otherwise should be in your pockets – remember your life is more important than your iPod.

-11. You’ve got 90 seconds to get out. According to studies, 90 seconds is the time needed to evacuate before the plane starts burning, before there can be a very large fire or explosions, or before fumes fill the cabin. It takes, on average, just 90 seconds for a fire to burn through the plane’s aluminum fuselage and consume everything and everyone in it. That’s all the time you’ve got to get off a burning craft.

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To Prepare for The Crash:

Make sure that your seat belt is tightly fastened and that your chair back is fully upright. If you are told to adopt the brace position, then do so. The brace position prevents you from flying forward and hitting the seat in front of you and reduces your chances of being knocked unconscious. Get your torso as low as possible to reduce the jackknife effect at impact; stop yourself from flying forward and hitting the seat or other parts of the aircraft interior; and preventing injury to your legs and ankles that will hinder your escape from the aircraft. To assume a brace or crash position is an instruction that can be given to prepare for a crash, such as on an aircraft; the instruction to ‘brace for impact!’ or ‘brace! brace!’ is often given if the aircraft must make an emergency landing on land on water. There are many different ways to adopt the brace position, with many countries adopting their own version based on research performed by their own aviation authority or that of other countries. The most common in passenger airliners being the forward-facing seat version, in which the person bracing places their head against or as close as possible to the surface it is likely to strike (and in the process bending over to some degree), placing their feet firmly on the floor, and their hands either on their head or the seat in front.

Alternative brace positions in an aircraft:

Research has shown that brace positions do indeed up the chances of survival in an emergency crash landing. The positions help reduce the velocity of your head when it inevitably slams into the seat in front of you. Moreover, they help minimize limb flailing. If you don’t have your seatbelt on and aren’t braced, your head and limbs will rattle around a lot more. This leads to higher chances of serious head injuries, broken bones, and even death. However, in a more serious crash where the plane is on fire or there’s explosive decompression, bracing probably won’t help much. In fact, you might not even have time to brace. Whether you’re in that turtle position or not, the impact may be enough to sever your spinal column. Or destroy your bones and organs. Or leave you so crippled that you can’t get away from the flames or sinking wreckage.

We would be safer if planes were designed with seats facing backwards, rather than forwards – unfortunately people don’t like being seated in an opposite direction to the direction of travel, so aircraft manufacturers don’t design them like that. On a train it is possible to sit with your back facing the direction of travel, and that would be a safer seat on a train.

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Can jumping out of a plane and into the sea without a parachute kill you?

Impacting water at terminal velocity is very much the same as impacting the ground. The human body takes 10–15 seconds to reach “terminal velocity” of about 120 mph (in round figures). At that speed, water will have essentially the same effect on the body as the ground. The important thing to realize is that 99.99 % of the time, departing an aircraft without a parachute is going to kill you.  

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Section-25

Error management and prevention of plane crash:   

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Accidents in air transport are dominated by the failure of human factor failure, i.e., that of the aircrew. Despite of a positive development in the trend of accidents recorded since the beginning of the 21st century, the number of air accidents is still unsatisfactory. Consequently, it is of paramount importance to do everything that would contribute to substantial reduction of the human factor failure in air transportation. A system of models appears to be an important tool for overall understanding of the complexity of human factors, serving as starting-points to an analytical and classificational research of the human factor. At the same time, these models enable qualified investigation and assessment of the causes of air accidents, thereby preventing them from repeated occurrence. 

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Investigations of air accidents: 

Determining of the causes of air accidents and preventing them from occurrence is an important part of the flight safety system. The most serious consequences of air accidents are those related to losses of human lives, while those of material are of secondary nature. For airline companies, even material loses are very important.

To them an air incident or accident means high financial load, as not small amounts are paid out as compensations for victims, and the average price of a commercial aircraft is 100 to 400 million $, an amount representing a serious problem to tackle. As a more, each air accident can cause losing thrust worthiness, causing drop in the volumes of customers interested in air travel. 

From the manufacturer´s point of view, an air accident is the predecessor of a costly lawsuit. However, it can on the one hand became a stimulus for increasing the level of safety while on the other hand it might lead to involuntariness in eliminating the error, as admitting such an accident can be interpreted as admitting an error in aircraft design or manufacturing. Regardless of the insurance companies and further persons or organizations affected by the accident, one can state an air accident with its consequences belongs to the worst disasters in transportation. 

Investigation of air accidents is a complex process focused on a mosaic of specific phenomena, the consequences of which and mainly their causes as objects of investigation.  Only a consistent and an all-round investigation of an air accident enables accepting and realizing a system of efficient measures for preventing accidents and incidents from reoccurring, thereby maximizing the efficiency of effect in improving the overall level of flight safety.  

All air-accident investigations are governed by the International Civil Aviation Organization (ICAO) and its set of treaties. Based in Montreal, the ICAO is an agency of the United Nations. Whether it’s a small plane or a large commercial passenger airliner, the fundamental principles of accident investigations are the same: an accident investigation is intended to improve safety for the future. It’s not intended to assign blame for something that has already happened.

The act of investigation is left to the competence of appropriate state authorities, whereby their jurisdiction is   given predominantly by the area where the accident happened.  Coordinated effort in this regard is expected from the manufacturer of the type suffering losses, the airline as the operator of the aircraft, local civil aviation authorities registering the aircraft as well as further subjects involved, depending on the circumstances of the accident. As a rule, the authority to investigate the air accidents and incidents falls to the civil aviation authority, however, there are countries where special organisations enjoy the exclusive right to investigate such accidents. At any rate, participation of organs of criminal investigation is a matter of course, should a suspicion of criminal cause of the accident arises. 

Investigation is focused on determining and analyzing the circumstances of the accident, flight proficiency of the aircrew, organization of the flight, status of the aviation equipment, medical status and professional competence of the aircrew as well.  

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Prevention of air accidents:

Measure to prevent accident rate from increasing are developed by operators as a result of an analysis focused on activities and causes of them. Prevention should primarily focus on training and education of the aircrew, care for the aviation equipment, technical support to air traffic, organizational and control issues as well as the field of care for the labour force etc. However, prevention should prove inefficient if not carried out on a basis of planning and steadiness. As its substantial part is made up of the analyses of air accidents, the operator is liable to make constant use of all the technical tools of objective control mostly flight data recorders, magneto phone tapes etc… The tools must be held in perfect technical status and follow innovation in time. Some airlines may find it financially too demanding, but investments into prevention are not meant as money through out of the window.  It can be said for sure that any air accident is much more expensive than the costs of the preventive measures. 

Air accident is seldom a result of a single cause. It is typical for them to originate from a combination of factors.  It is the cumulation of these events, which will eventually result in air accident. Thus, by prevention of   accidents is meant timely detection and elimination of the causes before it develops into an event. For a substantial progress in air transportation safety to be achieved, its necessary to focus on the most frequently occurring and types of air accidents, such as the CFIT and loss of control over the aircraft. It is also important to focus on the phases of flight especially on its beginning(takeoff) and end (landing). 

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5M Model of commercial air safety:

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Threat and error management (TEM):  

TEM involves the effective detection and response to internal or external factors that have the potential to degrade the safety of an aircraft’s operations. Methods of teaching TEM stress replicability, or reliability of performance across recurring situations. TEM aims to prepare crews with the “coordinative and cognitive ability to handle both routine and unforeseen surprises and anomalies.”  The desired outcome of TEM training is the development of ‘resiliency’. Resiliency, in this context, is the ability to recognize and act adaptively to disruptions which may be encountered during flight operations. TEM training occurs in various forms, with varying levels of success. Some of these training methods include data collection using the line operations safety audit (LOSA), implementation of crew resource management (CRM), cockpit task management (CTM), and the integrated use of checklists in both commercial and general aviation. Some other resources built into most modern aircraft that help minimize risk and manage threat and error are airborne collision and avoidance systems (ACAS) and ground proximity warning systems (GPWS). With the consolidation of onboard computer systems and the implementation of proper pilot training, airlines and crew members look to mitigate the inherent risks associated with human factors.

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Threat and error management (TEM) is an overarching safety management approach that assumes that pilots will naturally make mistakes and encounter risky situations during flight operations. Rather than try to avoid these threats and errors, its primary focus is on teaching pilots to manage these issues so they do not impair safety. Its goal is to maintain safety margins by training pilots and flight crews to detect and respond to events that are likely to cause damage (threats) as well as mistakes that are most likely to be made (errors) during flight operations.

TEM allows crews to measure the complexities of a specific organization’s context — meaning that the threats and errors encountered by pilots will vary depending upon the type of flight operation — and record human performance in that context. TEM also considers technical (e.g., mechanical) and environmental issues, and incorporates strategies from Crew Resource Management to teach pilots to manage threats and errors.

The TEM framework was developed in 1994 by psychologists at University of Texas based on the investigation of accidents of high capacity Regular Public Transport (RPT) airlines. However, an evaluation method was needed to identify threats and errors during flight operations and to add information to existing TEM data. A Line Operations Safety Audit (LOSA) serves this purpose and involves the identification and collection of safety-related information — on crew performance, environmental conditions, and operational complexity — by a highly trained observer.  LOSA data is used to assess the effectiveness of an organization’s training program and to find out how trained procedures are being implemented in day-to-day flights.

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Importance of TEM:

Threat and error management is an important element in the training of competent pilots that can effectively manage in-flight challenges. Many strategies have been developed (e.g., training, teamwork, reallocating workload) that were focused on improving on stress, fatigue, and error. Flight crew training stressed the importance of operational procedures and technical knowledge, with less emphasis placed on nontechnical skills, which became isolated from the real-world operational contexts. Safety training, including TEM, is important because a crew’s nontechnical (safety) knowledge helps more in managing errors effectively than crews’ familiarization with operations through experience. Candidates who are shortlisted during selection and training processes must demonstrate analytical and coordination capabilities. Possessing these nontechnical skills allows pilots and crew members to carry out their duties efficiently and effectively.

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Line operations safety audit (LOSA):

LOSA is a structured observational program designed to collect data for the development and improvement of countermeasures to operational errors. Through the audit process, trained observers are able to collect information regarding the normal procedures, protocol, and decision making processes flight crews undertake when faced with threats and errors during normal operation. This data driven analysis of threat and error management is useful for examining pilot behavior in relation to situational analysis. It provides a basis for further implementation of safety procedures or training to help mitigate errors and risks. Observers on flights which are being audited typically observe the following:

Potential threats to safety

How the threats are addressed by the crew members

The errors the threats generate

How crew members manage these errors (action or inaction)

Specific behaviors known to be associated with aviation accidents and incidents

LOSA was developed to assist crew resource management practices in reducing human error in complex flight operations. LOSA produces beneficial data that reveals how many errors or threats are encountered per flight, the number of errors which could have resulted in a serious threat to safety, and correctness of crew action or inaction. This data has proven to be useful in the development of CRM techniques and identification of what issues need to be addressed in training.

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Crew resource management (CRM) to manage threat and error in aviation:

Given the ubiquity of threat and error, the key to safety is their effective management. One safety effort is training known as crew resource management (CRM). This represents a major change in training, which had previously dealt with only the technical aspects of flying. It considers human performance limiters (such as fatigue and stress) and the nature of human error, and it defines behaviours that are countermeasures to error, such as leadership, briefings, monitoring and cross checking, decision making, and review and modification of plans. Crew resource management is now required for flight crews worldwide, and data support its effectiveness in changing attitudes and behaviour and in enhancing safety.

Simulation also plays an important role in crew resource management training. Sophisticated simulators allow full crews to practice dealing with error inducing situations without jeopardy and to receive feedback on both their individual and team performance. Two important conclusions emerge from evaluations of crew resource management training: firstly, such training needs to be ongoing, because in the absence of recurrent training and reinforcement, attitudes and practices decay; and secondly, it needs to be tailored to conditions and experience within organisations.

Understanding how threat and error and their management interact to determine outcomes is critical to safety efforts. To this end, a model has been developed that facilitates analyses both of causes of mishaps and of the effectiveness of avoidance and mitigation strategies. A model should capture the treatment context, including the types of errors, and classify the processes of managing threat and error. Application of the model shows that there is seldom a single cause, but instead a concatenation of contributing factors. The greatest value of analyses using the model is in uncovering latent threats that can induce error.

By latent threats we mean existing conditions that may interact with ongoing activities to precipitate error. For example, analysis of a Canadian crash caused by a take-off with wing icing uncovered 10 latent factors, including aircraft design, inadequate oversight by the government, and organizational characteristics including management disregard for de-icing and inadequate maintenance and training. Until this post-accident analysis, these risks and threats were mostly hidden. Since accidents occur so infrequently, an examination of threat and error under routine conditions can yield rich data for improving safety margins.

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CRM is the “effective use of all available resources by individuals and crews to safely and effectively accomplish a mission or task, as well as identifying and managing the conditions that lead to error.” CRM training has been integrated and mandatory for most pilot training programs, and has been the accepted standard for developing human factors skills for air crews and airlines. Although there is no universal CRM program, airlines usually customize their training to best suit the needs of the organization. The principles of each program are usually closely aligned. According to the U.S. Navy, there are seven critical CRM skills:

Decision making – the use of logic and judgement to make decisions based on available information

Assertiveness – willingness to participate and state a given position until convinced by facts that another option is more correct

Mission analysis – ability to develop short and long term contingency plans

Communication – clear and accurate sending and receiving of information, instructions, commands and useful feedback

Leadership – ability to direct and coordinate activities of pilots & crew members

Adaptability/flexibility – ability to alter course of action due to changing situations or availability of new information

Situational awareness – ability to perceive the environment within time and space, and comprehend its meaning

These seven skills comprise the critical foundation for effective aircrew coordination. With the development and use of these core skills, flight crews “highlight the importance of identifying human factors and team dynamics to reduce human errors that lead to aviation mishaps.”

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Application and effectiveness of CRM:

Since the implementation of CRM circa 1979, following the need for increased research on resource management by NASA, the aviation industry has seen tremendous evolution of the application of CRM training procedures. The applications of CRM has been developed in a series of generations:

First generation: emphasized individual psychology and testing, where corrections could be made to behavior.

Second generation: featured a shift in focus to cockpit group dynamics.

Third evolution: diversification of scope and an emphasis on training crews in how they must function both in and out of the cockpit.

Fourth generation: CRM integrated procedure into training, allowing organizations to tailor training to their needs.

Fifth generation (current): acknowledges that human error is inevitable and provides information to improve safety standards.

Today, CRM is implemented through pilot and crew training sessions, simulations, and through interactions with senior ranked personnel and flight instructors such as briefing and debriefing flights. Although it is difficult to measure the success of CRM programs, studies have been conclusive that there is a correlation between CRM programs and better risk management.

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Cockpit task management (CTM):

Cockpit task management (CTM) is the “management level activity pilots perform as they initiate, monitor, prioritize, and terminate cockpit tasks.”] A ‘task’ is defined as a process performed to achieve a goal (i.e., fly to a waypoint, descend to a desired altitude). CTM training focuses on teaching crew members how to handle concurrent tasks which compete for their attention. This includes the following processes:

Task initiation – when appropriate conditions exist

Task monitoring – assessment of task progress and status

Task prioritization – relative to the importance and urgency for safety

Resource allocation – assignment of human and machine resources to tasks which need completion

Task interruption – suspension of lower priority tasks for resources to be allocated to higher priority tasks

Task resumption – continuing previously interrupted tasks

Task termination – the completion or incompletion of tasks

The need for CTM training is a result of the capacity of human attentional facilities and the limitations of working memory. Crew members may devote more mental or physical resources to a particular task which demands priority or requires the immediate safety of the aircraft. CTM has been integrated to pilot training and goes hand in hand with CRM. Some aircraft operating systems have made progress in aiding CTM by combining instrument gauges into one screen. An example of this is a digital attitude indicator, which simultaneously shows the pilot the heading, airspeed, descent or ascent rate and a plethora of other pertinent information. Implementations such as these allow crews to gather multiple sources of information quickly and accurately, which frees up mental capacity to be focused on other, more prominent tasks.

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Checklists:

The use of checklists before, during and after flights has established a strong presence in all types of aviation as a means of managing error and reducing the possibility of risk. Checklists are highly regulated and consist of protocols and procedures for the majority of the actions required during a flight. The objectives of checklists include “memory recall, standardization and regulation of processes or methodologies.” The use of checklists in aviation has become an industry standard practice, and the completion of checklists from memory is considered a violation of protocol and pilot error. Studies have shown that increased errors in judgement and cognitive function of the brain, along with changes in memory function are a few of the effects of stress and fatigue. Both of these are inevitable human factors encountered in the commercial aviation industry. The use of checklists in emergency situations also contributes to troubleshooting and reverse examining the chain of events which may have led to the particular incident or crash. Apart from checklists issued by regulatory bodies such as the FAA or ICAO, or checklists made by aircraft manufacturers, pilots also have personal qualitative checklists aimed to ensure their fitness and ability to fly the aircraft. An example is the IM SAFE checklist (illness, medication, stress, alcohol, fatigue/food, emotion) and a number of other qualitative assessments which pilots may perform before or during a flight to ensure the safety of the aircraft and passengers. These checklists, along with a number of other redundancies integrated into most modern aircraft operation systems, ensure the pilot remains vigilant, and in turn, aims to reduce the risk of pilot error.

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How to locate a vanished plane:  

Disappearance of Malaysian flight MH370 made experts think how we should redesign planes to avoid such an event happening again. In our modern world of always-on connectivity, having a plane like Malaysian flight MH370 vanish without a trace seemed implausible.

So how can we make sure that we never lose a plane again?

It turns out there are a number of smart and simple technologies waiting to be adopted if the airline industry chooses to take them up.

-1. Upgraded black box

Black boxes – actually painted orange – are ripe for an upgrade, according to more than one aviation expert. For the last three decades, ‘black box’ recorders have been the most important recoverable equipment pieces from which experts can piece together what actually happened. Yet while recovering the boxes from known crash locations is straightforward, it’s less easy for a case like MH370. Air France Flight 447, which crashed into the Atlantic Ocean in 2009, is the case that springs most readily to mind. While bodies and debris were found within days, the Airbus’s flight recorders were not recovered until two years after the crash, nearly 5km beneath the ocean’s surface.

So how might they be upgraded?

Both airliners and black boxes could be fitted with state-of-the-art detachable transmitters that…allow their position to be pin-pointed within a few meters. The beacons would be positioned on and around the tail as this is the part of the airliner most likely to survive the impact. Using accelerometers, one or two would break off and there would be another, which is crew-released. A similar technology is used for deep-diving nuclear-powered submarines. Batteries could be sea-water powered, solar powered or have long life lithium cells. Other tweaks could improve the battery life. An important but fairly simple change would be to have the black box emit the sonar location pulse not as often as every second; if you have it send one pulse every 10 seconds, we could extend the lifetime to almost one year instead of one month – a much larger window to find the black box.

Of course, flight recorders could be fitted with more modern technology so that they transmit information in real time. Canadian company Flyht Aerospace Solutions makes the Automated Flight Information System, or AFIRS, which automatically monitors data such as location, altitude, and performance. And it can live stream information when something goes wrong. Flyht director Richard Hayden contends that we would have more answers today if that technology had been on Flight 370. “We would know where the aircraft has gone, where it is, and we would have information on what had happened in the meantime,” he said. The main objection to this type of live-streaming has been cost. A typical installation would cost $100,000 including the box and the installation parts and the labor. 

-2. Cockpit broadcasting

Current airplanes make several different kinds of services available to passengers: interactive media, movies, games, music, internet. You can also make satellite calls from your seat. This means that airliners are always interconnected in some way. Why not use one of these channels to report the CVR (Cockpit Voice Recorder) and FDR (Flight Data Recorder) position in real time? This could be costly however, because satellite bandwidth is expensive.

-3. Triggered transmission

It’s a proposed technique for monitoring and locating aircraft that arose in the wake of Air France Flight 447, the Airbus A330 that crashed into the Atlantic Ocean in 2009. Floating wreckage was found within the first few days, but it still took two years to locate the main wreckage on the sea bed. The BEA – the French national air crash investigation agency – set up a working group to investigate what could be done to help locate wreckage in future accidents. They recommended triggered transmission, which only broadcasts an alert when something out of the ordinary happens. It monitors flight parameters such as height, speed, pitch, roll, and so on. It aims to identify when something unusual is happening which might be an accident. The system then sends an alert signal that is picked up on the ground. The advantage of triggered transmission over the continuous streaming of flight data is that far less information needs to be broadcast by global air traffic, and only from aircraft potentially in trouble. The challenge is avoiding false alarms.

-4. Prevent aircrews ‘switching off’

At the moment, the aircrew can make the plane almost invisible to radar. By switching off any on-board system, [aircrews] may really make identification and tracking difficult. This should be avoided. If we introduce a “new” system to send the black box position to ground receiving stations via satellite, it should be designed in such a way that pilots wouldn’t be able to switch it off.

The satellite provider Inmarsat has created a new communication service for planes called SwiftBroadband, which could provide accurate position information – even if the communication systems are switched off in the cockpit. It could also be used to download information stored by the black box, the company says.

-5. Continuous satellite imagery of oceans:

It took a long time to find images of possible debris from the MH370 crash on the ocean surface. Several groups have proposed continuous imagery of all the Earth’s surface. Optical satellite imagery might only work in daylight, but it could at least spot aircraft flying above the clouds. Another type of satellite, using radar, could give all-weather, day and night coverage. But it’s not cheap – cost figures in the region of two to five billion dollars have been suggested for these concepts.

-6. Take a leaf from global shipping

Finally, a small and inexpensive tweak could be made to improve the way planes speak to GPS satellites. With satellite systems already installed in planes, the simplest tweak would be to have airlines subscribe to the most basic and fairly inexpensive service offered by satellite companies, which includes the transmission of the GPS coordinates at regular intervals, for example every hour or every five minutes, or continuously in the case of distress. Ships on the ocean already use a simple satellite location system. It’s only a “matter of time” before such a system could be deployed on aircraft. The technology is relatively straightforward.

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Not pilot error but system failure:

When accidents occur, they are often blamed on human error. However, a book by NASA psychologist Key Dismukes, PhD, and Ben Berman and Loukia Loukopoulos, PhD, of the San Jose State University Research Foundation takes a more nuanced look at this assumption, showing that a complex web of factors likely contributes to such incidents. The three are uniquely qualified to assess these incidents: Dismukes is chief scientist for aerospace human factors in the Human-System Integration Division at NASA-Ames; Berman, a captain at Continental Airlines, was previously chief of major accident investigations at the National Transportation Safety Board (NTSB), and Loukopoulos is a former Navy aviation psychologist.

Their book, “The Limits of Expertise: Rethinking Pilot Error and the Causes of Airline Accidents” (Ashgate, 2007), dissects the 19 major accidents in the United States that the NTSB attributed to crew error between 1991 and 2000. (The NTSB attributed the other 18 accidents that occurred in the same period to mechanical failures.)

Their conclusions? The errors blamed on skilled experts, such as airline pilots, are most often manifestations of inherent weaknesses and limitations in the overall air transport system-factors such as inadequate information, competing organizational goals, time pressure and the limitations of human information processing. For example, juggling multiple tasks at the same time can significantly increase human vulnerability to error, the authors write.

To improve the system, the authors say airlines should identify and analyze the threats pilots routinely encounter and provide tools to help manage them. For example, when bad weather forces pilots to decide whether to continue to a destination or divert, airlines could draw on research on plan continuation bias, the tendency of people to continue with plans that are no longer viable.

Further, since some amount of human error is inevitable, airlines should train pilots to catch and manage slipups so they don’t escalate into accidents, the authors say. One way to aid this process is to apprise pilots, managers and instructors on how task demands and organizational policies can interact with human cognitive processes to drive pilots’ decision-making, Dismukes says.

Finally, airlines, regulatory agencies and the flying public should acknowledge the inherent tension between airlines’ safety goals and the public demand to arrive on time at a planned destination. Where and how that tension is balanced should be a part of public policy, Dismukes believes. Psychological researchers can help to elucidate the factors that affect this balance by studying the interaction of skilled performance with real-world task demands and organizational factors, he says.

“You get what you invest in,” Dismukes maintains. “If you want to maintain and improve flight safety, you have to invest in human factors research.”

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Safety tips for GA pilots:

According to the NTSB, these 5 safety tips will help you avoid the most fatal mistakes pilots make.

-1) Don’t get slow, especially down low

Stall/spin accidents usually don’t end well. And since you can stall at any airspeed, it’s crucial to keep your speed up. Remember, your stall speed is 41% higher at 60 degrees bank.

-2) Don’t fly VFR in low visibility

According to the NTSB, 66% of all low-visibility accidents are fatal. Most often it’s due to controlled flight into terrain or spatial disorientation.

-3) When your plane makes noises you’re not used to, get on the ground

The third most common type of fatal GA accident results from powerplant or component failure.

-4) Good maintenance saves lives

When components fail in flight, the chances of a fatal accident increase dramatically. Make sure you’re getting the proper maintenance done on your plane, and remember that even if you’re a pilot, you can always pop open the cowling and look for signs of leaks or unusual wear.

-5) Don’t make risky decisions, and when in doubt, stay on the ground

External pressures, get-there-itis, and a whole gamut of decision making errors can lead to an accident. In fact, the NTSB says that nearly every fatal GA accident has some type of poor risk management or aeronautical decision-making involved.. Aeronautical decision-making (ADM) is decision-making in a unique environment—aviation. It is a systematic approach to the mental process used by pilots to consistently determine the best course of action in response to a given set of circumstances.  

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Aircraft fire trainer:

An aircraft fire trainer is a firefighting simulator designed to practice rescue of passengers and crew during an aircraft accident. Aircraft fire training simulators allow firefighters to re-create different emergency scenarios such as large-scale external fuel spill, wing, engine and tail fires. They can also help to develop realistic internal rescue scenarios for seat, cockpit, cabin and cargo fire. Fire training simulators also offer flexibility for the right training activity while providing maximum safety at all times. They are used by municipal, industrial fire and rescue departments, international airports and military throughout the world. Ground collisions and accidents can be created as a part of a large-scale training exercise involving fire, ambulance and police cruise, ground staff and air crews. In addition, secondary incidents can be developed providing training on controlling incidents that can occur around the aircraft. Every activity is managed and viewed from the control tower.

When aircraft crashes, specialized firefighting and rescue tactics are required. However, using multi million dollar aircraft is not a viable option – even for the largest of companies. Full size mock-ups of several types of aircraft exist that are realistic training tools. These are dramatically less expensive to produce and are reusable.

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Approach-and-Landing Accidents Reduction (ALAR):

The Flight Safety Foundation (FSF) ALAR Task Force was created in 1996 as another phase of the Controlled Flight Into Terrain (CFIT) accident reduction program launched in the early 1990s. The FSF ALAR Task Force collected and analyzed data related to a significant set of approach-and-landing accidents, including those resulting in controlled-flight-into-terrain CFIT).  The Task Force developed conclusions and recommendations for practices that would improve safety in approach-and-landing, in the following domains:

• Air Traffic Control – Training and Procedures;
• Airport Facilities;
• Aircraft equipment; and,
• Aircraft Operations and Training.

All conclusions and recommendations were data driven and supported by factual evidence of their relevance to the reduction of approach-and-landing incidents and accidents.

Statistical Data:

Approach-and-landing accidents (i.e., accidents that occur during initial approach, intermediate approach, final approach or landing) represent every year 55 % of total hull losses and 50 % of fatalities. These statistical data have not shown any down trend over the past 40 years! The flight segment from the outer marker to the completion of the landing roll represents only 4 % of the flight time but 45 % of hull losses.

The following types of events account for 75 % of approach-and-landing incidents and accidents:

• CFIT (including landing short of runway);
• Loss of control;
• Runway overrun;
• Runway excursion; and,
• Non-stabilized approaches.

The conclusions of the Flight Safety Foundation ALAR Task Force identify the following operations and training issues as frequent causal factors in approach-and-landing accidents, including those involving CFIT:

• Standard operating procedures;
• Decision-making in time-critical situations;
• Decision to initiate a go-around when warranted;
• Rushed and unstabilized approaches;
• Pilot/controller understanding of each other’ operational environment;
• Pilot/controller communications;
• Awareness of approach hazards (visual illusions, adverse wind conditions or operations on contaminated runway); and,
• Terrain awareness.

The prevention of approach and landing accidents (ALA) is one of the top priorities of the aviation industry. One effort, spearheaded by the Flight Safety Foundation, is the Approach-and-Landing Accident Reduction (ALAR) Tool Kit, a collection of tools and awareness material designed to help reduce the frequency and severity of approach and landing accidents and incidents, including controlled flight into terrain (CFIT) accidents. The ALAR Tool Kit presents a wide range of information to ensure that all segments of the aviation industry find it applicable and useful. The Flight Safety Foundation has organized the CFIT/ALAR Action Group (CAAG) to direct the implementation of the ALAR Tool Kit throughout the aviation industry. The group has assigned regional team leaders to adapt the toolkit to their respective regions of the world through language translations, workshops, and regulations. Regional team leaders have been established in Africa, Australia, Central and South America, Iceland, Indonesia, Malaysia, the Middle East, Myanmar, South Africa, South Asia, Southeast Asia, and Thailand.

In North America, the ALAR Tool Kit is being implemented by the Commercial Aviation Safety Team (CAST), which is a joint effort of government organizations, industry associations, and individual aerospace companies, including Boeing. CAST was formed in June 1998 to significantly reduce the rate of fatal commercial aviation accidents. In Europe, a similar team—the Joint Aviation Authorities Safety Strategy Initiative—is leading implementation efforts.

Boeing has distributed the ALAR Tool Kit to all its airplane customers. Boeing also is actively involved in the CAAG and in assisting regional team leaders.

The aviation industry can reduce the ALA rate by increasing awareness of ALA hazards and methods of prevention. The ALAR Tool Kit, which contains quantitative data, conclusions, recommendations, and training materials, is a valuable resource in this effort. Implementation of the toolkit is under way worldwide.  

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Tombstone mentality:  

In aviation air safety, a tombstone mentality informally is a pervasive attitude of ignoring design defects until people have died because of them.

Strictly speaking, tombstone mentality decisions are examples where there is no incentive for an economic actor to be a ‘first mover’ and promote safety. Sometimes this is a result of market pressures (nobody wants to pay for extra safety, despite their talk), or, it may be a result of legal disincentives such as product liability lawsuits (if a design change is made that is not government approved and somebody is injured, even if the design change was not the reason for the injury, the company may be liable).

The theory suggests safety improvements are only made to aircraft after an accident illuminates a fatal defect. Perhaps the most recent example was Air France flight 447 in 2009, which crashed into the sea off Brazil with the loss of 228 lives. Accident investigators eventually blamed discrepancies in data provided to pilots from airspeed indicators, causing the American Federal Aviation Administration (FAA) to order replacements to be installed on all relevant aircraft.

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Flying get so reliable in part, because previous accidents triggered crucial safety improvements. Out of these tragedies arose major technological advances in flight safety that keep air travel routine today.

-1. Jet Engines

Now taken for granted by international travellers, the jet engine revolutionized aviation like no other technology in history. As piston powered engines were gradually replaced during the 1950s with their vastly more reliable counterparts, so fatal crashes were reduced. According to FAA data, global aviation averaged 3.5 fatal air carrier accidents per year due to engine failure before the introduction of jet engines. (It must also be remembered the total number of flights was also significantly smaller during this period.)

-2. Controlled Flight into Terrain

While the popular perception of a plane crash conjures images of a burning aircraft hurtling toward the ground, the truth is likely to be very different. Indeed one of the most common causes of such disasters is termed controlled flight into terrain (CFIT). This scenario sees a perfectly airworthy aircraft, under the control of a trained pilot, unintentionally flying into the ground. Notable examples include the loss of Alitalia Flight 771 in India during 1962, TWA Flight 128 in Kentucky five years later and, more recently, Garuda Indonesia Flight 152 in North Sumatra, Indonesia.

The introduction of pressurized cabins in the 1940s – allowing planes to fly well above most terrain while en route – initially lowered the number of accidents of this kind, but it was not until the development of VHF omni-directional radio range calculators (VOR) and instrument landing systems (ILS) CFIT accidents were significantly reduced. Radar in the 1950s changed the environment again, while the introduction of VOR/ Distance measuring equipment (DME) made further improvements. The latest incarnation of this type of safety mechanism is the ground-proximity warning system (GPWS), which is designed to alert pilots if an aircraft is in immediate danger of flying into the ground. While earlier systems suffered from blind spots these newer incarnations – including the latest enhanced ground proximity warning systems (EGPWS) – allow pilots to calculate their position with more accuracy than ever before. Such systems are legally mandated by the FAA.

-3. Traffic Collision Avoidance System

As systems were developed to minimize risk of controlled flight into terrain, fatal mid-air collisions presented another common accident scenario. In 1958, for example, a United Airlines passenger airliner struck a Trans World Airlines aircraft over the Grand Canyon in Arizona, resulting in the crash of both planes and 128 fatalities. The 1976 Zagreb accident was also attributed to this cause. The incident saw British Airways Flight 476 collided in mid-air with Inex-Adria Aviopromet Flight 550 over Croatia with the loss of 176 lives. To combat the problem, traffic collision avoidance systems were mandated by UN International Civil Aviation Organisation for all aircraft carrying over 19 passengers. This has dramatically reduced the number of accidents attributed to this cause – but not eradicated the problem. Human error can still play a part in any crash – as with the Gol Transportes Aéreos Flight 1907 disaster, which cost 154 lives in 2006.

-4. Wind Shear

For decades the impact of wind shear on commercial aircraft during takeoff and landing was underestimated by operators, prompting a number of potentially avoidable disasters.

Essentially the phenomenon sees strong outflows from thunderstorms produce rapid changes in three-dimensional wind velocity, creating a headwind and prompting pilots to reduce engine power. As an aircraft passes into the region of the downdraft, the localised headwind diminishes, reducing the aircraft’s airspeed and increasing its sink rate. Then, when an aircraft passes through the other side of the downdraft, the headwind becomes a tailwind, reducing airspeed further, leaving the aircraft in a low-power, low-speed descent. This can lead to an accident if the aircraft is too low to initiate a recovery before ground contact. Between 1964 and 1985 wind shear was directly cited as a caused or contributed to 26 major civil transport aircraft accidents – costing over 600 lives. These include the loss of Delta Air Lines Flight 191, which crashed while on approach to the Dallas-Fort Worth Airport in 1985 killing 135 people, and a 1982 incident which saw Pan Am Flight 759 lost over Louisiana taking 145 lives. As the result of these accidents, the FAA mandated in 1988 all commercial aircraft had on-board wind shear detection systems by 1993. Since this decision incidence of wind shear related accidents have fallen to approximately one per decade.

-5. Pilot Training

Even with the sophisticated systems outlined, human error still remains a factor in a number of crashes. Some 156 passengers were killed when Northwest Airlines Flight 255 crashed during take-off in 1987 in an accident caused by pilot error for example. But while it cannot be eradicated, human error can be minimized. Licences demonstrating applicable training ensure only the rigorously qualified are allowed into the cockpit, while modern six-axis simulators ensure pilots experience real flight before they step onto a plane. Pilots learn – in a risk-free environment – how to handle an engine failure, wind shear, or failed flight controls.

-6. Cockpit teamwork

United Flight 173, a DC-8 approaching Portland, Ore., with 181 passengers, circled near the airport for an hour as the crew tried in vain to sort out a landing gear problem. Although gently warned of the rapidly diminishing fuel supply by the flight engineer on board, the arrogant captain waited too long to begin his final approach. The DC-8 ran out of fuel and crashed in a suburb, killing 10.

In response, United revamped its cockpit training procedures around the then-new concept of Cockpit Resource Management (CRM). Abandoning the traditional “the captain is god” airline hierarchy, CRM emphasized teamwork and communication among the crew, and has since become the industry standard.

-7. Lav smoke sensors

The first signs of trouble on Air Canada 797, a DC-9 flying at 33,000 ft. en route from Dallas to Toronto, were the wisps of smoke wafting out of the rear lavatory. Soon, thick black smoke started to fill the cabin, and the plane began an emergency descent. Barely able to see the instrument panel because of the smoke, the pilot landed the plane at Cincinnati. But shortly after the doors and emergency exits were opened, the cabin erupted in a flash fire before everyone could get out. Of the 46 people aboard, 23 died.

The FAA subsequently mandated that aircraft lavatories be equipped with smoke detectors and automatic fire extinguishers. Within five years, all jetliners were retrofitted with fire-blocking layers on seat cushions and floor lighting to lead passengers to exits in dense smoke. Planes built after 1988 have more flame-resistant interior materials.

-8. Retiring tin

As Aloha Flight 243, a weary, 19-year-old Boeing 737 on a short hop from Hilo, Hawaii, to Honolulu, leveled off at 24,000 ft., a large section of its fuselage blew off, leaving dozens of passengers riding in the open-air breeze. Miraculously, the rest of the plane held together long enough for the pilots to land safely. Only one person, a flight attendant who was swept out of the plane, was killed.

The National Transportation Safety Board (NTSB) blamed a combination of corrosion and widespread fatigue damage, the result of repeated pressurization cycles during the plane’s 89,000-plus flights. In response, the FAA began the National Aging Aircraft Research Program in 1991, which tightened inspection and maintenance requirements for high-use and high-cycle aircraft. Post-Aloha, there has been only one American fatigue-related jet accident—the Sioux City DC-10.

-9. Rudder Rx

When USAir Flight 427 began its approach to land at Pittsburgh, the Boeing 737 suddenly rolled to the left and plunged 5000 ft. to the ground, killing all 132 on board. The plane’s black box revealed that the rudder had abruptly moved to the full-left position, triggering the roll. But why? USAir blamed the plane. Boeing blamed the crew. It took nearly five years for the NTSB to conclude that a jammed valve in the rudder-control system had caused the rudder to reverse: As the pilots frantically pressed on the right rudder pedal, the rudder went left.

As a result, Boeing spent $500 million to retrofit all 2,800 of the world’s most popular jetliner. And, in response to conflicts between the airline and the victims’ families, Congress passed the Aviation Disaster Family Assistance Act, which transferred survivor services to the NTSB.

-10. Fire prevention in the hold

Although the FAA took anti-cabin-fire measures after the 1983 Air Canada accident, it did nothing to protect passenger jet cargo compartments—despite NTSB warnings after a 1988 cargo fire in which the plane managed to land safely. It took the horrific crash of ValuJet 592 into the Everglades near Miami to finally spur the agency to action. The fire in the DC-9 was caused by chemical oxygen generators that had been illegally packaged by SabreTech, the airline’s maintenance contractor. A bump apparently set one off, and the resulting heat started a fire, which was fed by the oxygen being given off. The pilots were unable to land the burning plane in time, and 110 people died. The FAA responded by mandating smoke detectors and automatic fire extinguishers in the cargo holds of all commercial airliners. It also bolstered rules against carrying hazardous cargo on aircraft.

-11. Electrical spark elimination

It was everybody’s nightmare: a plane that blew up in midair for no apparent reason. The explosion of TWA Flight 800, a Boeing 747 that had just taken off from JFK bound for Paris, killed all 230 people aboard and stirred great controversy. After painstakingly reassembling the wreckage, the NTSB dismissed the possibility of a terrorist bomb or missile attack and concluded that fumes in the plane’s nearly empty center-wing fuel tank had ignited, most likely after a short circuit in a wire bundle led to a spark in the fuel gauge sensor.

The FAA has since mandated changes to reduce sparks from faulty wiring and other sources. Boeing, meanwhile, has developed a fuel-inerting system that injects nitrogen gas into fuel tanks to reduce the chance of explosions. It will install the system in all its newly built planes, starting in 2008. Retrofit kits for in-service Boeings will also be available.

-12. Insulation swap-out

About an hour after takeoff, the pilots of Swissair’s Flight 111 from New York to Geneva—a McDonnell Douglas MD-11—smelled smoke in the cockpit. Four minutes later, they began an immediate descent toward Halifax, Nova Scotia, about 65 miles away. But with the fire spreading and cockpit lights and instruments failing, the plane crashed into the Atlantic about 5 miles off the Nova Scotia coast. All 229 people aboard were killed.

Investigators traced the fire to the plane’s in-flight entertainment network, whose installation led to arcing in vulnerable Kapton wires above the cockpit. The resulting fire spread rapidly along flammable Mylar fuselage insulation. The FAA ordered the Mylar insulation replaced with fire-resistant materials in about 700 McDonnell Douglas jets.

-13. Manual training to fix over-dependence on automation

Around three hours into its journey from Rio to Paris, Air France Flight 447, an Airbus A330-200, headed into an area of severe thunderstorm activity—it was never heard from again. From an envelope-pushing altitude of 38,000 feet, the aircraft entered an aerodynamic stall before plunging into the depths of the southern Atlantic Ocean, killing all 228 people aboard.  Several days later, pieces of the wreckage were spotted floating on the water’s surface, but the whereabouts of the rest of the jet remained a mystery for more than two years, when a privately funded search located the bulk of the fuselage, bodies of the victims, and the vital black box recorders.

Investigators had already solved part of the puzzle, relying on automated messages sent from the crippled plane as it went down, revealing that the pitot tubes that track speed had frozen and malfunctioned, setting off a cascading series of events.  With the wreckage now found, the evidence led experts to conclude the crash was caused by the pilots’ failure to take corrective action to recover from the stall.  The findings cast a harsh light on fly-by-wire technology and its reliance on computers, rather than humans, to make the final call on flight decisions.  Boeing and Airbus both use fly by wire, but Boeing gives pilots the ability to override automation.  The crash prompted a renewed effort to retrain pilots to manually fly the plane–no matter what the computer is telling them. 

Fly-by-Wire (FBW) is the generally accepted term for those flight control systems which use computers to process the flight control inputs made by the pilot or autopilot, and send corresponding electrical signals to the flight control surface actuators.

-14. Upgrade (pending): Real-time flight tracking

There was no May Day call or sign of trouble when Malaysia Airlines Flight 370, a 777 carrying 239 people en route from Kuala Lumpur to Beijing, dropped off the radar screens on March 8, 2014. Many years later, it is still aviation’s most agonizing mystery. The biggest question: why the plane’s transponders were apparently disabled, making the jet almost invisible as it unaccountably changed course and headed south, where some experts believe it flew for up to seven hours on autopilot before running out of fuel and crashing into the Indian Ocean. In the absence of hard evidence—with few clues in the form of some barnacled flotsam found off Africa–many competing theories of what happened have arisen, from hypoxia caused by rapid decompression (also the cause of the Helios Flight 522 crash in Greece), to intentional sabotage from a crew member or passenger.

One thing is clear: the world wouldn’t still be looking for the plane if it had been equipped with real-time tracking, which safety experts had been demanding ever since Air France 447. As a result of MH370, the International Civil Aviation Organization has ordered all airlines to install tracking equipment that will keep closer tabs on planes, especially those over the ocean, and aircraft manufacturers are also developing black boxes that would eject and float automatically when a plane hits water.

So what could make us even safer?

There are now no “common causes” of aviation accidents; each must have its own unique set of circumstances; in order to negate the sophisticated systems in place to prevent just such an occurrence. Only greater communication between operators, manufacturers, repair stations, suppliers and the wider aviation community with regard to the causes of accidents could make us safer.

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“Smart” cockpit could help prevent plane crashes:

The General Aviation Joint Steering Committee (GAJSC) has determined that pilots who use “smart” procedures, including automated checklists for normal and emergency operations, predictive aircraft performance, and performance monitoring, might help reduce their chances for a Loss of Control (LOC) accident, which involves an unintended departure of an aircraft from controlled flight. LOC can happen when the aircraft enters a flight regime that is outside its normal flight envelope and quickly develops into a stall or spin. It can introduce an element of surprise for the pilot.

Automation which is currently available can help reduce accidents in general aviation (GA). Implementing the Automatic Dependent Surveillance-Broadcast (ADS-B) technology is the first step in achieving a “smart” cockpit that also takes advantage of electronic ignition and engine control, interconnected devices, and flight information stream flow.

ADS-B:

Automatic Dependent Surveillance–Broadcast (ADS–B) is a surveillance technology in which an aircraft determines its position via satellite navigation or other sensors and periodically broadcasts it, enabling it to be tracked. The information can be received by air traffic control ground stations as a replacement for secondary surveillance radar, as no interrogation signal is needed from the ground. It can also be received by other aircraft to provide situational awareness and allow self-separation. ADS–B is “automatic” in that it requires no pilot or external input. It is “dependent” in that it depends on data from the aircraft’s navigation system. Those who have already equipped know the advantages of ADS-B. It provides more precision and reliability than the current radar system. It also provides improved aircraft position data, which is critical in collision avoidance. ADS-B In has a data link for environmental information, which can also be used for air traffic control (ATC) communications, notices to airmen (NOTAM), and up-to-the-minute temporary flight restriction information.

Electronic ignition and engine control:

If your car has a start button, you know what this is all about. Electronic Engine Control (EEC) systems are more reliable, more efficient, and less costly to purchase and maintain than analog systems. EECs evaluate input from engine and environmental sensors hundreds of times per minute, which keep your engine running at peak efficiency for your operational environment. Those same sensors will also give you a clear picture of your power plant’s health. If there’s a problem, a light will let you know you need to schedule maintenance.

Interconnected devices:

Interconnected devices turn your cockpit into an information powerhouse. Air-to-ground data links can provide air traffic clearances and instructions as well as current weather and field condition reports and NOTAMs.

Link your phone to access even more information safely and securely. You’ll be able to see where you’re going without “fumble-fingering” your route. Information is transferred directly from your flight plan to your aircraft.

Flight Information Stream:

With a flight information stream, a pilot can get complete information on your aircraft’s health from a variety of internal and external sources that are available now, or will be soon. This information can be formed, updated, and presented in a graphical and text form.

In the future, ATC communications and aircraft configuration will be integrated, and smart checklists for normal and emergency operations will appear as needed.

With all that information, the aircraft will be able to predict performance in takeoff, cruise, approach, and landing operations. Pilots will know how much runway they’ll need for every take-off and landing.

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ASRS:

The Aviation Safety Reporting System, or ASRS, is the US Federal Aviation Administration’s (FAA) voluntary confidential reporting system that allows pilots and other aviation professionals to confidentially report near misses or close call events in the interest of improving aviation safety. The ASRS collects, analyzes, and responds to voluntarily submitted aviation safety incident reports in order to reduce the likelihood of aviation accidents. The ASRS was designed by NASA. The ASRS is operated by NASA; who is seen as a neutral third-party due to its lack of enforcement authority and relations with airlines. The confidential and independent nature of the ASRS is key to its long-term success in identifying numerous latent system hazards in the National Airspace System (NAS). Under the FAA’s authority, NASA extends limited immunity to individual aviation workers for reporting safety events which do not result in an accident, as defined by the FAA. This has the effect of encouraging these potential reporters to come forward with systemic safety issues without fear of reprisal. The success of the system stands as a positive example used as a model by other industries seeking to make improvements in safety. Other industries who have modeled similar systems on the ASRS include the rail, medical, firefighters, and off-shore petroleum production.

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Bird Strike Prevention Radar System:

The Accipiter® NM1-8A Avian Radar System is a software-definable, 2D surveillance radar specially designed to detect and track birds around airports. The system includes one radar sensor integrated into a NEMA-4 rated environmental enclosure, which houses the radar sensor electronics, digital radar processors, radar remote controller, radar data manager, power management and data communications components. The Radar System includes a high-resolution, X-band transceiver with 8’ array antenna that can be operated in either a horizontal or vertical orientation. An optional ground-tracking channel for surface movement, and aircraft tracking channel for aircraft movement are also available. The Accipiter® NM1-8A is well suited for use at civil and military airports.

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WEATHER-Eye (WEATHER-Endurance Aircraft Technology to Hold, Evade and Recover by Eye):

Weather conditions have a major impact on aircraft operation. Winter brings with it some of the world’s harshest conditions for aircraft. For example, the adherence of snow and ice to the airframe has a significant impact on aircraft operation, particularly during takeoff. Snow accumulation on runways increases the risk of an overshoot. Aircraft are designed to maintain a measure of safety even if they are subjected to the adherence of snow and ice or a lightning strike, and so on. It is also true that measures are taken to ensure they are operated more safely even at the expense of efficiency. In the event of weather conditions that exceed our assumptions, serious accidents and malfunctions may occur.

In order to efficiently maintain airframe safety against weather conditions, JAXA is conducting research and development of WEATHER-Eye (WEATHER-Endurance Aircraft Technology to Hold, Evade and Recover by Eye), which is a group of technologies designed to detect airframe, runway, and weather conditions, and predict and protect against weather impact. The technologies that comprise WEATHER-Eye are contaminated runway detection technology, lightning risk prediction technology, lightning protection technology, engine anti-icing/deicing technology, and engine CMAS (Calcium-Magnesium-Alumino-Silicate) prevention technology, and gust alleviation technology.

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Machine learning to prevent plane crash:

Data mining refers to extraction of information from huge chunks of the dataset. It’s also called information mining. It is exercised in numerous fields like medicine, environment, education, crime, etc. In this research work crash investigation and analysis of the flights are done. Flight crashes may be caused due to pilot error, mechanical failure, bad weather, sabotages or human error. Institute for Software Integrated Systems (ISIS) researchers are mining regional airline data to build the Vehicle Integrated Prognostic Reasoner (VIPR), which uses knowledge derived from advanced data mining and machine-learning techniques to diagnose and detect potential problems in an airplane before an accident or emergency landing. The VIPR project aims to find evolving faults in aircraft systems, such as the engine and the avionics system, as well as anomalies that occur due to pilot actions and unusual environmental conditions, such as inclement weather or the orientation of a runway in a particular airport.

“We are one of the first projects that has taken this data and tried to apply intelligent analysis to help isolate, detect, and prevent adverse events,” said Gautam Biswas, professor of computer science and computer engineering, who leads the NASA-funded VIPR project. Even though plane crashes are rare, the growing complexity of aircraft systems has increased the chances for unexpected occurrences; hence the need to combine machine-driven exploration with human expertise to understand these situations, said Biswas. “We’re reaching limits in terms of how effectively human experts can analyze unusual situations,” he said. “We must therefore find ways to use all our resources—human expertise and research in data mining and machine learning—to enhance existing knowledge. Analyzing the huge amounts of operational data that we have collected over the years will improve decision-making during flight operations, maintenance, scheduling, and overall airline management. The most important goal is improved airline safety and efficiency.”

VIPR uses advanced data mining and machine-learning techniques to explore and analyze large amounts of flight data to derive new and useful knowledge. Human experts then use that knowledge to improve diagnostic monitors and reasoning systems available on today’s aircraft.

Biswas sift through the data collected by numerous sensors and monitors for up to fifty flights before an adverse event occurred. They consider mitigating factors, such as weather conditions, degrading equipment, and pilot error, and look for sequences of events that might have been overlooked, such as an evolving degradation in a fuel injection system that caused an engine to overheat and eventually shut down. More recently, they’ve generalized their approach to exploration methods that search for anomalies in terabytes of flight data. “We found that in many cases, you could have reliably detected the likelihood of a particular problem occurring by thorough and careful analysis of available data,” Biswas said.

Biswas said real airline disasters and averted disasters alike motivate his work. For example, data analysis of Air France Flight 447 en route from Rio de Janeiro to Paris when it crashed into the Atlantic Ocean in 2009 indicated a junior pilot failed to understand sensor data and alarms that went off in the aircraft. On the other hand, the now famous Captain Sully had the experience and training to safely crash-land a U.S. Airways flight in the Hudson River that same year with no casualties.

The data mining technologies developed by ISIS may also help inform training methods, improve software-integrated design, and find systematic ways of analyzing the vast reams of data the FAA requires airlines to collect to inform decisions, rather than relying on current ad hoc methods for identifying problems.

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Moral of the story:

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-1. Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere (i.e., air flight or aviation) or through the vacuum of outer space (i.e., spaceflight).

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-2. An aircraft is any vehicle that can fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), gliders, paramotors and hot air balloons. An airplane is a specific type of aircraft that has fixed wings, propelled forward by thrust from a jet engine, propeller, or rocket engine; and capable of sustained, powered, and controlled flight. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. 

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-3. Civil (non-military) flight operations are usually categorized as commercial or general aviation (GA). Commercial aviation concerns scheduled flights from larger tarmac airports that involve the transportation of passengers or cargo. All non-scheduled flights that are not operated by commercial airlines or by the military are identified as general aviation. GA supports diverse activities such as law enforcement, forest fire fighting, flight instruction, air ambulance, agriculture, logging, fish and wildlife spotting, and other vital services flown in a variety of aircraft of all sizes and types, including airplanes, helicopters, balloons, and gliders. The majority of civil aviation crashes, deaths, and injuries are attributed to general aviation operations. Figures from the National Transportation Safety Board indicate that a staggering 97 percent of aviation fatalities occur in general aviation, not in commercial flights.

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-4. A commercial pilot in typical airline service is allowed, at maximum, to fly about (1) 100 hours of flight time in any 28 consecutive days; (2) 900 hours of flight time in any calendar year; and. (3) 1,000 hours of flight time in any 12 consecutive calendar months. This does not include other duty time (like time between flights), and can be lower based on airline internal rules or contracts.

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-5. Commercial air travel is regarded as one of the safest forms of transport in the world. Worldwide, commercial aviation transports more than four billion passengers annually on airliners and transports more than 200 billion ton-kilometers of cargo safely at their destinations. In 2020, due to coronavirus pandemic, the number of scheduled passengers boarded by the global airline industry dropped to 1.8 billion people. This represents a 55 percent loss in global air passenger traffic.

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-6. Travel by airplane is a safer way to transport than bus, rail and car when risk is calculated against distance travelled. Bus and rail are safer form of transport than airplane when risk is calculated against number of journeys and against number of hours of travel. Airplane is a safer way to transport than car when you compare number of fatalities to number of people travelled but not when you compare number of fatalities to number of journeys. In the ten years from 2008 to 2017, there were 1,410 hull loss (aircraft damaged beyond economical repair, resulting in a total loss) accidents worldwide involving fixed-wing aircraft with six or more seats, yet from those accidents only 8,530 people died.  For comparison, an estimated 1.25 million people worldwide die from road accidents every year.  

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-7. Over the past four decades fatalities on airplanes due to accidents have declined even as the number of travelers has increased almost ten-fold. This proves increased aviation safety over time. It has never been safer to fly on commercial airlines. A study finds that between 2008 and 2017, airline passenger fatalities fell significantly compared to the previous decade, as measured per individual passenger boarding — essentially the aggregate number of passengers. Globally, that rate is now one death per 7.9 million passenger boarding, compared to one death per 2.7 million boarding during the period 1998-2007, and one death per 1.3 million boarding during 1988-1997. Going back further, the commercial airline fatality risk was one death per 750,000 boarding during 1978-1987, and one death per 350,000 boarding during 1968-1977. The worldwide risk of being killed in plane crash had been dropping by a factor of two every decade since 1970s and reached factor of three last decade. 

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-8. In the early days of flight (since 1903), approximately 80 percent of airplane accidents were caused by the machine and 20 percent were caused by human error. Today that statistic has reversed. Approximately 80 percent of airplane accidents are due to human error (pilots, air traffic controllers, mechanics, etc.) and 20 percent are due to machine (equipment) failures.   

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-9. Any pilot will tell you that the most critical times of a flight are during takeoff and landing. Most accidents and fatalities take place during the departure (take off / climb) and arrival (approach/ landing) phases of flight. It has been found out that as much as 50 % of all the accidents took place during the approach to landing, which represents only 4 % of the total flight time. Another 27 % of accidents occurred during takeoff and initial climbs representing only some 2 % of the flight time. A simple addition of the percentages reveals that more than ¾ of all air accidents occur within a relatively short legs of flight. So about 80 percent of all plane crashes happen within the first three minutes of a flight or in the last eight minutes before landing. These are the crucial 11 minutes when you need to be alert on an airplane. Stay sober, hold off on your nap, and don’t bury your face in a book. Make sure your seatbelt is securely fastened — low and tight.

Reasons why accidents are most common during landing and takeoff are as follows:

Takeoff and landing are when planes are closest to the ground and in a more vulnerable configuration than during other flight phases. There is often not enough time or altitude for the pilots to take corrective action. There is less time to recover from a mistake and less time to react to problems. Planes are traveling slower, closer to their stalling speeds, and forced to do more manoeuvring during these critical times. The crew have to deal with a high workload and reduced manoeuvre margins.

However, accidents during landing and takeoff are the most survivable – they occur close to airports where the aircraft are already travelling low and slow, and emergency services can respond with a moment’s notice.

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-10. Propulsion is the net force that results from unequal pressures. Gas (air) under pressure in a sealed container exerts equal pressure on all surfaces of the container; therefore, all the forces are balanced and there are no forces to make the container move. If there is a hole in the container, gas (air) cannot push against that hole and thus the gas escapes. While the air is escaping and there is still pressure inside the container, the side of the container opposite the hole has pressure against it. Therefore, the net pressures are not balanced and there is a net force available to move the container. This force is called thrust. A gas turbine engine is a container with a hole in the back end (tailpipe or nozzle) to let air inside the container escape, and thus provide propulsion. Inside the container is turbomachinery to keep the container full of air under constant pressure.  

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-11. All commercial aircraft designed in the last 40 years (other than aircraft with fewer than a dozen passengers) are powered by gas turbine engine (jet engine). A jet engine develops thrust by accelerating a relatively small mass of air to very high velocity, as opposed to a propeller, which develops thrust by accelerating a much larger mass of air to a much slower velocity. The key difference between turbofan jets and propeller planes is that jets produce thrust through the discharge of gas instead of powering a drive shaft linked to a propeller. This allows jets to fly faster and at higher altitudes Most modern subsonic jet aircraft use complex high-bypass turbofan jet engines. They give higher speed and greater fuel efficiency than propeller aeroengines over long distances. The greater the speed, the greater the engine’s thrust. The 1500 degree Celsius hot exhaust exits the engine at incredible speeds, up to three times the speed of sound, pushing the plane forward.

A piston engine cannot produce thrust on its own. It provides power to a spinning propeller, which produces thrust by creating a pressure difference between the front and back of the propeller, resulting in a forward force pulling the aircraft forward while pushing the air behind it. Piston engines, even the largest available, are limited to around 300 horsepower each. In turboprop jet engines, the exhaust jet produces only about 10% of the total thrust while higher proportion of the thrust comes from the propeller at low speeds and less at higher speeds. Turboprop jet engines coupled to a propeller, generally produce from around 450 horsepower to 2,000 horsepower and more. For an aircraft like a Boeing 777 with two GE 90-115B turbofan jet engines, each engine produces roughly 30,843 horsepower during cruise flight with a fully loaded aircraft. Turbofan jet engines have no propeller as compared to piston engines and turboprop jet engines.

All conventional twin engine planes will lose approximately 80 percent of their ability to climb after an engine failure. Having more power of engine translates not only to greater overall performance, but also to greater overall safety.  

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-12. Federal Aviation Administration studies indicate that piston engines in aircraft have a failure rate, on average, of one every 3,200 flight hours while turbine engines have a failure rate of one per 375,000 flight hours. Accordingly, for every turbine engine experiencing a failure, 117 piston engines would have failed. Although turbine powered aircraft are typically more expensive to buy and to operate than their piston powered counterparts, they do provide an unparalleled degree of performance, productivity, and safety. The failure rate of aircraft jet engines has reached an all-time low. This means that many flight crews of commercial airliner will never face an engine failure during their career, other than those in the flight simulator.  

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-13. Twin engine aircraft can go faster, carry more useful load, provide system redundancy, and afford better climb performance than their single engine counterparts. A twin-engine aircraft can fly perfectly well on only one engine. In fact, it can even continue the take-off and then safely land with just one engine. Due to engine failure/shutdown, asymmetric thrust that will be produced. The other engine’s thrust is increased to stop a decay in airspeed. This results in the aircraft wanting to turn away from the working engine and entering a turn. If left unchecked, this will result in loss of control of the aircraft. This usually has to be corrected manually by the pilots through the rudder pedals.

A passenger airplane will glide perfectly well even if all its engines have failed, it won’t simply fall out the sky. Airplanes are designed in a way that allows them to glide through the air even with no engine thrust. A passenger jet could glide for up to about 60 miles if it suffers a total engine failure at its cruising altitude and the airplane may have as much as 20 – 30 minutes of airborne time to find somewhere to land.   

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-14. Thrust, drag, lift, and weight are forces that act upon all aircraft in flight. Understanding how these forces work and knowing how to control them with the use of power and flight controls are essential to flight.

Drag is a force exerted on an object moving through air; it is always oriented in the direction of relative air flow (try running against a high wind and you’ll feel drag pushing you back in the direction of relative air flow). Drag occurs because the air and the object exchange momentum when impacting, creating a force opposing the motion of the object. As a general rule, drag opposes thrust and acts rearward parallel to the relative wind.

Lift is another force that is produced by the dynamic effect of the air acting on the airfoil, and acts perpendicular to the flight path through the center of lift (CL) and perpendicular to the lateral axis. In level flight, lift opposes the downward force of weight that is pulling object down to Earth. 

Thrust is the third force produced by powered flight opposing the drag force. To fly at a steady speed in a completely horizontal direction, an object must generate enough thrust to equal the drag forces on it. As a general rule, it acts parallel to the longitudinal axis. However, this is not always the case, as explained below.

Weigh is the combined load of the aircraft itself, the crew, the fuel, and the cargo or baggage. Weight is a force that pulls the aircraft downward because of the force of gravity. It opposes lift and acts vertically downward through the aircraft’s center of gravity (CG).

For flight, an aircraft’s lift must balance its weight, and its thrust must exceed its drag. A plane uses its wings for lift and its engines for thrust. Drag is reduced by a plane’s smooth shape and its weight is controlled by the materials it is constructed of.

The usual explanation states that thrust equals drag and lift equals weight. Although true, this statement can be misleading. The refinement of the old “thrust equals drag; lift equals weight” formula explains that a portion of thrust is directed upward in climbs and slow flight and acts as if it were lift while a portion of weight is directed backward opposite to the direction of flight and acts as if it were drag. In glides, a portion of the weight vector is directed along the forward flight path and, therefore, acts as thrust. In other words, any time the flight path of the airplane is not horizontal; lift, weight, thrust, and drag vectors must each be broken down into two components, horizontal and vertical. 

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-15. A wing generates lift by encouraging attached flow of the air around its surface. Attached flow is the tendency of an airstream to “stick” to a surface as it passes it. It might be natural to think that when a wing’s curvature displaces air upward, air is compressed resulting in increased pressure atop the wing. However curved upper surface of wing has greater area than flat lower surface, so number of air molecules deflected by upper surface is more than lower surface, and more deflected molecules will generate relative paucity of molecules in vicinity of surface resulting in reduced pressure over curved surface compared to flat surface. But more importantly, air is pushed downward due to AOA and this downwash of air hitting lower surface of wing pushes on the wing both vertically (producing lift) and horizontally (producing drag). The upward push exists in the form of higher pressure below the wing, and this higher pressure is a result of simple Newtonian action and reaction. The more air that the aerofoil deflects, the greater the lift force.   

Remember, due to positive AOA, air is merely flowing over upper surface of wings while pushed hard on the lower surface of wings. This pushed hard hitting air molecules generate lift and drag. Even if the upper surface of wing was not curved but flat, lift and drag will be produced by air molecules hitting lower surface of wings due to AOA. If the AOA of a symmetrical airfoil is zero, there would be no lift no drag. On the other hand, if AOA is zero of cambered airfoil, slight lift will be produced by the curvature of upper surface insufficient to make airplane airborne from ground.  That is why wings are typically mounted at a small positive angle with respect to longitudinal axis of the aircraft (i.e., wings are already at small angle of attack, even on the ground) and that is why airplane is rotated-nose up pitch (increase AOA by using elevator) at Vr speed at takeoff to make airplane airborne. The nose is raised to a nominal 5°–15° nose up pitch attitude to increase lift from the wings and effect lift-off. For most aircraft, attempting a takeoff without a pitch-up would require cruise speeds while still on the runway.     

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-16. Airfoil surface generates lift and drag. The amount of lift and drag generated by an airfoil depends on its shape (camber), surface area, angle of attack, air density and speed through the air. The objective of airfoil design is to achieve the best compromise between lift and drag for the flight envelope in which it is intended to operate.

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-17. Angle of attack (AOA) is fundamental to understanding many aspects of airplane performance, stability, and control. The AOA is defined as the acute angle between the chord line of the airfoil and the direction of the relative wind. Angle of Attack is the angle at which relative wind meets an airfoil. An increase in angle of attack results in an increase in both lift and induced drag, up to a point. Too high an angle of attack (usually more than 15 degrees) and the airflow across the upper surface of the aerofoil becomes detached, resulting in a loss of lift, otherwise known as a stall. The forces necessary to bend the air to such a steep angle are greater than the viscosity of the air will support, and the air begins to separate from the wing. This separation of the airflow from the top of the wing is a stall.  

Out of 2,015 accidents involving stalls over a 15-year period, nearly 95 percent of them (1,901) occurred on non-commercial flights. Stalls are extremely rare in the airlines. Stalls are easily recoverable (the pilot points the nose down and increases the airspeed i.e., engine power) and are only deliberately created in testing new aircraft and training new pilots.  

Stall recovery is possible only if airplane is at sufficient altitude because stall recovery involves some loss of altitude and if the altitude is low enough, recovery from stall may not be possible before contact with ground.  

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-18. An important fact related to the principle of lift (for a given airfoil shape) is that lift varies with the AOA and airspeed. Therefore, a large AOA at low airspeeds produces an equal amount of lift at high airspeeds with a low AOA. Lift is proportional to the square of the aircraft’s velocity. For example, an airplane traveling at 200 knots has four times the lift as the same airplane traveling at 100 knots, if the AOA and other factors remain constant. Since speed is result of thrust by engines, it is the thrust that is generating lift. So, engine power is important not only in generating speed but also lift.  

Two major aerodynamic factors from the pilot’s viewpoint are lift and airspeed because they can be controlled readily and accurately by changing thrust (engine power) and AOA.

If thrust decreases and airspeed decreases, lift will become less than weight and the aircraft will start to descend. To maintain level flight, the pilot can increase the AOA an amount that generates a lift force again equal to the weight of the aircraft. While the aircraft will be flying more slowly, it will still maintain level flight. The AOA is adjusted to maintain lift equal weight. As thrust is reduced and airspeed decreases, the AOA must increase in order to maintain altitude. If speed decreases enough, the required AOA will increase to the critical AOA. Any further increase in the AOA will result in the wing stalling. Therefore, extra vigilance is required at reduced thrust settings and low speeds so as not to exceed the critical angle of attack.

In an approach to landing, when the pilot wishes to land as slowly as practical, it is necessary to increase AOA near maximum permissible to maintain lift equal to the weight of the aircraft.

In level flight, when thrust is increased, the aircraft speeds up and the lift increases. The aircraft will start to climb unless the AOA is decreased just enough to maintain the relationship between lift and weight.

As the airspeed varies due to thrust, the AOA must also vary to maintain level flight. At very high speeds and level flight, it is even possible to have a slightly negative AOA.

All other factors being constant, for every AOA there is a corresponding airspeed required to maintain altitude in steady, unaccelerated flight (true only if maintaining level flight).

In order to maintain a constant airspeed, thrust and drag must remain equal, just as lift and weight must be equal to maintain a constant altitude.

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-19. Stall speed is simply the minimum speed needed for an airplane to produce lift. If an airplane drops below its specified stall speed, it will no longer produce lift no matter angle of attack. Stall speeds vary depending on many factors, some of which include the airplane’s weight, dimensions, altitude, turning and even the weather dimensions.  Stalls occur not only at slow airspeed, but at any speed when the wings exceed their critical angle of attack. A wing can stall at any airspeed; all that is required is exceeding the critical angle of attack. Stall speed is the speed at which the angle of attack required to generate sufficient lift for level flight is the critical angle of attack. In other words, any further reduction of speed would require an increase in angle of attack beyond the critical angle of attack, therefore creating a stall.

When airplane slows, lift decreases if angle of attack is not increased resulting in descent. This is merely the condition of descent, not a stall. It would become stall if airplane speed falls below stall speed. The stalling speed in a landing configuration for a Boeing 737 is probably around 108 knots.  

Remember, engine stall and airplane stall are very different.    

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-20. The greater the takeoff mass the greater the aircraft weight. This means that greater lift force is required to overcome the weight, therefore greater speed is necessary for takeoff. Thus a longer takeoff distance is required in order to achieve this speed, because the rate of acceleration is reduced (inversely proportional to the mass) and the wheel drag will be greater due to increased load.

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-21. The lower the airspeed, the greater the AOA required to produce lift equal to the aircraft’s weight and, therefore, the greater induced drag. The amount of induced drag varies inversely with the square of the airspeed. Conversely, parasite drag increases as the square of the airspeed. Thus, in steady state, as airspeed decreases to near the stalling speed, the total drag becomes greater, due mainly to the sharp rise in induced drag. Similarly, as the aircraft reaches its never-exceed speed (VNE), the total drag increases rapidly due to the sharp increase of parasite drag. At some given airspeed, total drag is at its minimum amount.

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-22. An airplane is equipped with certain fixed and movable surfaces or airfoil which provide for stability and control during flight. Each of the named airfoil is designed to perform a specific function in the flight of the airplane. The fixed airfoils are the wings, the vertical stabilizer, and the horizontal stabilizer. The movable airfoils called flight control surfaces are the ailerons, elevators, rudders, flaps etc. Aircraft flight control surfaces deflects the air during the flight of an aircraft to change attitude, altitude and speed of aircraft. These flight control surfaces are under pilot control or controlled by autopilot.

The motion about the aircraft’s longitudinal axis is “roll,” the motion about its lateral axis is “pitch,” and the motion about its vertical axis is “yaw.” The three motions of the conventional airplane (roll, pitch, and yaw) are controlled by three control surfaces. Roll is controlled by the ailerons; pitch is controlled by the elevators; yaw is controlled by the rudder.

The elevator is the small moving section at the rear of the horizontal stabilizer that is attached to the fixed sections by hinges. Because the elevator moves, it varies the amount of force generated by the tail surface and is used to generate and control the pitching motion of the aircraft. The elevator is used to control the position of the nose of the aircraft and the angle of attack of the wing. This, in turn, causes the aircraft to climb or dive.

The rudder is attached to the vertical stabilizer, located on the tail of the aircraft. It works identically to a rudder on a boat, helping to steer the nose of the aircraft left and right; this motion is referred to as yaw. Unlike the boat however, it is not the primary method of steering; rather, it is used to overcome adverse yaw induced by turning or, in the case of a multi-engine aircraft, by engine failure and also allows the aircraft to be intentionally slipped when required.

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-23. The ailerons are located at the rear of the wing, typically one on each side. They work opposite to each other, meaning that when one is raised, the other is lowered.  Their job is to increase the lift on one wing while reducing the lift on the other.  By doing this, they roll the aircraft sideways, causing the aircraft to turn. This is the primary method of steering a fixed-wing aircraft. Airplanes turn because of banking created by the ailerons, not because of a rudder input.

When you’re flying straight and level, the lift that your wings produce points straight up, opposing gravity. But when you start to bank, that lift vector starts moving too. You now have two components of lift: a vertical component, and a horizontal component. When you combine the two, you get a total (or resultant) lift vector.

The horizontal component of lift is what makes your airplane turn, and the vertical component is what makes your airplane maintain altitude. If the total lift is kept constant, the vertical component of lift will decrease. As the weight of the aircraft is unchanged, this would result in the aircraft descending if not countered. To maintain level flight requires increased positive (up) elevator to increase the angle of attack, increase the total lift generated and keep the vertical component of lift equal with the weight of the aircraft. The airspeed will usually decrease slightly as a result of this. For steeper bank angles an aircraft pilot will usually increase the power setting to keep the speed up.

A constant-altitude turn with 45 degrees of bank imposes 1.4 Gs load factor. Stall speed increases in proportion to the square root of load factor. A 60 degree banked turn produces 2 Gs of load factor. And since the square root of 2 is 1.41, that means that your stall speed will be 41% faster in a 60 degree constant altitude coordinated turn than it would be in straight and level flight. So while making a turn, ensure that your speed is above stall speed and AOA sufficient to maintain lift. Bank angle on a commercial aircraft is limited to 30 degrees under normal conditions resulting in 1.15 G load factor.

Civil aircraft certification requirements for airliners demand normal operations be possible up to 2.5G load factor for Boeing 747. Beyond that airframe structure may break.     

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-24. The wings have additional hinged, rear sections near the body that are called flaps. Flaps are a “high lift / high drag” device mounted on the trailing edge of the wing to increase both lift and induced drag for any given AOA. Flap deflection of up to 15° primarily produces lift with minimal drag. Flap deflection beyond 15° produces a large increase in drag. Aircraft use takeoff flap settings that are usually between 5-15 degrees (most jets use leading edge slats as well). That’s quite a bit different than landing, when aircraft typically use 25-40 degrees of flaps. Why the reduced flap setting in takeoff? By extending the flaps a little bit, your plane benefits from the increase in lift (due to camber), but it doesn’t pay the high drag penalty caused by fully extended flaps.

When you’re landing, you typically extend your flaps close to maximum setting. By putting the flaps out all the way, you maximize the lift and drag that your wing produces. This gives you two distinct advantages:

-You have a slower stall speed, which means you can land slower, and

-You produce more drag, which allows you to fly a steeper descent angle to the runway.   

A larger wing will provide more lift and reduce the distance and speeds required for takeoff and landing, but will increase drag, which reduces performance during the cruising portion of flight. Modern passenger jet wing designs are optimized for speed and efficiency during the cruise portion of flight, since this is where the aircraft spends the vast majority of its flight time. High-lift devices like wing flaps and slats compensate for this design trade-off by adding lift at takeoff and landing, reducing the distance and speed required to safely land the aircraft, and allowing the use of a more efficient wing in flight. The high-lift devices on the Boeing 747-400, for example, increase the wing area by 21% and increase the lift generated by 90%.   

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-25. Winglets are vertical extensions of wingtips that improve an aircraft’s fuel efficiency and cruising range. The effect of wingtip vortices is to increase drag and reduce lift that results in less flight efficiency and higher fuel costs. Winglets produce a forward thrust inside the circulation field of the vortices and reduce their strength. Weaker vortices mean less drag at the wingtips and lift is restored. Winglets allow the wings to be more efficient at creating lift, which means planes require less power from the engines. That results in greater fuel economy, lower CO2 emissions, and lower costs for airlines.  

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-26. Whereas the first autopilots were devices that simply maintained an aircraft in straight and level flight, modern computers permit an autopilot system to guide an aircraft from takeoff to landing, incorporating continuous adjustment for wind and weather conditions and ensuring that fuel consumption is minimized.

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-27. Whenever an airfoil is producing lift, induced drag occurs and wingtip vortices are created. Just as lift increases with an increase in AOA, induced drag also increases. This occurs because as AOA is increased, there is a greater pressure difference between the top and bottom of the airfoil, and a greater lateral flow of air; consequently, this causes more violent vortices to be set up, resulting in more turbulence and more induced drag. An airplane will create wingtip vortices with maximum strength occurring during the takeoff, climb, and landing phases of flight. These vortices lead to a particularly dangerous hazard to flight, wake turbulence.

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-28. The maximum wind limits for commercial aircraft depend on the aircraft, airport, phase of flight and the direction of the wind compared to the direction of the take-off or landing. A crosswind above about 40mph and tailwind above 10mph can start to cause problems and stop commercial jets taking off and landing. Pilots prefer to land and takeoff in headwind because it increases the lift. In headwind, a lower ground speed and a shorter run is needed for the plane to become airborne. Landing into the headwind has the same advantages. It uses less runway, and ground speed is lower at touchdown. When landing in a strong crosswind, use the minimum flaps setting required for the field length. The maximum allowable crosswind is dependent upon pilot capability as well as aircraft limitations. With average pilot technique, direct crosswinds of 17-18 mph can be handled safely.

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-29. Commercial passenger aircraft fly by so-called instrument flight rules or IFR (essentially, meaning that they do not fly by sight, but following instrument readings) and according to filed flight plans. This means that the aircraft are under the control of air traffic controllers for the entire duration of the flight, in order to maintain proper separation between them. 

Visual flight rules (VFR) is the most common mode of operation for small aircraft in general aviation. Typical daytime VFR minimums for most airspace is 3 statute miles of flight visibility and a distance from clouds of 500 feet below, 1,000 feet above, and 2,000 feet horizontally. Any aircraft operating under VFR, the view outside of the aircraft is the primary source for keeping the aircraft straight and level (orientation), flying to the intended destination (navigation), and avoiding obstacles and hazards (separation). If the weather is less than VMC, pilots are required to use instrument flight rules, and operation of the aircraft will primarily be through referencing the instruments rather than visual reference.

ICAO specify minimum vertical separation for IFR flight as 1000 ft (300 m) below FL290 (29,000 feet) and 2000 ft (600 m) above FL290, except where Reduced Vertical Separation Minima (RVSM) apply. RVSM approval allows aircraft to fly with a vertical separation of 1,000 feet reduced from 2,000 feet between FL290 and FL410 inclusive. Over the ocean, beyond radar coverage, the vertical separation minimum can be a little as 1,000 feet.

In controlled airspace, the required minimum horizontal separation between aircraft flying at the same altitude (one after another or parallel) is five nautical miles, which is just over 9 kilometers. In the terminal area airspace, horizontal separation decreases to three nautical miles.   

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-30. Commercial aircraft typically fly between 31,000 and 38,000 feet — about 5.9 to 7.2 miles — high and usually reach their cruising altitudes in the first 15 minutes of a flight. Planes can fly much higher than this altitude, but that can present safety issues. Flying higher means it would take a longer time to return to a safe altitude in case of an emergency, like rapid decompression. It also isn’t the most efficient use of fuel to fly that high in the first place, since planes can fly at a lower altitude with the assistance of wind. Another reason why planes don’t fly higher is due to the weight of the aircraft. The more you weigh, the harder it is to get to a certain altitude.

When the plane gets too high, there is insufficient oxygen to fuel the engines. Most aircraft are limited by engine power. The air is less dense at altitude, so the engine can suck in less and less air per second as it goes higher and at some point the engine can no longer develop sufficient power to climb.

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-31. Airplane pilots measure speed in two different ways. First is airspeed – how fast the wind would feel if you stuck your hand out the window. The second is ground speed – how fast the plane is moving over the ground. When you fly in the jet stream, your airspeed always stays the same, but your ground speed can change a lot because the air around the plane is moving. Suppose you are flying with an airspeed of 500 mph. But because the jet stream is blowing against your airplane – called a headwind – at 100 mph, you are actually only moving across the ground at 400 mph. But flying in opposite direction, the jet stream blows from behind the plane and pushes it forward. You are still flying with an airspeed of 500 mph, but the 100 mph tailwind means that your airplane is moving across the ground at 600 mph. It takes longer to fly from east to west as compared to west to east on the same route because jet streams generally blow from the west to the east around the Earth.     

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-32. The Landing Flare is the transition phase between the final approach and the touchdown on the landing surface. This sub-phase of flight normally involves a simultaneous increase in aircraft pitch attitude and a reduction in engine power/thrust, the combination of which results in a decrease in both rate of descent and airspeed. If not executed correctly, the flare could result in a hard landing, the collapse of the landing gear, a tail strike or in a runway overrun or excursion.

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-33. Larger aircraft including wide bodies will usually require at least 8,000 ft (2,400 m) runway at sea level and somewhat more at higher altitude airports.

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-34. The normal sink rate of an airplane on landing is two to three feet per second (i.e., soft landing); when a pilot lands at seven to eight feet per second, it will feel harder than normal. It is firm landing. Hard landing means any landing that may have resulted in an exceeding of limit load on the airframe or landing gear, with a sink rate of 10 feet per second with zero roll at touchdown. Hard landing is one kind of typical landing incidents that can cause passenger discomfort, aircraft damage and even loss of life.

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-35. The main purpose of ILS is to enable pilots to land the plane when they can’t see the runway at night or in bad weather. Landings at major international airports with modern airliners can be safely conducted with as little as 50 m (150 ft) of visibility.  

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-36. Aviation safety means the state of an aviation system or organization in which risks associated with aviation activities, related to, or in direct support of the operation of aircraft, are reduced and controlled to an acceptable level. It encompasses the theory, practice, investigation, and categorization of flight failures, and the prevention of such failures through regulation, education, and training. Aviation safety should not be confused with aviation security which includes all of the measures taken to combat intentional malicious acts.

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-37. Airworthiness is the measure of an aircraft’s suitability for safe flight. An aircraft is airworthy “when it meets its type design and is in a condition for safe operation” and therefore starting a flight in an airworthy aircraft is an important part of the achieving acceptable levels of safety. New commercial aircraft are designed and tested to operate in conditions far more severe than those encountered on nearly any actual flight.

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-38. Qantas, Australia’s flag carrier is world’s safest airline. Qantas has been the lead airline in virtually every major operational safety advancement over the past 60 years and has not had a fatality in the pure-jet era. Some of the safety techniques that have set the 100-year-old Qantas apart include its use of a Future Air Navigation System for improved communication between pilots and air traffic controllers; real-time monitoring of engines across its fleet; flight data recorders to monitor plane and crew performance; and implementing technology for precision approaches and automatic landings.

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-39. Aircraft incidents and accidents almost always result from a series of events, each of which is associated with one or more cause factors. Thus, the cause of an accident or incident has many aspects. For accident to occur, many factors are involved. If any one of these factors had not been present, or if some of the factors had occurred in a different order, the accident would not have happened. The most effective accident prevention strategy must take into account all the links in the chain of events that lead to incidents and accidents. One example might be pilot fatigue, coupled with bad weather and a technical problem. If any one of these single factors were not present, the crash wouldn’t have happened. Ability to know the causes of air crashes and disasters will go in a long way to prevent or reduce greatly their occurrence. The knowledge of causes in other countries’ aviation industries is equally important to ascertain if there is any similarity in pattern/causes.  

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-40. Both the FDR and CVR are invaluable tools for any aircraft investigation. These are often the lone survivors of airplane accidents, and as such provide important clues to the cause that would be impossible to obtain any other way. It’s looking increasingly likely that the little black box will be replaced by streaming all essential data in real time directly to a ground-based station which help to eliminate the desperate search for a box, help locate the crashed aircraft and more importantly saving time that might lead to support being provided to a flight in trouble much sooner – possibly averting a crisis/crash. 

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-41. A plane crash is an accident or sabotage which occurs between the time of boarding and disembarking, ends with a fatality or a serious injury, and ends either with the plane involved having been damaged to some degree or completely destroyed. While plane crashes are infrequent, they are highly visible and often involve significant numbers of fatalities. According to PlaneCrashInfo.com accident database, survival rate of passengers on aircraft involved in fatal accidents carrying 19+ passengers is 5.8 % in last decade.

North America had the lowest fatal accident rate of all the regions. North America had more cases of air crashes over other regions but when compared with the volume of traffic in this region one will understand why they had many more crashes than others. They can be adjudged to be safer than some other regions such as Asia and Africa. The fatal accident rate for African operators was over seven times greater than that for all operators combined. 

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-42. Pilot error has been identified as a contributing factor in 85% of general aviation crashes and 68% of commercial aviation crashes. Even with all the fail-safes and extensive flight training, pilot error is still the number one cause of aircraft accidents worldwide. On the other hand, errors blamed on airline pilots are most often manifestations of inherent weaknesses and limitations in the overall air transport system.

To reduce the chance of errors, pilots use checklists to ensure they have done essential tasks, as well as using quick reference guides to handle onboard issues and emergencies.

Many plane crashes officially blamed on pilot error are truly caused by pilot fatigue that led to pilot error. Fatigue is particularly prevalent among pilots because of “unpredictable work hours, long duty periods, circadian disruption, and insufficient sleep”. Regulators attempt to mitigate fatigue by limiting the number of hours pilots are allowed to fly over varying periods of time. 

Inaction, omission, failure to act as required, disregard for information from co-pilots and air traffic controllers, impulsivity, willful disregard of safety procedures, disdain for rules and unjustifiable risk-taking by pilots have led to accidents and incidents. Juggling multiple tasks at the same time can significantly increase human vulnerability to error, be it pilot or ATC.

Peak piloting skills and performance are required in equipment malfunctions, instrument flight conditions, bad weather, final approach, and landing. If pilot is distracted, fatigued, inebriated, having sleep inertia, having spatial disorientation or airsick, he/she may lose control over airplane.  

Pilot experience based on several measures e.g., age, flight time, certification, currency (currently frequently flying), and profession (fly professionally) is related to accident occurrence. Increased levels of capability do seem to provide a protective effect. Conversely, with increased experience comes elevated accident exposure risk. 

The 1981 introduction of cockpit/crew resource management (CRM), as it is known, was a large contributing factor in driving down the number of fatal airliner accidents. Crew resource management is a set of training procedures for use in environments where human error can have devastating effects. Used primarily for improving aviation safety, CRM focuses on interpersonal communication, leadership, and decision making in the cockpit of an airliner. Abandoning the traditional “the captain is god” airline hierarchy, CRM emphasized teamwork and communication among the crew, and has since become the industry standard. The captain, first officer, crew members, and control tower must work together to ensure the safety of the flight and its passengers. Lack of respect, intimidation, distractions, pilot/co-pilot arguments and pride can get in the way and create serious problems that jeopardize lives.

After a number of accidents were found to be caused by distracted flight crews, the Federal Aviation Administration (FAA) implemented the sterile cockpit rule. This regulation requires pilots and all flight crew members to refrain from nonessential activities during critical phases of flight below 10,000 feet. This rule was implemented in 1981. Even with the rule, accident still happen when pilots are distracted from the task at hand while the plane is taking off, climbing, descending or landing. A report has revealed that the pilots of the Pakistan International Airlines Flight 8303 that crashed in 2020 were distracted over conversation about the coronavirus, leading to a failed attempt at landing.     

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-43. Personnel error (human factors) is the most common cause of both incidents and accidents. CFIT and LOC-I accidents, which almost by definition involve human factors, account for more than half of all fatal accidents.

Controlled Flight into Terrain (CFIT) occurs when an airworthy aircraft under the complete control of the pilot is inadvertently flown into terrain, water, or an obstacle. The pilots are generally unaware of the danger until it is too late. Most CFIT accidents occur in the approach and landing phase of flight and are often associated with non-precision approaches. CFIT accidents are often caused by issues with visual contact, disorientation, weather conditions, descending below the minimum safe altitude (MSA), and procedural mistakes.

A loss of control in-flight (LOC-I) is the most common cause of general aviation accidents. Loss of control happens in all phases of flight. It can happen anywhere and at any time. Loss of control in-flight typically occurs when a plane deviates from its “flight envelope,” i.e., the aerial region within which an aircraft operates safely. This envelope varies per aircraft and defines the safe degrees to which a plane can pitch and bank, as well as the aircraft’s appropriate speed (which can also vary according to weather conditions). A broad spectrum of issues causes loss of control in-flight, including: stalls, weather conditions, and/or pilot error.

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-44. Although ATC accounted for only 5% of commercial aircraft accidents, which is comparatively lower than other factors, it should not be overlooked that pilot errors either directly or indirectly involves ATC because the cooperation between a pilot and an air traffic controller composes a significant part of aircraft operation. Pilots receive most of their instructions through auditory communication from air traffic controllers, and these verbal messages can be forgotten, misinterpreted, or even never heard at all. Pilots and air traffic controllers must have a good knowledge of the English language, and use standard vocabulary to communicate with each other to ensure there are no misunderstandings.

It is of vital importance to use standardized phraseology in radio communications. No pilot should actually commence the takeoff roll until ATC tells him ‘cleared for takeoff’. The word ‘takeoff’ is only used when the plane is actually ‘cleared for takeoff’. Otherwise, the word ‘departure’ is used.  

The recent International Air Transport Association (IATA) Phraseology Study found the use of non-standard and/or ambiguous phraseology by ATC was the biggest communication issue for 2,070 airline pilots surveyed. Ambiguous messages consist of words, phrases or sentences with more than one meaning. Numbers are particularly vexing, especially homophones (words that sound the same as other words), such as “two” (“to”) and “four” (“for”). Ambiguous usage or interpretation of these four words — cited as the second biggest communication problem identified by pilots in the Phraseology Study.

Some pilots and co-pilots have had difficulty in communicating between themselves and air traffic control due to their culture resulting in plane crashes. Major airlines have been training pilots and co-pilots in communication to overcome cultural barriers.

It is adopted by ICAO that in such situations when there is contradiction between ATC and TCAS instructions; TCAS Advisory is to be followed by both aircraft irrespective of ATC instruction.   

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-45. Weather is one of the major cause and explicit factor of aviation accidents and incidents. Weather is responsible for 13% of plane crashes. Aviation is highly weather dependent. Weather factor contribute to accident to occur and enhance the probability and effects of other factors such as heavy weather and poor visibility may increase the possibility of pilot errors and collision with terrain or with other aircraft. In unsuitable weather conditions it is very difficult for a pilot to take decision. Weather phenomenon may also increase the delay of flight. To mitigate the safety risks associated with weather hazards in the different phases of flight, state‐of‐the‐art aircraft incorporate a variety of systems and sensors, including de‐icing systems and weather radars. These airborne systems, in combination with other systems (e.g., global navigation satellite systems, instrument landing systems) and services (e.g., the provision of frequently updated, accurate weather forecasts), have allowed a significant and continued reduction in the ratio of accidents and incidents per number of aircraft operations.

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-46. Heavy rain can impair pilot visibility. Other weather conditions (winds, lightning, etc.) can accompany heavy rain.  “Flameouts” can occur, require pilots to re-ignite engines. High-altitude rain can freeze and cause a plane to “stall”. Freezing rain at ground level can present additional dangers. More often takeoff is conveniently delayed due to rain and/or storms, thus preventing the aircraft from being exposed to a high level of risk, while conversely landing under rain and/or storms is unfortunately attempted more than it should due to, for example, low fuel level.  Boeing studies showed that airliners are struck by lightning twice per year on average; aircraft withstand typical lightning strikes without damage.

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-47. Even a small amount of icing or coarse frost can greatly impair the ability of a wing to develop adequate lift, which is why regulations prohibit ice, snow or even frost on the wings or tail, prior to takeoff. Stall speed is higher when ice or frost has attached to the wings and/or tail stabilizer. The more severe the icing, the higher the stall speed, not only because smooth airflow over the wings becomes increasingly more difficult, but also because of the added weight of the accumulated ice. Icing generates false instrument readings, and compromises control of the aircraft. The presence of ice and snow on the runway reduces the available tire– pavement friction needed for retardation and directional control of aircraft.

Pilots should develop a comprehensive understanding of icing (type, environments, signs, etc.) and the impacts it can have on the performance of their aircraft. They should obtain current information regarding icing location, type, and severity along their route of flight just before departure, always make certain that frost/ice is removed prior to takeoff, and have an exit strategy in place in the event an unexpected icing encounter does occur.

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-48. A wind shear is a change in wind speed and/or direction over a relatively short distance in the atmosphere. Microburst is a violent short-lived localized downdraft that creates extreme wind shears at low altitudes and is usually associated with thunderstorms. The terms “microburst” and “wind shear” are often used interchangeably because the vast majority of dangerous wind shears result from microbursts. The microburst exhibits severe, low-altitude wind-shear gradients that are experienced by a landing aircraft as rapid changes in the relative wind vector, sometimes to an extent that the performance capabilities of the airplane are exceeded, which results in ground impact. Roughly half of microbursts are truly hazardous to aircraft. The additional hazard of turbulence is often associated with wind shear.

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-49. All commercial airline planes are designed to fly through storms and have to comply with safety regulations. A rainstorm is unlikely to cause damage to the aircraft. The only danger of flying through a rainstorm is the risk of freezing rain. Even though aircraft are built to withstand heavy rain and strong winds, and pilots are trained to navigate through these conditions, flying through a storm can be a safety hazard. Besides safety issue, thunder clouds are bumpy. The US FAA recommends that aircraft (including gliders) stay at least 20 nautical miles away from a severe thunderstorm. Jet aircraft can safely fly over thunderstorms only if their flight altitude is well above the turbulent cloud tops. The most intense and turbulent storms are often the tallest storms, so en route flights always seek to go around them.

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-50. Avoid the temptation of using other pilots’ success on landing as an indicator of safety in bad weather.

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-51. In a detailed analysis of 93 major world-wide accidents which occurred between 1959 and 1983, it was revealed that maintenance and inspection were factors in 12% of the accidents.  

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-52. As of 11 November 2019, bird strikes were determined to have caused 618 hull losses and 534 fatalities since the beginning of aviation. Two to eight percent of all recorded bird strikes result in actual aircraft damage in civil aviation. Bird strikes typically occur four to six times per 10,000 aircraft movements. About 95% of all strikes occur below 2500 ft (70% below 200 ft) and the probability decreases with increasing altitude. However, the share of damaging bird strikes increases with increasing altitude. Contributing factors are a higher kinetic energy due to increasing bird size and rising aircraft velocity. While mitigation measures at airports have been shown to be successful in reducing the number and consequences of bird strikes, outside the airport boundaries, the options for counteracting measures are limited.

When operating in the presence of bird flocks, pilots should seek to climb above 3,000 feet (910 m) as rapidly as possible as most bird strikes occur below 3,000 feet (910 m). Additionally, pilots should slow down their aircraft when confronted with birds. Aircraft speed is a major factor in crashes due to bird strikes. That is because the kinetic energy that is dissipated during a bird strike increases with the aircraft speed.

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-53. Pilots are concerned that cockpit automation has eroded basic flying skills that may be required in an emergency. Automation is supposed to relieve an aircraft pilot’s workload and reduce errors. The reality can unfortunately be very different sometimes. When the pilot and the aircraft do not interact as foreseen, automation technology can be the cause of disturbing instability, which has resulted in catastrophic failures.

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-54. Software is central to aircraft flight operation, and by the same token it is playing an increasing role in aircraft incidents and accidents. Pilot is not a computer engineer or scientist. Pilots must be trained to use software correctly, detect software malfunction and override software function if necessary.

The beleaguered aircraft Boeing 737 Max was grounded worldwide on March 13, 2019, after two crashes, one in Indonesia in 2018 and the other in Ethiopia in 2019, that killed a combined total of 346 people. In both cases, the planes kept pushing their noses down despite the pilots’ efforts to correct it. Boeing 737 MAX planes were equipped with two angle of attack (AOA) sensors, one on either side of the fuselage nose, but a flight control software fix called Maneuvering Characteristics Augmentation System (MCAS) was relying on data from just one of the sensors. The biggest failing of MCAS was that it relied on only one angle-of-attack sensor located on either side of the plane, not both. Those sensors fail all the time when they get hit by a bird or freeze, and engineers decided to use only one of them, which is mind-boggling. The false report triggered an automated system MCAS. This system tried to point the aircraft’s nose down so that it could gain enough speed to fly safely. In the Ethiopian Airlines crash in March 2019, a faulty angle of attack sensor went from 12 degrees to 70 degrees in less than a second, but MCAS trusted that reading in making a pitch adjustment instead of comparing the reading with the other angle of attack sensor on the other side of the aircraft. The MCAS software didn’t have any basic sanity checks to confirm the data was bad.  

Boeing has fixed the anomaly. MCAS now compares data from both angle of attack sensors before activating and will only respond if data from both sensors agree. MCAS also will activate a single time only and never provide more input than the pilot can counteract using the control column alone. 

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-55. Spatial orientation is our natural ability to maintain our body orientation and/or posture in relation to the surrounding environment (physical space) at rest and during motion. Spatial orientation in flight is difficult to achieve because numerous sensory stimuli (visual, vestibular, and proprioceptive) vary in magnitude, direction, and frequency. Any differences or discrepancies between visual, vestibular, and proprioceptive sensory inputs result in a sensory mismatch that can produce illusions and lead to spatial disorientation. Spatial disorientation is defined as a state characterized by an erroneous sense of one’s position and motion relative to the plane of the earth’s surface. Statistics show that between 5 to 10% of all general aviation accidents can be attributed to spatial disorientation, 90% of which are fatal. In all cases of spatial disorientation, the pilot must rely on the flight instruments when making control inputs – and must be patient until the false sensations dissipate. If you are one of two pilots in an aircraft and you begin to experience a visual illusion, transfer control of the aircraft to the other pilot, since pilots seldom experience visual illusions at the same time.

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-56. Depressurization (decompression) of the aircraft cabin occurs a result of structural failure, pressurization system malfunction, explosion, or an inadvertent crew action. Sixty per cent of corporate jet depressurizations are caused by uncontained engine failures. Most others are caused by doors or windows departing the aeroplane. When decompression warning is alerted, pilots must immediately put on the oxygen mask, descend the airplane to the required 8,000 ft (2,400 m) to compensate for the loss of cabin pressure, and then look to problem solving. The reason you should not work the problem early is that hypoxia interferes with your ability to solve problems and limits your time of useful consciousness.     

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-57. Aviation infrastructure represented by per-capita GDP is important in determining plane accidents. In all regression models, nations with higher levels of per-capita GDP tended to have fewer plane accidents.

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-58. A 2007 study found that passengers sitting at the back of a plane are 40% more likely to survive a crash than those sitting in the front, although this article also quotes Boeing, the FAA and a website on aircraft safety, all claiming that there is no safest seat.

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-59. Practice opening your seat belt a few times and always wear your seat belt throughout the flight except going to toilet. In event of crash landing, you have to open seat belt quickly and get off airplane before fire catches you. 

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-60. Fatal blunt injury (head, chest) secondary to deceleration forces is the most common cause of death in plane crash. The currently used lap belt is insufficient in protecting passengers from decelerative injuries in aviation crashes. We need more effective restraint systems (3-point lap and shoulder harness system) as well as crashworthy seats and airframes. Seats must be built to withstand crash forces equivalent to 16 times the force of gravity. Also, in airline crashes more people die in the post-crash fire (burns and smoke inhalation) than die in the actual crash. It takes, on average, just 90 seconds for a fire to burn through the plane’s aluminium fuselage and consume everything and everyone in it. That’s all the time you’ve got to get off a burning craft.   

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-61. Airplanes are designed with features that can dissipate the kinetic energy of the occupants and minimize injury in the event of a crash landing. If a crash landing is necessary, pilots are taught to keep the plane under control, to land in an upright position at the slowest possible speed, and to avoid obstacles as much as possible.

Fly in bigger planes if possible. Larger planes have more energy absorption in a crash which means you’re subjected to less deadly force, and that may equate to a better survival rate. Also avoid regional carriers if possible — they have an accidents and incidents rate double that of national carriers and their pilots are often less experienced and overworked.

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-62. Approach-and-landing accidents (i.e., accidents that occur during initial approach, intermediate approach, final approach or landing) represent every year 55 % of total hull losses and 50 % of fatalities. The responsible parties involved with reducing the risk of approach and landing accidents include the aircraft manufacturers, aircraft operators, aircrews, air traffic management, regulators, and airports. The prevention of approach and landing accidents (ALA) is one of the top priorities of the aviation industry. One effort, spearheaded by the Flight Safety Foundation, is the Approach-and-Landing Accident Reduction (ALAR) Tool Kit, a collection of tools and awareness material designed to help reduce the frequency and severity of approach and landing accidents and incidents, including controlled flight into terrain (CFIT) accidents. The ALAR Tool Kit presents a wide range of information to ensure that all segments of the aviation industry find it applicable and useful.

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-63. Tombstone mentality in aviation suggests that safety improvements are only made to aircraft after an accident illuminates a fatal defect. Flying get so reliable in part, because previous accidents triggered crucial safety improvements. Out of these tragedies arose major technological advances in flight safety that keep air travel routine today. Determining of the causes of plane crash, leaning from mistakes, correcting mistakes and preventing them from occurrence is an important part of the flight safety system.

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-64. Since plane crash of commercial airliner is so rare, there are now no “common causes” of aviation accidents, each must have its own unique set of circumstances, in order to negate the sophisticated systems in place to prevent just such an occurrence. Only greater communication between operators, manufacturers, repair stations, suppliers and the wider aviation community with regard to the causes of accidents could make us even safer.  

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Dr Rajiv Desai. MD.   

May 28, 2021

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Postscript:

When I was a child of 8-10 years old, someone asked me what I want to be when I grow up, I said pilot because I was fascinated by airplanes flying in the sky. I could not become pilot but I can assist pilots by publishing this article.  

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