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Aviation safety is the study and practice of managing risks inaviation. This includes preventingaviation accidents and incidents through research, educating air travel personnel, passengers and the general public, as well as the design of aircraft and aviation infrastructure. The aviation industry is subject to significant regulations and oversight.[1]
Aviation security is focused on protecting air travelers, aircraft and infrastructure from intentional harm or disruption, rather than unintentional mishaps.
Aviation is safer today than it has ever been. Modern commercial aviation boasts an accident rate of approximately 1 fatal accident per 16 million flights, far lower than historic numbers.[3]
On December 14, 1903, theWright Brothers conducted a test flight of their powered airplane from slope of Big Kill Devil Hill in North Carolina. Upon takeoff, the airplane lifted about 15 feet off the ground, stalled, and crashed into the sand.[4] Only three days later, on December 17, 1903, Wilbur's brother,Orville Wright, would fly the airplane for the world's first powered, sustained, and controlled heavier-than-air flight in history. Although the failed test flight on December 14 would be mostly forgotten in aviation, it remains to this day one of the firstaviation accidents in history.
In the early years of air travel, accidents were exceedingly common. 1929 was named the year of "The Great Crash" due to the frequency of aircraft accidents that occurred during the year, with 24 fatal accidents reported.[5] In 1928 and 1929, the overall accident rate was about 1 in every million miles (1.6 million kilometers) flown.[5] In today's industry, that accident rate would translate to about 7,000 fatal accidents each year.
For the ten-year period 2002 to 2011, 0.6 fatal accidents happened per one million flights globally, 0.4 per million hours flown, 22.0 fatalities per one million flights or 12.7 per million hours flown.[6]
From 310 million passengers in 1970, air transport had grown to 3,696 million in 2016, led by 823 million in the United States, then 488 million inChina.[7]In 2016, there were 19 fatal accidents of civil airliners of more than 14 passengers, resulting in 325 fatalities, the second safest year ever after 2015 with 16 accidents and 2013 with 265 fatalities.[8]For planes heavier than 5.7 t, there were 34.9 million departures and 75 accidents worldwide with 7 of these fatal for 182 fatalities, the lowest since 2013 : 5.21 fatalities per million departures.[9]
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In 2017, there were 10 fatal airliner accidents, resulting in 44 occupant fatalities and 35 persons on the ground: the safest year ever for commercial aviation, both by the number of fatal accidents as well as in fatalities.[10]By 2019, fatal accidents per million flights decreased 12 fold since 1970, from 6.35 to 0.51, and fatalities per trillionrevenue passenger kilometre (RPK) decreased 81 fold from 3,218 to 40.[11]
Runway safety represents 36% of accidents, ground safety 18% and loss of control in-flight 16%.[9]
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Loss of control inflight represents 35% of the fatal accidents,Controlled flight into terrain 21%,runway excursions 17%, system orcomponent failure: 6%, Touchdown off therunway: 5%,Abnormal Runway Contact: 4% andfire: 2%.[12]
Safety has improved from betteraircraft design process, engineering and maintenance, the evolution of navigation aids, and safety protocols and procedures.
There are three main ways in which the risk of fatality in a certain mode of travel can be measured: (1) deaths per billion typicaljourneys taken, (2) deaths per billionhours traveled, and (3) deaths per billionkilometers traveled. The following table displays these statistics for the United Kingdom (1990–2000),[13] and has been appended. (Note that aviation safety does not include travelling to the airport.)[14][failed verification]
| Transportation type | Deaths per billion | ||
|---|---|---|---|
| Journeys | Hours | Kilometers | |
| Bus | 4.3 | 11.1 | 0.4 |
| Rail | 20 | 30 | 0.6 |
| Van | 20 | 60 | 1.2 |
| Private Car | 40 | 130 | 3.1 |
| Foot | 40 | 220 | 54.2 |
| Water | 90 | 50 | 2.6 |
| Air | 117 | 30.8 | 0.05 |
| Pedal cycle | 170 | 550 | 44.6 |
| Motorcycle | 1640 | 4840 | 108.9 |
| Paragliding[b] | 8850[16][17] | ||
| Skydiving | 7500[18] | 75000[19] | |
| Space Shuttle[20] | 17000000 | 70000 | 6.6 |
The first two statistics are computed for typical travels by their respective forms of transport, so they cannot be used directly to compare risks related to different forms of transport in a particular travel "from A to B". For example, these statistics suggest that a typical flight fromLos Angeles toNew York would carry a larger risk factor than a typical car travel from home to office. However, car travel from Los Angeles to New York would not be typical; that journey would be as long asseveral dozen typical car travels, and thus the associated risk would be larger as well. Because the journey would take a much longer time, the overall risk associated with making this journey by car would be higher than making the same journey by air, even if each individual hour of car travel is less risky than each hour of flight.
For risks associated with long-range intercity travel, the most suitable statistic is the third one: deaths per billion kilometers. Still, this statistic can lose credence in situations where the availability of an air option makes an otherwise inconvenient journey possible.
Aviation industry insurers base their calculations on thedeaths per journey statistic while the aviation industry itself generally uses thedeaths per kilometre statistic in press releases.[21]
Since 1997, the number of fatal air accidents has been no more than 1 for every 2,000,000,000 person-miles[c] flown,[citation needed] and thus is one of the safest modes of transportation when measured bydistance traveled.
The Economist notes that air travel is safer by distance travelled, but trains are as safe as planes.[22] It also notes that cars are four times more hazardous for deaths per time travelled, and cars and trains are respectively three times and six times safer than planes by number of journeys taken.[22]
Because the above figures are focused on providing a perspective to the realm of everyday transportation, air travel is taken to include only standard civil passenger aviation, as offered commercially to the general public. Military and special-purpose aircraft are excluded.
Between 1990 and 2015, there were 1874 commuter andair taxi accidents in the U.S. of which 454 (24%) were fatal, resulting in 1,296 deaths, including 674 accidents (36%) and 279 fatalities (22%) in Alaska alone.[23]
The number of deaths per passenger-mile on commercial airlines in the United States between 2000 and 2010 was about 0.2 deaths per 10 billion passenger-miles.[24][25] For driving, the rate was 150 per 10 billion vehicle-miles for 2000: 750 times higher per mile than for flying in a commercial airplane.
There were no fatalities on large scheduled commercial airlines in the United States for over nine years, between theColgan Air Flight 3407 crash in February 2009, and a catastrophic engine failure onSouthwest Airlines Flight 1380 in April 2018.[26]
Another aspect of safety is protection from intentional harm orproperty damage, also known assecurity.
Theterrorist attacks of 2001 are not counted as accidents. However, even if they were counted as accidents they would have added about 1 death per billion person-miles. Two months later,American Airlines Flight 587 crashed in New York City, killing 265 people, including 5 on the ground, causing 2001 to show a very high fatality rate. Even so, the rate that year including the attacks (estimated here to be about 4 deaths per billion person-miles), is safe compared to some other forms of transport when measured by distance traveled.
The first aircraft electrical or electronic deviceavionics system wasLawrence Sperry'sautopilot, demonstrated in June 1914.[27] TheTranscontinental Airway System chain of beacons was built by theCommerce Department in 1923 to guideairmail flights.[27]
Gyrocopters were developed byJuan de la Cierva to avoidstall andspin accidents, and for that inventedcyclic and collective controls used byhelicopters.[27] The first flight of a gyrocopter was on 17 January 1923.
During the 1920s, the first laws were passed in the United States of America to regulatecivil aviation, notably theAir Commerce Act of 1926, which required pilots and aircraft to be examined and licensed, for accidents to be properly investigated, and for the establishment of safety rules and navigation aids; under the Aeronautics Branch of theUnited States Department of Commerce (US DoC).
A network ofaerial lighthouses was established in the United Kingdom and Europe during the 1920s and 1930s.[28] Use of the lighthouses has declined with the advent of radio navigation aids such asnon-directional beacon (NDB),VHF omnidirectional range (VOR), anddistance measuring equipment (DME). The last operational aerial lighthouse in the United Kingdom is on top of thecupola over theRAF College main hall atRAF Cranwell.
One of the first aids forair navigation to be introduced in the United States in the late 1920s wasairfield lighting, to assist pilots in making landings in poor weather or after dark. ThePrecision Approach Path Indicator (PAPI) was developed from this in the 1930s, indicating to the pilot the angle of descent to the airfield. This later became adopted internationally through the standards of theInternational Civil Aviation Organization (ICAO).
Jimmy Doolittle developedinstrument rating and made his first 'blind' flight in September 1929. The March 1931 wooden wing failure ofa Transcontinental & Western Air Fokker F-10 carryingKnute Rockne, coach of theUniversity of Notre Dame's football team, reinforced all-metalairframes and led to a more formalaccident investigation system.
On 4 September 1933, aDouglas DC-1 test flight was conducted with one of the two engines shut down during the takeoff run, climbed to 8,000 feet (2,438 metres), and completed its flight, proving twinaircraft engine safety. With greater range than lights and weather immunity,radio navigation aids were first used in the 1930s, like the AustralianAeradio stations guiding transport flights, with a light beacon and a modifiedLorenz beam transmitter (the German blind-landing equipment preceding the moderninstrument landing system - ILS).[27] ILS was first used by a scheduled flight to make a landing in a snowstorm atPittsburgh, Pennsylvania, in 1938, and a form of ILS was adopted by the ICAO for international use in 1949.
Hardrunways were built worldwide for World War II to avoid waves and floating hazards plaguingseaplanes.[27]
Developed by the U.S. and introduced during World War II,LORAN replaced the sailors' less reliablecompass andcelestial navigation over water and survived until it was replaced by theGlobal Positioning System.[27]
Following the development ofradar in World War II, it was deployed as a landing aid for civil aviation in the form ofground-controlled approach (GCA) systems then as theairport surveillance radar as an aid toair traffic control in the 1950s.
A number of ground-basedweather radar systems can detect areas of severe turbulence.
A modernHoneywell Intuvue weather system visualizes weather patterns up to 300 miles (480 km) away.[citation needed]
Distance measuring equipment (DME) in 1948 andVHF omnidirectional range (VOR) stations became the main route navigation means during the 1960s, superseding the low frequency radio ranges and thenon-directional beacon (NDB): the ground-based VOR stations were often co-located with DME transmitters and the pilots could establish their bearing and distance to the station.[29]
To highlight thejetliner evolution,Airbus split them in four generations:
The fatal accident rate fell from 3.0 per million flights for the first generation to 0.9 for the next, 0.3 for the third and 0.1 for the last.[12]
With the arrival ofWide Area Augmentation System (WAAS), satellite navigation has become accurate enough for altitude as well as positioning use, and is being used increasingly for instrument approaches as well as en-route navigation. However, because the GPS constellation is asingle point of failure, on-boardInertial Navigation System (INS) or ground-based navigation aids are still required for backup.
In 2017,Rockwell Collins reported it had become more costly to certify than to develop a system, from 75% engineering and 25% certification in past years.[30]It calls for a global harmonization between certifying authorities to avoid redundant engineering and certification tests rather than recognizing the others approval and validation.[31]
Groundings of entire classes of aircraft out of equipment safety concerns is unusual, but this has occurred to thede Havilland Comet in 1954 after multiple crashes due to metal fatigue and hull failure, theMcDonnell Douglas DC-10 in 1979 after the crash ofAmerican Airlines Flight 191 due to engine loss, theBoeing 787 Dreamliner in 2013 after itsbattery problems, and theBoeing 737 MAX in 2019 after two crashes preliminarily tied to a flight control system.
Parts manufactured without an aviation authority's approval are described as "unapproved". Unapproved parts include inferior counterfeits, those used beyond their time limits, those that were previously approved but not properly returned to service, those with fraudulent labels, production overruns that were not sold with the agency's permission, and those that are untraceable.[32] Unapproved faulty parts have caused hundreds of incidents and crashes, some fatal, including about 24 crashes between 2010 and 2016.[33][34]
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. In 2000,Air France Flight 4590 crashed after hitting a part that had fallen from a departing Continental Airlines DC-10.
A pilot misinformed by a printed document (manual, map, etc.), reacting to a faulty instrument or indicator (in the cockpit or on the ground),[35][36] or following inaccurate instructions or information from flight or ground control can losesituational awareness, or make errors, and accidents or near misses may result.[37][38][39][40] The crash ofAir New Zealand Flight 901 was a result of receiving and interpreting incorrect coordinates, which caused the pilots to inadvertently fly into a mountain.
Boeing studies showed that airliners are struck bylightning twice per year on average; aircraft withstand typical lightning strikes without damage.
The dangers of more powerfulpositive lightning were not understood until the destruction of aglider in 1999.[41] It has since been suggested that positive lightning might have caused the crash ofPan Am Flight 214 in 1963. At that time, aircraft were not designed to withstand such strikes because their existence was unknown. The 1985 standard in force in the US at the time of the glider crash, Advisory Circular AC 20-53A,[41] was replaced by Advisory Circular AC 20-53B in 2006.[42] However, it is unclear whether adequate protection against positive lightning was incorporated.[43][44]
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. Modern airliners like theBoeing 787 Dreamliner with exteriors and wings made fromcarbon-fiber-reinforced polymer have been tested and shown to receive no damage from lightning strikes during testing.[45]
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Ice andsnow can be major factors in airline accidents. In 2005,Southwest Airlines Flight 1248 slid off the end of arunway after landing in heavy snow conditions, killing one child on the ground.
Even a small amount oficing or coarsefrost can greatly impair the ability of a wing to develop adequatelift, which is why regulations prohibit ice, snow or even frost on the wings or tail, prior to takeoff.[46]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 ofAmerican Eagle Flight 4184 in 1994, andComair Flight 3272 in 1997. Both aircraft wereturboprop airliners, with straight wings, which tend to be more susceptible to inflight ice accumulation, than are swept-wing jet airliners.[47]
Airlines and airports ensure that aircraft are properlyde-iced beforetakeoff whenever the weather involvesicing conditions. Modern airliners are designed to prevent ice buildup onwings,engines, and tails (empennage) by either routing heated air fromjet engines through theleading edges of the wing, and inlets,[48] or on slower aircraft, by use of inflatable rubber "boots" that expand to break off any accumulated ice.
Airline flight plans requireairline dispatch offices to monitor the progress of weather along the routes of their flights, helping thepilots to avoid the worst of inflight icing conditions. Aircraft can also be equipped with anice detector in order to warn pilots to leave unexpected ice accumulation areas, before the situation becomes critical.[49]Pitot tubes in modern airplanes and helicopters have been provided with the function of "Pitot Heating" to prevent accidents likeAir France Flight 447 caused by the pitot tube freezing and giving false readings.
Awind shear is a change in wind speed and/or direction over a relatively short distance in the atmosphere. Amicroburst 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.[50]
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 effect 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.[51]
An engine may fail to function because offuel 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 tometal 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 adiversion 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 anemergency landing is not possible, result in the aircraft crashing.
Examples of failure of aircraft structures caused bymetal fatigue include thede Havilland Comet accidents (1950s) andAloha Airlines Flight 243 (1988). Improper repair procedures can also cause structural failures includeJapan Air Lines Flight 123 (1985) andChina Airlines Flight 611 (2002). Now that the subject is better understood, rigorous inspection andnondestructive testing procedures are in place.
Composite materials consist of layers offibers embedded in aresin matrix. In some cases, especially when subjected tocyclic 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 (oftenultrasound-based) have to be used to detect such a material failure. In the 1940s severalYakovlev Yak-9s experienced delamination ofplywood in their construction.
Stalling an aircraft (increasing theangle of attack to a point at which the wings fail to produce enoughlift) 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:
Safety regulations control aircraft materials and the requirements for automated fire safety systems. Usually these requirements take the form of required tests. The tests measureflammability of materials andtoxicity ofsmoke. When the tests fail, it is on a prototype in an engineering laboratory rather than in an aircraft.
Fire and its toxic smoke have been the cause of accidents. An electrical fire onAir 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 theBritish 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 atCranfield Institute to try to measure what makes a good evacuation route, which led to the seat layout byOverwing exits being changed by mandate and the examination of evacuation requirements relating to the design of galley areas. The use ofsmoke 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 automatedhalon fire extinguishing systems to combat a fire that might occur in the baggage holds. In May 1996,ValuJet Flight 592 crashed into the FloridaEverglades a few minutes after takeoff because of a fire in the forward cargo hold. All 110 people on board were killed.
At one time, fire fightingfoam paths were laid down before an emergency landing, but the practice was considered only marginally effective, and concerns about the depletion of firefighting capability due to pre-foaming led the United States FAA to withdraw its recommendation in 1987.
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 wasSwissair Flight 111 in 1998 due to an arc in the wiring ofIFE which ignited flammableMPET insulation. These are difficult to detect once the aircraft is on the ground. However, there are methods, such asspread-spectrum time-domain reflectometry, that can feasibly test live wires on aircraft during flight.[52]
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.[53] The hazards of ingesting birds beyond the "designed-for" limit were shown onUS 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 andlanding in the vicinity ofairports, and during low-level flying, for example by military aircraft, crop dusters and helicopters. Some airports use active countermeasures, including a person with ashotgun, playing recorded sounds of predators through loudspeakers, or employingfalconers. Poisonous grass can be planted that is not palatable to birds, nor to insects that attractinsectivorous birds. Passive countermeasures involve sensible[clarification needed] land-use management, avoiding conditions attracting flocks of birds to the area (e.g.landfills). Another tactic found effective is to let the grass at the airfield grow taller (to approximately 12 inches or 30 centimetres) as some species of birds won't land if they cannot see one another.
Human factors, includingpilot error, are another potential set of factors, and currently the factor most commonly found in aviation accidents.[54][55] Much progress in applying human factors analysis to improving aviation safety was made around the time ofWorld War II by such pioneers asPaul Fitts andAlphonse Chapanis. However, there has been progress in safety throughout the history of aviation, such as the development of the pilot'schecklist in 1937.[56] CRM, orcrew resource management, is a technique that makes use of the experience and knowledge of the complete flight crew to avoid dependence on just one crew member, and to improvepilot decision making.
Pilot error and improper communication are often factors in thecollision of aircraft. This can take placein the air (1978Pacific Southwest AirlinesFlight 182) (TCAS) or on the ground (1977Tenerife disaster) (RAAS). The barriers to effective communication have internal and external factors.[57] The ability of the flight crew to maintainsituational awareness is a critical human factor in air safety. Human factors training is available to general aviation pilots and calledsingle pilot resource management training.
Failure of the pilots to properly monitor the flight instruments caused the crash ofEastern 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 ofPrinair Flight 191 on landing, also in 1972.
TheInternational 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."[58] The phenomenon places great risk on the crew and passengers of an airplane because it significantly increases the chance ofpilot error.[59] Fatigue is particularly prevalent among pilots because of "unpredictable work hours, long duty periods,circadian disruption, and insufficient sleep".[60] These factors can occur together to produce a combination ofsleep deprivation, circadian rhythm effects, and 'time-on task' fatigue.[60] Regulators attempt to mitigate fatigue by limiting the number of hours pilots are allowed to fly over varying periods of time. Experts in aviation fatigue[who?] often find that these methods fall short of their goals.
Rarely, flight crew members are arrested or subject to disciplinary action for beingintoxicated on the job. In 1990, threeNorthwest Airlines crew members were sentenced to jail for flying while drunk. In 2001, Northwest fired a pilot who failed abreathalyzer test after a flight. In July 2002, both pilots ofAmerica 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.[61] At least one fatal airliner accident involving drunk pilots occurred whenAero Flight 311 crashed at Kvevlax, Finland, killing all 25 on board in 1961. Another example is the crashAeroflot Flight 821, in which the captain's intoxication contributed to the accident, killing all 88 on board.
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There have been rare instances ofsuicide by pilots. Although most air crew arescreened for psychological fitness, a very few authorized pilots have flown acts of suicide and evenmass murder.[62]
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 1997,SilkAir Flight 185 suddenly went into a high dive from its cruising altitude. The speed of the dive was so high that the aircraft began to break apart before it finally crashed nearPalembang,Sumatra. After three years of investigation, the Indonesian authorities declared that the cause of the accident could not be determined. However, the US NTSB concluded that deliberate suicide by the captain was the only reasonable explanation.
In 1999 in the case ofEgyptAir Flight 990, it appears that thefirst officer deliberately crashed into the Atlantic Ocean while the captain was away from his station.[63]
Crew involvement isone of the speculative theories in the disappearance ofMalaysia Airlines Flight 370 on 8 March 2014.
On 24 March 2015,Germanwings Flight 9525 (anAirbus A320-200) crashed 100 kilometres (62 miles) north-west of Nice, in theFrench 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 authorised personnel to be present in the cockpit at all times. Three days after the incident, theEuropean Aviation Safety Agency (EASA) 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.
Inaction,omission, failure to act as required, willful disregard of safety procedures, disdain for rules, and unjustifiable risk-taking by pilots have also led toaccidents 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.
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 onTurkish 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 ofJapan Air Lines Flight 123 in 1985, improper repair of previous damage led to explosive decompression of the cabin, which in turn destroyed thevertical stabilizer and damaged all four hydraulic systems which powered all the flight controls.
Controlled flight into terrain (CFIT) is a class of accidents in which an aircraft is flown under control into terrain or man-made structures. CFIT accidents typically result from pilot error or of navigational system error. Failure to protectILS critical areas can also cause CFIT accidents[dubious –discuss]. In December 1995,American Airlines Flight 965 tracked off course while approachingCali,Colombia, and hit a mountainside despite aterrain awareness and warning system (TAWS) terrain 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. As of February 2008[update], over 40,000 aircraft had enhanced TAWS installed, and they had flown over 800 million hours without a CFIT accident.[64]
Another anti-CFIT tool is theMinimum 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, theair traffic controller receives an acoustic and visual warning and then alerts the pilot that the aircraft is too low.[65]
The use of certain electronic equipment is partially or entirely prohibited as it might interfere with aircraft operation,[66] such as causingcompass deviations.[citation needed] 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. Use of amobile phone is prohibited on most flights because in-flight usage creates problems with ground-based cells.[66][67] Wireless devices such as cellphones feature anairplane mode.
Variousground 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 onAlaska Airlines Flight 536 in 2005. During ground services, abaggage handler hit the side of the aircraft with a tug towing a train ofbaggage 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.[68]
Plumes ofvolcanic ash near activevolcanoes can damagepropellers,engines and cockpit windows.[69][70] 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.[71]
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.[72]Volcanic Ash Advisory Centers enable liaison betweenmeteorologists,volcanologists, and the aviation industry.[73]
Types of runway safety incidents include:
The last two types can be prevented withairport surveillance and broadcast systems, aRunway Awareness and Advisory System, and landing navigation systems (e.g.transponder landing system,microwave landing system,instrument landing system).
Aircrew are normally trained to handlehijack situations.[74][75] Since theSeptember 11, 2001 attacks, stricterairport andairline security measures are in place to preventterrorism, such as security checkpoints and locking the cockpit doors during flight.
In the United States, theFederal Flight Deck Officer program is run by theFederal 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.
Passenger planes have rarely been attacked in both peacetime and war. Examples:
Earlier tragedies investigations and improved engineering has allowed many safety improvements that have allowed an increasing safer aviation.[50]
Airport design and location can have a large impact on aviation safety, especially since some airports such asChicago 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 arunway safety area, usually extending 150 metres (500 ft) to each side and 300 metres (1,000 ft) 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.[77] Many older airports do not meet this standard. One method of substituting for the 300 metres (1,000 ft) at the end of a runway for airports in congested areas is to install anengineered materials arrestor system (EMAS). These systems are usually made of lightweight, crushable concrete that absorbs the energy of the aircraft to bring it to a rapid stop. As of 2008[update], they have stopped three aircraft atJFK Airport.
According to a 2000 report by theNational 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 theevacuation slide. In aTime article on the subject, Amanda Ripley reported that 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. In her article, Ripley provided tips on how to make it down the airplane slide without injury.[78]Another improvement to airplane evacuations is the requirement by theFederal 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.[50][77]
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.[50] 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.[77]
As the result of the accidents due to wind shear and other weather disturbances, most notably the 1985 crash ofDelta Air Lines Flight 191, the U.S.Federal Aviation Administration mandated that all commercial aircraft haveon-board wind shear detection systems by 1993.[51] 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 Dopplerweather radar units on the ground (NEXRAD).[79] The installation of high-resolutionTerminal 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.[80]
Air safety investigators are trained and authorized to investigate aviation accidents and incidents: to research, analyse, and report their conclusions. They may be specialized in flight operations, training, aircraft structures, air traffic control, flight recorders or human factors. They are employed by government organizations responsible for aviation safety, manufacturers or unions, though only government organizations have statutory powers to investigate.
The safety improvement initiatives are aviation safety partnerships between regulators, manufacturers, operators, professional unions, research organisations, and international aviation organisations to further enhance safety.[81]Some major safety initiatives worldwide are:
After the disappearance ofMalaysia Airlines Flight 370, in June 2014, theInternational Air Transport Association said it was working on implementing new measures to track aircraft in flight in real time. A special panel was considering a range of options including the production of equipment especially designed to ensure real-time tracking.[82]
Since pilot error accounts for between one-third and 60% of aviation accidents, advances in automation and technology could replace some or all of the duties of theaircraft pilots. Automation since the 1980s has already eliminated the need forflight engineers. In complex situations with severely degraded systems, the problem-solving and judgement capability of humans is challenging to achieve with automated systems, for example the catastrophic engine failures experienced byUnited Airlines Flight 232 andQantas Flight 32.[83] However, with more accurate software modeling of aeronautic factors, test planes have beensuccessfully flown in these conditions.[84]
While theaccident rate is very low, to ensure they do not rise with theair transport growth, experts recommend creating a robust culture of collecting information from employees without blame.[85]
Can air travel keep on getting safer and safer?
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