Σάββατο, 30 Οκτωβρίου 2010

Air safety [EN]

Navigation aids and instrument flight

One of the first navigation aids to be introduced (in the USA in the late 1920s) was airfield lighting to assist pilots to make landings in poor weather or after dark. The Precision Approach Path Indicator 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 the International Civil Aviation Organization (ICAO).
In 1929 Jimmy Doolittle developed instrument flight.
With the spread of radio technology, several experimental radio based navigation aids were developed from the late 1920s onwards. These were most successfully used in conjunction with instruments in the cockpit in the form of Instrument landing systems (ILS), first used by a scheduled flight to make a landing in a snowstorm at Pittsburgh in 1938. A form of ILS was adopted by the ICAO for international use in 1949.
Following the development of radar in World War II, it was deployed as a landing aid for civil aviation in the form of Ground-controlled approach (GCA) systems, joined in 1948 by distance measuring equipment (DME), and in the 1950s by airport surveillance radar as an aid to air traffic control. VHF omnidirectional range (VOR) stations became the predominate means of route navigation during the 1960s, superseding the low frequency radio ranges and the Non-directional beacon (NDB). The ground based VOR stations were often co-located with DME transmitters and then labeled as VOR-DME stations on navigation charts. VORTAC stations, which combined VOR and TACAN features (military TACtical Air Navigation) — the latter including both a DME distance feature and a separate TACAN azimuth feature, which provides military pilots data similar to the civilian VOR, were also used in that new system. With the proper receiving equipment in the aircraft, pilots could know their radials in degrees to/from the VOR station, as well as the slant range distance to/from, if the station was co-located with DME or TACAN.
All of the ground-based navigation aids are being supplemented by satellite-based aids like Global Positioning System (GPS), which make it possible for aircrews to know their position with great precision anywhere in the world. With the arrival of Wide Area Augmentation System (WAAS), GPS navigation has become accurate enough for vertical (altitude) as well as horizontal use, and is being used increasingly for instrument approaches as well as en-route navigation. However, since the GPS constellation is a single point of failure that can be switched off by the U.S. military in time of crisis, onboard Inertial Navigation System (INS) or ground-based navigation aids are still required for backup.

Air safety topics

Misinformation and lack of information

Herzliya Airport (Israel) Runway location and airfield traffic pattern chart (left) was erroneously printed as a result of "black layer" 180° misplacement. The corrected chart is on the right.
A pilot might fly the plane in an accident-prone manner when misinformed by a printed document (manual, map etc.), by reacting to a faulty instrument or indicator (either in cockpit or on ground) or by following inaccurate instructions or information from flight or ground control. Lack of information by the control tower, or delayed instructions, are major factors contributing to accidents.


Boeing studies have shown that airliners are struck by lightning on average of twice per year. While the "flash and bang" is startling to the passengers and crew, aircraft are able to withstand normal lightning strikes.
The dangers of more powerful positive lightning were not understood until the destruction of a glider in 1999. It has since been suggested that positive lightning may have caused the crash of Pan Am Flight 214 in 1963. At that time aircraft were not designed to withstand such strikes, since their existence was unknown at the time standards were set. The 1985 standard in force at the time of the glider crash, Advisory Circular AC 20-53A, was replaced by Advisory Circular AC 20-53B in 2006, however it is unclear whether adequate protection against positive lighting was incorporated.
The effects of normal lightning on traditional metal-covered aircraft are well understood and serious damage from a lightning strike on an airplane is rare. However, as more and more aircraft, like the upcoming Boeing 787, whose whole exterior is made of non-conducting composite materials take to the skies, additional design effort and testing must be made before certification authorities will permit these aircraft in commercial service.

Ice and snow

Snowy and icy conditions are frequent contributors to airline accidents. The December 8, 2005 accident where Southwest Airlines Flight 1248 slid off the end of the runway in heavy snow conditions is just one of many examples. Just as on a road, ice and snow buildup can make braking and steering difficult or impossible.
The icing of wings is another problem and measures have been developed to combat it. Even a small amount of ice or coarse frost can greatly decrease the ability of a wing to develop lift. This could prevent an aircraft from taking off. If ice builds up during flight the result can be catastrophic as evidenced by the crash of American Eagle Flight 4184 (an ATR 72 aircraft) near Roselawn, Indiana on October 31, 1994, killing 68, or Air Florida Flight 90.
Airlines and airports ensure that aircraft are properly de-iced before takeoff whenever the weather threatens to create 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, tail, and inlets, or on slower aircraft, by use of inflatable rubber "boots" that expand and break off any accumulated ice.
Finally, airline dispatch offices keep watch on weather along the routes of their flights, helping the pilots avoid the worst of inflight icing conditions. Pilots can also be equipped with an ice detector in order to leave icy areas they have flown into.

Engine failure

Although aircraft are now designed to fly even after the failure of one or more aircraft engines, the failure of the second engine on one side for example is obviously serious. Losing all engine power is even more serious, as illustrated by the 1970 Dominicana DC-9 air disaster, when fuel contamination caused the failure of both engines. To have an emergency landing site is then very important.
In the 1983 Gimli Glider incident, an Air Canada flight suffered fuel exhaustion during cruise flight, forcing the pilot to glide the plane to an emergency deadstick landing. The automatic deployment of the ram air turbine maintained the necessary hydraulic pressure to the flight controls, so that the pilot was able to land with only a minimal amount of damage to the plane, and minor (evacuation) injuries to a few passengers.
The ultimate form of engine failure, physical separation, occurred in 1979 when a complete engine detached from American Airlines Flight 191, causing damage to the aircraft and loss of control.

Metal fatigue

Metal fatigue has caused failure either of the engine or of the aircraft body.
  • the January 8, 1989 Kegworth air disaster
  • De Havilland Comets incidents in 1953 and 1954
  • Aloha Airlines Flight 243 in 1988
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 fibers may tear off the matrix, the layers of the material then separate from each other - a process called delamination, and form a mica-like structure which then falls apart. 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.
Aircraft have developed delamination problems, but most were discovered before they caused a catastrophic failure. Delamination risk is as old as composite material. Even in the 1940s, several Yakovlev Yak-9s experienced delamination of plywood in their construction.


Stalling an aircraft (increasing the angle of attack to a point at which the wings fail to produce enough lift), can be dangerous and can result in a crash unless the pilot reacts in the proper manner. Upon entering a stall, the pilot will need an adequate altitude buffer to regain control, reduce the angle of attack to a point where the boundary layer reattaches to the wing, and airspeed is brought up to where level flight can resume. Stalls are most dangerous at low altitudes, which occur during takeoff and landing.
Devices have been developed to warn the pilot when the plane's speed is coming close to the stall speed. These 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 plane to go too slow for the particular weight and configuration at the time. However, because flow separation (stall) is purely a function of angle of attack, most aircraft can be pushed hard enough to cause a stall even at high speeds (those that can't simply lack the control authority to change the angle of attack enough at speed to induce a stall).

Notable crashes, caused by a full stall of the airfoils:
  • British European Airways Flight 548, June 18, 1972
  • United Airlines Flight 553, December 8, 1972
  • Aeroflot Flight 7425, July 10, 1985
  • Arrow Air Flight 1285, December 12, 1985
  • Northwest Airlines Flight 255, August 16, 1987
  • Delta Air Lines Flight 1141, August 31, 1988
  • The Paul Wellstone King Air Charter crash, October 25, 2002
  • Colgan Air Flight 3407, February 12, 2009
  • Turkish Airlines Flight 1951, February 25, 2009


Safety regulations control aircraft materials and the requirements for automated fire safety systems. Usually these requirements take the form of required tests. The tests measure flammability and the toxicity of smoke. When the tests fail, they fail on a prototype in an engineering laboratory, rather than in an aircraft.
Fire on board the aircraft, and more especially the toxic smoke generated, 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. Two years later 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 1985 British Airtours Flight 28M. That accident raised serious concerns relating to survivability, something that prior to 1985 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. A large amount of research into evacuation and cabin and seating layouts was carried 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.
The cargo holds of most airliners are equipped with "fire bottles" (essentially remote-controlled fire extinguishers) to combat a fire that might occur in the baggage holds, below the passenger cabin. In May 1996 ValuJet Airlines Flight 592 crashed into the Florida Everglades a few minutes after takeoff after a fire broke out in the forward cargo hold. All 110 aboard were killed.
At one time fire fighting foam paths were laid down before an emergency landing, but the practice was considered only marginally effective, and concerns about the depletion of fire fighting capability due to pre-foaming led the United States FAA to withdraw its recommendation in 1987.

Bird strike

Bird strike is an aviation term for a collision between a bird and an aircraft. It is a common threat to aircraft safety and has caused a number of fatal accidents. In 1988 an Ethiopian Airlines Boeing 737 sucked pigeons into both engines during take-off and then crashed in an attempt to return to the Bahir Dar airport; of the 104 people aboard, 35 died and 21 were injured. In another incident in 1995, a Dassault Falcon 20 crashed at a Paris airport during an emergency landing attempt after sucking lapwings into an engine, which caused an engine failure and a fire in the airplane fuselage; all 10 people on board were killed. Canada Geese were ingested into the engines of US Airways 1549 causing the engines to fail on the Airbus A320 that crash landed onto the Hudson River.
Modern jet engines have the capability of surviving an ingestion of a bird. Small fast planes, such as military jet fighters, are at higher risk than heavy multi-engine ones. This is due to the fact that the fan of a high-bypass turbofan engine, typical on transport aircraft, acts as a centrifugal separator to force ingested materials (birds, ice, etc.) to the outside of the fan's disc. As a result, such materials go through the relatively unobstructed bypass duct, rather than through the core of the engine, which contains the smaller and more delicate compressor blades. Military aircraft designed for high-speed flight typically have pure turbojet, or low-bypass turbofan engines, increasing the risk that ingested materials will get into the core of the engine to cause damage.
The highest risk of the bird strike is during the takeoff and landing, in low altitudes, which is in the vicinity of the airports. Some airports use active countermeasures, ranging from a person with a shotgun through recorded sounds of predators to employing falconers. Poisonous grass can be planted that is not palatable to birds, nor to insects that attract insectivorous birds. Passive countermeasures involve sensible 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 (approximately 12 inches (30 centimetres)) as some species of birds won't land if they cannot see one another.
Bird strike can also break windshields and wound the pilot.

Ground damage

Aircraft are occasionally damaged by ground equipment at the airport. In the act of servicing the aircraft between flights a great deal of ground equipment must operate in close proximity to the fuselage and wings. Occasionally the aircraft gets bumped or worse.
Damage may be in the form of simple 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. A dent that may look no worse than common "parking lot damage" to an automobile can be serious enough to ground an airplane until a repair can be made.
An example of the seriousness of this problem was the December 26, 2005 depressurization incident on Alaska Airlines flight 536. 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 metres) the damaged section of the skin gave way due to the growing difference in pressure between the inside of the aircraft and the outside air. The cabin depressurized with a bang, frightening all aboard and necessitating a rapid descent back to denser (breathable) air and an emergency landing. Post landing examination of the fuselage revealed a 12 in × 6 in (30 cm × 15 cm) hole between the middle and forward cargo doors on the right side of the airplane.
The three pieces of ground equipment that most frequently damage aircraft are the passenger boarding bridge, catering trucks, and cargo "beltloaders." However, any other equipment found on an airport ramp can damage an aircraft through careless use, high winds, mechanical failure, and so on.
The generic industry colloquial term for this damage is "ramp rash", or "hangar rash".

Volcanic ash

Plumes of volcanic ash near active volcanoes present a risk especially for night flights. The ash is hard and abrasive and can quickly cause significant wear on the propellers and turbocompressor blades, and scratch the cockpit windows, impairing visibility. It contaminates fuel and water systems, can jam gears, and can cause a flameout of the engines. Its particles have low melting point, so they melt in the combustion chamber and the ceramic mass then sticks on the turbine blades, fuel nozzles, and the combustors, which can lead to a total engine failure. It can get inside the cabin and contaminate everything there, and can damage the airplane electronics.
There are many instances of damage to jet aircraft from ash encounters. In one of them in 1982, British Airways Flight 9 flew through an ash cloud, lost all four engines, and descended from 36,000 ft (11,000 m) to only 12,000 ft (3,700 m) before the flight crew managed to restart the engines. A similar incident occurred on December 15, 1989 involving KLM Flight 867.
With the growing density of air traffic, encounters like this are becoming more common. In 1991 the aviation industry decided to set up Volcanic Ash Advisory Centers (VAACs), one for each of 9 regions of the world, acting as liaisons between meteorologists, volcanologists, and the aviation industry.
Prior to the European air travel disruption of April 2010, aircraft engine manufacturers had not defined specific particle levels above which engines were considered to be at risk. 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.
The April 2010 eruptions of Eyjafjallajökull caused sufficient economic difficulties that aircraft manufacturers were forced to define specific limits on how much ash is considered acceptable for a jet engine to ingest without damage. In April, the CAA, in conjunction with engine manufacturers, set the safe upper limit of ash density to be 2 mg per cubic metre of air space.
From noon 18 May 2010, the CAA revised the safe limit upwards to 4 mg per cubic metre of air space.
In order to minimise the level of further disruption that this and other volcanic eruptions could cause, the CAA announced the creation of a new category of restricted airspace called a Time Limited Zone. Airspace categorised as TLZ is similar to airspace experiencing severe weather conditions in that the restrictions are expected to be of a short duration; however, the key difference with TLZ airspace is that airlines must produce certificates of compliance in order for their aircraft to enter these areas. Flybe was the first airline to conform to these regulations and their aircraft will be permitted to enter airspace in which the ash density is between 2 mg and 4 mg per cubic metre.
Any airspace in which the ash density exceeds 4 mg per cubic metre is categorised as a no fly zone.

Aviation risks of flight through downstream ash clouds

It is important to make a distinction between flight through (or in immediate vicinity of) the eruption plume and flight through so-called affected airspace. Volcanic ash in the immediate vicinity of the eruption plume is of an entirely different particle size range and density to that found in downwind dispersal clouds which contain only the finest grade of ash. The ash loading at which this process affects normal engine operation is not established beyond the awareness that relatively high ash densities must exist. Whether this silica-melt risk remains at the much lower ash densities characteristic of downstream ash clouds is currently unclear. This is therefore a serious safety hazard which invites preventive risk management strategies in line with other comparable aviation risks.

Human factors

Human factors including pilot error are another potential danger, and currently the most common factor of aviation crashes. Much progress in applying human factors to improving aviation safety was made around the time of World War II by people such 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. 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 ability of the flight crew to maintain situational 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 resulted in the crash of Eastern Air Lines Flight 40 in 1972 (CFIT), and error during take-off and landing can have catastrophic consequences, for example cause the crash of Prinair Flight 191 on landing, also in 1972.
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 from Fargo, North Dakota to Minneapolis-Saint Paul International Airport while drunk. In 2001, Northwest fired a pilot who failed a breathalyzer test after flying from San Antonio, Texas to Minneapolis-Saint Paul. In July 2002, two America West Airlines pilots were arrested just before they were scheduled to fly from Miami, Florida to Phoenix, Arizona because they had been drinking alcohol. The pilots have been fired from America West and the FAA revoked their pilot's licenses. As of 2005 they await trial in a Florida court. The incident created a public relations problem and America West has become the object of many jokes about drunk pilots. At least one fatal airliner accident involving drunk pilots has occurred when Aero Flight 311 crashed killing all 25 on board in 1961, which underscores the role that poor human choices can play in air accidents.
Human factors incidents are not limited to errors by the pilots. The failure to close a cargo door properly on Turkish Airlines Flight 981 in 1974 resulted in the loss of the aircraft - however the design of the cargo door latch was also a major factor in the incident. In the case of Japan Airlines Flight 123, improper maintenance resulted in the loss of the vertical stabilizer.

Controlled flight into terrain

Controlled flight into terrain is a class of accident in which an undamaged aircraft is flown, under control, into terrain or man-made structures. CFIT accidents typically are a result of pilot error or of navigational system error. Some pilots, convinced that advanced electronic navigation systems such as GPS and inertial guidance systems (inertial navigation system or INS) coupled with flight management system computers , or over-reliance on them, are partially responsible for these accidents, have called CFIT accidents "computerized flight into terrain". Failure to protect Instrument Landing System critical areas can also cause controlled flight into terrain. One of the most notable CFIT accidents was in December 1995 in which American Airlines flight 965 tracked off course while approaching Calí, Colombia and hit a mountainside after the speedbrakes were left deployed despite an aural terrain warning in the cockpit and an attempt to gain ample altitude in the nighttime contidions. Crew awareness and monitoring of navigational systems can prevent or eliminate CFIT accidents. Crew Resource Management is a modern method now widely used to improve the human factors of air safety. The Aviation Safety Reporting System, or ASRS is another.
Other technical aids can be used to help pilots maintain situational awareness. A ground proximity warning system is an on-board system that will alert a pilot if the aircraft is about to fly into the ground. Also, air traffic controllers constantly monitor flights from the ground and at airports.


Terrorism can also be considered a human factor. Crews are normally trained to handle hijack situations. Prior to the September 11, 2001 attacks, hijackings involved hostage negotiations. After the September 11, 2001 attacks, stricter airport security measures are in place to prevent terrorism using a Computer Assisted Passenger Prescreening System, Air Marshals, and precautionary policies. In addition, counter-terrorist organizations monitor potential terrorist activity.
Although most air crews are screened for psychological fitness, some may take suicidal actions. In the case of EgyptAir Flight 990, it appears that the first officer deliberately dived his aircraft into the Atlantic Ocean while the captain was away from his station, in 1999 off Nantucket, Massachusetts. Motivations are unclear, but recorded inputs from the black boxes showed no mechanical problem, no other aircraft in the area, and was corroborated by the cockpit voice recorder.
The use of certain electronic equipment is partially or entirely prohibited as it may interfere with aircraft operation, such as causing compass deviations. Use of personal electronic devices and calculators may be prohibited when an aircraft is below 10,000', taking off, or landing. The American Federal Communications Commission (FCC) prohibits the use of a cell phone on most flights, because in-flight usage creates problems with ground-based cells. There is also concern about possible interference with aircraft navigation systems, although that has never been proven to be a non-serious risk on airliners. A few flights now allow use of cell phones, where the aircraft have been specially wired and certified to meet both FAA and FCC regulations.

Attack by a hostile country

Aircraft, whether passenger planes or military aircraft, are sometimes attacked in both peacetime and war. Notable examples of this are:
  • On February 21, 1973 Libyan Arab Airlines Flight 114 727-224 entered the then-Israeli-controlled airspace over the Sinai Peninsula, was intercepted by two Israeli F-4 Phantom IIs and shot down while trying to re-enter Egyptian airspace after failing to follow instructions issued by the Israeli pilots. Of the 113 people on board, there were 5 survivors, including the co-pilot.
  • 1 September 1983 downing by the Soviet Union of Korean Air Lines Flight 007, carrying 269 people (including a sitting U.S. Congressman Larry McDonald),
  • 3 July 1988 shoot-down by United States Navy of Iran Air Flight 655, carrying 290 people.
  • 4 October 2001 shoot-down by Ukrainian Air Force of Russian flight 1812 (Tel-Aviv - Novosibirsk), carrying 78 people.

Airport design

Airport design and location can have a big impact on air 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. Since this is a recent rule, many airports do not meet it. 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, or EMAS. These systems are usually made of a lightweight, crushable concrete that absorbs the energy of the aircraft to bring it to a rapid stop. They have stopped three aircraft (as of 2005) at JFK Airport.


On an airplane, people sit in a confined space for extended periods of time, which increases the risk of transmission of airborne infections. For this reason, airlines place restrictions on the travel of passengers with known airborne contagious diseases (e.g. tuberculosis). During the severe acute respiratory syndrome (SARS) epidemic of 2003, awareness of the possibility of acquisition of infection on a commercial aircraft reached its zenith when on one flight from Hong Kong to Beijing, 16 of 120 people on the flight developed proven SARS from a single index case.
There is very limited research done on contagious diseases on aircraft. The two most common respiratory pathogens to which air passengers are exposed are parainfluenza and influenza. In one study, the flight ban imposed following the attacks of September 11, 2001 was found to have restricted the global spread of seasonal influenza, resulting in a much milder influenza season that year, and the ability of influenza to spread on aircraft has been well documented. There is no data on the relative contributions of large droplets, small particles, close contact, surface contamination, and no data on the relative importance of any of these methods of transmission for specific diseases, and therefore very little information on how to control the risk of infection. There is no standardisation of air handling by aircraft, installation of HEPA filters or of hand washing by air crew, and no published information on the relative efficacy of any of these interventions in reducing the spread of infection.

Emergency airplane evacuations

According to a 2000 report by the National Transportation Safety Board, emergency airplane 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 airplane slide. In a TIME article on the subject, Amanda Ripley reported that when a new supersized Airbus A380 underwent mandatory evacuation tests in 2006, 33 of the 873 evacuating volunteers got hurt. While the evacuation was generally considered a success, one volunteer suffered a broken leg, while the remaining 32 received slide burns. Such accidents are common. In her article, Ripley provides tips on how to make it down the airplane slide without injury.

Runway safety

Several terms fall under the flight safety topic of runway safety, including incursion, excursion, and confusion.
Runway excursion is an incident involving only a single aircraft, where it makes an inappropriate exit from the runway. This can happen because of pilot error, poor weather, or a fault with the aircraft. Overrun is a type of excursion where the aircraft is unable to stop before the end of the runway. A recent example of such an event is Air France Flight 358 in 2005. Further examples can be found in the overruns category.
Runway event is another term for a runway accident.
Runway incursion involves a first aircraft, as well as a second aircraft, vehicle, or person. It is defined by the U.S. FAA as: "Any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and take off of aircraft."
Runway confusion involves a single aircraft, and is used to describe the error when the aircraft makes "the unintentional use of the wrong runway, or a taxiway, for landing or take-off". An example of a runway confusion incident is Comair Flight 191.
Runway excursion is the most frequent type of landing accident, slightly ahead of runway incursion. For runway accidents recorded between 1995 and 2007, 96% were of the 'excursion' type.
The U.S. FAA publishes a lengthy annual report on runway safety issues, available from the FAA website here. New systems designed to improve runway safety, such as Airport Movement Area Safety System (AMASS) and Runway Awareness and Advisory System (RAAS), are discussed in the report. AMASS prevented the serious near-collision in the 2007 San Francisco International Airport runway incursion.

Safety Improvement Initiatives

The Safety Improvement Initiatives are aviation safety partnerships between regulators, manufacturers, operators and professional unions, research organisations, international organisations to further enhance safety. The major Safety initiatives worldwide are:
  • Commercial Aviation Safety Team (CAST) in the US. The Commercial Aviation Safety Team (CAST) was founded in 1998 with a goal to reduce the commercial aviation fatality rate in the United States by 80 percent by 2007.
  • European Strategic Safety Initiative (ESSI) . The European Strategic Safety Initiative (ESSI) is an aviation safety partnership between EASA, other regulators and the industry. The initiative objective is to further enhance safety for citizens in Europe and worldwide through safety analysis, implementation of cost effective action plans, and coordination with other safety initiatives worldwide.

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