Aviation safety hazards
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 & other parts of the aircraft. Air France Flight 4590 crashed after hitting a part that fall from another aircraft.
Misleading information and lack of information[]
A pilot misinformed by a printed document (manual, map, etc.), reacting to a faulty instrument or indicator or following inaccurate instructions or information from flight or ground control can lose spatial orientation, or make another mistake, & consequently, lead to accidents or nearmisses.[
Lightning[]
The dangers of more powerful positive lightning were not understood until the destruction of a glider in 1999.[11] It has since been suggested that positive lightning might have caused the crash of Pan 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
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.
Ice and snow[]
Ice and snow can be 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.
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 & 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.[]
Engine failure[]
An engine may fail to function because of fuel starvation (e.g. British Airways Flight 38), fuel exhaustion (e.g. Gimli Glider), 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.
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). 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. In the 1940s several Yakovlev Yak-9s experienced delamination of plywood in their construction.
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:
· The Paul Wellstone crash (2002)
· Turkish Airlines Flight 1951 crash (2009)
· Colgan Air Flight 3407 (2009)
· Air France Flight 447 (2009)
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. These are difficult to detect once the aircraft is on the ground.
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 & to not lose more than a specified amount of thrust.
The highest risk of a bird strike occurs during takeoff and landing in the vicinity of airports, and during low-level flying by military aircraft, crop dusters and helicopters for example. 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.
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 in (30 cm) hole on the right side of the airplane.[20]
Volcanic ash[]
Plumes of volcanic ash near active volcanoes can damage propellers, engines and cockpit windows.[21] [22] 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.[23]
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.[24] Volcanic Ash Advisory Centers enable liaison between meteorologists, volcanologists, and the aviation industry.[25]
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 andAlphonse Chapanis. However, there has been progress in safety throughout the history of aviation, such as the development of the pilot'schecklist in 1937.[26] And CRM, or Crew Resource Management, is a technique that makes use of the experience and knowledge of the complete flight crew to avoid dependence on just the captain.
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 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.
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, two America West Airlines pilots 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.[27] At least one fatal airliner accident involving drunk pilots occurred when Aero Flight 311 crashed at Koivulahti , Finland
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. In December 1995, American Airlines Flight 965tracked off course while approaching & hit a mountainside despite a terrain awareness & 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, over 40,000 aircraft had enhanced TAWS installed, and they had flown over 800 million hours without a CFIT accident.[]
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 his aircraft is too low.[29]
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', taking off, or landing. Use of a mobile phone is prohibited on most flights because in-flight usage creates problems with ground-based cells.[]
Runway safety[]
Types of runway safety incidents include:
· Runway excursion – an incident involving a single aircraft making 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).
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.
Deliberate aircrew action[]
Although most air crews are screened for psychological fitness, some have taken suicidal actions. 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
In 1982, Japan Airlines Flight 350 crashed while on approach to the Tokyo Haneda Airport
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 near Palembang, 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.
Military action[]
Passenger planes have rarely been attacked in both peacetime and war. Examples:
· In 1973, Israel
· In 1983, the Soviet Union shot down Korean Air Lines Flight 007.
· In 1988, the United States
· In 2001, the Ukrainian Air Force accidentally shot down Siberia Airlines Flight 1812 during an exercise.
· In 2014, an as of yet undetermined party in Ukraine
Accident survivability
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). These systems are usually made of a lightweight, crushable concrete that absorbs the energy of the aircraft to bring it to a rapid stop. As of 2008, they have stopped three aircraft at JFK Airport.
According to a 2000 report by the National Transportation Safety Board, emergency aircraft evacuations happen about once every 11 days in the U.S.
According to the 2014 ICAO safety report,[31] the total number of plane accidents in 2013 was 90 world-wide. Only 9 of these accidents were fatal accidents, that is, accidents involving fatalities. The Global Fatal Accident Review of the Civil Aviation Authority gives a total number of 0.6 fatal accidents per one million flights for the ten-year period 2002 to 2011.[32] When expressed as per million hours flown, this number is 0.4. The corresponding number of fatalities is 22.0 fatalities per one million flights or 12.7 when expressed as per million hours flown. The total number of fatalities in 2013 was 173, which is the smallest number of fatalities since 2000, even though the total number of departures in 2013 was with 32.1 million as high as never before. This corresponds to 5.39 fatalities per one million departures in 2013. The following chart shows the development of the rate of fatal and non-fatal accidents in recent years.
|
Year
|
Number of accidents per one million departures
|
|
2009
|
4.1
|
|
2010
|
4.2
|
|
2011
|
4.2
|
|
2012
|
3.2
|
|
2013
|
2.8
|
Not all phases of flight are equally prone to accidents. Most accidents (55%) occur during landing or take-off. Only 10% occur when the aircraft is en route.
|
Phase
|
Percentage of accident that occur in this phase
|
|
Landing
|
43
|
|
Approach
|
18
|
|
Take-off
|
12
|
|
En route
|
10
|
|
Standing
|
9
|
|
Taxi
|
8
|
These individuals are trained and authorized to conduct aviation accident and incident investigations for the government organizations responsible for aviation safety. They possess specialized expertize and training in specific fields, such as aircraft structures, air traffic control, flight recorders and human factors. They may be employed by governments, manufacturers or unions and perform fact-finding, analyses, and report writing as part of their duties.[38]
The Safety Improvement Initiatives are aviation safety partnerships between regulators, manufacturers, operators, professional unions, research organisations, and international aviation organisations to further enhance safety. Some major safety initiatives worldwide are:
· Commercial Aviation Safety Team (CAST) in the US United States
· 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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