Accident Threat Categories

Accident summaries organized relative to the threat category that was a major factor in each accident.

Accident Threat Categories
Bird Hazards
Photo: Transport Airplane landing near large flock of birds.
Photo: Transport Airplane landing near large flock of birds.

Collisions between airplanes and birds have occurred from nearly the beginning of aviation. Although rare, these collisions have occasionally resulted in catastrophic damage to the airplane. Currently, protection from the hazards of birds is the result of both measures taken to keep the collision from happening, such as bird control programs at certain airports, as well as providing robust airplane and engine designs so that even severe encounters are able to be withstood.

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Cabin Safety / Hazardous Cargo
Photo: Saudi Arabian Airlines flt #163
Photo: Saudi Arabian Airlines flt #163
L1011-100
August 19, 1980
Riyadh, Saudi Arabia

Civil aircraft cabin safety was initially limited to seat static load requirements, incorporation of seat belts, and cabin exit requirements. In the late 1960's transport category cabin safety requirements began to evolve with the interest of protecting aircraft occupants during and following "survivable" crash scenarios that might be experienced in hard landings, runway overruns or land-short accidents.

Hazardous cargo's capacity to generate fire, smoke or fumes, has received increased attention in the wake of the 1996 Valujet accident. Threat management relies on the proper recognition, identification, and handling of hazardous cargo.

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Flight Deck Layout / Avionics Confusion
Photo: British Midlands flt #92
Photo: British Midlands flt #92
B737-400
January 8, 1989
Kegworth, England

Flight deck layout and alert/warning display strategies influence a crew's ability to interface with their airplane, and can include issues with the arrangement, and/or visibility of flight deck displays/controls. Regulations require that displays must be visible and usable, without inducing unnecessary concentration or fatigue. With increased flight deck sophistication and avionics complexity, methods of conveying critical information to flight crews have evolved. Variations in information presentation, and/or differences in function can create confusion if not carefully evaluated and examined through a range of operational situations. Human factors engineers and flight test pilots work together to determine proper arrangement of flight deck components and methods of conveying information.

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Crew Resource Management
Photo: Eastern Airlines flt #401
Photo: Eastern Airlines flt #401
Lockheed Model L-1011
December 29, 1972
Everglades, Florida

The cause of many accidents is inadequate communications between crewmembers. In the early years of commercial aviation, the captain's decisions were always the "right" ones with little or no input from the other crewmembers. Beginning in the late 70's, Crew Resource Management (CRM) taught pilots how to integrate human factors with the technical skills of flying airplanes.

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Fuel Exhaustion
Photo: United Airlines flt #173
Photo: United Airlines flt #173
DC-8-60
December 28, 1978
Portland, OR

Fuel exhaustion and the subsequent loss of thrust from more than one engine, and potentially all engines, is often a catastrophic event. Although transport airplanes are capable of controlled flight during an all-engine out event, the high descent speeds and absence of a safe landing area, result in approximately half of the all-engine out events that have occurred in recent years to be crashes with substantial loss of life. The reasons for fuel exhaustion range from undiscovered fuel leaks, fuel system mismanagement, navigation errors (e.g. being lost), inattention to the fuel gauges, and other reasons.

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Fuel Tank Ignition
Photo: Trans World Airlines flt #800
Photo: Trans World Airlines flt #800
B747-100
July 17, 1996
Long Island, NY

Aviation fuel tank safety has been predicated upon the absence of any form of heat or spark within the fuel tank ullage space that could ignite fuel. While this approach has been fairly successful, several fuel tank explosions over the last 20 years has caused this strategy to be called into question. The accidents included in this category have been instrumental in shaping the safety requirements currently being applied, and are helping determine alternative approaches which may be applied to future designs.

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Inclement Weather / Icing
Photo: Scandinavian Airlines flt #751
Photo: Scandinavian Airlines flt #751
MD-80
December 27, 1991
Stockholm, Sweden

Transport airplanes and their engines are capable of operation in virtually all forms of atmospheric weather conditions in nearly every part of the globe. Like all other safety categories, however, the standards related to weather, both design and operation, have evolved as the technology has improved and the lessons related to the environmental threats have been better understood. Safety of flight is achieved by a combination of robust airplane capability, and operation in a manner such that hazardous weather conditions are avoided.

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Incorrect Piloting Technique
Photo: Air France flt #072
Photo: Air France flt #072
B747-400
September 13, 1993
Tahiti Faaa Airport

All pilots use the flight controls in the same way, whether the plane is a small general aviation airplane or a large commercial airliner. Mistakes made by a low-time pilot generally reflect inexperience and lack of training: either the basic manipulation of the flight controls is not yet automatic and the pilot does not demonstrate a proper "feel" for the aircraft, or the pilot lacks the specific training and knowledge to make correct avionic or aeronautical decisions. Incorrect piloting technique in an airline pilot, however, who possesses more experience and whose control or avionic inputs are more instinctive, tend to occur from more subjective factors, such as stress, fatigue, and/or confusion. However, similar to the inexperienced pilot, insufficient or improper training and checking can also play a role with the airline pilot due to upgrade, transition or initial training on new or different equipment flown.

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In-flight Upsets
Photo: American Airlines flt #587
Photo: American Airlines flt #587
A300-600
November 12, 2001
Belle Harbor, NY

Inflight upsets can result from a number of causes, ranging from external atmospheric anomalies to internal airplane failures such as flight control or structural failures. Any unintended deviation from the planned flight path is an upset, but the degree of upset can greatly affect a flight crew's ability to recover to normal flight. An upset is generally characterized by a loss of airplane control, at least for a short period. This category describes the history of inflight upsets, and the accidents that have resulted from the variety of upset causes.

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Lack of System Isolation / Segregation
Photo: American Airlines flt #191
Photo: Japan Airlines flt #123
B747-100SR
August 12, 1985
Tokyo, Japan

Lack of system isolation/segregation involves a condition where a malfunction or failure condition affects more than one system, or cascades a failure condition into subsequent failures.  This can be a result from a major event such as a structural failure, a fire that consumes multiple systems, or lack of system architecture itself that allows a failure condition to impact multiple systems or functions.

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Landing / Takeoff Excursions
Photo: Continental Airlines flt #603
Photo: Continental Airlines flt #603
DC-10-10
March 1, 1978
Los Angeles, CA

Takeoff or landing runway excursions have historically been a factor in a number of high profile accidents. High energy departures from the end, or sides of a runway during takeoff or landing have, on numerous occasions, had catastrophic results. In response to runway excursion accidents, the industry has adopted new criteria both operationally, and in certification requirements, to mitigate the occurrence rate of runway excursions, and to alleviate the catastrophic effects should an excursion occur.

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Midair / Ground Incursions
Photo: Pacific Southwest Airlines flt #182
Photo: Pacific Southwest Airlines flt #182
B727-200
September 25, 1978
San Diego, CA

The purpose of Air Traffic Control (ATC) is to separate aircraft so they do not collide, and to move them efficiently through the airspace. Airline traffic is typically required to fly under Instrument Flight Rules (IFR) and fly only assigned “airway routes,” or over the ocean, “tracks”. A collision occurs when two aircraft come into contact during flight or ground operation, often resulting in a catastrophic accident.  Accidents included in this category have been the catalyst for advances in equipment and procedures that have resulted in reductions in the rates of collisions between airplanes.

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Pressurization / Decompression Failures
Photo: Helios Airlines flt #522
Photo: Helios Airlines flt #522
B737-300
August 14, 2005
Grammatikos, Greece

Modern transport airplanes can fly at altitudes that are too high to sustain human life. For this reason, and for passenger comfort, airplanes are pressurized so the conditions inside the airplane generally remain at comfortable temperatures and at pressures below 8,000 feet, even when the airplane is flying as high as 51,000 feet. Loss of pressurization in flight presents different hazards depending on how quickly the loss occurs. Without pressurization, airplane occupants can suffer the physiological effects from the extreme cold temperatures as well as lack of oxygen, or hypoxia.

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Structural Failure
Photo: Aloha Airlines flt #242
Photo: Aloha Airlines flt #242
B737-200
April 28, 1988
Kahului, HI

In general terms, structural components are found to be adequately robust by a process that initially identifies the structural loading spectrum that the assembly, part, or surface will be expected to experience while in service. This includes the identification of the most severe, but none the less, expected loading conditions. Often, accidents involve the realization that either the original loading conditions are more severe than expected, or the capability of the component, structure, or system had deteriorated due to some unanticipated condition being present.

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Uncommanded Thrust Reversal
Photo: Luxair flt #9642
Photo: Luxair flt #9642
Fokker F-27
November 6, 2002
Niederanven, Luxembourg

The earliest reversing designs involved propeller blade angle control systems which were used as deceleration devices following landing, and were found to be very effective in assisting the airplane brakes in stopping. In contrast, the early turbojet thrust reverser systems were primarily used to help cancel the high idle thrusts of the early turbojet engines, but were not very effective at contributing significant reversing forces used in assisting braking action following landing. As the effectiveness of the reversing systems increased, so did the potential for the hazardous effects of their malfunctions.

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Uncontained Engine Failure
Photo: Delta Airlines flt #1288
Photo: Delta Airlines flt #1288
MD-88
July 6, 1996
Pensacola, FL

When turbine engines were first introduced into commercial aviation in the mid 1950's, very little was known about the various failure modes that would soon be experienced involving failures of internal rotating engine parts. These failures often resulted in high energy debris that would penetrate the engine case and occasionally impact the airplane, causing significant damage. As failures continued, lessons were learned about methods needed to reduce the potential for the failures as well as steps that could be taken to protect the airplane.

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Uncontrolled Fire / Smoke
Photo: British Airtours flt #KT28M
Photo: British Airtours flt #KT28M
B737-200
August 25, 1985
Manchester, England

Uncontrolled fire and smoke represents one of the most serious safety threats of all categories. An uncontrolled fire can threaten the airplane and safety of the occupants during ground or flight operations, or following a crash. The threat is related to both the flames and the corresponding heat and smoke, which can become so dense that vision is impaired. Many kinds of smoke also contain toxic gasses that can quickly lead to incapacitation and death.  An uncontrolled fire is usually the result of an ignition source (such as electrical arcing) and a substantial or continuous source of fuel (such as aircraft fuel). The accidents included in this threat category represent some of the most significant in helping shape safety requirements and policies related to fire, heat, and smoke threats.

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Windshear
Photo: Delta Airlines flt #191
Photo: Delta Airlines flt #191
L1011-300
August 2, 1985
Dallas/Ft. Worth, TX

Windshear is an atmospheric phenomenon created by a sudden change in wind direction and speed, and can be associated with thunderstorm activity, or can be created by terrain or large buildings. An airplane is most vulnerable when close to the ground, such as during takeoff or landing. In the thunderstorm-related phenomenon, a "microburst" spreading downward and outward first manifests itself as a rapidly increasing headwind, and is sensed by the airplane as an increase in airspeed. The accidents discussed in this category were the catalysts for the development of currently existing windshear mitigation strategies.

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Accident Groupings

Accident summaries organized relative to the grouping that was a major factor in each accident.

Accident Groupings
Loss of Control
Photo: American Airlines Flt #191
Photo: American Airlines Flt #191
McDonnell Douglas DC-10-10
May 25, 1979
Chicago, Illinois

Loss of Control (LOC) is a significant, unintended departure from a normal/expected trajectory, characterized by a transition from a stable condition into an unstable condition that precludes rapid recovery.  LOC may result from airplane failures (icing contamination, flight controls, automated systems), incorrect piloting technique, or encounters with unexpected weather phenomena.  LOC may also include ground events during takeoff and landing.

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Controlled Flight into Terrain
Photo: American Airlines Flt #965
Photo: American Airlines Flt #965
Boeing - 757
December 20, 1995
Cali, Columbia

Controlled flight into terrain (CFIT) occurs when an airworthy aircraft is flown, under pilot control, into terrain (water or obstacles) with inadequate awareness on the part of the pilot of the impending collision.

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Approach and Landing
Photo: American Airlines Flt #1420
Photo: American Airlines Flt #1420
McDonnell Douglas  MD-82
June 1, 1999
Little Rock, Arkansas

Approach and Landing accidents are accidents that occur during an approach, landing, or rejected landing maneuver.  This group may also include accidents that occurred during a missed approach procedure. Approach and landing accidents have historically occurred at a significantly higher rate than takeoff accidents.

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Automation
Photo: Indian Airlines #605
Photo: Indian Airlines #605
Airbus A320-231
February 14, 1990
Bangalore, India

Automation in airplane systems has provided a significant improvement in nearly every aspect of aviation safety. However, occasionally, gaps in the automation/human interface have resulted in accidents.

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