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Post Crash Fires

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Category: Fire Smoke and Fumes Fire Smoke and Fumes
Content source: SKYbrary About SKYbrary
Content control: SKYbrary About SKYbrary

POST IMPACT FIRE

Definition

Post Crash Fires are fires which occur after an aircraft has crash landed or has impacted obstacles or other aircraft during ground movement, runway incursion, or runway excursion.

Description

In the event of an impact with the ground or an obstacle, which results in structural damage to an aircraft, a fuel and/or oil fed fire can start if fuel comes into contact with ignition sources. Equally, if flammable material, being carried as dangerous goods on a Civil aircraft or as cargo by a military aircraft, is damaged or the containment compromised, it may ignite as a consequence of impact, contact with hot surfaces or, in the case of spillage of unstable chemicals, the atmosphere.

Fire can spread quickly to the fuselage and through the cabin generating heat, smoke, and toxic decomposition products. If the temperature of trapped smoke and gasses reaches the auto-ignition temperature, flashover will occur and an aircraft fuselage can be rapidly engulfed by flames.

Effects

Depending upon the severity of the crash, and any resulting fire, the effect on the aircraft can vary from minor damage to total hull loss. Similarly, the potential casualty consequence of a crash/fire event ranges from no injuries to the loss of life of all on board. Collateral damage and casualties are possible dependent upon the location of the crash.

For aircraft with a maximum certified take-off weight of 5700 kilograms or less, post-impact fire contributes significantly to injuries and fatalities in accidents that are otherwise potentially survivable.

Defences

  • Aircraft Design. Aircraft structures and fuel systems can be designed to minimise the quantity of fuel spillage
  • Fuel - Virtually all large passenger aircraft burn jet fuel and not AVGAS. The much higher flashpoint of jet fuel reduces the potential for a post crash fire.

Solutions

  • Preparation of the aircraft - where the crash landing is anticipated, for example if an off-field landing is necessary or the aircraft has a landing gear malfunction, then there are several things that can be done to reduce the probability and severity of a fire:
    • Dump Fuel - if time and aircraft design allow, dump to reduce the amount of fuel and improve the handling of the aircraft. For aircraft not fitted with Fuel Dump capability, the aircraft can loiter in the vicinity of the landing airfield to burn gas. Note that, in the case of an onboard fire, smoke, or fumes, any delay to landing the aircraft, inclusive of dumping fuel, should not be considered.
    • Isolate fuel systems - close crossfeed valves.
    • Cabin - Prepare the cabin for emergency landing.
    • Cargo - Jettison flammable cargo if possible and practical.
  • Aircraft Evacuation - Expeditious emergency evacuation of the aircraft will minimise the loss of life in the event of a post crash fire. Consequently, robust training of the cabin crew in evacuation procedures is essential.
  • Engine Shutdown & Aircraft Systems - To minimize the potential for injury during the evacuation, the flight deck crew will take all necessary actions to shut down and, using fire handles, condition levers, or fire push button (depending on aircraft type) isolate the aircraft engines. Depending upon the degree of damage to the aircraft, this may not always be possible.
  • Rescue and Fire Fighting Services - Rescue and Fire Fighting Services (RFFS) are instrumental in saving lives and minimizing the damage from a post crash fire. If the crash occurs within the airfield boundaries, the initial RFFS response units will be on site within a very short period of time; often less than a minute. Response to an off airfield crash may take considerably longer due to the time it may take to locate the crash and to the accessibility of crash site.

Contributing Factors

Large amounts of fuel can be carried by modern aircraft and an aircraft crash has the potential to rupture the fuel tanks. Should the spilling fuel be exposed to a spark or open flame a fire may occur. This is particularly true of fuels with low flashpoints such as AVGAS. While jet fuels have a higher flashpoint and are less susceptible to sparks, exposing them to operating engines or to hot engine components may raise the temperature of the fuel to its auto-ignition point and a fire will result.

Accidents and Incidents

A selection of incidents from the SKYbrary database related to Post Crash Fire:

  • A320, vicinity Karachi Pakistan, 2020 (On 22 May 2020, an Airbus A320 made an extremely high speed unstabilised ILS approach to runway 25L at Karachi and did not extend the landing gear for touchdown. It continued along the runway resting on both engines before getting airborne again with the crew announcing their intention to make another approach. Unfortunately, both engines failed due to the damage sustained and the aircraft crashed in a residential area near the airport and was destroyed by impact forces and a post-crash fire. 97 of the 99 occupants died and four persons on the ground were injured with one subsequently dying.)
  • B744, Taipei Taiwan, 2000 (On 31 October 2000, the crew of a Singapore Airlines Boeing 747-400 taxiing for a night departure at Taipei in reduced (but not 'low') visibility with an augmenting crew member present on the flight deck failed to follow their correctly-confirmed taxi instructions and commenced take off on a partially closed runway. The subsequent collision with construction equipment and resultant severe post crash fire destroyed the aircraft killing over half the 170 occupants and injured 71 others. All three flight crew survived.)
  • AT72, vicinity Tyumen Russian Federation, 2012 (On 2 April 2012, the crew of an ATR72-200 which had just taken off from Tyumen lost control of their aircraft when it stalled after the flaps were retracted and did not recover before it crashed and caught fire killing or seriously injuring all occupants. The Investigation found that the Captain knew that frozen deposits had accumulated on the airframe but appeared to have been unaware of the danger of not having the airframe de-iced. It was also found that the crew had not recognised the stall when it occurred and had overpowered the stick pusher and pitched up.)
  • CL60, Almaty Kazakstan, 2007 (On 26 December 2007, the crew of a Bombardier Challenger 604 which had received a 2-stage ground de/anti icing treatment lost roll control as the aircraft got airborne from a snow-covered runway at Almaty in freezing mist and light snow conditions and it crashed within the airport perimeter before continuing through the perimeter fence and catching fire. The Investigation concluded that the loss of control was probably caused by contamination of the wing leading edge with frozen deposits during the take off roll as a result of the crew's decision not to select wing anti-ice on contrary to applicable procedures.)
  • C550, vicinity Cagliari Sardinia Italy, 2004 (On 24 February 2004, a Cessna 550 inbound to Cagliari at night requested and was approved for a visual approach without crew awareness of the surrounding terrain. It was subsequently destroyed by terrain impact and a resultant fire during descent and all occupants were killed. The Investigation concluded that the accident was the consequence of the way the crew conducted the flight in the absence of adequate visual references and with the possibility of a ‘black hole’ effect. It was also noted that the aircraft was not fitted, nor required to be fitted, with TAWS.)

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