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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:

  • 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.)
  • MD82, Detroit MI USA, 1987 (On 16 August 1987, an MD-82 being operated by Northwest Airlines on a scheduled passenger flight from Detroit MI to Phoenix AZ failed to get properly airborne in day VMC and, after damaging impact with obstacles within the airport perimeter after climbing to a maximum height of just under 40 ft, impacted the ground causing the destruction of the aircraft by impact forces and a subsequent fire. All but one of the 157 occupants were killed with the single survivor suffering serious injury. On the ground, 2 people were killed, 2 more seriously injured and 4 more suffered minor injury with several buildings vehicles and structures damaged or destroyed.)
  • C500, vicinity Wiley Post Airport, Oklahoma City OK USA, 2008 (On 4 August 2008, a Cessna 500 on a business charter flight encountered a flock of very large birds shortly after take off from a small Oklahoma City airport. Wing damage from at least one bird collision with a force significantly greater than covered by the applicable certification requirements made it impossible for the pilot to retain control of the aircraft. Terrain impact followed. Both engines also ingested a bird. The Investigation noted that neither pilot nor aircraft operator were approved to operate commercial charter flights but concluded that this was not directly connected to the loss of the aircraft.)
  • L35 / EUFI, manoeuvring, Olsberg-Elpe, Germany 2014 (On 23 June 2014, a civil-operated Learjet 35 taking part in a German Air Force interception training exercise collided with the intercepting fighter aircraft as it began a follow-me manoeuvre. It became uncontrollable as a result of the damage sustained in the collision and crashed into terrain, killing both pilots. The Investigation found that whilst preparation for the exercise by all involved had been in compliance with requirements, these requirements had been inadequate, especially in respect of co-ordination between all the pilots involved, with both the civil and military safety regulatory authorities failing to detect and act on this situation.)
  • A140, vicinity Tehran Mehrabad Iran, 2014 (On 10 August 2014, one of the engines of an Antonov 140-100 departing Tehran Mehrabad ran down after V1 and prior to rotation. The takeoff was continued but the crew were unable to keep control and the aircraft stalled and crashed into terrain near the airport. The Investigation found that a faulty engine control unit had temporarily malfunctioned and that having taken off with an inappropriate flap setting, the crew had attempted an initial climb with a heavy aircraft without the failed engine propeller initially being feathered, with the gear remaining down and with the airspeed below V2.)

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