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Post Crash Fires
From SKYbrary Wiki
|Category:||Fire Smoke and Fumes|
POST IMPACT FIRE
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 hot surfaces. 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.
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.
- 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.
- 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.
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:
- B462, Stord Norway, 2006 (On 10 October 2006, a BAE Systems 146-200 being operated by Danish airline Atlantic Airways on a passenger flight from Sola to Stord overran the end of runway 33 at destination at a slow speed in normal visibility at dawn (but just prior to the accepted definition of daylight) before plunging down a steep slope sustaining severe damage and catching fire immediately it had come to rest. The rapid spread of the fire and difficulties in evacuation resulted in the death of four of the 16 occupants and serious injury to six others. The aircraft was completely destroyed.)
- MD11, Hong Kong China, 1999 (On 22 August 1999, a Boeing MD11 being operated by China Airlines on a scheduled passenger flight from Taipei to Hong Kong carried out a normal ILS approach to Runway 25 Left in a strong crosswind and some turbulence but the night landing on a wet runway surface in normal visibility was very hard after a high sink rate in the flare was not arrested. The right main landing gear collapsed, the right wing separated from the fuselage and the aircraft caught fire and became inverted and reversed ending up on the grass to the right of the runway. Rapid attendance by the RFFS facilitated the escape of most of the 315 occupants but there were 3 deaths and 50 serious injuries as well as 153 minor injuries. The aircraft was 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.)
- B732, Medan Indonesia, 2005 (On 5 September 2005, a Boeing 737-200 being operated by Mandala Airlines on a scheduled domestic passenger flight from Medan, Indonesia to Jakarta failed to become properly airborne during the attempted take off from from runway 23 in day VMC and, after failing to remain airborne, overran the end of the runway at speed finally coming to a stop outside the airport perimeter. The aircraft was destroyed by impact forces and a subsequent fire and 100 of the 117 occupants were killed and 15 seriously injured. The aircraft collided with residential property, vehicles and various other obstructions and as a result a further 49 people on the ground were killed and a further 26 seriously injured.)
- A320, São Paulo Congonhas Brazil, 2007 (On 17 July 2007, the commander of a TAM Airlines Airbus A320 being operated with one thrust reverser locked out was unable to stop the aircraft leaving the landing runway at Congonhas at speed and it hit buildings and was destroyed by the impact and fire which followed killing all on board and others on the ground. The investigation attributed the accident to pilot failure to realise that the thrust lever of the engine with the locked out reverser was above idle, which by design then prevented both the deployment of ground spoilers and the activation of the pre-selected autobrake.)