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 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.
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:
- CL60, Montrose USA, 2004 (On 28 November 2004, the crew of a Bombardier Challenger 601 lost control of their aircraft soon after getting airborne from Montrose and it crashed and caught fire killing three occupants and seriously injuring the other three. The Investigation found that the loss of control had been the result of a stall caused by frozen deposits on the upper wing surfaces after the crew had failed to ensure that the wings were clean or utilise the available ground de/anti ice service. It was concluded that the pilots' lack of experience of winter weather operations had contributed to their actions/inactions.)
- B734, Yogyakarta Indonesia, 2007 (On 7 March 2007, a Boeing 737-400 being operated by Garuda landed on a scheduled passenger flight from Jakarta to Yogyakarta overran the end of the destination runway at speed in normal daylight visibility after a late and high speed landing attempt ending up 252 metres beyond the end of the runway surface in a rice paddy field. There was a severe and prolonged fire which destroyed the aircraft (see the illustration below taken from the Investigation Report) and 21 of the 140 occupants were killed, 12 seriously injured, 100 suffered minor injuries and 7 were uninjured.)
- GLF4, Bedford MA USA, 2014 (On 31 May 2014, a Gulfstream IV attempted to take off with the flight control gust locks engaged and, when unable to rotate, delayed initiating the inevitable rejected take off to a point where an overrun at high speed was inevitable. The aircraft was destroyed by a combination of impact forces and fire and all seven occupants died. The Investigation attributed the accident to the way the crew were found to have habitually operated but noted that type certification had been granted despite the aircraft not having met requirements which would have generated an earlier gust lock status warning.)
- B735, vicinity Kazan Russia, 2013 (On 17 November 2013, the crew of a Boeing 737-500 failed to establish on the ILS at Kazan after not following the promulgated intermediate approach track due to late awareness of LNAV map shift. A go around was eventually initiated from the unstabilised approach but the crew appeared not to recognise that the autopilot used to fly the approach would automatically disconnect. Non-control followed by inappropriate control led to a high speed descent into terrain less than a minute after go around commencement. The Investigation found that the pilots had not received appropriate training for all-engine go arounds or upset recovery.)
- F50, vicinity Luxembourg, 2002 (On 6 November 2002, a Fokker 50 operated by Luxair, crashed on approach to Luxembourg Airport following loss of control attributed to intentional operation of power levers in the ground range, contrary to SOPs.)
- Safety issues investigation report SII A05-01 Post-impact fires resulting from small-aircraft accidents, TSB Canada, 2006
- CAP 699 - Framework for the competence of rescue and fire fighting service (RFFS) personnel, January 2017
- Aviation Accident Checklist, by ATSB, 7th edition, June 2017
- Hazards at Aviation Accident Sites - Guidance for Police and Emergency Personnel, by ATSB, 7th edition, June 2017