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:
- G115 / G115, near Porthcawl South Wales UK, 2009 (On 11 February 2009, the plots of two civil-registered Grob 115E Tutors being operated for the UK Royal Air Force (RAF) and both operating from RAF St Athan near Cardiff were conducting Air Experience Flights (AEF) for air cadet passengers whilst in the same uncontrolled airspace in day VMC and aware of the general presence of each other when they collided. The aircraft were destroyed and all occupants killed)
- H25B, vicinity Akron OH USA, 2015 (On 10 November 2015, the crew of an HS 125 lost control of their aircraft during an unstabilised non-precision approach to Akron when descent was continued below Minimum Descent Altitude without the prescribed visual reference. The airspeed decayed significantly below minimum safe so that a low level aerodynamic stall resulted from which recovery was not achieved. All nine occupants died when it hit an apartment block but nobody on the ground was injured. The Investigation faulted crew flight management and its context - a dysfunctional Operator and inadequate FAA oversight of both its pilot training programme and flight operations.)
- B732, vicinity Tamanrassat Algeria, 2003 (On 6 March 2003, a Boeing 737-200 being operated by Air Algerie had just become airborne during a daylight departure when the left hand engine suddenly failed just after the PF had called for “gear up”. Shortly afterwards, the aircraft commander, who had been PNF for the departure, took control but the normal pitch attitude was not reduced to ensure that a minimum airspeed of V2 was maintained and landing gear was not retracted. The aircraft lost airspeed, stalled and impacted the ground approximately 1nm from the point at which it had become airborne. A severe post crash fire occurred and the aircraft was destroyed and all on board except one passenger, were killed.)
- SW4, vicinity Red Lake ON Canada, 2013 (On 10 November 2013 the left engine of a Fairchild SA227 on final approach suddenly ceased to produce any power at approximately 500 feet whilst continuing to operate. The crew did not identify what had happened in time to avoid losing control of the aircraft which then impacted terrain, caught fire and was destroyed. The Investigation found that premature failure of engine components had caused the engine malfunction and noted that some pilots may believe that the Negative Torque Sensing (NTS) System provided for the engines on this aircraft type will always detect high drag conditions arising from power loss.)
- SW4, en-route, North Vancouver BC Canada, 2015 (On 13 April 2015, a Swearingen SA226 Metro II which had recently departed on a cargo flight was climbing normally when it suddenly entered an unexplained and steep descent a few minutes after takeoff. There were no communications from the pilots. It was later found to have impacted terrain after a rate of descent exceeding 30,000 fpm had created aerodynamic forces which caused structural disintegration to begin before impact. The Investigation could not determine why but concluded that “alcohol intoxication almost certainly played a role” and noted that indications that the Captain was a chronic alcoholic had not prompted any intervention.)
- Passenger Cabin Fire
- Aircraft Emergency Evacuation
- Dangerous Goods
- Hydraulic Fluid as a Fire Source
- Light Aircraft Post-crash Fires
- 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