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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:

  • PRM1, vicinity Samedan Switzerland, 2010 (On 19 December 2010, a Raytheon 390 inbound to Samedan from Zagreb made a daylight approach to runway 21 at destination in marginal VMC which involved a steep and unstable descent from which a landing was not possible. The subsequent go around was followed by entry to a visual right hand circuit which was contrary to local procedures due to terrain constraints. Overbanking in the turn towards final approach was followed by a stall and loss of control which led to ground impact which, with the post crash fire, destroyed the aeroplane and fatally injured both occupants.)
  • S76, vicinity Moosonee ON Canada, 2013 (On 31 May 2013 the crew of an S76A helicopter positioning for a HEMS detail took off VFR into a dark night environment and lost control as a low level turn was initiated and did not recover. The helicopter was destroyed and the four occupants killed. The Investigation found that the crew had little relevant experience and were not "operationally ready" to conduct a night VFR take off into an area of total darkness. Significant deficiencies at the Operator and in respect of the effectiveness of its Regulatory oversight were identified as having been a significant context for the accident.)
  • B190 / BE9L, Quincy IL USA, 1996 (On 19 November 1996, a Beech 1900C which had just landed and a Beech King Air A90 which was taking off collided at the intersection of two runways at the non-Towered Quincy Municipal Airport. Both aircraft were destroyed by impact forces and fire and all occupants of both aircraft were killed. The Investigation found that the King Air pilots had failed to monitor the CTAF or properly scan visually for traffic. The loss of life of the Beech 1900 occupants, who had probably survived the impact, was attributed largely to inability to open the main door of the aircraft.)
  • B742 / B741, Tenerife Canary Islands Spain, 1977 (On 27 March 1977, a KLM Boeing 747-200 began its low visibility take-off at Tenerife without requesting or receiving take-off clearance and a collision with a Boeing 747-100 backtracking the same runway subsequently occurred. Both aircraft were destroyed by the impact and consequential fire and 583 people died. The Investigation attributed the crash primarily to the actions and inactions of the KLM Captain, who was the Operator's Chief Flying Instructor. Safety Recommendations made emphasised the importance of standard phraseology in all normal radio communications and avoidance of the phrase "take-off" in ATC Departure Clearances.)
  • SH36 / SH36, manoeuvring, Watertown WI USA, 2006 (On 5 February 2006, two Shorts SD-360-300 aircraft collided in mid air while in formation near Watertown, WI, USA; both aircraft suffered damage. One aircraft experienced loss of control and impacted terrain while the other made an emergency landing, overunning the runway, at a nearby airport.)

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