Engine Fire warning and complacency.
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Engine Fire warning and complacency.
There is a generally held view that recall actions to combat an engine fire warning on take off should not be initiated below 400 feet. This international standard height presumably originates from certification rules which state the lowest altitude to commence the third segment acceleration is 400 ft.
In swept wing jet transport aircraft it is often difficult for the pilots to actually see an engine that is on fire where the first indication to the crew is the fire warning light and associated warning bell. Over the years Pprune Tech Log readers have offered a wide range of their views on engine fires including the argument that maybe there is no great hurry to take action to combat an engine fire. Even Boeing in it's FCTM suggests that a minimum of 400 ft be attained before recall items are initiated.
The following extract from the USAF magazine makes for sobering reading.
"The United States Air Force has published a document titled Safety Investigation16 which includes a chapter on aircraft fire investigation. That chapter included the following information: • aircraft epoxy paint blisters at 454 – 510 degrees C • aluminium sheeting melts at about 635 degrees C • in-flight fire temperatures typically exceed 1370 degrees C due to the slipstream"
The effect of slipstream on an airborne fire is startling and might I say downright frightening. There is no need for complacency just because it is a fire warning only. Seconds could be vital when it comes to initiating recall drills to combat an engine fire because if you cannot see the fire from the cockpit it is all to easy to delay action in order to meet an arbitary certification-based minimum altitude before the initial action is requested by the PF. Assuming the aircraft is under control when the fire warning occurs there should be no delay before firing the first bottle. In the simulator it is common to observe delays up to one minute after the fire warning bell goes off before the crew get around to firing the first bottle. Meanwhile the 150 knot 1370 degrees centigrade slipstream is taking it's toll on the engine and it's surrounding area.
In swept wing jet transport aircraft it is often difficult for the pilots to actually see an engine that is on fire where the first indication to the crew is the fire warning light and associated warning bell. Over the years Pprune Tech Log readers have offered a wide range of their views on engine fires including the argument that maybe there is no great hurry to take action to combat an engine fire. Even Boeing in it's FCTM suggests that a minimum of 400 ft be attained before recall items are initiated.
The following extract from the USAF magazine makes for sobering reading.
"The United States Air Force has published a document titled Safety Investigation16 which includes a chapter on aircraft fire investigation. That chapter included the following information: • aircraft epoxy paint blisters at 454 – 510 degrees C • aluminium sheeting melts at about 635 degrees C • in-flight fire temperatures typically exceed 1370 degrees C due to the slipstream"
The effect of slipstream on an airborne fire is startling and might I say downright frightening. There is no need for complacency just because it is a fire warning only. Seconds could be vital when it comes to initiating recall drills to combat an engine fire because if you cannot see the fire from the cockpit it is all to easy to delay action in order to meet an arbitary certification-based minimum altitude before the initial action is requested by the PF. Assuming the aircraft is under control when the fire warning occurs there should be no delay before firing the first bottle. In the simulator it is common to observe delays up to one minute after the fire warning bell goes off before the crew get around to firing the first bottle. Meanwhile the 150 knot 1370 degrees centigrade slipstream is taking it's toll on the engine and it's surrounding area.
Your examples and reference do not apply to the discussion in the previous thread about engine fires on commercial jets.
The previous discussions had to do with podded multiple engines in a nacelle system with an effective fire suppression system and fire barriers certified under Part25 etc, slipstream effects only come into play if the fire is external to the nacelle and in that case the most effective action is to shut off the fuel. Sure you can shut off the fuel pretty damn quick by pulling a fire handle but the statistical side of haste, in this regard, has combined with pilot error more times than it has helped by stopping the fire bell.
Also in commericial podded engines there are fire barriers (enough metal etc.) between the common sources of engine fires and critical aircraft sytems. These fire barriers are intended to not be affected by slipstream effects and to provide enough time for the crew to aviate first before addressing the fire.
The previous discussions had to do with podded multiple engines in a nacelle system with an effective fire suppression system and fire barriers certified under Part25 etc, slipstream effects only come into play if the fire is external to the nacelle and in that case the most effective action is to shut off the fuel. Sure you can shut off the fuel pretty damn quick by pulling a fire handle but the statistical side of haste, in this regard, has combined with pilot error more times than it has helped by stopping the fire bell.
Also in commericial podded engines there are fire barriers (enough metal etc.) between the common sources of engine fires and critical aircraft sytems. These fire barriers are intended to not be affected by slipstream effects and to provide enough time for the crew to aviate first before addressing the fire.
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Also...statistical average time from fire detection to catastrophic structral failure was 12 mins (average of all multi engine jet a/c up to four years ago). Pulling the fire handle with associated loss of thrust and destabilisation at low alt is much more dangerous than waiting a few seconds for 400 feet...identifying the correct engine etc. Too many people think they know better than the manufacturers. As most people know the reality of an engine fire is that you will retain thrust for a considerable period (unlike the sim. scenario).
Last edited by RMC; 24th Oct 2007 at 15:57. Reason: To include last sentance
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Having had done the training for alot of 'first time' Turbine/Jet pilots, the fear of engine fire seems to come from their piston engined days. The engine/engines are very solidly bolted on to the FRONT of the cockpit or fuel tanks in the wings.
Know if I was flying 'little' aircraft' an engine fire would grab my IMEDIATE attention.
Know if I was flying 'little' aircraft' an engine fire would grab my IMEDIATE attention.
