Centaurus
24th Oct 2007, 13:29
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.