B757 fire detection ?
Thread Starter
Joined: Sep 2000
Posts: 185
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From: London, England
B757 fire detection ?
I've just read an article in may edition of Flyer about a 757 which had an engine fire on rotation,(supposedly based on a true story)
"Boeing aircraft inhibit fire detection from 80kts till 400ft so as not to distract the pilot in this critical flight phase"
At 400 feet the fire bell and lights went off and the crew dealt with it.
Is this true? my boeing experience is limited to a few hours in a 737sim and fire warnings are not inhibited on this.
Also 80kts is well below V1 and a fire at this speed should be a STOP.
Perhaps some 757 chaps could explain this as it sounds like rubbish to me.
"Boeing aircraft inhibit fire detection from 80kts till 400ft so as not to distract the pilot in this critical flight phase"
At 400 feet the fire bell and lights went off and the crew dealt with it.
Is this true? my boeing experience is limited to a few hours in a 737sim and fire warnings are not inhibited on this.
Also 80kts is well below V1 and a fire at this speed should be a STOP.
Perhaps some 757 chaps could explain this as it sounds like rubbish to me.
Joined: Sep 2002
Posts: 9
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From: stn
As bizzare as it sounds, this statement is in fact true. According to my 757 maintenance training notes.
"The fire bell inhibit logic exists from nose strut extension on take off for 20 secs or until the airplane altitude is greater than four hundred feet above take off altitude or when the nose strut compresses."
"The fire bell inhibit logic exists from nose strut extension on take off for 20 secs or until the airplane altitude is greater than four hundred feet above take off altitude or when the nose strut compresses."
Joined: Jul 2002
Posts: 7
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From: USA
Almost correct, "it will do the trip" 's statement is entirely correct - however he didn't correct the verbiage FatFlyer posted. As per the Boeing 757 Manual "The Master Warning lights and fire bell are inhibited for fire during part of the takeoff. The inhibit begins at rotation and continues until the first to occur: 1) 400' AGL or 2) 20 seconds elapsed time." So, the 80kts part is incorrect. You would abort for an engine fire up to V1 and therefore receive fire warning indications all the way up until you rotate. Each operator has their own outlook on high speed aborts and that is where the 80 kts part comes in. Some operators view that above 80 knots the takeoff should be aborted only for engine failure, engine fire, unsafe configuration or other situation signifcantly affecting safety of flight. For example, it is usually much better to continue a takeoff after experiencing a tire failure 20 knots prior to V1 than trying to stop. High speed aborts are usually much more dangerous than taking any number of problems into the air. (The engine fire, failure, etc. list above excepted.) Anyway, for what it is worth...
Cunning Artificer
Joined: Jun 2001
Posts: 3,125
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From: The spiritual home of DeHavilland
A little knowledge can be a dangerous thing - there are three warning levels associated with the EICAS. It is the "Master Cautions" that are inhibited from 80 Kts to 400' AGL. The "Master Warning" system inhibits the Fire Warning Lights and Bells from Rotation to 400'AGL. The EICAS still displays the fire warning message, only the audio and visual prompts are inhibited. [A fourth level provides Maintenance Messages, but only on the ground and if the system is interrogated.]
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Through difficulties to the cinema
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Through difficulties to the cinema
