777 VNAV EO Takeoff
Thread Starter
Joined: Oct 2011
Posts: 3
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From: FL390
777 VNAV EO Takeoff
Hello 777 drivers.
I am looking for a reference of the condition(s) activating VNAV engine out acceleration at takeoff.
Is it only when an engine is sensed failed (N2/N1) ? Or is there an additional condition like Fuel control switch Cutoff ?
If flying through engine out acceleration height with memory items not yet completed, what will happen ?
Pretty much sure I read this already but can’t find it anymore…
Thanks !
I am looking for a reference of the condition(s) activating VNAV engine out acceleration at takeoff.
Is it only when an engine is sensed failed (N2/N1) ? Or is there an additional condition like Fuel control switch Cutoff ?
If flying through engine out acceleration height with memory items not yet completed, what will happen ?
Pretty much sure I read this already but can’t find it anymore…
Thanks !
Joined: Mar 2002
Posts: 172
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From: UK
Just talking pitch modes…
Assuming you have VNAV armed for takeoff it will engage at 400’ regardless of whether you have an engine failure or not. The engine out acceleration height is entered during pre-flight and may differ from the all engine acceleration entered on the same (TAKEOFF REF PG 2) page. So the aircraft ‘senses’ the engine failure and decides which acceration height to use. The fuel control switch would only come into the equation for e.g. engine fire with no loss of thrust since the engine hasn’t ‘failed’ until the fuel control switch is moved to cutoff. Other failures would be sensed earlier as the engine goes below idle speed. With VNAV engaged the acceleration will start automatically. If you need to delay the acceleration for whatever reason, use speed intervention. e.g. requirement to maintain V2 to V2+15 for a turn.
Assuming you have VNAV armed for takeoff it will engage at 400’ regardless of whether you have an engine failure or not. The engine out acceleration height is entered during pre-flight and may differ from the all engine acceleration entered on the same (TAKEOFF REF PG 2) page. So the aircraft ‘senses’ the engine failure and decides which acceration height to use. The fuel control switch would only come into the equation for e.g. engine fire with no loss of thrust since the engine hasn’t ‘failed’ until the fuel control switch is moved to cutoff. Other failures would be sensed earlier as the engine goes below idle speed. With VNAV engaged the acceleration will start automatically. If you need to delay the acceleration for whatever reason, use speed intervention. e.g. requirement to maintain V2 to V2+15 for a turn.
Joined: Jan 2000
Aviation Qualifications: ATPL
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From: US via Oz, Honkers & Blighty.
Joined: Jul 2013
Aviation Qualifications: Non-Aircrew
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From: Everett, WA
I don't know if any other systems use the logic from that message.
Joined: Mar 2018
Posts: 212
Likes: 36
From: UK
Is it not a 10% difference in THRUST. Hence if the aircraft can not calculate the thrust, due for example to damage to the various probes and sensors then TAC will not kick in initially. It MAY subsequently be available once the engine is secured as the aircraft now knows it is shut down and by definition has 10% less thrust than the other one?
Joined: Jan 2000
Aviation Qualifications: ATPL
Posts: 382
Likes: 70
From: US via Oz, Honkers & Blighty.
Is it not a 10% difference in THRUST. Hence if the aircraft can not calculate the thrust, due for example to damage to the various probes and sensors then TAC will not kick in initially. It MAY subsequently be available once the engine is secured as the aircraft now knows it is shut down and by definition has 10% less thrust than the other one?
