"Relight speeds are there to ensure required air density and N1. While the speed of 300kts in engine failure cruise is from mandatory requirement for twins on non ETOPS to have an alternate within one hour on one engine. That requirement is considered to have met at .78/300kts."
So I guess the 300kts is just to comply with regulation. So the theory I heard from one instructor that we used 280kt instead of 300kt during dual engine flame out to minimize the descent rate might be rubbish after all. Haha.
I still don't get it. Engine failure at cruise level. Fly the a/c. Decide if you can cruise descend for a windmill start, or need to drift down first then do x-bleed or accelerate again for windmill. The decision making time depends on 'the mind' and crew composition. If you are not sure, and in crowded RVSM, then you need a few seconds to think & decide and coordinate; hence set up for a drift down is perhaps 1st reaction, then modify as necessary once that decision has been made. That might be a 300kts descent.
The 300kts for ETOPS/non-ETOPS is a nominal speed used to calculate the diameter of the diversion circles to alternates. It is not a necessarily a practical speed. If you drift down first, then divert you will have first slowed down and then you'll consider what level to descend to and what speed to accelerate to. That is something that happens after the engine failure(s)
Dual engine failure enquires a very different reaction and speed is very relevant.
What has been told here seems to be a one size fits all in the single engine or dual engine failure case. Hm? Life ain't like that.
Last edited by RAT 5; 13th Nov 2017 at 20:16.