Originally Posted by Gretchenfrage
Aerodynamically it makes basically no sense at high altitude to destroy something we are normally struggling for, namely lift.
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So why would any manufacturer want lift destruction to counteract high speed??
One of them because his FBW would climb in case of massive overspeed and I hope we all agree that this is undesirable.
Aerodynamically speedbrake extension creates drag to slow down the airplane. There is no lift destruction. Lift is maintained otherwise the airplane would start descending. Speedbrake extension reduces the maximum lift capability, but that is irrelevant because, firstly, the airplane is far removed from the maximum lift capability in an overspeed situation and, secondly, if the airplane slowed down to near its minimum speed it encounters buffet well before reaching the maximum lift capability, which is immediately restored upon retraction of the speedbrakes.
AFAIK the recommendation to use speed brake has no relation to the functioning of the overspeed protection feature.
Another one because he wants thrust levers only halfway back due to its engines unusual long spool-up time.
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Why does the manufacturor not cure the sickness and simply fights the symptom? I say:
Get the FBW or EEC logic right before you suggest manoevers that put us in a worse situation to counteract the flaw!
I don't know the reason for the long spool-up time at high altitude, but I think it is more likely to be the engine's surge margins than a 'flaw' in the FBW or EEC logic.