Originally Posted by
Rananim
Re manual trim...have we had any engineering input as to just when manual trim no longer becomes available in the flight envelope?
We've had lots of discussion about that, albeit without any numbers.
Is it primarily speed dependent, stabilizer positon-dependent, yoke dependent, or a combination of all 3?
All of the above contribute to the load on the stab, which determines the force you have to overcome in getting the trim wheel to move.
Originally Posted by
bill fly
Dave and others,
At ultra high speed the stab can only be trimmed after releasing up-elevator. This is because of loading to the stab mechanism.
This is the reason for elevator release during upset training.
But if you are at tree top height you can’t do that.
So trim, Manual or Electric is, as the man said, not possible under certain conditions - and those were the conditions encountered here.
With respect, we don't have any evidence of that being a factor here - there are no points in the FDR trace that show trim input without corresponding stab movement. Even the last two very brief ANU inputs appear to have had an effect, although the stab only moved by a fraction of a degree before the the inputs ceased.