Originally Posted by
FullWings
I think the only reasonably foolproof way to check if the surfaces are working would be have somebody look at them while you were exercising the controls. You are relying on sensors otherwise. The “carry away” I got from the discussion I had was that it was important to exercise the controls through their full range of motion (to the stops) to pick up anything untoward; the comparison logic is active as soon as things are powered up, so “control checks” are ongoing throughout the whole flight.
(putting on my un-earned engineering hat)
I imagine the systems display would get information from the surface position sensor.
I’m imagining a failure mode where you turn the wheel left, but computers get a right turn signal, and move the surface for a right turn. I imagine it would pass the internal check in that case.
I suppose Boeing has controlled for that eventuality.
(pilot hat back on)
Thanks for the info. Good to know why we’re doing what we’re doing.