Originally Posted by
Flagon
I'm afraid I disagree. For 'a long time', stick pushers worked on IAS alone, and for an AoA driven pusher to 'malfunction' would require it to 'achieve' a critical AoA in the first place - in which case its 'shout' was probably valid!
I know of one type that's been using AOA driven pusher functionality since the late 70s, which was why i was saying a "long time". I'm actually quite surprised to hear of pushers functioning based on speed, since that would be no protection against stalling at elevated 'g', and stalls at 'g' have been part of the cert requirements for a long time as well.
While it's true to say that most scenarios for a stuck/frozen AOA require you to have been at that AOA when the system was working 9just before failure0 it doesn't mean that the warning will be valid. In a similar fashion to the scenario AB has laid out, I can conceive of the AOAs ona pusher equipped aircraft freezing at relatively low speeds (perhaps shortly after TO) at which point you are still well clear of pusher. if the crew was unaware and the system kept treating the AOA as valid 9albeit a constant value0 then as you accelerated and climbed the pusher activation angle would usually drop - an aircraft retracting slats would probably see a major reduction in the pusher AOA at that point, in fact. Which might bring the activation angle BELOW the frozen sensor value, triggering the pusher to fire. The only way to stop it would be to get slow and back in the original config - and slowing down is not something that comes to mind as a reaction to pusher activation.
We typically consider erroneous pusher activation as a potential loss-of-control event, so while it's not quite as bad as the Ab scenario, it'd be pretty bad news. (Its easier to turn off a pusher than to turn off FBW systems, and the pusher is only a small component of the FCS, so you degrade the aircraft less by turning it off. But it wouldn't be fun getting to that point)