PPRuNe Forums - View Single Post - Is it possible to stall an Airbus fly-by -wire aircraft in Normal Law ?
Old 27th Sep 2011, 18:21
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Lonewolf_50
 
Join Date: Aug 2009
Location: Texas
Age: 64
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Dani:

Not suggesting suicidal attitude, but I appreciate your attempt to explain this to me.

What you suggests to me is that the robot will bail out on you before you stall, then hand it to you as you stall? (WTF?) (On second thought, Wind Shear is a real bugger no matter what features your aircraft has ...)

The idea I have is that if you were flying in an approach configuration, and with stall AoA being about 1.3 of your current AoA, would a rapid reduction of throttle to minimum/idle induce a rapid enough deceleration (I do understand inertia and momentum) of sufficient magnitude to induce a stall?

What you (and Dozy) are telling me (I think) is that
IF that were to occur (call it a condition considered in system design)
THEN the Normal Law stall protection would keep adjusting the pitch (regardless of SS input) to seek an AoA greater than (continuously computed) stall AoA, and by design the computerized flight control system has suffient rate authority to do so, even in that bizarre circumstance.

You could liken it to being on approach and eating a whole flock of geese all at once in both engines ... and the engines failing in spectacular fashion. So there you are, going down, not having a Hudson River as Sully did, and being prevented from stalling by the robot until you hit earth.

What chance of a flare before impact, I wonder ... not a good situation, for any pilot in any plane, of course.

For purposes of discussion: coupled approaches, and A/P, and Landing Mode laws are known to exist, but let's leave them out of this for the moment.

My idea is to understand what the Normal Law can or will do for you while it is active ... once in Alt Law, the question in the Opening Post becomes irrelevant, since it was asked regarding Normal Law.

Do I understand the system correctly (or close enough?)

Last edited by Lonewolf_50; 27th Sep 2011 at 18:38.
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