c5load
Topic Author
Posts: 344
Joined: Tue Sep 16, 2008 9:40 pm

Elevator: Up And Down At The Same Time?

Fri Apr 23, 2010 5:19 pm

I didn't know how else to word the title, but I was watching "Air Emergency" yesterday and the case of Egyptair 990. One of the scenarios of the crash was that the Capt and FO were putting opposite inputs on the yolk causing the elevator to deflect up and down at the same time. How is this possible? And even if complete opposite inputs were the case, why did the airplane still go nose down, wouldn't it cancel each other out?
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KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Elevator: Up And Down At The Same Time?

Fri Apr 23, 2010 5:32 pm

Quoting c5load (Thread starter):
One of the scenarios of the crash was that the Capt and FO were putting opposite inputs on the yolk causing the elevator to deflect up and down at the same time.

In a GA plane with dual controls, this would be impossible, the stronger person would win (or you'd break the control system by battling each other   ). I don't know how a transport category jet with mechanical controls (like the 767) is different, but I would think that there would be some sort of combiner in the control system.

In a dual control GA plane, if you turn or push or pull the yoke (not the yolk    , that's what's in the middle of my egg in the mornig), the other one does exactly the same thing. Same with the rudder pedals.
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Goldenshield
Posts: 5017
Joined: Sun Jan 14, 2001 3:45 pm

RE: Elevator: Up And Down At The Same Time?

Fri Apr 23, 2010 6:00 pm

Quoting KELPkid (Reply 1):
I don't know how a transport category jet with mechanical controls (like the 767) is different, but I would think that there would be some sort of combiner in the control system.

All transport category aircraft have not one, but two ways to control the plane. The captain will have control of the left side, and the first officer, the right, with each control connected to each other via a control interlock, so this way you can seperate the ailerons, rudder, or elevator. Thus, in the event that one side sticks, the other side can be disconnected and operated freely. Or, in the situation you described, opposite inputs would cancel out.

[Edited 2010-04-23 11:03:00]
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