PPRuNe Forums - View Single Post - AF 447 Thread No. 8
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Old 17th May 2012, 15:18
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DozyWannabe
 
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Thanks for the vote of confidence gums - much appreciated.

Just to clarify - the computer does make use of AoA, otherwise alpha protections wouldn't work. Those protections are *inhibited* in Alternate Law because the systems are not designed to work from a single data value (in this case AoA).

Even in Normal Law however, the flight computers cannot *command* the aircraft to change attitude without input from a human pilot or the autopilot (which is a separate and distinct system from the flight computers). Alpha Protection simply maintains pitch attitude slightly below alpha max for the current airspeed. The only positive command that comes out of the protections is when Alpha Floor orders TOGA - and again, autothrust needs to be functional to do this.

@CONF - Obviously anything we have regarding FD behaviour is completely speculative. If rudderrudderrat's right (and I'm inclined to think he is), then the FDs would have been reset to the attitude the aircraft was holding when they returned. Given the significant drop in V/S alone those FDs would not have looked stable for very long. The lack of any indication on the CVR that they thought they were out of the woods, along with the fact that they never tried to re-engage automatics when the FDs came back casts some doubt on the "followed the FD into stall" theory. It's a possibility for sure - but not a certainty.

Last edited by DozyWannabe; 17th May 2012 at 15:29.
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