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Old 6th Jul 2012, 14:59
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rudderrudderrat
 
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Hi DozyWannabe,
FDs need to be changed in terms of their appearance in marginal systems behaviour
I agree.

On page 3 of Appendix 2 FDR Chronology, at time 2.10.47 "The FD 1 and 2 become available again (modes HDG/VS). The selected heading is 34°. The vertical speed is 1,500 ft/min."

The FDs will presumably command a pitch attitude to satisfy +1500ft per min, whilst displayed.

At time 2.11.22 - 2.11.35 "The vertical speed changes from -3, 900 ft/min to -6,800 ft/min." At time 2.11.40 "The FD 1 and 2 become unavailable. The angles of attack 1 and 2 become invalid (NCD status) while the angle of attack 3 is 33°."

I suggest the flight directors will have commanded high nose up pitch attitudes, in order to satisfy +1500 ft per min even as the aircraft entered the stall and started to descend rapidly.

I understand the wisdom of turning off the flight directors during "Unreliable Airspeed", but when the FDs disappear out of view automatically, it's difficult to remember to still have to switch them off.
There was no help from the automatic reappearance of the FDs.

Last edited by rudderrudderrat; 6th Jul 2012 at 15:06.
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