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Old 29th Aug 2011, 00:58
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DozyWannabe
 
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LW_50 :

According to the documents I've got, inhibition of A/P is not necessarily the case as a result of Alternate Law latching, in fact the only control law where the manuals specifically state A/P is unavailable is Direct. However, the A/P disconnect in this case was due to ADR disagree. If I recall correctly, it was possible in some cases to re-engage A/P once stability was restored, but according to the Flight article below, EASA are mandating a change to inhibit A/P for as long as ADR disagree is active. They don't say if this behaviour should be latched.

A330/340 change to inhibit autopilot if airspeed unreliable

It's curious in a way, because it appears the AF447 crew did not try to re-engage A/P, but maybe as part of the simulator testing they've discovered anomalous behaviour if you try.
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