A33Zab,
Two comments:
Originally Posted by EASA AD No : 2011-0199R1
Since that AD was issued, new FCPC software standards have been developed that will inhibit autopilot engagement under unreliable airspeed conditions.
Does it also inhibit reappearance of the FD?
The BUSS, if fitted, must not be used above FL250. The main
reason for that is that the back-up stall warning threshold does not change with Mach number and the selected value of 8.6 degrees is too high above FL250.