Originally Posted by
EMIT
Vessbot
All aircraft, not just Airbus, will have Flight Directors and Autopilots that, by default, initiate in HEADING HOLD and (present) VERTICAL SPEED. Those modes are the only ones that can start from scratch (meaning present conditions).
All other modes need certain parameters to be established ALREADY to continue the guidance along that condition.
What I'm saying is that if turned off automatically for whatever reason (such as invalid air data in this case), it should stay off until manually set. Do you see the problem with coming on commanding VS 6.0 at the performance ceiling of the plane?