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.
Concours77
You are misinterpreting non-sensical exclamations by the AF447 crew as technical realities.
That crew talked about "the screens being crazy" - that is a very unprofessional observation for pilots. Those "screens" are displays that portray a multitude of information from many different, independent sources.
True, the speed indication was weird for a short while, the altitude indication dipped a bit at the very beginning, but the ATTITUDE INDICATION, that is THE MOST IMPORTANT CONTROL INSTRUMENT in INSTRUMENT FLYING, was indicating with perfect precision what was happening.
A transport aircraft at cruise altitude is flown with the nose about 3 degrees above the horizon, for a climb a maximum of 1 degree higher, for a descent about 1 degree lower, for an idle descent about on the horizon, but NEVER, NEVER NEVER at 15 degrees above the horizon.
The communication between the co-pilots was all about CLIMBING or GOING DOWN, but NEVER ABOUT THE PITCH ATTITUDE that was required.
Note, that by zooming up untill all speed was bled off, the climb automatically was turned into a descent (GO DOWN), but the way in which they went down was not a wise one.
The captain had the bad luck to enter the flight deck just as the ALTITUDE was about 35.000 ft again, just the same value as when he had left the flight deck, so he had completely missed the zoom climb and the susequent drop down. The co-pilots could tell him nothing useful, so it took a while for him to figure out wat the rapidly decreasing altitude indication really meant.
Please note that failures of display screens are also monitored situations, monitored by ECAM that is, and the flight data showed no abnormality at all in that respect.
Note that I have used capital letters to write things like ATTITUDE, because people do often, in postings, confuse the word with an L and a T with the version with double T, and that is quite a crucial difference for a pilot flying on instruments.