The one very real way in which you can complicate your recovery from a loss of control (spin or whatever) is to have the autopilot surreptitiously auto-trim in as much back-trim as possible. However the pilot doesn't need to organize that, the autopilot will do that all by itself, quite unnoticed by the pilot - as the speed erodes. That pitfall of an autopilot disguised contrary control force is why medium size turboprop airliners are required to be handflown in heavy icing conditions. The phenomenon of autopilot kickout immediately followed by autorotation (i.e. a spin) has been the undoing of many an inattentive crew - after a short period of ice accumulation. We have the recent examples of the DHC8-400 in the US and the Turkish 737 at Amsterdam to emphasize the stealthy suckertrap of auto-trim.
But what was happening to the THS (trimmable horizontal stabilizer) and auto-trim aboard AF447 when the pitot malfunction occurred? Could that pitot icing indication glitch have emulated the icing performance loss scenario? Can the pitot's induced false speed reading predicate the auto-trim's response? Can the auto-trim then be well out of whack nose-up and yet the autopilot still soak up the "stick"-load in order to maintain the stipulated altitude?
If this was in fact (or could've been) the case, what would have happened when autopilot, auto-thrust and (presumably) auto-trim dropped out? How difficult (or improbable) would recovery be if the autopilot kicked out due to it holding greater than a kick-out threshold force of forward elevator?
I imagine a pitch-up into a stall and a wing-drop flick into autorotation would likely be an instant development. Would the pilot, now in manual control and Alternate Law, have any clue as to what was happening? - such that he could correct the out-of-trim configuration and regain control?
Or is it more likely that the combination of unaccustomed manual flight at high altitude, sudden IMC, Alternate Law and roll/pitch/yaw could mask the
back-trim and leave the pilot totally flummoxed?... You only need scant seconds of very nose-low to exceed VNe. And of course we're disregarding here what could have happened to one or both engines thrust during that pitch-up - which may have provided the asymmetry for spin entry.
I've got first hand experience of what happens to a JP5A (Jet Provost) pilot subjected to loads of elevator back-trim when handed over to for spin recovery. They were always non-plussed. The learning experience exceeded the syllabus for spinning but similar to inspin and outspin aileron's effects, it was a worthwhile exercise to file away in instant recall.
in order to enter a stall, the aircraft would had to have changed to Direct Law.
Is this statement still operative once the speed input to the ADIRS is wholly corrupted? The aerodynamics of a pitch-up at high altitude would trump that law - methinks.
If the cg is behind the C/L of stalled wings, the nose will not drop, and the plane will not regain flying speed. This is a flat spin. It does not require rotation. As above, for rotation there has to be a partly unstalled wing. Per Wiki, the flat spin angle of attack will be between 65 and 90
degrees, which means there could be some forward speed.
Modern airliners are intentionally flown at aft cg near the safe limit. A load shift will put the cg behind the C/L, and this has happened countless
times, usually with cargo.
More food for thought. Think centrifugal force in a large aircraft spin. Even if it wasn't a flat spin to begin with, anybody/anything loose in the cabin will migrate towards the rear, pushing the CofG even further AFT. Even with baffles, this might also be the case for some of the fuel. Any thrust left on the engines will also tend to flatten the spin. Any heavily back-trimmed aircraft will tend to want to remain in a flat spin, particularly as the thrust increases with height loss (for any given set throttle lever position).
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