PJ2 Thank you once again.
Under normal (design) circumstances, all AC and DC busses remain powered; there is some load shedding, (galleys) in loss of generation.
As you say, the ECAM would display the failures and the required actions. FLR/WRN category messages would be generated and recorded by the FIDS, (Fault Isolation and Detection System), collated by the CMS (Central Maintenance System) and sent to the ACARS for maintenance action. In short, they would be a part of any transmitted messages.
I take from that, it is almost impossible that a power plant failure occurred at or before 02h14z, therefore AC1 and ACARS were most likely operating and able to report any anomalies in engine operation (whilst the ACARS aerial was pointed skyward at least). What of ACARS (and AC1) after 02h14 if the 'controlled flight' theory were at all possible?
Which brings me neatly to another issue (amongst the many possible variables). The NW FO comment as provided by Greybeard
Here's what the FO wrote in an email the day after:
... Entering the cloud tops we experienced just light to moderate turbulence. (The winds were around 30kts at altitude.) After about 15 sec. we encountered moderate rain. We thought it odd to have rain streaming up the windshield at this altitude and the sound of the plane getting pelted like an aluminum garage door. It got very warm and humid in the cockpit all of a sudden. Five seconds later the Captains, First Officers, and standby airspeed indicators rolled back to 60kts. The auto pilot and auto throttles disengaged. The Master Warning and Master Caution flashed, and the sounds of chirps and clicks letting us know these things were happening.
MY bolding
Assuming no 'recollection' error (event sequence and/or timing), the AP and AT disengaged AFTER the speed indications had rolled back to 60kts, which based on exhaustive information provided here (including the ADR thinking time before DISAGREE), means the cascade of faults (in the AF447 case) might suggest the last recorded rudder travel limit prior to ALTN would have been a very low speed index (high travel available)? I followed that discussion very carefully, and it is still not clear in my mind if the above were possible/probable!? Which brings me back to your comment
In cruise, an engine failure would require an immediate but small application of rudder, (gently!). As with all high-altitude flight one must be careful with the use of controls because thin air provides so little damping effect. Providing rudder is used judiciously, roll-due-to-yaw is not a problem.
You see my line of query i.e. due speed related upset prior to 02h14, or assem thrust related rudder application after 0214z following upset!
Along the same lines:-
surplus1
All of that is quite logical but again, you are basing it on the VS being attached to the rest of the airplane during the flat spin. Is there some reason why you have decided that it could not have separated before that flat spin began and thus caused the flat spin? Is it impossible that the forces on it after the upset could have caused its rearmost attach point to fail first? What if the horizontal stabilizer failed downwards and tore loose from it then causing it to come off? There are so many possibilities.
On the other hand I am suggesting that there would not be a flat spin if the VS remained attached. What would cause the flat spin would be the failure of the entire tail cone [aft of the pressure bulkhead], or of the VS alone. In turn, either one of those would likely cause the engines to leave their mounts. What was then remaining would be the fuselage and the wings. They would then fall near vertically, somewhat like a leaf, with very little rotation, until impact.