A few thoughts after reading this prelimanary report, and the many questions it raises. I write in a modest way, as it has been some years since I flew those planes, and I have forgotten a lot.
My very sad and friendly thoughts to the pilots of this flight.And everyone aboard, of course.
The THS (trimmable hydraulic stabilizer) auto trims the plane, the PRIM 1 is normally in charge of that job. The report does not say if the PRIMs (there are three) were lost, which is possible after losing speed information, and it does not say (understandably, it will come later) if from normal law, then alternate, the plane ended in direct law, then changed back etc…(possible resettings, speed indications coming back…)
If in direct law, there is not automatic trim, the horizontal stabilizer stays where it is and you have to use manually the trim wheel which a warning on the PFD, among very many other warnings in that case, tells you to do.(I am reminded of the Perpignan accident where the captain fought with the plane but if I remember correctly, never trimmed manually, with a very UP THS, exactly as described here, though for other reasons of course).
The THS is very effective, and even with sidestick applied fully down, if it stays at 13 degrees up, I think lowering the nose will be difficult…
From what I understand, having been familiar with this company, the captain went to take a rest, asked the most experienced of the two copilots (who had the appropriate qualification) to take his seat (left one) and the copilot in the right seat was PF. This is quite normal. If, and I do not believe it for a second, the PF was « lost » and applying full aft sidestick, while on the instruments, all kinds of understandable things happened, with chimes, alarms, synthetic voices etc…the copilot in the left seat , and even the captain coming back and sitting between them, had no way at all of knowing this, and could believe that he was applying the correct inputs, unsuccessfully. In the old days (and I am a very old-timer), putting your hand on the trimwheel was a habit…Nowadays, you don’t even know you have one, except for checking its position at take-off, which is not the same as using it in manual flight. Rolling it manually far forward, and that is always possible, in all modes or laws (correct me if I’m wrong, active bus drivers) and applying cruise thrust might have solved the problem, but that is easy to say from where I sit. I am quite sure of one thing, as you all are, but it bears to be repeated : thos pitot probes were changed by an efficient management, many months before, in another company, after an icing incident. The management of Air France truly thinks, not having done anything, that they did everythin very well, since it was not mandatory. Food for thought. May they sleep in peace.