PJ2, in answer to your post #258 :
PRIM2 which "remained in Normal Law"
More accurately, it did not
remain in Normal, it would have
returned to it at the end of the 10 seconds monitoring process. This ADRs monitoring process by PRIMs specifically allow return to Normal law in some cases. During the process itself, it is in Alternate 2.
was "in control", (do you claim it was the "Master FCPC"?)
No I do not. I expect it would have acted upon its sole authority following Normal law and quite possibly its protections, interfering badly with what PRIM1 was doing according to PF orders. Being in Normal while Master was in Alternate 2, it would have deemed its Normal law better than what was asked by Master PRIM (PRIM1), thus resisting it.
Any "partial input/control" by other than the Master FCPC is prevented "by design".
Not quite. Especially on elevator control, the need to activate all servos simultaneously under certain conditions make it necessary to cater for dual PRIM outputs onto parallel servos. Such thing is therefore not positively excluded from the design.
The theory must reconcile the comment from the PNF about "Alternate Law"
Alternate 2 law was latched by at least Master PRIM1, and likely PRIM3, thus triggering the Alternate law ECAM and PFD effects.
The BEA states that the pitch-up was caused by a side-stick being pulled back.
Not quite. Their wording was extremely careful (
BEA text in italics):
From 2h10min05, the A/P then A/THR disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input.
The monitoring process takes place in Alternate 2. 10 seconds elapsed, then :
At 2h10min16, the PNF said "so, we've lost the speeds" then "alternate law [...]".
The airplane pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs.
The climb is not correlated with the initial left nose-up input. 10 seconds between the two. Time for PRIM2 to return to Normal. I posit these nose-down inputs were an unsuccessful reaction to the zoom-climb/pitch-up (manual THS should have been used then, easy to say now of course), and not the initiators of the following :
The vertical speed, which had reached 7000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left.
I posit these are only the result of depleting kinetic energy. No updraft here, speed lost for height gained, no added energy. Roll variations might be the result of conflicting actions of PRIM1 and PRIM2 in different laws over ailerons and roll spoilers which the PF would therefore have had enormous difficulty controlling.
I think we need to re-focus on why the side stick was pulled back after a stall warning
I agree that we should be questioning this action. After flight controls have cleared the investigation filter
why it was held fully back for thirty seconds while the aircraft was on the way down at >10,000fpm.
It was actually "to the nose-up and left stops".
If flight controls were compromised, as the theory I offer seriously suggests (this is no fancy), then PF actions cannot be understood without the full traces of computers states, surfaces actuation/position, and so on, simply because his actions and the aircraft reactions would make no sense to him. This could lead him to trying things which would make no sense to us.