Originally Posted by
WideScreen
Actually, my understanding is, MCAS-1 were 2 independent systems L/R, which did not communicate, but with only some kind of logic to switch-over on airplane boot-up. With MCAS-2, these systems now communicate with each-other to interact about (at least) the presumed health of the AoA input values. With one AoA input out of action, the AoA issue handling is returned to the pilot, according Boeing philosophy.
Regarding the synthetic AoA, this has been "agreed", though also tied to the MAX -10 (maybe also the -7) appearance. No -10 and the synthetic AoA might end up with a premature death. The FAA will be having weak knees, due to Congressional pressure, though It has to be seen, what EASA and China think about this. It was EASA, which was firmly after the 3rd AoA sensor, with the degrade compromise, it might be synthetic.
But my point is they did all that without a major change to the avionic architecture - had the MCAS hazard category been properly identified during the original development, they could have fixed it within the existing avionic architecture.
My understanding is that the third AoA is a hard agreement with EASA - so Boeing needs to come up with something if they expect to keep delivering MAX aircraft in the EASA world. Congress has already approved an extension for the MAX-10, so I'm pretty sure that program will stay intact. As for China, with the current state of relations between the US and China, I think Boeing has pretty much given up on future China deliveries of the MAX (my understanding is that China
still hasn't approved the MCAS fix and lifted the MAX grounding).