Originally Posted by
QuagmireAirlines
They didn't need to turn it off. Not stalling. Pitch was high, yet with an empty aircraft, velocity vector was high too.
It does raise a related issue: What pitch angle and/or vertical speed should MCAS be safely disabled?
I might have implemented a disable for pitch angle < 6 degrees, and possibly add an AND condtion with vertical speed < 0 which would keep the nose from auto-trimming down when descending at a low or negative pitch angle.
What condition would you disable MCAS down-trim on? Boeing isn't buying any of that of course, yet doesn't keep us from suggesting something else.
MCAS (a proper one) would need to be active at any pitch angle and vertical speed. One can pull to a stall while going up, level or down.
And for those suggesting that artificial feel is not powerful enough, I don't agree, it makes one sweat if it goes haywire, does it not. That's not the problem, the problem is that it uses all its power in some circumstances now so it would be saturated if we superposed a new one. (And if it wouldn't, it would be too strong to physically overcome anyway).
Obvious solution: we would need to reduce the feel by a factor of 0.8 across all range and then use the new 20% headroom for MCAS. The rule is concerned about the linearity, I am almost sure that the feel in the 737 has a lot of margin to be softened.
I'm talking a fairly small double sided cylinder with 20% more area in the downstream side, feel computer connected to one chamber, feel swinging assembly to the other; and a big ass solenoid to supplement the pressure in the event of an MCAS event. One for each feel hydraulic circuit.
The feel "computer" (impressive bunch of pistons and springs and little pipes) would not need upgrading. And feel system is always possible to handle if something goes completely wrong (remember it is a peculiar system, force is always zero in the center by design).
Still I would prefer an aero solution like the vanes described before, it would involve much harder design but much easier retrofit.