Originally Posted by
MechEngr
Because MCAS provides a correction opposite to the manual inputs from a pilot. If the plane is heading towards a stall because the pilot is hauling back on the wheel, then having MCAS cutout when the pilot hauls back on the wheel defeats the purpose of MCAS.
The point is that in making this change, they went from a system where the pilot could overrule the automation to one where the automation could overrule the pilot.
This is fundamental and was certainly not explained to the FAA and operators when deciding on grandfathering approval and pilot training.
I still don't see why they decided to remove the AUTO trim cutout switch and replace it with a "B/U" which seems to do exactly the same as "PRI"
This leaves pilots with just the nuclear option of disabling all electric trim and reverting to the reduced size manual trim wheel.
The only explanation is that they felt that MCAS was so important that it should not be possible for the pilot to fly without it in which case why did they not classify MCAS as DAL-A.