Originally Posted by
Derfred
Or simply using main electric trim, which is a normal part of manual flight.
Which is fine, unless you are cognitively overloaded.
MCAS sounds like a SAS to maintain adequate stick force gradient at high alpha. The earlier B737s had a speed trim that worked for a short window of operation in the acceleration phase to ensure that when hand flown the stick force gradient was acceptable, This didn't function at high AOA. The longer fuselage will result in less downwash at the stabiliser than the earlier aircraft, and would otherwise need a larger span tailplane to be incorporated, or strakes etc to be installed. There are other fixes for that, but the easy one is to have an AOA triggered trim bias to offset an unacceptably low inherent stick g, or inadequate positive gradient of the curve.
Presumably the trim system still is observed to move and the trim in motion clacker has not been removed from the SLUF. Forewarned, a crew would be expected to isolate the trim, but that all depends on the remaining cognitive capacity. The CVR will show a saturated crew almost certainly.
As an industry we don't cope well with sensor failures, and as systems become more integrated the problem will grow.
Initially it sounded like an enhancement as it could be done... after some thought, I doubt that is the case at all.
The normal B737 handles high AOA pretty well. I have fully stalled, to the break the 3,4,500's at mid altitude, and at cruise altitude, The mid altitude was in all configurations, and both cases in accelerated and unaccelerated stalls. The Classic at least had straight forward control through the stall, it can have a modest wing drop, but quite manageable, slat rigging makes a difference. The longer bodies have slightly higher effectiveness in pitch control, but the stick force gradient would reduce. Haven't stalled them so cannot comment.
Next crew to have this sort of issue will have some prior knowledge that this crew did not have.