Tom, #3002.
Thanks for the explanations; these are today’s aircraft - ‘as is’. The interesting issues are ‘what could be’ based on the latest reports, after modification.
The number of ‘Disagree’ alerts and attention-getting stick shake, all result from one failure (AoA), is a concern for the NTSB - pilot workload. Additionally, the consequential ‘Feel Diff ’ alert, AP disengage, and inaccurate EFIS low speed awareness, add distraction.
MCAS modifications could introduce further confusion. If MCAS remains part of the existing Speed Trim (I am not convinced that it is), then the necessary Speed Trim alert would also be given - exacerbating NTSB concerns, and also difficulty in selling the change to other regulators.
There is also need to consider AoA failures where MCAS would be unavailable immediately, not just after takeoff.
After takeoff, even with many distractions, pilots should conclude that stall avoidance and unreliable airspeed actions are required, neither require immediate awareness of MCAS state - it would be distracting.
However, with an AoA failure flaps up, then awareness of MCAS state is important. If MCAS failure / inhibit has to be deduced from many coincident alerts, more than currently deemed acceptable in other 737 variants, would again conflict with the NTSBs views.
There is little if any information on the extent of the flight envelope affected without MCAS operative - no ‘church arch’ diagram of speed / altitude.
‘Stab out of trim’ is currently only with AP engaged; so why raise the point now. If AoA for MCAS is to use both FCCs (most likely) then might this imply that there is a change in AP - MCAS relationship, AP remains engaged, but MCAS unavailable would again have to be deduced, strengthening the need for a new MCAS Unavailable alert.
Without technological detection and alerting for Stab Trim Runaway (not MCAS related after modification), these tasks still depend entirely on human perception. Thence irrespective of how much training is given, correct and timely perception cannot be assured, but in engineering terms assurance is essential for a range of situations including extremes of an uncontrollable aircraft and /or unrecoverable situations due to maximum trim offset.