After modification - additional layers of protection - crews should not be exposed to the hazards of extreme MCAS pitch trim.
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With up to 5.5 deg disagreement between AoA vanes, MCAS will only make ‘one input’; more than 5.5 deg (+10 sec ?) MCAS is disabled.
When would MCAS reset? With a reduction of AoA disagreement from less than 5.5 to near zero split (what is the minimum split), will this re-enable the ‘one input’ option.
When would MCAS be rest from an inhibit condition? With reduction in AoA to less than 5.5 deg, or only near zero. Do any of the reset states require an ‘on ground’ condition; and what happens if the AoA error is not detectable when ‘on ground’, as with Lion aircraft.
What would the maintenance corrective action be for an AoA Disagree - pilot report / electronic maint log?
At what value of split is the AoA Disagree alert shown? Some texts indicate 5.5 deg, what happens below 5.5 deg, how will other systems using AoA be affected ?
With ‘AoA Disagree’ how can the crew determine if MCAS is in a ‘one input’ mode or fully disabled.
What indications alert the crew to the need for careful pitch handing with MCAS disabled? Crews either do not know, or do not have indication of the MCAS AoA trigger point (AoA indicators show units not degrees).
AoA indicators are of little value; with error, which one is correct - either hi/lo or lo/hi. AoA Disagree would be shown for either of these two conditions and then for the MCAS to be either ‘one input’, or be disabled.
The additional mandated alerts and display do not provide crews with information to determine the situation or a course of action. If the AoA indicators remain in view this is misleading or even hazardous information - remove them with error.
It might be possible to determine MCAS state by inference from alerts, or even by looking at the trim, but this would increase crew workload and add distraction. And when trim is operating, is this normal or a runaway condition which still applies.
Over focus on MCAS detracts from the many other systems which could be affected by AoA Disagree - stick shake, low speed awareness, airspeed differences, IAS / ALT Disagree, Feel Diff Press, no autopilot. It could be argued that these also require protection to improve resilience to the limitations of AoA input.
* https://www.boeing.com/commercial/73...e-updates.page