QUOTE]Hans Brinker wrote:
Definitely Boeing needs to:
-Limit MCAS authority, and preferably by adding aerodynamic fixes like tail strakes.
-Disable MCAS in the case of AOA disagree.
-Install the AOA indicator and AOA-disagree indicator, preferably better than the current way.
-Install an AOA left/norm/right switch that limits error messages/stall warnings for those cases where it is clear to the crew which one is wrong.
-Bring back the option to disable auto trim (AP, STS ,MCAS, LAM), without losing the thumb-trim.
-Improve the NNC, to differentiate between MCAS and "regular" runaway trim.
-Verify it is possible to trim the aircraft back to in-trim from a runaway trim, aircraft full AND situation at low altitude, and see if there is any speed restrictions required for this, for all B737.
Obviously all of this should be paid by Boeing.[/QUOTE] What stands out most to me in reading this entire thread is that, while MCAS appears to have been activated in error on 4 occasions in some 500,00 total cycles of the MAX fleet, it appears to have activated correctly precisely zero times. This suggests to me
1) that the certification requirement that MCAS was intended to meet was excessive and not really required for safe operation of the aircraft; and
2) that, had MCAS been designed to deactivate itself upon AoA disagree and
done nothing else (including notify the flight crew), neither these two accidents would have happened nor would have any other related to the certification requirement.
Based on the numbers to date, the statistical probability of an AoA disagree sufficient to deactivate a well-designed MCAS happening
on the same flight on which the flight crew managed to get near to an accelerated stall is vanishingly small.
Regarding much of the MAX design being grandfathered under the certification process, it's worth noting that the NG series (which was also grandfathered) has essentially the same accident/fatality rate as the A320 series, which suggested that grandfathering the NG had no effect on operational safety.
Hans Brinker also wrote:
1). I flew the F50, and you could silence all/most alarms with a dedicated switch on one panel. I have read several accident reports that made me wonder if the crew would have done better without distracting and conflicting (stick shaker and over-speed simultaneously on Aeroperu flight PL603) error messages. Having a switch to deselect a system that gives an erroneous indication is an established concept in certifying aircraft (, and I think it should be a mandatory re-fit to all B737). Having one stick shaker go of on the failed AOA side with no other way to switch it off than going through the CB-panel isn't good enough.
Perhaps the user interface aspect of a cockpit where multiple alarms are going on and off deserves more attention than it has received to date. In particular, the issue of the stick shaker creating such a racket seems to be a real issue. It's far easier to be overwhelmed by aural cues than by visual ones.