Mac,
But ‘sensible girl’ (AF447) did not know, could not know, that all sources of speed were corrupt; that was the underlying problem that the situation was beyond the comparator system’s (allowable) certification specification.
In many ways this is similar with the 737 accidents. The crews were presented with a tactile warning of approach to stall, low speed awareness of the same condition, and several alerts from other systems which at the time might not appeared to be related. What would ‘sensible girl’ say, based on those features, and having to consider individual or combined failures.
And again, with flaps up when the trim started to move - MCAS was operating as designed, and again MCAS continued to move trim according to the ‘allowable’ as-designed system. ‘Sensible girl’ thinks OK, and without means of cross comparing AoA, because with only two installed it is impossible to determine which one is correct (another comparator issue). Thus there was no means by which to enter the system logic to identify design weaknesses and conclude that AoA was the initiating factor, and thus correctly alert the crew.
“Good to have trim-wheels that clack-clack as they rotate, but I'm sure that that repeated noise moves into the background.”
Yes, but why was this feature used in the orrigional design? History, but we forget hard lessons learnt.
Was this feature (and others) robust enough to alert the crew against MCAS, or did the failure condition to which the crew should be alerted overcome all warning systems’ and the crew’s ability to deduce the nature, severity, and consequences of the failure?
Back to the drawing board.