Bergerie, #1647; a key question.
I fear the answer involves a cheap and cheerful solution to a shortfall in meeting certification requirements, particularly if late in the program, where alternative arguments for equivalent safety were unacceptable. i.e. everything from the forgotten NASA lesson ‘Faster, Better, Cheaper’, isn’t.
Therein lies the underlying assumptions about the likely outcome of an AoA failure, and particularly that a crew will both understand and manage the situation; unfortunately in parallel, the understanding and management guidance were absent.
Furthermore the discussions in this thread suggest that even with descriptions and checklists the situation which pilots might face could be beyond their capability - understanding and strength.
Thus although we have the EAD drill, significant risk exists which pilots are expected to manage.
Add to the AoA issue, my previous question about the display of AoA, an option which Lion did not have.
If the DISAGREE a message does not remove the AoA display then pilots are presented with misleading, probably hazardous information (judged by the esteem by which AoA is held by Pprune).
Add to this, the question whether the associated alerts IAS, stickshake, and erroneous low speed awareness (AoA dependent) would be apparent as soon as the AoA was in error (disagree). If not why should these be subject to the MCAS inhibit conditions for trim operation (flap up), prior to which the AoA display would be showing conflicting information?
Re 2 out of 3 sensor comparison logic, there is a debatable area between using an automated a triple system, and the alternative of using human judgement of dual comparison and then selection of the third system. If nothing else the human is directed (Comparator) to the erroneous system opposed to the confusion of many consequential system alerts.