Takwis, no disagreement with #2472, except that the issues are identified with hindsight. For real learning we need to understand the processes which enabled them; look from the other end of the tube. What was the situation at that time, as understood by those in the process.
The situation for most people in the process, as far as is known, all was well.
The design theory, engineering, safety assessment, and certification were all adequate, yet each had existing weakness and flawed reasoning. Most of these have been discussed add nauseam in various threads, except that we don’t yet know why latent factors were not seen or how all of the issues came together in such a critical way; there opens as ever, the human factor and speculation.
Safety should not be based on speculation.
TimTuffy, #2475
You provide a plausible, knowledgable view that opposed to trim speed stability, the dominant problem was manoeuvre stability.
Whilst a conventional approach might consider stick force / g, the Boeing solution was to substitute AoA for g, possibly with other non linear aerodynamic considerations. Thus in software terms instead of having a ‘g’ function (or ‘g’ plus AoA or bank angle) where a malfunction might be detected with multiple inputs, the lesser integrity of dual AoA was ‘overlooked’.
Some malfunction ‘protection’ was provided by the flap selection - when MCAS was required, opposed to higher integrity defences when MCAS (trim operation) was not required preventing operation with sensor failure. A side thought: what would have been the effect of a flap position sensor failure - false open at low speed - MCAS not required, or false closed, inhibited MCAS when required.
Bend alot, #2477, link
Pinkman / Gordon.
AoA failure, excepting that we don’t yet know the precise nature of the erroneous AoA input. Hardware, electrics / software - in which part of the system, the extent of any previous failures, critical or not so.