GT may well be correct however it begs the question about why otherwise competent crew members become incompetent in this Boeing aircraft!
If an independent safety assessment had been done to support this iteration of the B737 then my non-airline pilot safety training would have detected a couple of hazards (see emails released to the public for evidence) which would require mitigation/barriers:
1. There is a single point of failure in the MCAS, the AOA sensor. The only mitigation being (correct me if I am wrong) that one AoA sensor was for the captain and the other for the FO;
2. There was, however, to be no mention of the MCAS during crew training. The mitigator being that it was automatic and would recover the aircraft without crew input. (is this true?) and that for point 1 that the crew would realise that the two AOA vanes were disagreeing even though they did not know this was a potential hazard (is this true?)
3. MCAS can only be over-ridden by switching the system off, unlike runaway trim. The crews, however, were not informed therefore no mitigator existed;
4. MCAS only operates when the auto-pilot is disengaged. Mitigator is therefore to leave auto pilot engaged.
5. Auto-pilot will not however not engage if aircraft is outside of flight envelope (is this true?). Therefore hazard above not mitigated if the aircraft is in a stalled condition, or thinks it is due erroneous AOA indications.
6. It cannot be assumed that all pilots are equally competent and the lead operator has a sub-optimal safety record. Mitigator - hope nothing goes wrong!
I won't bore you to death with more but regardless of whether the aircraft design is faulty or Lion/Ethiopian pilots are poorly trained, these factors should have been considered by the Boeing Safety Management System (mandated by the FAA) and appropriate mitigators put in place to return the risk to as low as reasonably practicable. (For definitions see: NOPSEMA Guidance Note: ALARP, N-04300-GN0166, Australia, Revision 4, December 2012. Regulatory Guidance). In Australia the High Court has said "if a measure is practicable and it cannot be shown that the cost of the measure is grossly disproportionate to the benefit gained, then the measure is considered reasonably practicable and must be implemented."
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