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Old 16th Apr 2019, 08:08
  #4075 (permalink)  
Join Date: Dec 2002
Location: UK
Posts: 1,765
Alchad, timely and relevant questions; as to be expected from ‘West of the M5’

“ …very keen to see this background data, and exactly how much of the flight envelope is actually covered …’

This is an important issue. One scenario is that Boeing FAA accepted previous data from the 737 NG, or even 737 classics for the MAX; based on the aerodynamic design, wind tunnel and flight tests - grandfather rights. This probably involved some extrapolation, thus the associated processes are of interest.
Did Boeing convince themselves - and then the FAA, that the MAX is sufficiently similar to the NG so that deep questioning was glossed over. Unfortunately the MAX is not the same as witnessed by MCAS - probably a late addition to meet certification (not to be the same as precious variants), etc, etc.

From a flight test viewpoint (hindsight), the tests required would be very hazardous; thus data as far as was flown for certification opposed to simulator information beyond the recognised flight envelope would depend on extrapolation. Without ‘real’ data, the aircraft and simulator certification could be based on previous variants and ‘linear’ interpretations (not mathematically linear) for simulation - it’s good enough for training, because the pilots won’t get into that situation, the system does not fail that way, etc, etc.

Thus the FAA and other regulators could (should) be reconsidering these aspects, and based on piloting experiences, the concerns about trim forces and practicality of recovery for trim runaway (not MCAS because that won’t malfunction in the same way post mod) could be well founded, and thus a much bigger problem for Boeing.

If the certification approvals for the aircraft and simulator meet current requirements there should not be need for more data; this should be (has been) collected for certification approval, proof that the failures can be managed by human alleviation, and that pilots ‘will not’ (certification probability) encounter such situation again.

No need to move on, dig-in for the long battle; certification ramifications and possibly Boeing rework / rethink.
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