Old 11th Feb 2019, 16:32
  #8 (permalink)  
PEI_3721
 
Join Date: Mar 2006
Location: England
Posts: 838
jimtex,
the problem is not a simple issue of trimming the aircraft.
Automatic application of trim appears to be used to improve marginal pitch stability in specific areas of the flight envelope. e.g. with high thrust the aircraft might pitch up faster than could be managed with normal stick input, thus nose down trim reduces the flying task and risk of loss of speed.
No MCAS, no certification, #7.

The delay is probably a complex interaction of embarrassments; Boeing certification, FAA oversight, EASA talking away doubts, interpretation of required levels of safety, system probabilities, and any other issue which might have been ‘overlooked’ - signed off under grandfather rights / common type certification and pilot rating. Once you have opened a box of issues then all need reconsideration.

In addition, having opened the electronic ‘box’ containing AoA computation, then what else is in that box which could be, or was affected.
Erroneous low speed awareness, misleading and unwarranted stick shake, feel system, and the difficult question of how much credit should the claimed for pilot intervention in detecting and managing failed systems - particularly where the so called fail-safe system (or process) had failed.

There was a brief discussion on slats in another thread; slats appear to be related to the AoA input in one of the computations. The slats might not have operated, but if the safety integrity of the protection system was lost, then there might be opportunity for an eye watering deployment at high speed.

Last edited by PEI_3721; 11th Feb 2019 at 17:44. Reason: Deleted technical inexactitude.
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