Originally Posted by
GlobalNav
The primary problem is the design. PERIOD
It’s fine when things are normal, deadly when they are not. It was not designed for fault tolerance. If AOA inputs are invalid, perhaps with IAS disagree, the initial procedures (pitch & power), coupled with unwanted nose down trim will naturally lead pilots to maintain proper pitch, speed increases, MCAS trim down more and on and on. Pilots hit Trim Cutout and are left with manual (slow) trim which becomes increasingly difficult to use as speed increases, until it becomes impossible. Can’t unload (nose down) at 1000 feet, and there’s too much nose down trim to control the airplane.
The other primary problem is the Emergency AD. It ignores an accelerating aircraft, low altitude, low pitch, and increasing stab load, and then asks to cutout electrical trim, without any prerequisite. It leaves manual trim as the sole remedy, which is highly reduced and slow.
This certification statement about the authority of the trim wheel over the entire flight envelope is certainly not correct, if the trim wheel cannot be cranked ANU at 10000 ft, 320 KIAS.
The holes line up in the cheese: Boeing, crew, FAA, EASA, ...
Litigation - where Boeing will claim that QRHs, NNCs are more a recommendation for great independant airmen, while Lion/ET and victims lawyers will claim that a manual/NNC is to be followed exactly, including what's not in there shall not be done.