Originally Posted by
HundredPercentPlease
Rog - you don't have that quite right. It's high AoA that results in different stick forces. In normal operations the pilot would not ever create an AoA that would allow him to explore the new stick forces. Boeing logic was that if the pilot inadvertently found himself in such a high AoA condition, then all would feel normal because MCAS would trigger. Boeing just failed to explore what would happen if the single input to MCAS failed causing it to repeatedly trigger when not wanted.
Apart from this lack of 'fail safe', add the failure to inform pilots of MCAS having been fitted, to install an 'MCAS on' warning and to signal the need for appropriate training including how to disable MCAS if required. Did Boeing also not fail to advise the FAA of a change in the scale or parameters of MCAS*?
*Ref Schmerik above : "There's the change of the rate of trim applied made late in the testing stages (from 0.6 units to 2.5 units per time period?)"