Originally Posted by
GordonR_Cape
We do not know that for sure, since nobody has provided any definitive proof, and the pilots that tried clearly failed. It is clearly in Boeing's interest to imply that there was pilot error, but an objective crash investigation may find differently. It may turn out that some weird software glitch, or wiring error, or activation of speed trim (in addition to MCAS), may have prevented the pilots from raising the nose.
I'm not sure what level of definitive proof you are looking for, however, if you look at the DFDR output in the ET302 preliminary report, you will see that the Captain was making stab trim inputs and the stab was indeed moving. If you look closely at about the 5:40:25 mark, you will even see a pilot nose up trim input that stopped and reversed the ongoing MCAS input. This is strong evidence that the system was working as designed. As previously mentioned, Speed Trim was not active after the flaps were retracted, nor were there any indications on the DFDR trace of any automatic trim inputs other than MCAS. The Elevator Feel Shift module may have been active thus increasing elevator control pressures, but that would have only accentuated the need to trim off the control pressures.
As I keep saying, there were multiple causes to these accidents. Design issues, oversight issues, maintenance issues, and training issues. However, there were also crew performance issues. They all need to be addressed.
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