Originally Posted by
737 Driver
As far as defeating the MCAS input, the ONLY thing required of the Captain was to trim the aircraft normally. The yoke trim switch will trump MCAS every single time. He did not need the strength of his arms, he only need the strength of this left thumb.
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.