Originally Posted by
knackered IV
And therein lies the whole problem. If you had read the complete accident report, it was found that the procedure using the cutoff switches was found to be ineffective because of the aerodynamic loads put on the stab in the out of trim condition, which meant that a manual re-trimming of the aircraft was physically impossible. The only way to re-trim was to to relax the pressure on the controls and then madly try manually re-trimming. This would be a daunting proposition with the nose pointing at the ground.
In the original design of this system, before MCAS, this may have been feasible with early intervention, but with the additional and repeated input of MCAS it would quickly become impractical. This is why the Stab Trim switches were put back to Normal, to try and recover some trim control, not knowing of course that the MCAS was still adding nose down trim.
So the crux of the problem was that the pilots were applying an outdated response to a problem that they didn't, and couldn't understand.
The way I read it was because they didn’t act soon enough, the “outdated method” became untenable.
If the pilots had followed QRH when the issue became apparent the aerodynamic loads would have been manageable.
Once left to develop, the problem became overwhelming.