Originally Posted by
MechEngr
The trim cutout switches in the control column are a red herring. The Lion Air preliminary report gave the exact steps that were taken to save the plane and the exact steps that crashed the same plane the next day. I also looked at the FCOM page that was sent to Ethiopian Airlines explaining the system, information posted by a pilot in Ethiopian Air employ.
In addition - depending on those column cutouts in the event of trim runaway is not a smart thing to do. Whatever causes trim runaway is unlikely to read the manual of how things are supposed to work, so if there is a short circuit or other wiring failure, those switches are useless and there had better be a plan B to use the instant plan A fails.
From the view of this interested SLF re yoke-column cutout switch. Believe you may be missing a point. AFIK ALL NG versions for the last several decades had operable yoke cutout swiches such that if pilot pulled yoke in muscle memory reaction to a sudden or noticeable AND ( dive), pulling the yoke would stop- disconnect the stabilizer, and unless another improbable fault happened, the stabilizer would stop moving and the elevator trim switches would still work. Sort of like if your car due to a flat tire swerves to right or left, your immediate reaction ( unless on smart phone ) would be to twist wheel in opposition.
The pilots in both Lion and Ethopia were never told that the addition of MCAS ( aka HAL ) essentially bypassed that switch. And if they did NOT regain near neutral ( level ) trim before using console cutout switches which cut all power to switches and autopilot and ??, the manual trim wheel was essentially unuseable. And as I recall, one of the recordings showed that a few seconds before flight termination, both pilots were pulling back maximum forc on the yoke which IF in the NG would have stopped the stabilizer AND still left the electric trim switches operable.
Just my armchair opinion
