Originally Posted by
MechEngr
If the decision tree for MCAS had added "Crew won't trim and won't reduce thrust," particularly after LNI610, then the workable solution wasn't to remind crews about how to manage trim runaway but to simply disable electric trim for all flights. However no one noticed that branch was missing, so no one made a decision based on it.
I know that "Decision Trees" are the taught academic way to devise the logic for such items, but in my experience they principally facilitate those who don't actually have a detailed background to document the issues. What is needed in addition is someone, separate, to go through things specifically looking for Single Points Of Failure, and someone again who looks at the resulting logic, and from their long understanding says "do you know what, that is going to be tough".