Originally Posted by
Tomaski
Because the current procedure actually delays the crew response to an actual runaway stab trim. I believe this may have been one of the issues in the E-CAB test failure in which the FAA determined that the procedure took too long to implement.
I think that's one possibility / interpretation, but back in June at
theaircurrent.com Jon Ostrower suggested that it took too long because the test pilot "
found the electric trim switches on the pilot’s yoke unresponsive". If that is correct and the cause of delay is overwhelmed FCC (as is also stated in that article) then the implication is that manual electric trim doesn't override autopilot (with relays or switches) but rather manual trim is a request to HAL which then decides
(in software) if it will allow you to override its trim command.
I will state very clearly:
I struggle to believe that interpretation and the implication, because I can't see how you could do it that way without triplex redundancy and voting etc. - but I may very well be wrong. I await more definitive information with interest.