Originally Posted by
MemberBerry
The first step in your mantra is "turn off the magic". What Boeing did by implementing MCAS severely undermines that first step, because they added an additional bit of "magic", that can't be turned off using the old procedures (A/P off, A/T off, FD off). Instead, turning off this bit of "magic" requires disabling manual electric trim as well, with the cutout switches.
I think it wouldn't hurt if Boeing would implement some way to disable automatic trim independently from manual electric trim. Something that can disable both STS and MCAS without forcing you to use the trim wheels for the rest of the flight.
Since making significant changes to the cockpit like adding switches is probably out of the question, maybe there should be a way to completely disable automatic trim, using existing switches. For example using the existing cutout switches. Placing them in the cutout position, waiting a few seconds, then switching them back to normal could be used as a way to disable automatic trim, but leave manual electric trim functional. That would require just a software change.
Then your mantra would work just fine, if you include this additional sub-step of "Auto-Trim Off" as part of "turn off the magic".
I assume that you are aware that there are other potential sources of uncommanded and undesired stabilizer trim movement besides MCAS? We do not have separate disconnects for them either. The runaway stab trim procedure is completely and absolutely agnostic as to the source of the uncommanded movement, nor should the flight crew waste precious time trying to diagnosis the source.
As to the mantra, you may have noted that one of the steps was “Trim the Aircraft.” At all times, the MCAS input could be stopped and reversed by the use of Main Electric Trim. The flying pilot was fully capable of countering every MCAS input until such time that the crew got around to executing the runaway stab trim procedure.
BTW, it is not procedural to fiddle with the cutout switches once they have been used.