Originally Posted by
fotoguzzi
[Not a pilot] After STAB TRIM cutout, the Ethiopian pilots were apparently wondering why the electric trim was not working. After one minute of this, the First Officer requested permission to try manual trim, which would seem to be the handwheel. After eight seconds, he declared that it was not working.
My question: Is it possible that the Pilot in Command flipped only one STAB TRIM cutout switch thinking that it would still allow electric trim as on previous 737s?
I'm not qualified to say how MAIN ELECT and AUTO PILOT work on previous series planes, but might a scenario like this explain the wasted minute until the first officer spoke up?
Honestly, after reading the transcript several times it is hard for me to clearly determine what the two pilots were trying to communicate. Statements like "trim with me" or "the trim isn't working" don't reference electric vs manual so it isnt obvious what they were talking about or what they assumed to be the condition of the trim system. I'm guessing that English may not have been either pilot's primary language, so it also understandable that under stressful conditions precise terminology was lacking. It has been discussed elsewhere in this and other threads that prior to these accidents, training in Runaway Stab trim and use of manual trimming had been pretty spotty, ironically because the 737 stab trim system had historically been very reliable, so it is also possible that neither pilot had any recent training experience in these procedures. That might explain in part slow reaction times. I'm not in any way a fan of putting video cameras in the cockpit, but I'll admit that this is one time that it would have been helpful.
As far as the functionality of the two switches, procedurally these switches are always used together whether on the NG or MAX and frankly I don't see this crew having either the awareness or the inclination to make this kind of distinction and diverge from procedure and use just one of the switches.