Trimming is about second or third one learns during pilot training. It shouldn’t require an AD to tell pilots to put the plane in trim. Trim is like managing thrust. In UPT, if you weren’t “in trim” they’d just reach under your arm and push up hard to get you to release the stick, followed by an abrupt nose going in up or down reinforcing the importance of trim. Then, you start formation and really discover the need for trim. IPs would wear out the thumb in their gloves trimming.
That's not a problem, the problem is that the tool you're trying to use to put the plane in trim, the manual trim, is broken.
But, the manual ELECTRIC trim (yoke switches) was not broken and the FDR traces show functional inputs that were too brief to position the stab into a trimmed condition. Pilots were simply not aggressive enough and the the stab get so far out of position that the wheels wouldn’t work under the aerodynamic loads. If your flight SOP is autopilot ON at 400’ and OFF at 200’ on an ILS (an all too frequent training or laziness outcome), you’ll use the trim switches to the degree necessary during various speed and configuration changes. In fact, you probably get away never trimming. Trimming is not Chuck Yeager skills, either.
There is NO evidence that the pilots did not properly use electric trimming. Au contraire, the FDR charts clearly show the use of electric up-trimming being applied many times. So they did understand how that works . . .
I'm baffled that some on here find it necessary to explain that (electric) “trimming is about second or third one learns during pilot training
”, suggesting that these pilots did not know how to trim a 737. That borders at the R word.
The FDR traces show a total of four electric up-trims after MCAS became alive. And ALL FOUR of them stopped at exactly the same pitch trim: 2.3 degrees. Coincidence? Can any crew do such a thing on purpose? I'm having a hard time accepting that.
It must be noted that after take-off, electric trimming was applied several times (both up and down) resulting in a balanced control column. So again, they clearly knew how that works . . .
I’m baffled (AGAIN) why no one seems to be interested in this very peculiar behaviour of pitch trimming (stopping at 2.3 deg Pitch Trim), and trying to explore what the dynamics behind this behaviour would/could be, but in stead jump on the “crew doesn’t understand electric (and manual) up-trimming” bandwagon.
Why on earth would even “poorly trained third world operator crew
” stop electric up-trimming way way before the control column is anywhere near being in balanced pitch condition??? That does not make any sense, at all.
The cut out switches were flipped before the control column was balanced in pitch. You ASSUME that was by pilot action. We have no evidence of that. All we know is that:
a) At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and First-Officer confirmed stab trim cut-out. (page 11);
b) At 05:40:37, electric up-trimming stopped (FDR trace);
c) At 05:40:42, MCAS command did not affect pitch trim, so at that point the cut-out switches were in flipped position (FDR trace).
Therefore, between 05:40:37 and 05:40:42, the cut-out switches were flipped.
So the question is, a) did up-trimming stop because the cut-out switches were flipped, or b) did they flip the switches because electric up-trimming stopped (uncommandedly) and was not working for them (beyond 2.3 deg Pitch Trim)?
I can’t find that answer in the report nor the FDR traces.
Further, I find following line (page 11) also very interesting: “At 05:40:27, the Captain advised the First-Officer to trim up with him.”:
At 05:40:00, MCAS became alive and completed a full 9 second cycle. This was quickly followed by electric up-trimming which stopped at . . . . 2.3 deg Pitch Trim.
At 05:40:21, second MCAS cycle, which was cut short by electric up-trimming (!!). This time the electric up-trimming is much longer in duration, but stopped AGAIN at . . . wait for it . . . 2.3 deg Pitch Trim.At 05:40:27, the Captain advised the First-Officer to trim up with him.
Why would the captain ask the FO to trim up with him”
That would suggest that his up-trimming was cut short not by his own choice, but by something else outside his control. Why else would he ask for help in up-trimming?
Why did up-trimming each time stop at 2.3 deg Pitch Trim?
Coincidence??? I don’t think so.
Crew not understanding up-trimming? I’m not buying that at this point, without strong evidence. Which has not (yet) been presented.
All in all, I have a lot of questions and am no way convinced that the crew did not understand electric up-trimming.
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