PPRuNe Forums - View Single Post - Boeing 737 Manual Stabiliser Trim - an Historical Fact
Old 2nd Jan 2020, 19:53
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Grebe
 
Join Date: Sep 2019
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centarus posted this interesting bit
...Contrary to the advice mentioned by Sean Broderick of “take the counterintuitive step of not pulling back on the yoke even though the aircraft is trimmed nose down,” you can see the Boeing advice is to initially raise the nose well above the horizon with elevator control.
Seems to this SLF that in the extreme case with stabilizer flipping up to give AND, pulling the yoke which normally raises elevator to give nose up is likkely to make it harder to trim stabilizer nose up. ( assuming that elevator is not blanked re airflow over the extreme nose down stabilizer )

I believe this was well covered in satcom.guru and the following links


https://www.satcom.guru/2019/10/flaw...-disaster.html

https://leehamnews.com/2019/11/29/bj...-crash-part-5/


https://www.moonofalabama.org/2019/0...g-737-ngs.html



B737 Max threads

https://www.satcom.guru/2019/03/taki...aiting-on.html

and from an earlier post *** NOT MINE***
" I agree it's a flawed design. And I used to work there. I'm glad I don't now.

Regarding the trim wheels: When the NG was being introduced, I happened to be the Lead Engineer in charge of them and a whole lot of other stuff. There were some issues. The new display system created a pinch point between the dash and the wheel. We had to make the wheel smaller. And the new trim motor resulted in the wheel, which is directly connected to the stabilizer by a long cable, springing back when electric trim was used. It was an undamped mass on the end of a spring. We had to add a damper.
Result: Depending on the flight conditions, the force to manually trim can be extremely high. We set up a test rig and a very fit female pilot could barely move it.
As I said, I'm glad I'm no longer there."

Last edited by Grebe; 2nd Jan 2020 at 22:11. Reason: clarification
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