Thread: Boeing 737 MAX
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Old 03-15-2019, 06:37 AM   #70
twistedtree
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City: Vermont
Join Date: Jan 2013
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I've been reading all this with great interest, and want to thank all the knowledgeable people who have contributed. As I said a while back, I know practically nothing about flying and planes, but have learned a ton here.


Most of the articles that have been linked are great examples of why I don't read or listen to the news anymore. It's just sensationalized garbage, loosely inspired by facts.


Based on what I've read, here's my understanding, and I would appreciate comment and correction...


- The design changes in the MAX changed it's flight characteristics, making it want to climb and potentially stall under some circumstances.


- To help compensate/guard against this being a problem, the auto trim system was enhanced to progressively nudge the nose down when a potential stall condition was detected.


- In all 737s trim is normally controlled by a thumb switching on the wheel/stick.


- If the thumb switches aren't working, or trim is not operating as expected for whatever reason, standard procedure is to disable the thumb trim control and use the manual wheel trim controls by the throttles. This has always been the case, and still is.



- If the MAX trim automation kicks in, whether correctly or erroneously due to a bad sensor, etc., it is immediately over-ridden by any pilot trim control on the thumb switches, and remains disabled for 10 seconds.


- The new trim automation is not described in the flight manual, so pilots are unaware of this new behavior. Regardless, procedures in the event of miss-operation are the same as they have always been - if you don't like trim, adjust with the thumb switches. And if that doesn't work, switch to manual trim with the wheels.



- Questions: This nudge-down trim automation is new, but is there other trim automation that has been in 737s previously? Or is trim all pilot controlled, either by the thumb switches or the wheel?


- Question: I also read somewhere about the stick providing a vibrating feedback to indicated something. What was that?
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