How much longer to fix the 737 Max

Sluggo63 said:
My point was (and I understand there are a lot of interrelated aerodynamic forces at play) that the faster they went, the more "in-trim" they got.
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But you can't let the airplane fly "in-trim" in that situation as it would nose over at a very fast rate. The high airspeed increases the force that the stabilizer is able to generate. At excessive airspeeds, that force pushing against the jackscrew makes it increasingly difficult to turn.

I did this in the sim last month. The slower you go, the easier it is to manually trim.

Sluggo63 said:
I'm not a 737 guy, and never have been. But what I understand of the system the major difference between the two is that the stabilizer trim brake, which would be operational for a normal runaway stab trim is disabled during MCAS operation.
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The stab trim brake is irrelevant. It works with the speed-trim system to stop its automatic inputs when they are not needed.

The easiest way to (temporarily) stop an unscheduled MCAS activation is with the primary electric trim (yoke tumb switches) just as you would with any other out-of-trim condition, regardless of cause. In an unscheduled MCAS situations, the use of primary electric trim stops the MCAS activation, allows full trim authority to remove the erroneously applied trim inputs from MCAS, then causes MCAS to pause for an additional five seconds after the primary electric trim switches are released.

The accident airplanes could have been flown indefinitely in those condition if the crews had continued to re-trim each time MCAS starting to trim nose-down. The Lion Air accident Captain did exactly that and kept the airplane in-trim through 21 MCAS activations. It wasn't until he transferred control to the first officer, without mentioning to him that he needed to keep trimming nose-up, that MCAS was able to progressively move the stabilizer to the full nose-down position over 5 additional MCAS activations.

If the nose gets heavy, trim up. If it keeps happening again, and again, and again, do the runaway stabilizer procedure.
 
Larry in TN said:
The easiest way to (temporarily) stop an unscheduled MCAS activation is with the primary electric trim (yoke tumb switches) just as you would with any other out-of-trim condition, regardless of cause. In an unscheduled MCAS situations, the use of primary electric trim stops the MCAS activation, allows full trim authority to remove the erroneously applied trim inputs from MCAS, then causes MCAS to pause for an additional five seconds after the primary electric trim switches are released. The accident airplanes could have been flown indefinitely in those condition if the crews had continued to re-trim each time MCAS starting to trim nose-down.
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That part still bothers me. Yes, it was an unanticipated action on the part of the aircraft, but once the captain found something that worked, then why for the love of all that's holy did he not stay with it? Doesn't get more simple than that. Guess that stick shaker got him all rattled.
 
Question about the stick shaker:

My understanding is that the left stick shaker is tied in with the left AOA vane, and the right stick shaker is tied into the right AOA vane? Is that correct?

Does the stick shaker have any connection with an auto trim function? Or does it act only as a tactile high AOA alarm?
 
Matthew said:
My understanding is that the left stick shaker is tied in with the left AOA vane, and the right stick shaker is tied into the right AOA vane? Is that correct?

Does the stick shaker have any connection with an auto trim function? Or does it act only as a tactile high AOA alarm?
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No connection to trim. Left stick shaker is activated from the left AoA and the right shaker from the right AoA. The full stall warning, both shakers, only occurs if both AoA vanes indicate an impending stall.
 
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