4 ms·

> Now, from what I understand, appying nose-up electric trim should override MCAS, and so this course of action should be possible. I'm not so sure. Will have

by phire 8y ago

> Now, from what I understand, appying nose-up electric trim should override MCAS, and so this course of action should be possible. I'm not so sure. Will have to wait for the final report to be sure, but I feel like the Lion Air flight should have survived if the pilot's trim up commands took priority over MCAS's trim down commands. They were fighting it with trim up commands and they lost. I fail to see how they could have lost this fightunless MCAS takes probity. I know MCAS activates in 5 second on, 10 second off cycles and I'm getting the impression that the pilots can only trim up during the 10 second gap.

treis 8y ago
You're right, but since 10 > 5 the pilot should always be able to "win". You can see it happening in the Lion Air flight: https://spectrum.ieee.org/image/MzE4Mjg2OQ.jpeg https://spectrum.ieee.org/image/MzE4Mjg2OQ.jpeg I count 20 cycles of MCAS -> Pilot correction. It's not clear why the pilots lost the 21st cycle. It could be that they stopped making corrections or another yet to be identified airplane failure.
- phire 8y ago
  The MCAS activation just after 23:33:53 pushes the stabiliser down slightly further than it did at any point previously. After this point, the stabiliser looks like it stops responding to trim up commands. The pilots do a few more trim up commands, but the is never a significant upwards response again. Perhaps this is because the pilot's trim up commands appear to be shorter, or perhaps the pilots are pressing the trim up button, hearing a loud girding noise from the electric trim motor as nothing moves, so they stop holding trim up. With all this talk about aerodynamic forces being too strong on the Ethiopian Airlines flight for pilots to manually trim up, I'm wondering if the Lion Air flight experienced aerodynamic forces so strong that even the electric motor was struggling to trim up.

by phire 8y ago

treis 8y ago

You're right, but since 10 > 5 the pilot should always be able to "win". You can see it happening in the Lion Air flight: https://spectrum.ieee.org/image/MzE4Mjg2OQ.jpeg https://spectrum.ieee.org/image/MzE4Mjg2OQ.jpeg I count 20 cycles of MCAS -> Pilot correction. It's not clear why the pilots lost the 21st cycle. It could be that they stopped making corrections or another yet to be identified airplane failure.

phire 8y ago
The MCAS activation just after 23:33:53 pushes the stabiliser down slightly further than it did at any point previously. After this point, the stabiliser looks like it stops responding to trim up commands. The pilots do a few more trim up commands, but the is never a significant upwards response again. Perhaps this is because the pilot's trim up commands appear to be shorter, or perhaps the pilots are pressing the trim up button, hearing a loud girding noise from the electric trim motor as nothing moves, so they stop holding trim up. With all this talk about aerodynamic forces being too strong on the Ethiopian Airlines flight for pilots to manually trim up, I'm wondering if the Lion Air flight experienced aerodynamic forces so strong that even the electric motor was struggling to trim up.