3 ms·

Yeah, from the report: > 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.

by hencq 8y ago

Yeah, from the report: > 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. [...] > At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. > At 05:41:54, the First-Officer replied that it is not working. [...] > At 05:43:04, the Captain asked the First Officer to pitch up together and said that pitch is not enough. > At 05:43:11, about 32 seconds before the end of the recording, at approximately 13,4002 ft, two momentary manual electric trim inputs are recorded in the ANU direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units. > At 05:43:20, approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds. The aircraft began pitching nose down. Additional simultaneous aft column force was applied, but the nose down pitch continues, eventually reaching 40° nose down. The stabilizer position varied between 1.1 and 0.8 units for the remainder of the recording. Seems this debunks the initial implicit commentary how this was due to 'third world' pilots and couldn't happen in the US.

ams6110 8y ago
Interesting, that when they turned the electric trim back on, they only momentarily blipped the switches to trim up, and the stabilizer did move. Then five seconds later MCAS pitched down again and it was over. Wonder why didn't they trim up more when they turned the electric trim back on. On the surface it appears that was their last chance to salvage the situation.
- rootusrootus 8y ago
  That's what I think is most interesting. Given the position they found themselves in, going against the directive from Boeing to leave the trim cutout for the duration of the flight, means they were desperate to get the trim back up. So why did they not immediately make use of the reenabled electric trim control to counteract MCAS for as long as it took? They had kept the plane flying up until reenabling the electric trim, but that one action pushed it over the edge and could not be reversed? Confusing.
  - phire 8y ago
    They made two small trim up commands. But looking at the flight data graph, the stablizer on the bearly moves. The motor was probably stugling against the aerodynamic forces too. Prehaps they didn't think it moved at all and decided they stablizer was jammed. 5 seconds later, MCAS commands down and because that's in the same direction as the aerodynamic forces it moved a lot easier.
    - zaroth 8y ago
      They are also pulling with all their might on the yoke and have been for several minutes. At this point probably fighting fatigue or even getting close to muscle failure (how many pounds of force for how long?) and starting to question their sanity. Yeah, from my computer screen I can wonder why they didn’t sit on that ANU switch hard and long. But in that cockpit Boeing had already sealed their fate.
ec109685 8y ago
For comparatively trivial things like what to do when we get too much traffic on servers, engineers do “game day” testing. How does anyone expect pilots to run through these crazy scenarios and perform flawlessly unless they have done it in a simulator many times?
- jpatokal 8y ago
  Um, they do? Endless simulator drills of various emergency scenarios is a large part of becoming a pilot and staying certified.
  - bunderbunder 8y ago
    Yes, normally. But a whole lot of social and political engineering was put into ensuring that simulator drills of emergency scenarios related to this system would not be part of any pilot's training.
  - acqq 8y ago
    Here, no pilot had any simulator training for the new MAX. Because Boeing was selling the planes as the "same as old ones, no training needed." It seems Boeing also claimed up to just a few days ago that the simulator training is still not going to be needed for the MAX, just the "one hour iPad" game.
  - alkonaut 8y ago
    And if training for this scenario in a MAX-specific simulation was recommended/required then Boeing wouldn’t sell many planes because that would mean buying simulator time and retraining your existing 737 pilots. For specific training to be reqired I assume it would need to be made a different certification entirely? Is that even a plausible scenario that this could change?

by hencq 8y ago

ams6110 8y ago

Interesting, that when they turned the electric trim back on, they only momentarily blipped the switches to trim up, and the stabilizer did move. Then five seconds later MCAS pitched down again and it was over. Wonder why didn't they trim up more when they turned the electric trim back on. On the surface it appears that was their last chance to salvage the situation.

rootusrootus 8y ago
That's what I think is most interesting. Given the position they found themselves in, going against the directive from Boeing to leave the trim cutout for the duration of the flight, means they were desperate to get the trim back up. So why did they not immediately make use of the reenabled electric trim control to counteract MCAS for as long as it took? They had kept the plane flying up until reenabling the electric trim, but that one action pushed it over the edge and could not be reversed? Confusing.
- phire 8y ago
  They made two small trim up commands. But looking at the flight data graph, the stablizer on the bearly moves. The motor was probably stugling against the aerodynamic forces too. Prehaps they didn't think it moved at all and decided they stablizer was jammed. 5 seconds later, MCAS commands down and because that's in the same direction as the aerodynamic forces it moved a lot easier.
  - zaroth 8y ago
    They are also pulling with all their might on the yoke and have been for several minutes. At this point probably fighting fatigue or even getting close to muscle failure (how many pounds of force for how long?) and starting to question their sanity. Yeah, from my computer screen I can wonder why they didn’t sit on that ANU switch hard and long. But in that cockpit Boeing had already sealed their fate.

ec109685 8y ago

For comparatively trivial things like what to do when we get too much traffic on servers, engineers do “game day” testing. How does anyone expect pilots to run through these crazy scenarios and perform flawlessly unless they have done it in a simulator many times?

jpatokal 8y ago
Um, they do? Endless simulator drills of various emergency scenarios is a large part of becoming a pilot and staying certified.
- bunderbunder 8y ago
  Yes, normally. But a whole lot of social and political engineering was put into ensuring that simulator drills of emergency scenarios related to this system would not be part of any pilot's training.
- acqq 8y ago
  Here, no pilot had any simulator training for the new MAX. Because Boeing was selling the planes as the "same as old ones, no training needed." It seems Boeing also claimed up to just a few days ago that the simulator training is still not going to be needed for the MAX, just the "one hour iPad" game.
- alkonaut 8y ago
  And if training for this scenario in a MAX-specific simulation was recommended/required then Boeing wouldn’t sell many planes because that would mean buying simulator time and retraining your existing 737 pilots. For specific training to be reqired I assume it would need to be made a different certification entirely? Is that even a plausible scenario that this could change?