4 ms·

Post Lion Air, they should have known that.

simion314 8y ago
Why exactly? if Boeing did not updated the manuals and checklists how would pilots know that? from internet forums? Should a pilots ignore the checklists and try steps he read on the internet ? I could not find if Boeing updated their manuals/checklists after the first crash.
- cjbprime 8y ago
  Yes, Boeing issued this service bulletin after Lion Air: http://www.avioesemusicas.com/wp-content/uploads/2018/10/TBC-19-Uncommanded-Nose-Down-Stab-Trim-Due-to-AOA.pdf http://www.avioesemusicas.com/wp-content/uploads/2018/10/TBC... And the FAA made it an emergency airworthiness directive in response. The steps on it were broadly followed by the Ethiopian flight.
  - cladari 8y ago
    Am I missing it because I don't see flaps mentioned anywhere in that link.
    - cjbprime 8y ago
      You're not missing it. The pilots followed the instructions, and the instructions do not mention flaps.
  - JRKrause 8y ago
    This bulletin notes that electric stabilizer can be used to neutralize the control column prior to STAB CUTOUT, which it appears the Ethiopian crew did not do.
    - msbarnett 8y ago
      They did so repeatedly. The bulletin completely fails to note that if you don't time the STAB CUTOUT immediately after you use manual electronic control but instead the MCAS acts again before you cutout, you're left trying to manually trim the stabilizers in a situation where the elevators are putting so much force on the jackscrew that manual stabilizer trim may be impossible. That's what got this flight.
    - cmurf 8y ago
      Appears? Where are you reading this to come to that conclusion? Page 11 of the preliminary report, 05:40:35 "stab trim cut-out". Page 26, five manual trim up inputs before that time. Manual trim is electric trim instigated with yoke toggle switch. What is not certain (to me) is if continuous nose up toggle for sure would have inhibited the automatic nose down from MCAS shown at 05:40:45. It really looks like pitch trim still needed to come up more in order to relieve the control column force to bring it back to neutral. Why didn't they continue to manually trim (electric) after 05:40:35 to relieve yoke back pressure and also to improve climb rate and also reduce speed? I suspect they actually got ahead of themselves, setting trim stab cutoff too soon, not realizing how much more insideous the MCAS upset case is compared to runaway stabilizer trim. And that is the problem with no training. They had no way to iterate various scenarios of working and failed MCAS behaviors.
      - cjbprime 8y ago
        It seems the "yo-yo manoeuvre" required to manually trim when severely mistrimmed with deflected elevator stopped being taught or mentioned in Boeing manuals decades ago.
- ams6110 8y ago
  Pilots should have known that MCAS is inactive with flaps extended, per information from Boeing.
  - msbarnett 8y ago
    Nope. The Boeing/FAA directive re: MCAS does not instruct them to extend flaps. Further, there's other things going on in the cockpit due to the malfunctioning AoA sensor that's the root of all this. Specifically one of the effects is that they get an Unreliable Airspeed Indication, and run that checklist. That checklists memory items include maintaining the current flap configuration (in this case, flaps up). The Boeing/FAA directive does not instruct them to deviate from this and extend flaps. They have a checklist memory item instructing them to in fact do the exact opposite, and not touch flaps.
    - ams6110 8y ago
      You're correct that the AD and runaway trim procedure does not instruct them to extend flaps. What I was addressing was the statement upthread that "Flaps out supposedly would have kept MCAS off but the pilots weren't expected to know that." If I'm a 737 MAX pilot, after the Lion Air crash I'm learning absolutely everything I can about MCAS. And from information Boeing provided I would learn that it operates with autopilot off, flaps up, at high indicated AoA. You mention unreliable airspeed, that was actually their first problem. Flaps were extended at that point, as according to the narrative they were not retracted until after the AoA disagree, stick shaker, and airspeed disagree. In fact it almost reads like they were intending to continue the flight, engage autopilot, and climb to 32,000 ft with the stick shaker going the whole time. That seems very odd to me.
      - simion314 8y ago
        >If I'm a 737 MAX pilot, after the Lion Air crash I'm learning absolutely everything I can about MCAS. And from information Boeing provided I would learn that it operates with autopilot off, flaps up, at high indicated AoA. And in a crisis situation you skip the checklists and think fast and apply your instincts because you read something on a forum? Sure if you have a lot of time you can try thinking but this is not debugging a bug where you have hours to observe the issue, try different inputs, observe again, Google some questions etc..

Why exactly? if Boeing did not updated the manuals and checklists how would pilots know that? from internet forums? Should a pilots ignore the checklists and try steps he read on the internet ? I could not find if Boeing updated their manuals/checklists after the first crash.

cjbprime 8y ago
Yes, Boeing issued this service bulletin after Lion Air: http://www.avioesemusicas.com/wp-content/uploads/2018/10/TBC-19-Uncommanded-Nose-Down-Stab-Trim-Due-to-AOA.pdf http://www.avioesemusicas.com/wp-content/uploads/2018/10/TBC... And the FAA made it an emergency airworthiness directive in response. The steps on it were broadly followed by the Ethiopian flight.
- cladari 8y ago
  Am I missing it because I don't see flaps mentioned anywhere in that link.
  - cjbprime 8y ago
    You're not missing it. The pilots followed the instructions, and the instructions do not mention flaps.
- JRKrause 8y ago
  This bulletin notes that electric stabilizer can be used to neutralize the control column prior to STAB CUTOUT, which it appears the Ethiopian crew did not do.
  - msbarnett 8y ago
    They did so repeatedly. The bulletin completely fails to note that if you don't time the STAB CUTOUT immediately after you use manual electronic control but instead the MCAS acts again before you cutout, you're left trying to manually trim the stabilizers in a situation where the elevators are putting so much force on the jackscrew that manual stabilizer trim may be impossible. That's what got this flight.
  - cmurf 8y ago
    Appears? Where are you reading this to come to that conclusion? Page 11 of the preliminary report, 05:40:35 "stab trim cut-out". Page 26, five manual trim up inputs before that time. Manual trim is electric trim instigated with yoke toggle switch. What is not certain (to me) is if continuous nose up toggle for sure would have inhibited the automatic nose down from MCAS shown at 05:40:45. It really looks like pitch trim still needed to come up more in order to relieve the control column force to bring it back to neutral. Why didn't they continue to manually trim (electric) after 05:40:35 to relieve yoke back pressure and also to improve climb rate and also reduce speed? I suspect they actually got ahead of themselves, setting trim stab cutoff too soon, not realizing how much more insideous the MCAS upset case is compared to runaway stabilizer trim. And that is the problem with no training. They had no way to iterate various scenarios of working and failed MCAS behaviors.
    - cjbprime 8y ago
      It seems the "yo-yo manoeuvre" required to manually trim when severely mistrimmed with deflected elevator stopped being taught or mentioned in Boeing manuals decades ago.
ams6110 8y ago
Pilots should have known that MCAS is inactive with flaps extended, per information from Boeing.
- msbarnett 8y ago
  Nope. The Boeing/FAA directive re: MCAS does not instruct them to extend flaps. Further, there's other things going on in the cockpit due to the malfunctioning AoA sensor that's the root of all this. Specifically one of the effects is that they get an Unreliable Airspeed Indication, and run that checklist. That checklists memory items include maintaining the current flap configuration (in this case, flaps up). The Boeing/FAA directive does not instruct them to deviate from this and extend flaps. They have a checklist memory item instructing them to in fact do the exact opposite, and not touch flaps.
  - ams6110 8y ago
    You're correct that the AD and runaway trim procedure does not instruct them to extend flaps. What I was addressing was the statement upthread that "Flaps out supposedly would have kept MCAS off but the pilots weren't expected to know that." If I'm a 737 MAX pilot, after the Lion Air crash I'm learning absolutely everything I can about MCAS. And from information Boeing provided I would learn that it operates with autopilot off, flaps up, at high indicated AoA. You mention unreliable airspeed, that was actually their first problem. Flaps were extended at that point, as according to the narrative they were not retracted until after the AoA disagree, stick shaker, and airspeed disagree. In fact it almost reads like they were intending to continue the flight, engage autopilot, and climb to 32,000 ft with the stick shaker going the whole time. That seems very odd to me.
    - simion314 8y ago
      >If I'm a 737 MAX pilot, after the Lion Air crash I'm learning absolutely everything I can about MCAS. And from information Boeing provided I would learn that it operates with autopilot off, flaps up, at high indicated AoA. And in a crisis situation you skip the checklists and think fast and apply your instincts because you read something on a forum? Sure if you have a lot of time you can try thinking but this is not debugging a bug where you have hours to observe the issue, try different inputs, observe again, Google some questions etc..