15 ms·

So... they put in software (MCAS) to try and auto-assist in certain situations so that flying the 737 Max would respond like flying the current 737. But seems

So... they put in software (MCAS) to try and auto-assist in certain situations so that flying the 737 Max would respond like flying the current 737. But seems like an indicator light to show when the sensors that activate that system trigger isn't standard equipment & the sensors may very well have a bad baseline read before takeoff and the system kicks into gear and auto-crashes the plane if you don't know how to disable it. Yeah, I'm never flying in one of those things :-)

WalterBright 8y ago
Pilots are trained in how to disable it - the stab trim cutoff switches are right there on the console. The mystery is why the pilots didn't follow their training.
- mikejb 8y ago
  I've seen different reports about what's in the training. I think the challenge here is to detect that the system is running haywire and then disabling it. It's not a common situation, never trained, and possibly only something the pilot might have read on the way to the airport. Not ideal for a high-stress situation.
  - WalterBright 8y ago
    On the 737 airplanes, when the stab trim is running a wheel on the side of the center console turns and makes a loud clacking sound. It is designed to be obvious. You can see a picture of the wheel here: https://www.quora.com/What-are-the-spinning-wheels-in-an-airliners-cockpit https://www.quora.com/What-are-the-spinning-wheels-in-an-air...
    - mikejb 8y ago
      You have to make the connection though: that clacking noise is probably that new system I read about doing something. Then you have to determine whether that system is the cause of the problem, and whether disabling the system will either fix the issue, or possibly make it worse.
      - WalterBright 8y ago
        The clacking sound happens whenever the stabilizer trim is in operation, which is frequently, and has been in 737s for decades. The pilots would be very familiar with the sound and what it represents. The trim wheel also spins when the trim is running, a large and obvious indication (I posted a link to a photo of it).
- lysp 8y ago
  https://www.aviation24.be/manufacturers/boeing/boeing-737-max-automatic-stall-prevention-system-mcas-not-in-flight-crew-operations-manual-fcom/ https://www.aviation24.be/manufacturers/boeing/boeing-737-ma... > Boeing issued a multi-operator message (MOM) explaining the MAX’s manoeuvring characteristics augmentation system (MCAS) “commands nose-down stabilizer” in certain flight profiles using “input data and other airplane systems.” MCAS is operated by the flight control computer and “activated without pilot input and only operates in manual, flaps-up flight,” and MCAS is not part of previous 737 designs. > The Allied Pilots Association (APA) told American Airlines (AA) pilots in a message on its website. “It is not in the AA 737 Flight Manual Part 2, nor is there a description in the Boeing FCOM. It will be soon.” > A multi-page document issued by the airline’s flight operations department that highlights the differences between the MAX and 737 NG does not mention MCAS or any other changes to the auto-trim system. > A multi-operator message (MOM) from Boeing on Nov. 6 cautioned that “an erroneous AOA” can trigger automatic nose-down pitch-trim. There are lots on indications that at least in the Lion Air case it was not in manuals or communications to pilots. Further here: https://www.wsj.com/articles/boeing-withheld-information-on-737-model-according-to-safety-experts-and-others-1542082575 https://www.wsj.com/articles/boeing-withheld-information-on-... https://outline.com/https://www.wsj.com/articles/boeing-withheld-information-on-737-model-according-to-safety-experts-and-others-1542082575 https://outline.com/https://www.wsj.com/articles/boeing-with...
  - WalterBright 8y ago
    For a pilot ignorant of MCAS, what he'd see is uncommanded stabilizer trim movement. The training says to stop that by throwing the stab trim cutoff switches. They're prominently located on the center console. The pilot of the same airplane on the prior flight to the Lion Air crash did just that.
    - taneq 8y ago
      Wait, are you saying that the aircraft actually exhibited the same failure in the prior flight but the pilot overrode it, and then they let it take off again without warning the new pilots?
- pauljurczak 8y ago
  It's easy to say with the hind sight. When you are flying a plane, which starts to behave abnormally, you have to analyze hundreds of possible causes and try not to kill everyone on board at the same time. There are multiple reports about poor MCAS manuals and lack of training.
  - WalterBright 8y ago
    In the case of runaway stab trim, this is not correct. Runaway stab trim is trained for, should be obvious, and the corrective action is in the manual and pilots are trained to handle it.
    - tigershark 8y ago
      Yeah, it’s so obvious that pretty much every country in the world agreed to ground that killing machine...
      - jonsen 8y ago
        Effectively they are also grounding untrained pilots.
    - lostmyoldone 8y ago
      If runaway stab trim caused by MCAS is indeed what's happened it might not have been obvious enough. It could well be that it is obvious for anyone with the proper training, but then maybe not all airline pilots get the proper training? Or if they have the training but are pushed to hard in the name of cutting costs, and profits? However, if it indeed was expected to be obvious to all pilots, why even - as I understand it - have the warning on the optional HUD? Seems like bad safety engineering to have extraneous warnings possibly increasing cognitive load in a a crisis situation.
- zaphirplane 8y ago
  Perhaps there is some inconsistencies between pilot training, work ethics in staying up to date, reaction under extreme stress

WalterBright 8y ago

Pilots are trained in how to disable it - the stab trim cutoff switches are right there on the console. The mystery is why the pilots didn't follow their training.

mikejb 8y ago
I've seen different reports about what's in the training. I think the challenge here is to detect that the system is running haywire and then disabling it. It's not a common situation, never trained, and possibly only something the pilot might have read on the way to the airport. Not ideal for a high-stress situation.
- WalterBright 8y ago
  On the 737 airplanes, when the stab trim is running a wheel on the side of the center console turns and makes a loud clacking sound. It is designed to be obvious. You can see a picture of the wheel here: https://www.quora.com/What-are-the-spinning-wheels-in-an-airliners-cockpit https://www.quora.com/What-are-the-spinning-wheels-in-an-air...
  - mikejb 8y ago
    You have to make the connection though: that clacking noise is probably that new system I read about doing something. Then you have to determine whether that system is the cause of the problem, and whether disabling the system will either fix the issue, or possibly make it worse.
    - WalterBright 8y ago
      The clacking sound happens whenever the stabilizer trim is in operation, which is frequently, and has been in 737s for decades. The pilots would be very familiar with the sound and what it represents. The trim wheel also spins when the trim is running, a large and obvious indication (I posted a link to a photo of it).
lysp 8y ago
https://www.aviation24.be/manufacturers/boeing/boeing-737-max-automatic-stall-prevention-system-mcas-not-in-flight-crew-operations-manual-fcom/ https://www.aviation24.be/manufacturers/boeing/boeing-737-ma... > Boeing issued a multi-operator message (MOM) explaining the MAX’s manoeuvring characteristics augmentation system (MCAS) “commands nose-down stabilizer” in certain flight profiles using “input data and other airplane systems.” MCAS is operated by the flight control computer and “activated without pilot input and only operates in manual, flaps-up flight,” and MCAS is not part of previous 737 designs. > The Allied Pilots Association (APA) told American Airlines (AA) pilots in a message on its website. “It is not in the AA 737 Flight Manual Part 2, nor is there a description in the Boeing FCOM. It will be soon.” > A multi-page document issued by the airline’s flight operations department that highlights the differences between the MAX and 737 NG does not mention MCAS or any other changes to the auto-trim system. > A multi-operator message (MOM) from Boeing on Nov. 6 cautioned that “an erroneous AOA” can trigger automatic nose-down pitch-trim. There are lots on indications that at least in the Lion Air case it was not in manuals or communications to pilots. Further here: https://www.wsj.com/articles/boeing-withheld-information-on-737-model-according-to-safety-experts-and-others-1542082575 https://www.wsj.com/articles/boeing-withheld-information-on-... https://outline.com/https://www.wsj.com/articles/boeing-withheld-information-on-737-model-according-to-safety-experts-and-others-1542082575 https://outline.com/https://www.wsj.com/articles/boeing-with...
- WalterBright 8y ago
  For a pilot ignorant of MCAS, what he'd see is uncommanded stabilizer trim movement. The training says to stop that by throwing the stab trim cutoff switches. They're prominently located on the center console. The pilot of the same airplane on the prior flight to the Lion Air crash did just that.
  - taneq 8y ago
    Wait, are you saying that the aircraft actually exhibited the same failure in the prior flight but the pilot overrode it, and then they let it take off again without warning the new pilots?
pauljurczak 8y ago
It's easy to say with the hind sight. When you are flying a plane, which starts to behave abnormally, you have to analyze hundreds of possible causes and try not to kill everyone on board at the same time. There are multiple reports about poor MCAS manuals and lack of training.
- WalterBright 8y ago
  In the case of runaway stab trim, this is not correct. Runaway stab trim is trained for, should be obvious, and the corrective action is in the manual and pilots are trained to handle it.
  - tigershark 8y ago
    Yeah, it’s so obvious that pretty much every country in the world agreed to ground that killing machine...
    - jonsen 8y ago
      Effectively they are also grounding untrained pilots.
  - lostmyoldone 8y ago
    If runaway stab trim caused by MCAS is indeed what's happened it might not have been obvious enough. It could well be that it is obvious for anyone with the proper training, but then maybe not all airline pilots get the proper training? Or if they have the training but are pushed to hard in the name of cutting costs, and profits? However, if it indeed was expected to be obvious to all pilots, why even - as I understand it - have the warning on the optional HUD? Seems like bad safety engineering to have extraneous warnings possibly increasing cognitive load in a a crisis situation.
zaphirplane 8y ago
Perhaps there is some inconsistencies between pilot training, work ethics in staying up to date, reaction under extreme stress