4 ms·

https://www.aviation24.be/manufacturers/boeing/boeing-737-max-automatic-stall-prevention-system-mcas-not-in-flight-crew-operations-manual-fcom/ https://www.avia

by 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?
  - WalterBright 8y ago
    That's what I read in the newspaper at the time.
  - RidingPegasus 8y ago
    The previous flight before the disaster actually made an emergency distress call to return back but after disabling the automatic system decided to continue onwards and did so with no further problems in the flight. Pilots are given all this information and are meant to read it before takeoff but there is no way to enforce that. Maintenance logs show the AoA vane was replaced, but Lion Air has a sketchy history with maintenance and what's written in the logs doesn't always reflect the reality, they are one of the cheapest airlines in the world and need to keep planes flying. I'd say that's likely the root of the issue combined with pilots not following the procedure books when faced with anomalous behavior. https://www.airlineratings.com/news/lion-air-plane-fault-four-previous-flights/ https://www.airlineratings.com/news/lion-air-plane-fault-fou...
- DanielBMarkham 8y ago
  So this was just a Darwinian exercise, where the plane kept malfunctioning until it found a crew that responded incorrectly? I hear you about runaway trim, but it seems that you are quite focused on the blades of grass and not looking so much at the lawn. Nobody has given me an adequate answer to one simple question: what is the indicator the industry will use to determine when it has made the cockpits so complex that the complexity itself becomes a danger? Because we can play this game for a few decades more: manufacturers mod-up old planes with new software, extra training is added to the pilot's schedules, there are crashes where commenters in good faith can say "but that's an obvious part of any pilot's training". Repeat and rinse -- with the proviso that with each round the overall complexity continues to increase. Technology developers, more than anyone else, are quite cognizant of the fact that we can create technology we ourselves cannot understand. Perhaps the aviation industry and the associated regulators somehow missed this?
  - WalterBright 8y ago
    I view it a bit like an engine failure. Jets have twin engines so they can keep flying if one quits. Pilots are trained to deal with an engine out. It doesn't particularly matter why the engine quit, just that the pilots know how to fly on one engine. The pilots are supposed to know how to deal with runaway stab trim. It doesn't matter why it was running away, just that the pilots know how to deal with it. Whether it was MCAS or the autopilot or a short circuit, does not matter. After it is safely back on the ground, then the specific cause of the failure can be ascertained and corrected.
    - DanielBMarkham 8y ago
      With respect, I believe you are viewing this in far too simplistic a manner. Let's take engine failure. When you're training twins, you're going to get one of the engines pulled on you quite a bit -- usually when you least expect it. That's because a lot of people died educating the industry to how important it is to be able to handle engine failure in all flight modes: takeoff, climb-out, cruise-climb, and so on. That reaction sequence has to be drilled into pilots to such a degree that there's no thinking involved. But runaway trim? Seriously? Sure, you'll get the training, but in all modes of flight? Drilled into you until you can handle it in your sleep? No way. That's preposterous. We _thought_ we knew that those kinds of problems don't happen at weird times to cause people to die. So if you're flying along in cruise and you've got a runaway trim, somebody does a mental lookup -- which might take 3 or 4 seconds -- locates the breaker, then throws it. We do this other type of training a lot too, but there are tons of subsystems on your average commercial airliner. We don't train for that the way we train for engine failure. We've got huge reams of checklists in commercial cockpits dedicated to this kind of slower problem-solving. So yes, in both cases a person could argue that training was either not given or not implemented by the crew. But that ignore the realistic limitations of trying to train crews on modern equipment. You simply can't do some kind of weird cross-tab grid where everything is trained everywhere and to the same degree. At some point the human factor has to come into play. People aren't robots. It looks like these accidents happened on takeoff/climb-out, one of the most busy and complex things a crew can do (not near the complexity of hand-flying the various instrument approaches, of course). You gotta ask yourself: if I'm watching my turbine numbers, my airspeed, looking for traffic, the copilot's talking to the pax, and so forth? Would I catch a runaway trim right away? More to the point, if I missed it, would the ensuing chaos, _in some cases_ prevent me from being able to cognitively switch back to diagnostic mode? After all, we teach pilot when all else fails, fly the plane first. Add to that systems like MCAS that might exist in the software that the pilots are unaware of? If these accidents turn out to be MCAS/runaway trim related, I would be interested in learning about the crew environment when it happened, specifically other issues taxing the pilots and whether or not the flight director was engaged. So yes, sure. You can train your way out of this. At some point, however, you have to ask if the cost we're paying in lives is worth the lessons we're learning which all seem to boil down to "people are cognitively limited in many ways"
- acqq 8y ago
  > The training says to stop that by throwing the stab trim cutoff switches. They're prominently located on the center console. Not so. First: before Lion Air accident, nobody knew there is a new device that can move the controls that way under these conditions (in that phase of flight etc). The whole device was kept secret by Boeing. Second: the pilots had the trained reflexes what they are to do, and with these, there are more steps to try to overcome such movements before the decision to use the switch. And that’s exactly what the pilots did: attempted the steps before. Which seemed to help, but MCAS kept misbehaving. As the seconds matter, then it was to late.
  - WalterBright 8y ago
    In the Lion Air crash, they struggled with the issue for 11 minutes, not a few seconds. The Ethiopian one, over 6 minutes. The reason the stab trim cutoff switches are there is so the pilot can stop runaway trim. The switches are prominently placed. I expect the failure of the pilots to throw those switches to be prominent in the eventual NTSB report on the accidents. The second accident would be especially perplexing because surely the pilots would have known about the Lion Air crash. If I was a 737MAX pilot, I'd be keenly interested in other crashes in the same aircraft, so I could ensure it wouldn't happen to me. Wouldn't you?
    - chopin 8y ago
      Problem is it seems that it is necessary to offload the stabilizer to be able to trim back. That means pushing the yoke probably being already close to the ground.
      - WalterBright 8y ago
        > Problem is it seems that it is necessary to offload the stabilizer to be able to trim back. The stabilizer trim motors are very powerful and do not need to be offloaded in order to work.
    - acqq 8y ago
      How your “11 minutes” claim fits to this: https://www.nytimes.com/interactive/2019/03/13/world/boeing-737-crash-investigation.html https://www.nytimes.com/interactive/2019/03/13/world/boeing-... Have you seen the graphs? There are 20 seconds intervals. They “fight” the plane, then something (the investigation is still on what) makes it worse again. That’s what confused the pilots: the misbehavior repeats after they think the plane returned to normal.

by lysp 8y ago

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?
- WalterBright 8y ago
  That's what I read in the newspaper at the time.
- RidingPegasus 8y ago
  The previous flight before the disaster actually made an emergency distress call to return back but after disabling the automatic system decided to continue onwards and did so with no further problems in the flight. Pilots are given all this information and are meant to read it before takeoff but there is no way to enforce that. Maintenance logs show the AoA vane was replaced, but Lion Air has a sketchy history with maintenance and what's written in the logs doesn't always reflect the reality, they are one of the cheapest airlines in the world and need to keep planes flying. I'd say that's likely the root of the issue combined with pilots not following the procedure books when faced with anomalous behavior. https://www.airlineratings.com/news/lion-air-plane-fault-four-previous-flights/ https://www.airlineratings.com/news/lion-air-plane-fault-fou...
DanielBMarkham 8y ago
So this was just a Darwinian exercise, where the plane kept malfunctioning until it found a crew that responded incorrectly? I hear you about runaway trim, but it seems that you are quite focused on the blades of grass and not looking so much at the lawn. Nobody has given me an adequate answer to one simple question: what is the indicator the industry will use to determine when it has made the cockpits so complex that the complexity itself becomes a danger? Because we can play this game for a few decades more: manufacturers mod-up old planes with new software, extra training is added to the pilot's schedules, there are crashes where commenters in good faith can say "but that's an obvious part of any pilot's training". Repeat and rinse -- with the proviso that with each round the overall complexity continues to increase. Technology developers, more than anyone else, are quite cognizant of the fact that we can create technology we ourselves cannot understand. Perhaps the aviation industry and the associated regulators somehow missed this?
- WalterBright 8y ago
  I view it a bit like an engine failure. Jets have twin engines so they can keep flying if one quits. Pilots are trained to deal with an engine out. It doesn't particularly matter why the engine quit, just that the pilots know how to fly on one engine. The pilots are supposed to know how to deal with runaway stab trim. It doesn't matter why it was running away, just that the pilots know how to deal with it. Whether it was MCAS or the autopilot or a short circuit, does not matter. After it is safely back on the ground, then the specific cause of the failure can be ascertained and corrected.
  - DanielBMarkham 8y ago
    With respect, I believe you are viewing this in far too simplistic a manner. Let's take engine failure. When you're training twins, you're going to get one of the engines pulled on you quite a bit -- usually when you least expect it. That's because a lot of people died educating the industry to how important it is to be able to handle engine failure in all flight modes: takeoff, climb-out, cruise-climb, and so on. That reaction sequence has to be drilled into pilots to such a degree that there's no thinking involved. But runaway trim? Seriously? Sure, you'll get the training, but in all modes of flight? Drilled into you until you can handle it in your sleep? No way. That's preposterous. We _thought_ we knew that those kinds of problems don't happen at weird times to cause people to die. So if you're flying along in cruise and you've got a runaway trim, somebody does a mental lookup -- which might take 3 or 4 seconds -- locates the breaker, then throws it. We do this other type of training a lot too, but there are tons of subsystems on your average commercial airliner. We don't train for that the way we train for engine failure. We've got huge reams of checklists in commercial cockpits dedicated to this kind of slower problem-solving. So yes, in both cases a person could argue that training was either not given or not implemented by the crew. But that ignore the realistic limitations of trying to train crews on modern equipment. You simply can't do some kind of weird cross-tab grid where everything is trained everywhere and to the same degree. At some point the human factor has to come into play. People aren't robots. It looks like these accidents happened on takeoff/climb-out, one of the most busy and complex things a crew can do (not near the complexity of hand-flying the various instrument approaches, of course). You gotta ask yourself: if I'm watching my turbine numbers, my airspeed, looking for traffic, the copilot's talking to the pax, and so forth? Would I catch a runaway trim right away? More to the point, if I missed it, would the ensuing chaos, _in some cases_ prevent me from being able to cognitively switch back to diagnostic mode? After all, we teach pilot when all else fails, fly the plane first. Add to that systems like MCAS that might exist in the software that the pilots are unaware of? If these accidents turn out to be MCAS/runaway trim related, I would be interested in learning about the crew environment when it happened, specifically other issues taxing the pilots and whether or not the flight director was engaged. So yes, sure. You can train your way out of this. At some point, however, you have to ask if the cost we're paying in lives is worth the lessons we're learning which all seem to boil down to "people are cognitively limited in many ways"
acqq 8y ago
> The training says to stop that by throwing the stab trim cutoff switches. They're prominently located on the center console. Not so. First: before Lion Air accident, nobody knew there is a new device that can move the controls that way under these conditions (in that phase of flight etc). The whole device was kept secret by Boeing. Second: the pilots had the trained reflexes what they are to do, and with these, there are more steps to try to overcome such movements before the decision to use the switch. And that’s exactly what the pilots did: attempted the steps before. Which seemed to help, but MCAS kept misbehaving. As the seconds matter, then it was to late.
- WalterBright 8y ago
  In the Lion Air crash, they struggled with the issue for 11 minutes, not a few seconds. The Ethiopian one, over 6 minutes. The reason the stab trim cutoff switches are there is so the pilot can stop runaway trim. The switches are prominently placed. I expect the failure of the pilots to throw those switches to be prominent in the eventual NTSB report on the accidents. The second accident would be especially perplexing because surely the pilots would have known about the Lion Air crash. If I was a 737MAX pilot, I'd be keenly interested in other crashes in the same aircraft, so I could ensure it wouldn't happen to me. Wouldn't you?
  - chopin 8y ago
    Problem is it seems that it is necessary to offload the stabilizer to be able to trim back. That means pushing the yoke probably being already close to the ground.
    - WalterBright 8y ago
      > Problem is it seems that it is necessary to offload the stabilizer to be able to trim back. The stabilizer trim motors are very powerful and do not need to be offloaded in order to work.
  - acqq 8y ago
    How your “11 minutes” claim fits to this: https://www.nytimes.com/interactive/2019/03/13/world/boeing-737-crash-investigation.html https://www.nytimes.com/interactive/2019/03/13/world/boeing-... Have you seen the graphs? There are 20 seconds intervals. They “fight” the plane, then something (the investigation is still on what) makes it worse again. That’s what confused the pilots: the misbehavior repeats after they think the plane returned to normal.