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> No-one's suggesting that large turbofan aircraft with pitch-up behaviour are inherently unsafe It is as long it keeps 737 MAX body and engines and doesn’t ha

by acqq 7y ago

> No-one's suggesting that large turbofan aircraft with pitch-up behaviour are inherently unsafe It is as long it keeps 737 MAX body and engines and doesn’t have something like MCAS I.e. Inherently unsafe under conditions under which MCAS was supposed to turn on when properly functioning. The certification requirements are the result of the clear safety goals not something invented “just so.”

salawat 7y ago
MCAS was a type certificate hack. The poster you're responding to is right; there isn't anything wrong with the behavior given the right training. It's just that the investment in that training, and extra certification hoops to jump through would have made WhateveroModelNumberus MAX a non-starter. It had to be a 737 to work at all.
- acqq 7y ago
  > there isn't anything wrong with the behavior given the right training. The behaviour without MCAS on 737 MAX is that minimal movements of pilot’s controls effectively activate what would be considered “amplification” of nose up movement, resulting in an uncontrollable plane and sure crash. It’s definitely not something that pilots or passengers should be exposed to: being punished for approaching more dangerous position by plane forcing a deadly outcome. Training pilots to not to move even minimally the controls in the “wrong” direction is maybe technically possible but in practice still totally wrong: It’s comparable to what Boeing told everybody before Ethiopian crash, and their attempts to blame the pilots. In reality, the pilots had almost no chance to rescue themselves and the plane. In engineering the “positive feedback loops” (amplification of control inputs) are bad the “negative feedback loops” (correction of the input) are good. The functioning MCAS provides a correction. The plane without MCAS amplification. Badly functioning MCAS also amplification and crash. That's why the wrong behavior was regulated, and that's why it had to be fulfilled for the certification. It’s that easy. To convince me that 737 MAX without the "properly functioning MCAS" isn't inherently dangerous under higher angles of attack you'd have to provide some explicit proofs.
  - caconym_ 7y ago
    > To convince me that 737 MAX without the "properly functioning MCAS" isn't inherently dangerous under higher angles of attack you'd have to provide some explicit proofs. I am legitimately curious, do you have any explicit proofs of the converse, that (as you say) "the behaviour without MCAS on 737 MAX is that minimal movements of pilot’s controls effectively activate what would be considered “amplification” of nose up movement, resulting in an uncontrollable plane and sure crash"? The standard should be that a an unimpaired pilot properly trained in flying the aircraft will normally (practically) be in no danger of a "sure crash".
    - acqq 7y ago
      > The standard should be that a an unimpaired pilot properly trained in flying the aircraft will normally (practically) be in no danger of a "sure crash". Exactly. And under that assumptions 737 MAX with no MCAS was never certified. Boeing didn't even want to admit that MCAS even exists to avoid even showing the flight characteristic of the plane "without MCAS." It's on Boeing to prove "737 MAX without MCAS" is safe, and up to now they did all they could to avoid that, and I expect they'll do more of that unless there is a pressure outside of both Boeing and FAA.
      - caconym_ 7y ago
        But there is a distinction between never getting certified because it is not safe, and never getting certified because Boeing didn't want to certify it as a new aircraft, because they wanted to sell it with the value proposition of not having to train pilots on a new type. Is that not correct? So it seems to me that the discussion in this subthread is really around that point: could the aircraft have been certified as a new type without the horribly dangerous MCAS system in place to paper over the change in flight characteristics? You seem to be saying no, and the other guy says yes, but you seem more to be talking past each other than offering proof of your assertions. He at least did point out (though without citing any proof, I think) that the 777 had a similar issue and was certified anyway (and I don't believe 777s have been falling out of the sky because of it). But, obviously, this is a different aircraft.

by acqq 7y ago

salawat 7y ago

MCAS was a type certificate hack. The poster you're responding to is right; there isn't anything wrong with the behavior given the right training. It's just that the investment in that training, and extra certification hoops to jump through would have made WhateveroModelNumberus MAX a non-starter. It had to be a 737 to work at all.

acqq 7y ago
> there isn't anything wrong with the behavior given the right training. The behaviour without MCAS on 737 MAX is that minimal movements of pilot’s controls effectively activate what would be considered “amplification” of nose up movement, resulting in an uncontrollable plane and sure crash. It’s definitely not something that pilots or passengers should be exposed to: being punished for approaching more dangerous position by plane forcing a deadly outcome. Training pilots to not to move even minimally the controls in the “wrong” direction is maybe technically possible but in practice still totally wrong: It’s comparable to what Boeing told everybody before Ethiopian crash, and their attempts to blame the pilots. In reality, the pilots had almost no chance to rescue themselves and the plane. In engineering the “positive feedback loops” (amplification of control inputs) are bad the “negative feedback loops” (correction of the input) are good. The functioning MCAS provides a correction. The plane without MCAS amplification. Badly functioning MCAS also amplification and crash. That's why the wrong behavior was regulated, and that's why it had to be fulfilled for the certification. It’s that easy. To convince me that 737 MAX without the "properly functioning MCAS" isn't inherently dangerous under higher angles of attack you'd have to provide some explicit proofs.
- caconym_ 7y ago
  > To convince me that 737 MAX without the "properly functioning MCAS" isn't inherently dangerous under higher angles of attack you'd have to provide some explicit proofs. I am legitimately curious, do you have any explicit proofs of the converse, that (as you say) "the behaviour without MCAS on 737 MAX is that minimal movements of pilot’s controls effectively activate what would be considered “amplification” of nose up movement, resulting in an uncontrollable plane and sure crash"? The standard should be that a an unimpaired pilot properly trained in flying the aircraft will normally (practically) be in no danger of a "sure crash".
  - acqq 7y ago
    > The standard should be that a an unimpaired pilot properly trained in flying the aircraft will normally (practically) be in no danger of a "sure crash". Exactly. And under that assumptions 737 MAX with no MCAS was never certified. Boeing didn't even want to admit that MCAS even exists to avoid even showing the flight characteristic of the plane "without MCAS." It's on Boeing to prove "737 MAX without MCAS" is safe, and up to now they did all they could to avoid that, and I expect they'll do more of that unless there is a pressure outside of both Boeing and FAA.
    - caconym_ 7y ago
      But there is a distinction between never getting certified because it is not safe, and never getting certified because Boeing didn't want to certify it as a new aircraft, because they wanted to sell it with the value proposition of not having to train pilots on a new type. Is that not correct? So it seems to me that the discussion in this subthread is really around that point: could the aircraft have been certified as a new type without the horribly dangerous MCAS system in place to paper over the change in flight characteristics? You seem to be saying no, and the other guy says yes, but you seem more to be talking past each other than offering proof of your assertions. He at least did point out (though without citing any proof, I think) that the 777 had a similar issue and was certified anyway (and I don't believe 777s have been falling out of the sky because of it). But, obviously, this is a different aircraft.