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Lion Air 737-Max missing, presumed down in the sea near CGK (Jakarta)

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  • ATLcrew
    replied
    Originally posted by Evan View Post
    You still don’t get it. This isn’t an aviation matter. It’s a matter of reckless management serving investor relations at the expense of safety. It’s a sort of industrial epidemic lately. And yes, the Times is a good place to find those truths.
    Noted.

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  • Evan
    replied
    Originally posted by ATLcrew View Post
    Oh aviation matters? I don't think so, Tim.
    You still don’t get it. This isn’t an aviation matter. It’s a matter of reckless management serving investor relations at the expense of safety. It’s a sort of industrial epidemic lately. And yes, the Times is a good place to find those truths.

    Leave a comment:


  • BoeingBobby
    replied
    Originally posted by ATLcrew View Post
    Then why, in Saint Agatha's name, did you let him anywhere near the sim?
    Not sure I have an answer for that. I will tell you that my friend that arranged it and ran the Sim, turned down the invitation for dinner afterwards. He was not a happy camper.

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  • 3WE
    replied
    From everything I’ve learned about MCAS this far, it seems that it was also REQUIRED to compensate for a serious safety concern at the limits of the safe envelope
    Dittos to Gabriel's comments: Source for this, or it's not true.

    There may be SOME validity, but conversely, I question whether a slow trim response is really appropriate for an unrecoverable stall...

    If unrecoverable stalls are an issue, I'd think a mega stick pusher might be more called for.

    As Gabbieee has repeatedly stated, the goal to not have special training requirements was very big too.

    I can see where special training to shove HARDER could be avoided with something MCASISH.

    Also, if it's UNRECOVERABLE stall, I'd speculate they would have done double AOA instead of single AOA reading for MCAS...

    If you just want to make it FEEL nicer, then what the heck, only one AOA vane is good enough.

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  • ATLcrew
    replied
    Originally posted by Evan View Post
    The New York Times would be a good place to start.
    Oh aviation matters? I don't think so, Tim.

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  • ATLcrew
    replied
    Originally posted by BoeingBobby View Post
    ...and did I ever mention the fact that when I arranged for Gabriel to get 2 hours in the 74 sim that he showed up an hour and 20 minutes late?
    Then why, in Saint Agatha's name, did you let him anywhere near the sim?

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  • Gabriel
    replied
    Originally posted by Evan View Post
    Ok, let me be more clear on this: certifying the A320 without trim force feedback REQUIRED envelope protections
    Again, not the case with any Boeing, all of them have trim force feedback.

    From everything I’ve learned about MCAS this far, it seems that it was also REQUIRED to compensate for a serious safety concern at the limits of the safe envelope
    I am eager to find a source for that.

    All airplanes with underslung engines have a strong tendency to pitch up when power is added from very low thrust to very high thrust especially at low airspeed and high AoAs. There were even serious incidents with different airplanes where control was lost due to this combined with improper pilot handling of the situation. The fact that the MAX has a stronger effect than the NG doesn't per se make it a more serious safety concern than it is in other types. However, it may imply specific training that Boeing was trying to avoid.

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  • Gabriel
    replied
    Originally posted by Evan View Post
    You need to read up more on MCAS. There were pitch behaviors created by the aerodynamic effects of the repositioned nacelles that resulted in serious concerns during approach to stall. The aircraft in this state was considered unsafe.
    Source please. It can be the case, but I could never find clarity on whether it was a feature that was required for certification (at any level) or if it was a feature that allowed commonality with the NG.

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  • Evan
    replied
    Originally posted by Schwartz View Post
    The Airbus control design is fundamentally different and a loose comparison is not valid. Remember, MCAS may have only been necessary to make the MAX feel exactly like the old 737, so no new training was required. I would not be surprised, if they mandate new training for the MAX now. On it's own, the MCAS may not have been required as a safety issue. To be fair, I'm not certain of that, but again, I don't think your comparison is valid. It seems to me, the plane is entirely flyable without MCAS and the override if properly programmed is something the pilots train for.
    You need to read up more on MCAS. There were pitch behaviors created by the aerodynamic effects of the repositioned nacelles that resulted in serious concerns during approach to stall. The aircraft in this state was considered unsafe. There were concerns that a recovery might be overcome by these effects. And, while more complexity does increase the risk of a single failure, triple modular redundancy DECREASES the consequences of a single failure and INCREASES the robustness of the larger system, which is all that matters.

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  • Evan
    replied
    Originally posted by Gabriel View Post
    Evan, I am not stating that it is unreasonable to require triple redundancy for the MCAS. What I am saying is that using the A320 certification as a basis for claiming so is not reasonable.

    In your own words:



    That's not the case with Boeing, with ANY Boeing, even with the previous version of the MCAS which was horrible and unacceptable for other reasons.
    Ok, let me be more clear on this: certifying the A320 without trim force feedback REQUIRED envelope protections, as they compensated for a serious safety concern (the A320 can not be dispatched for revenue service in alternate law). Therefore, triple modular redundancy was REQUIRED for air data systems that those protections depend on. Airbus FBW protections are fail-operational by design.

    From everything I’ve learned about MCAS this far, it seems that it was also REQUIRED to compensate for a serious safety concern at the limits of the safe envelope and the -MAX cannot be dispatched for revenue service with MCAS inop. Yet MCAS was designed (and certified) without redundancy and now redesigned to be fail-safe, not fail-operational, after a single-point failure.

    That seems a lot like a double standard to me. And I still would like to know why they didn’t require it to be fail-operational.

    Leave a comment:


  • Gabriel
    replied
    Originally posted by Evan View Post
    The odds of an A320 having a bad ‘final AoA’ are extremely remote, and this was the standard used to certify it. I don’t recall the actual odds used, but they were considered, for all intents and purposes, impossible (barring any maintenance stoogery, of course). Even so, there are procedures to quickly degrade to alternate law without losing controllability or FBW methodology (whether those procedures are widely known is another story). But the point is, every REASONABLE precaution was taken to ensure that envelope protections required to certify the aircraft would be fail-operational following the failure of a single air-data source.

    As I understand it, MCAS will now be inop following the failure of a single air-data source. It is now fail-safe but not fail-operational. That means the airplane, by certification criteria, is potentially unsafe (and we have learned many times over that aviation disasters often are the result of a rare but still foreseeable combination of failures and pilot error).

    So the question I would like answered is: why is requiring triple modular redundancy for MCAS unreasonable in an age where it is the standard for critical systems?
    Evan, I am not stating that it is unreasonable to require triple redundancy for the MCAS. What I am saying is that using the A320 certification as a basis for claiming so is not reasonable.

    In your own words:

    The A320 needed three AoA sensors to achieve certification. Why? Because AoA data can override pilot inputs.
    That's not the case with Boeing, with ANY Boeing, even with the previous version of the MCAS which was horrible and unacceptable for other reasons.

    Leave a comment:


  • Schwartz
    replied
    Originally posted by Black Ram View Post
    Stuff like that has happened, though not close to the ground. And usually you wouldn't expect AoA vanes contaminated with water to freeze when the plane is close to the ground as opposed to being at altitude. But there is a procedure to deal with this and it has been used successfully, though not avoiding a scary incident.

    The point is, I and many others feel Boeing is still moving in the wrong direction. At a time when 3 AoA vanes have been shown not to be bulletproof, when some airplanes come standard with 4 AoAs, Boeing is fixing a troubled system by keeping its 2 AoA vanes.
    That logic is predicated on MCAS being considered an essential safety system (vs a safety hazzard as it clearly was initially implemented). I have a feeling it is not considered such. I believe it was added to make it feel more like the old models. More sensors increases the odds of a failure and depending on the nature of typical failures for this type of sensor, perhaps it isn't all that unlikely that 2 fail close together.

    Leave a comment:


  • Schwartz
    replied
    Originally posted by Evan View Post
    These terms tend to be somewhat oblique depending on the context in which they are used, but the only term that matters here is an engineering term for designed redundancy: Triple modular redundancy. MCAS should be required to have triple modular redundancy, as the Airbus envelope protections were required to have. The apparent reasoning behind designing MCAS with no redundancy had to do with remaining in the NG certification. I suspect there is some behind the scenes negotiating going on to resolve the MCAS issues and get the fleet back in service that centers on not triggering additional certification. Perhaps adding a third vane and more robust comparator logic would do that. But the double-standard here is glaring.
    More complexity does not always = more safety. More parts certainly increases the odds of a failure in that system. I would venture to say that the odds of 2 independent failures of those sensors (meaning no MCAS) is far more likely than two simultaneously failing to the exact same values.

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  • Schwartz
    replied
    Originally posted by Evan View Post
    The A320 needed three AoA sensors to achieve certification. Why? Because AoA data can override pilot inputs. They needed that extra vane to allow the system to vote out a faulty vane with the two in agreement, to be assuredly safe.

    Sure. Pilots can always follow a procedure to override those system protections, but just requiring them to establish SA and take the correct steps carries a threat of upset or distraction. To be truly safe, any system that can override pilot commands must remain fail-passive after a single-point failure. Fail passive means the system retains redundancy. That requires three sensors.

    Boeing will get away with two. If one fails, the MCAS system will be unavailable. Now the risk that made MCAS necessary in the first place is present: you have a 737-MAX without MCAS. It may now be unrecoverable in certain stall avoidance situations.
    The Airbus control design is fundamentally different and a loose comparison is not valid. Remember, MCAS may have only been necessary to make the MAX feel exactly like the old 737, so no new training was required. I would not be surprised, if they mandate new training for the MAX now. On it's own, the MCAS may not have been required as a safety issue. To be fair, I'm not certain of that, but again, I don't think your comparison is valid. It seems to me, the plane is entirely flyable without MCAS and the override if properly programmed is something the pilots train for.

    Leave a comment:


  • Schwartz
    replied
    Originally posted by Black Ram View Post
    Oh, how nice. Very grateful to Boeing for that.

    I just thought that now, when this has dragged for like 8 months with practically no end in sight (at least until the end of the year), that the "defend them at all cost" people would be more chill. Not that they are really saying anything.

    Boeingbob, we miss you!

    Defend at all costs, please. Instead of waxing poetic why don't you point out the flaw in the logic? Or is that just rhetoric?

    Leave a comment:

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