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Wow. Isn't this a massive retreat on their part, which negates a lot of the business justification for the MAX? If they're going to require MAX-specific simula

by Seenso 7y ago

Wow. Isn't this a massive retreat on their part, which negates a lot of the business justification for the MAX? If they're going to require MAX-specific simulator training, could they just rip out MCAS and be done with it?

robdachshund 7y ago
Not when you've modified your center of thrust and center of mass and made an airplane that is no longer aerodynamic.
mannykannot 7y ago
I think that is unlikely. MCAS was not put in place to avoid training, it is there to fix what would otherwise be an unacceptable handling issue. It was attempting to add MCAS without training that led to all the problems (not mentioning it, using only a single sensor...), and if Boeing could have done without it, it would have done so.
- gizmo385 7y ago
  My understanding is that MCAS wasn't there to fix an unacceptable handling issue, but to make the 737 MAX have similar flight characteristics to previous 737 models. I didn't think there was anything about the plane itself that was fundamentally unstable or unsafe, it's just that a plane that flew with different flight characteristics wouldn't get grandfathered into the cert.
  - mannykannot 7y ago
    It wasn't just that the handling was unlike a 737 NG, it was considered unacceptable in its own right: https://leehamnews.com/2019/02/08/bjorns-corner-pitch-stability-part-9/ https://leehamnews.com/2019/02/08/bjorns-corner-pitch-stabil... https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the... Also, from the current article: "The crashes were caused in part by new software on the Max, MCAS, which triggered erroneously and sent the planes into nose dives. Boeing has developed a fix for the software..." (my emphasis.) Boeing would not be doing that now, if the only purpose of MCAS was to avoid training, with everything being otherwise acceptable without it.
  - salawat 7y ago
    It was both actually. It would have failed CFR 25.175 or some such, on the wind-up turn when the control stick force curve inverted at high AoA due to extra nacelle lift. Happens in high speed wind-ups, and low speed regimes as well, which is a no-no for civilian transport aircraft. They had to take care of that to even get it certified for people carrying, and do it in a way that wouldn't cause the FAA to come back and require simulator training. That caused the single-sensor input decision, which ended up representing a single point of failure with catastrophic consequences in it's original form. Another no-no. The other facet you mentioned, was the reasoning behind the system (to get it grandfathered), and to make it possible to avoid simulator training, and only have to provide pilot's with a 1 hour glorified PowerPoint course to bring them up to speed with handling the aircraft, which had no mention of the MCAS system to boot. It isn't exactly the easiest thing to keep track of.
- htk 7y ago
  Actually what I read was that the MCAS system was there to make the MAX fly exactly light a non-MAX 747, and thus avoiding the need for any additional training.
  - mark-r 7y ago
    Given that it didn't work, there's no question that additional training will be required. The question is the nature of the training. If they fix MCAS, the training will be how to recognize and compensate for a failure. If they removed MCAS, it will be how to fly the plane with different characteristics. It's unclear to me how much difference there would be in FAA approval between the two.

by Seenso 7y ago

robdachshund 7y ago

Not when you've modified your center of thrust and center of mass and made an airplane that is no longer aerodynamic.

mannykannot 7y ago

I think that is unlikely. MCAS was not put in place to avoid training, it is there to fix what would otherwise be an unacceptable handling issue. It was attempting to add MCAS without training that led to all the problems (not mentioning it, using only a single sensor...), and if Boeing could have done without it, it would have done so.

gizmo385 7y ago
My understanding is that MCAS wasn't there to fix an unacceptable handling issue, but to make the 737 MAX have similar flight characteristics to previous 737 models. I didn't think there was anything about the plane itself that was fundamentally unstable or unsafe, it's just that a plane that flew with different flight characteristics wouldn't get grandfathered into the cert.
- mannykannot 7y ago
  It wasn't just that the handling was unlike a 737 NG, it was considered unacceptable in its own right: https://leehamnews.com/2019/02/08/bjorns-corner-pitch-stability-part-9/ https://leehamnews.com/2019/02/08/bjorns-corner-pitch-stabil... https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the... Also, from the current article: "The crashes were caused in part by new software on the Max, MCAS, which triggered erroneously and sent the planes into nose dives. Boeing has developed a fix for the software..." (my emphasis.) Boeing would not be doing that now, if the only purpose of MCAS was to avoid training, with everything being otherwise acceptable without it.
- salawat 7y ago
  It was both actually. It would have failed CFR 25.175 or some such, on the wind-up turn when the control stick force curve inverted at high AoA due to extra nacelle lift. Happens in high speed wind-ups, and low speed regimes as well, which is a no-no for civilian transport aircraft. They had to take care of that to even get it certified for people carrying, and do it in a way that wouldn't cause the FAA to come back and require simulator training. That caused the single-sensor input decision, which ended up representing a single point of failure with catastrophic consequences in it's original form. Another no-no. The other facet you mentioned, was the reasoning behind the system (to get it grandfathered), and to make it possible to avoid simulator training, and only have to provide pilot's with a 1 hour glorified PowerPoint course to bring them up to speed with handling the aircraft, which had no mention of the MCAS system to boot. It isn't exactly the easiest thing to keep track of.
htk 7y ago
Actually what I read was that the MCAS system was there to make the MAX fly exactly light a non-MAX 747, and thus avoiding the need for any additional training.
- mark-r 7y ago
  Given that it didn't work, there's no question that additional training will be required. The question is the nature of the training. If they fix MCAS, the training will be how to recognize and compensate for a failure. If they removed MCAS, it will be how to fly the plane with different characteristics. It's unclear to me how much difference there would be in FAA approval between the two.