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"No it isn't. It is a stable design. To claim otherwise misunderstands the term." Well, then we just disagree on the term. "Because the 737 Max had been outfi

"No it isn't. It is a stable design. To claim otherwise misunderstands the term." Well, then we just disagree on the term. "Because the 737 Max had been outfitted with larger new engines that could cause its nose to pitch dangerously skyward" (Source: https://www.nytimes.com/2019/03/14/opinion/business-economics/boeing-737-max.html https://www.nytimes.com/2019/03/14/opinion/business-economic... ) I don't call this a stable design. You can crash every airplane (e.g. "stall") but the plane should not enter an unsafe flying mode during normal flying behavior. No good engineer would have chosen that design. An airplane that can only be kept in the air with a computer must not be necessary unsafe. As far as I know the stealth bombers can only fly with massive computer help. But this must be a rational, conscious decision and the pilot must be aware of this. Not a quick fix to stick huge engines on a plane that was designed in the 60ies. I can put a Ferrari engine in a Mercedes from the 20ies. And I am sure it will drive. But the car, the brakes, everything is not made for this combination.

WalterBright 7y ago
> Well, then we just disagree on the term. When you're talking aeronautics, you should use the definition used by aeronautical engineers.
- jayalpha 7y ago
  The author in the NYT is a pilot. "Unfortunately, in the case of the 737 Max, it seems that Boeing has built a plane with a fundamental aeronautical issue that it thought would be resolved by adding a new automated system. "
  - deleted 7y ago
    [deleted]
  - WalterBright 7y ago
    Mr. Wise is indeed a pilot, but not one for jetliners. Flying a high altitude jetliner is very different from flying a Cessna. Mr. Wise does not have a degree in aeronautical engineering, nor in engineering of any sort. http://jeffwise.net/about-the-author/ http://jeffwise.net/about-the-author/
  - FabHK 7y ago
    Note that he doesn't use the term "stable" incorrectly. He points out an issue (that would indeed preclude the 737 Max from being certified without MCAS, as I understand it).
    - WalterBright 7y ago
      > that would indeed preclude the 737 Max from being certified without MCAS It would not prevent certification. It would require pilots to be separately rated for the MAX.
      - FabHK 7y ago
        That's not my understanding. I understand (and PuffinBlue concurs, if I'm not mistaken) that the 737 Max would not be certifiable without MCAS.
PuffinBlue 7y ago
> Because the 737 Max had been outfitted with larger new engines that could cause its nose to pitch dangerously skyward I'm stretching to the limit of my understanding of the matter here but I'll try outline why that statement is misleading. To put it in basic terms, you want to avoid a situation where an aircraft can enter an 'accelerated stall'. I believe this to be the correct term. In the original documents to the FAA I think the exact quote of the wording was: > MCAS “was added to address potential nose-up pitching moment at high angles of attack at high airspeeds outside the normal flight envelope.” Specifically this was in a banked downward spiral, known as a 'wind-up turn' where instead of maintaining constant resistance on the control column, at a certain point the resistance to pulling back would lessen and this could allow entering an accelerated stall situation. NOTE - from there I think MCAS ballooned into other areas of control, but I believe that the original intent of MCAS. The reason this possibility arose was because the engines were moved forward, altering their thrush relationship to the center of gravity of the aircraft and, as I understand it, by the design of the engine pods themselves (flat bottomed and can add lift). Under normal flight conditions an airliner would never enter a wind up turn, but it is a test that must be passed as part of the certification process, as far as I understand it. So yes, there are circumstances where the characteristics of the 737 Max can make it easier to enter a dangerous nose up pitch. Note only 'easier' i.e. less resistance on the control column so pulling back with the same force in the same circumstance through the duration of a wind-up turn could allow it to be easier to enter a stall state. But in normal flight and under conditions an airliner would fly, the nose up pitching moment caused by the engines would be entirely 'normal' and in line with what many airliners do (i.e. control column resistance would remain linear) but would have caused the handling to be different is very specific circumstances and so would have needed a new type rating and pilot training to address. MCAS sought to avoid the need for that type rating by automatically applying trim to prevent any situation arising, even outside the normal flight parameters, that would cause different handling characteristics. Again, none of this relates to stability/instability as was my original point. Sources: I read about this level of detail here quite a long time ago: 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... In looking up this article I found this aviation.stackexchange.com answer that also comments on this: https://aviation.stackexchange.com/questions/66799/what-is-mcas-trying-to-fix-on-b737-max https://aviation.stackexchange.com/questions/66799/what-is-m...

WalterBright 7y ago

> Well, then we just disagree on the term. When you're talking aeronautics, you should use the definition used by aeronautical engineers.

jayalpha 7y ago
The author in the NYT is a pilot. "Unfortunately, in the case of the 737 Max, it seems that Boeing has built a plane with a fundamental aeronautical issue that it thought would be resolved by adding a new automated system. "
- deleted 7y ago
  [deleted]
- WalterBright 7y ago
  Mr. Wise is indeed a pilot, but not one for jetliners. Flying a high altitude jetliner is very different from flying a Cessna. Mr. Wise does not have a degree in aeronautical engineering, nor in engineering of any sort. http://jeffwise.net/about-the-author/ http://jeffwise.net/about-the-author/
- FabHK 7y ago
  Note that he doesn't use the term "stable" incorrectly. He points out an issue (that would indeed preclude the 737 Max from being certified without MCAS, as I understand it).
  - WalterBright 7y ago
    > that would indeed preclude the 737 Max from being certified without MCAS It would not prevent certification. It would require pilots to be separately rated for the MAX.
    - FabHK 7y ago
      That's not my understanding. I understand (and PuffinBlue concurs, if I'm not mistaken) that the 737 Max would not be certifiable without MCAS.

PuffinBlue 7y ago

> Because the 737 Max had been outfitted with larger new engines that could cause its nose to pitch dangerously skyward I'm stretching to the limit of my understanding of the matter here but I'll try outline why that statement is misleading. To put it in basic terms, you want to avoid a situation where an aircraft can enter an 'accelerated stall'. I believe this to be the correct term. In the original documents to the FAA I think the exact quote of the wording was: > MCAS “was added to address potential nose-up pitching moment at high angles of attack at high airspeeds outside the normal flight envelope.” Specifically this was in a banked downward spiral, known as a 'wind-up turn' where instead of maintaining constant resistance on the control column, at a certain point the resistance to pulling back would lessen and this could allow entering an accelerated stall situation. NOTE - from there I think MCAS ballooned into other areas of control, but I believe that the original intent of MCAS. The reason this possibility arose was because the engines were moved forward, altering their thrush relationship to the center of gravity of the aircraft and, as I understand it, by the design of the engine pods themselves (flat bottomed and can add lift). Under normal flight conditions an airliner would never enter a wind up turn, but it is a test that must be passed as part of the certification process, as far as I understand it. So yes, there are circumstances where the characteristics of the 737 Max can make it easier to enter a dangerous nose up pitch. Note only 'easier' i.e. less resistance on the control column so pulling back with the same force in the same circumstance through the duration of a wind-up turn could allow it to be easier to enter a stall state. But in normal flight and under conditions an airliner would fly, the nose up pitching moment caused by the engines would be entirely 'normal' and in line with what many airliners do (i.e. control column resistance would remain linear) but would have caused the handling to be different is very specific circumstances and so would have needed a new type rating and pilot training to address. MCAS sought to avoid the need for that type rating by automatically applying trim to prevent any situation arising, even outside the normal flight parameters, that would cause different handling characteristics. Again, none of this relates to stability/instability as was my original point. Sources: I read about this level of detail here quite a long time ago: 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... In looking up this article I found this aviation.stackexchange.com answer that also comments on this: https://aviation.stackexchange.com/questions/66799/what-is-mcas-trying-to-fix-on-b737-max https://aviation.stackexchange.com/questions/66799/what-is-m...