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> Design changes had forced the addition of this system in order to retain the same type rating because those design changes caused the aircraft to handle diffe

by acqq 7y ago

> Design changes had forced the addition of this system in order to retain the same type rating because those design changes caused the aircraft to handle differently to previous generations. It's not "just to retain the same type rating" that the MCAS worked as it worked. The MCAS, as it was implemented in the planes which crashed had to be implemented for the plane to pass the certification requirements which exist because of the safety. The plane is with its geometry inherently unsafe without some clever devices correcting the "inherent" behavior. Anybody who claims it's not "unstable" does misdirection of clinging to the technicalities of wording of the specific claim (as the plane can be technically-speaking "stable", if nothing unexpected happens, while still being the death trap under non-average conditions, and that's what happened here), as there are more elephants in the room remaining, to be specific: - The regulation exists to provide safety. - Boeing 737 MAX is unsafe to fly without some additional hardware and software which does the compensation. Nobody can sell or certify the Boeing 737 MAX as it is designed without adding some hardware and software that would do something similar to MCAS. "Just turning off MCAS" permanently or "just removing it" makes the plane non certifiable safety-wise, not only losing its "type rating." - MCAS design (its power) wasn't decided only once and implemented. The set of events was that only during the test flights the additional problems with the safety of the plane's response to the commands were detected, and the MCAS revisions added more power to MCAS (and less to the pilots) through the time. The result was that the MCAS which exists on all the planes sold (and the planes crashed) is not the MCAS from the initial specifications or claimed by Boeing after the crashes, as they still quoted the original characteristics. - The goal of Boeing of "keeping the same type rating" is the motivation why they decided to lie about what they implemented and why they actively reduced the safety of the plane to the point of plane actively being the death trap. - Specifically, Boeing misused the trust it had: through the years Boeing was allowed to do more and more of the certification work for their own planes. - Not to mention disastrous public claims there's nothing wrong with their planes even after the two crashes, a lot of information already public and most of the world already having grounded the planes. - Not only Boeing lied about what they did to the FAA and the rest of the world, even after the first crash happened, but while making the plane the engineering decisions have been made more than once just with the goal of preserving the false promises made by the Boeing managers as they have sold the planes: that's why there was the change in the behavior of the switches where there were separate switches before but they changed two switches to behave identically, only to actively hide what the new MCAS was doing. That's why the system was made glaringly non-redundant: adding redundancy would make it obvious that the system was (and it actually was) critical. In short, it's not misinformation that 737 MAX was a death trap made as such under the guidance of Boeing's managers. There are many levels of evilness Boeing managed to achieve in designing the plane and responding to the existing crashes. Some managers should be prosecuted for what they did. If that doesn't happen, the laws should be changed to allow that kind of responsibility the next time, or there will be even more victims.

PuffinBlue 7y ago
> The plane is with its geometry inherently unsafe without some clever devices correcting the "inherent" behavior. No it isn't. It is a stable design. To claim otherwise misunderstands the term. The 737 can be flown just fine without MCAS turned on as it has absolutely nothing to do with making the aircraft stable. Many people seem to want to shit on Boeing for making an 'unstable' aircraft. They simply did not make an unstable aircraft. They made an inherently stable aircraft that handled a little bit differently and then to save money (in order to prevent the need for a new type rating and pilot retraining) they used MCAS to make it handle like previous generations. To repeat, the 737 Max flies just fine without MCAS (indeed previous flights of one of the downed aircraft pulled the stabiliser cut out switches and flew just fine) and MCAS was about handling, keeping the same type rating and saving money.
- acqq 7y ago
  > the 737 Max flies just fine without MCAS No. Without the MCAS (but implemented correctly with the redundance etc) it behaves dangerously wrong in some ranges of its flight envelope: it effectively amplifies the small changes in the pilots control to the catastrophic results. Also see that the final MCAS was delivered non-redundant and also modified to turn itself on under more than one condition and also to exert much more power in overriding pilot than in the initial design. What you're claiming is a retelling of an initial belief about the MCAS as it was introduced, not about the MCAS as it was actually sold and as it was present in all the planes. The claim wasn't true then and isn't true now. Edit: What I'm talking about is documented here: 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... "This original version of MCAS, according to two people familiar with the details, was activated only if two distinct sensors indicated such an extreme maneuver: a high angle of attack and a high G-force." "About a third of the way through flight testing in 2016, as first reported by The Seattle Times in March, Boeing made substantial changes to MCAS. The flight-test pilots had found another problem: The same lack of smooth stick forces was also occurring in certain low-speed flight conditions. To cover that issue too, engineers decided to expand the scope and power of MCAS. Because at low speed a control surface must be deflected more to have the same effect, engineers increased the power of the system at low speed from 0.6 degrees of stabilizer nose-down deflection to 2.5 degrees each time it was activated. On the stabilizer, maximum nose down is about 4.7 degrees away from level flight. So with the new increased authority to move the stabilizer, just a couple of iterations of the system could push it to that maximum. Because there are no excessive G-forces at low speed, the engineers removed the G-force factor as a trigger. But that meant MCAS was now activated by a single angle-of-attack sensor." "While the changes were dramatic, Boeing did not submit documentation of the revised system safety assessment to the FAA." The "low-speed flight conditions" is effectively what was discovered only in 2016, what was changed in the implementation of the MCAS only then and what was not documented and what eventually caused the crash of both planes. And they had to add it for safety, not for "type rating." And it seems PuffinBlue is either not aware of that part of the story or intentionally ignores these findings in the comments, sticking to the the first part of the story, the MCAS as it was initially planned, not as it was actually implemented. The "type rating" motivation was why they lied about what they did. But the intention of the MCAS changes were to make it safer to fly, not to fit the type rating.

by acqq 7y ago

PuffinBlue 7y ago

> The plane is with its geometry inherently unsafe without some clever devices correcting the "inherent" behavior. No it isn't. It is a stable design. To claim otherwise misunderstands the term. The 737 can be flown just fine without MCAS turned on as it has absolutely nothing to do with making the aircraft stable. Many people seem to want to shit on Boeing for making an 'unstable' aircraft. They simply did not make an unstable aircraft. They made an inherently stable aircraft that handled a little bit differently and then to save money (in order to prevent the need for a new type rating and pilot retraining) they used MCAS to make it handle like previous generations. To repeat, the 737 Max flies just fine without MCAS (indeed previous flights of one of the downed aircraft pulled the stabiliser cut out switches and flew just fine) and MCAS was about handling, keeping the same type rating and saving money.

acqq 7y ago
> the 737 Max flies just fine without MCAS No. Without the MCAS (but implemented correctly with the redundance etc) it behaves dangerously wrong in some ranges of its flight envelope: it effectively amplifies the small changes in the pilots control to the catastrophic results. Also see that the final MCAS was delivered non-redundant and also modified to turn itself on under more than one condition and also to exert much more power in overriding pilot than in the initial design. What you're claiming is a retelling of an initial belief about the MCAS as it was introduced, not about the MCAS as it was actually sold and as it was present in all the planes. The claim wasn't true then and isn't true now. Edit: What I'm talking about is documented here: 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... "This original version of MCAS, according to two people familiar with the details, was activated only if two distinct sensors indicated such an extreme maneuver: a high angle of attack and a high G-force." "About a third of the way through flight testing in 2016, as first reported by The Seattle Times in March, Boeing made substantial changes to MCAS. The flight-test pilots had found another problem: The same lack of smooth stick forces was also occurring in certain low-speed flight conditions. To cover that issue too, engineers decided to expand the scope and power of MCAS. Because at low speed a control surface must be deflected more to have the same effect, engineers increased the power of the system at low speed from 0.6 degrees of stabilizer nose-down deflection to 2.5 degrees each time it was activated. On the stabilizer, maximum nose down is about 4.7 degrees away from level flight. So with the new increased authority to move the stabilizer, just a couple of iterations of the system could push it to that maximum. Because there are no excessive G-forces at low speed, the engineers removed the G-force factor as a trigger. But that meant MCAS was now activated by a single angle-of-attack sensor." "While the changes were dramatic, Boeing did not submit documentation of the revised system safety assessment to the FAA." The "low-speed flight conditions" is effectively what was discovered only in 2016, what was changed in the implementation of the MCAS only then and what was not documented and what eventually caused the crash of both planes. And they had to add it for safety, not for "type rating." And it seems PuffinBlue is either not aware of that part of the story or intentionally ignores these findings in the comments, sticking to the the first part of the story, the MCAS as it was initially planned, not as it was actually implemented. The "type rating" motivation was why they lied about what they did. But the intention of the MCAS changes were to make it safer to fly, not to fit the type rating.