rheinwaldner wrote:hivue wrote:scythemk wrote:
My understanding is that MCAS was implemented to make the handling resemble that of the 737NG in high thrust situations where the engine mounting caused upward pitch. It was a patch of sorts to make this handling difference transparent to the pilots and I believe was a condition required for it to be certified as essentially the same type rating as 737NG instead of its own type rating.
It's not because the plane became "uncontrollable". There's nothing that MCAS does while in operation that the pilot couldn't do themselves.
My understanding (gleaned months ago from the Lion Air thread so no documentation; anyone with documentation feel free to correct me) is that during the flight test campaign it was discovered that at certain points in the envelope the more forwardly located engines generated unanticipated (during the design and development phases) lift of a sufficiently robust nature to generate a nose-up moment, from where a stall could ensue. A stall is uncontrolled flight. The airplane was deemed not certifiable with this undesirable characteristic so MCAS was put together to mitigate it -- even though the situation likely would never be encountered in normal airline operations.
My thesis was, that due to initial problems with unreliable speed, they did cut off the trim, loosing as a result MCAS, and then while dealing with the unreliable speed they encountered those parts of the flight envelope, where they would have needed MCAS to fly a normal behaving, stable plane. Do you understand? The combination of having lost MCAS and being dependent on it at the same time.
To be clear, this thesis is only one of many possible. And probably not even the most probable one. But the impact would be severe: it would mean, that the trim cut off switches are not eligible to fix a malfunctioning MCAS.
Yes, I had a similar thought many pages ago. You stated it better. Although if flaps never reset, then they may have gotten themselves in a mess trying to climb and gone into a stall and MCAS had nothing to do with it.
The “similarities” are there between the two crashes, but there are also similarities with other crashes in the history of aviation that dont involve MCAS . So other than public hysteria and non-scientist government officials claiming a clear connection (or not), its no more logical to assume these crashes had the same cause than it is to blame all 737NG and ground them all, or all aircraft that use that brand if AoA sensor or pitot tubes or what have you.
This crash may very well be similar to the AF crash of the A330 but at a much lower altitude. They had no idea how fast they were going, tried to prevent stalling by putting the aircraft into a stall, and finally ran out of opportunities to get it wrong before all was lost. The difficulty in controlling the aircraft could come from losing and gaining and losing and gaining flow over the control surfaces.