3 ms·

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 mo

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.

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.