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Originally Posted by DenverBrian
(Post 30958102)
Apparently two new planes in five months had this "condition" or false "condition," and now 346 people are dead. @:-)
Not to mention, the day-before Lion Air recovery was only after some porpoising. I'm not interested in getting on a plane that has a history of needing to porpoise before it recovers - not my kind of "fun" experience. |
Originally Posted by Newman55
(Post 30943511)
It's not an unstable design. It's just different from previous 737s (like all derivatives).
As R. John Hansman, a professor of aeronautics at the Massachusetts Institute of Technology, told me in a March 28 interview,As I understand it, at high angles of attack the Nacelles -- which are the tube shaped structures around the fans -- create aerodynamic lift. Because the engines are further forward, the lift tends to push the nose up -- causing the angle of attack to increase further. This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition. It should be noted that many high performance aircraft have this tendency but it is not acceptable in transport category aircraft [emphasis mine] where there is a requirement that the aircraft is stable and returns to a steady condition if no forces are applied to the controls. |
Originally Posted by BF263533
(Post 30958554)
They called it roller-coastering for the Piper Cheyenne's SAS & pilot tug of war. SAS was reported to counter the nose up from Cheyenne's larger turboprop engines inserted into a piston Navajo's frame.
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Originally Posted by danielSuper
(Post 30958716)
According to whom?
As R. John Hansman, a professor of aeronautics at the Massachusetts Institute of Technology, told me in a March 28 interview,As I understand it, at high angles of attack the Nacelles -- which are the tube shaped structures around the fans -- create aerodynamic lift. Because the engines are further forward, the lift tends to push the nose up -- causing the angle of attack to increase further. This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition. It should be noted that many high performance aircraft have this tendency but it is not acceptable in transport category aircraft [emphasis mine] where there is a requirement that the aircraft is stable and returns to a steady condition if no forces are applied to the controls. |
ET Pilots Initially Followed Boeing’s Required Emergency Steps To Disable MCAS
Pilots at the controls of the Boeing Co. 737 MAX that crashed in March in Ethiopia initially followed emergency procedures laid out by the plane maker but still failed to recover control of the jet, according to people briefed on the probe’s preliminary findings.
After turning off a flight-control system that was automatically pushing down the plane’s nose shortly after takeoff March 10, these people said, the crew couldn’t get the aircraft to climb and ended up turning it back on and relying on other steps before the final plunge killed all 157 people on board. The pilots on Ethiopian Airlines Flight 302 initially reacted to the emergency by shutting off power to electric motors driven by the automated system, these people said, but then appear to have re-engaged the system to cope with a persistent steep nose-down angle...After first cranking a manual wheel in the cockpit that controls the same movable surfaces on the plane’s tail that MCAS had affected, the pilots turned electric power back on, one of these people said. They began to use electric switches to try to raise the plane’s nose, according to these people. But the electric power also reactivated MCAS, allowing it to continue its strong downward commands, the people said. |
Originally Posted by username
(Post 30955199)
What does the fact that the re-work seems to have run into difficulties and will take longer tell us?
6 months sounds pretty fast to me for any change in flight control software for a fleet of passenger aircraft. |
I am starting to think maybe the steps have to be:
1 - complete the investigations 2 - re-program and re-certify 3 - start flying That can take a long long time... |
Originally Posted by rdchen
(Post 30958985)
https://www.wsj.com/articles/ethiopian-airlines-pilots-initially-followed-boeings-required-emergency-steps-to-disable-737-max-system-11554263276]Pilots at the controls of the Boeing Co. 737 MAX that crashed in March in Ethiopia initially followed emergency procedures laid out by the plane maker but still failed to recover control of the jet, according to people briefed on the probe’s preliminary findings.[/url]
After turning off a flight-control system that was automatically pushing down the plane’s nose shortly after takeoff March 10, these people said, the crew couldn’t get the aircraft to climb and ended up turning it back on and relying on other steps before the final plunge killed all 157 people on board. The pilots on Ethiopian Airlines Flight 302 initially reacted to the emergency by shutting off power to electric motors driven by the automated system, these people said, but then appear to have re-engaged the system to cope with a persistent steep nose-down angle...After first cranking a manual wheel in the cockpit that controls the same movable surfaces on the plane’s tail that MCAS had affected, the pilots turned electric power back on, one of these people said. They began to use electric switches to try to raise the plane’s nose, according to these people. But the electric power also reactivated MCAS, allowing it to continue its strong downward commands, the people said. |
Originally Posted by PVDtoDEL
(Post 30959154)
I don't think this is good news for Boeing - this means that the ET pilots were aware of MCAS, followed the "just cut off electric trim" advice that Boeing has been spouting, and then still weren't able to recover control of the aircraft. A scary finding indeed.
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Originally Posted by halls120
(Post 30959159)
did you miss the part of the post where it said they turned the power back on? Yes, MCAS as it is configured on the Max has problems, but turning the power back on to the component that was causing the problem in the first place is pilot error. If the pilots followed their checklists and training (which it sounds like they did) and still weren't able to control the aircraft, then I don't see this as pilot error. Maybe they could have gotten a better result with more/better training, but keep in mind that ET shelled out for a MAX simulator that didn't even simulate MCAS because Boeing didn't want to push out the details about the system. It's hard to train for a failure the manufacturer doesn't want you to know is possible... |
Originally Posted by PVDtoDEL
(Post 30959186)
Did you miss the part about how they were unable to control the aircraft after turning MCAS off? Boeing didn't build this system for no reason - they built it to meet a certification requirement for the aircraft. Depending on their elevator and trim position when they cut out the electric trim, it could have been nearly impossible to manually trim for level flight.
If the pilots followed their checklists and training (which it sounds like they did) and still weren't able to control the aircraft, then I don't see this as pilot error. |
Originally Posted by PVDtoDEL
(Post 30959186)
Did you miss the part about how they were unable to control the aircraft after turning MCAS off? Boeing didn't build this system for no reason - they built it to meet a certification requirement for the aircraft. Depending on their elevator and trim position when they cut out the electric trim, it could have been nearly impossible to manually trim for level flight.
If the pilots followed their checklists and training (which it sounds like they did) and still weren't able to control the aircraft, then I don't see this as pilot error. Maybe they could have gotten a better result with more/better training, but keep in mind that ET shelled out for a MAX simulator that didn't even simulate MCAS because Boeing didn't want to push out the details about the system. It's hard to train for a failure the manufacturer doesn't want you to know is possible... “Jack Webb was Piper’s chief engineering test pilot during most of the Cheyenne development process. “As we were going along, I discovered a kind of scary dynamic-stability problem,” he says. It was the same problem the 737 Max would later have, for the same reason. And as Boeing would later do, Piper tried to fix the problem by adding automation — in its case, a device called a “stability-augmentation system” (SAS) that would push the nose down if it got too high. …………..” “Webb believes that, based on his experience with the Cheyenne, these fixes won’t eliminate the plane’s predilection for roller-coastering. ……..” “There is a straightforward solution for all the 737 Max’s problems: to reduce the plane’s pitch up tendency, Boeing could lengthen the landing gear and move the engines further back under the wing; and to increase stability, it could increase the size of the tail. …….” See: Is the Boeing 737 MAX Worth Saving? |
Originally Posted by PVDtoDEL
(Post 30959186)
Did you miss the part about how they were unable to control the aircraft after turning MCAS off? Boeing didn't build this system for no reason - they built it to meet a certification requirement for the aircraft. Depending on their elevator and trim position when they cut out the electric trim, it could have been nearly impossible to manually trim for level flight.
If the pilots followed their checklists and training (which it sounds like they did) and still weren't able to control the aircraft, then I don't see this as pilot error. Maybe they could have gotten a better result with more/better training, but keep in mind that ET shelled out for a MAX simulator that didn't even simulate MCAS because Boeing didn't want to push out the details about the system. It's hard to train for a failure the manufacturer doesn't want you to know is possible... |
Originally Posted by halls120
(Post 30959515)
There is no doubt that Boeing screwed up in their design and training, but the Lion Air flight the day before did not crash because a check pilot knew what to do. Same airplane, different outcome, which is apparently because a properly trained pilot correctly diagnosed this issue and the plane did not crash.
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Originally Posted by halls120
(Post 30959515)
There is no doubt that Boeing screwed up in their design and training, but the Lion Air flight the day before did not crash because a check pilot knew what to do. Same airplane, different outcome, which is apparently because a properly trained pilot correctly diagnosed this issue and the plane did not crash.
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