737 MAX grounded
11-24-2019 | 08:38 AM
#521
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Joined: Jul 2008
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In either case, engaging the A/P below 500' on takeoff during stick-shaker activation--particularly when engaging the autopilot on the same side as the stick-shaker--isn't a very smart thing to do. The autopilot isn't analogous to a BRS!
11-24-2019 | 09:44 AM
#522
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Joined: May 2005
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Lets say these guys got the stab trim switches off before the stab reached full travel. Maybe the plane was trimmed for 500 knots. At 300 knots, they were 200 knots out of trim. There's no way that wheel is moving if they were trying to hold level flight. As their speed increased, they would have gotten closer to "on-speed" and if they would have been able to reach the speed the plane was trimmed for (very fast), the air load on the stab would have been negligible and they would have been able to use the wheel as necessary. Obviously, they never got that chance. But, in my opinion, slowing down would have made everything worse, if that's even possible.
11-24-2019 | 02:41 PM
#524
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Joined: Jul 2008
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That way you're never significantly out of trim and manual trimming should not be difficult.
11-24-2019 | 03:17 PM
#525
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Joined: Sep 2010
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From: UAL retired
They did not cut out the stab trim until the trim position was nearly full nose-down and was flying at over Vmo (over 390kts vs Vmo of 340kts). When they turned the stab trim back on the captain repeatedly tried to engage the autopilot (which won't engage when out-of-trim) instead of using the primary electric trim, which might have had a chance of rolling the trim back up. That allowed additional unscheduled MCAS activations to roll it to the full nose-down stop.
The Captain didn't know what to do so he kept trying to engage the autopilot. He had tried the same thing less than 500' off the ground on takeoff (minimum autopilot engagement altitude on takeoff is 800'). In doing so, he briefly coupled the autopilot (CMD A) to the Flight Control Computer that was receiving bad data. This produced unstable pitch inputs from the autopilot and caused the autopilot to disconnect within 30 seconds.
While "STAB TRIM CUTOUT switches ... CUTOUT" is part of the applicable procedure, they did it far too late and without doing the previous steps--this one is the second-to-last step. Doing only one item on a checklist does not qualify as following the procedure.
They made many other procedural errors prior to that one including never just flying the airplane. i.e. when the nose gets heavy, trimming it back up with the primary electric trim. The Captain of the Lion Air accident flight kept the airplane in-trim through 21 unscheduled MCAS activations by doing just that. The trim didn't get significantly out-of-trim until he transferred control to the F/O who did not re-trim the airplane after each MCAS activation.
If you're interested in understanding the actions of both accidents crews, I'd recommend this (rather long) article from NY Times Magazine. It is the most detailed article that I have seen on the MAX crashes.
https://www.nytimes.com/2019/09/18/m...x-crashes.html
The Captain didn't know what to do so he kept trying to engage the autopilot. He had tried the same thing less than 500' off the ground on takeoff (minimum autopilot engagement altitude on takeoff is 800'). In doing so, he briefly coupled the autopilot (CMD A) to the Flight Control Computer that was receiving bad data. This produced unstable pitch inputs from the autopilot and caused the autopilot to disconnect within 30 seconds.
While "STAB TRIM CUTOUT switches ... CUTOUT" is part of the applicable procedure, they did it far too late and without doing the previous steps--this one is the second-to-last step. Doing only one item on a checklist does not qualify as following the procedure.
They made many other procedural errors prior to that one including never just flying the airplane. i.e. when the nose gets heavy, trimming it back up with the primary electric trim. The Captain of the Lion Air accident flight kept the airplane in-trim through 21 unscheduled MCAS activations by doing just that. The trim didn't get significantly out-of-trim until he transferred control to the F/O who did not re-trim the airplane after each MCAS activation.
If you're interested in understanding the actions of both accidents crews, I'd recommend this (rather long) article from NY Times Magazine. It is the most detailed article that I have seen on the MAX crashes.
https://www.nytimes.com/2019/09/18/m...x-crashes.html
I interpret your response as saying the pilots did not react properly and caused the accident. I respond by saying that the pilots reacted as humans who are startled and trying to save their lives, but that was not enough BECAUSE they were not taught ENOUGH about the POSSIBILITIES.
Today at UAL, we are all getting a chance to learn about upsets because we, pilots, have learned from past experience that upsets are the latest problem we are experiencing that is amenable to human intervention.
I do not believe the Ethiopian pilots reacted any differently than any other crew would have. The fault was not theirs, and more importantly Boeing management had enough data points to have prevented the accident, but they did NOT take the high ground, but rather chose the path to least pain.
11-24-2019 | 03:25 PM
#526
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Joined: Jun 2006
Posts: 431
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From: 737 FO/Capt/FO
Looking at an old Boeing FCTM...FAA certified the classic 300-500 for a/p Engagement at or above 1000’ and the NG at or above 400’
11-24-2019 | 03:27 PM
#527
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Joined: Mar 2018
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Regardless of how we got here, once the max returns to service, we’re going to get a bunch of them. 161 originally ordered and we all know that they’ll be buying more. I wouldn’t be surprised if United announces a large order for deeply discounted max somethings after this is over. We get cheap lift, and Boeing gets to announce sales and customer confidence in their product.
I guess the path to least pain kind of bit them in the rear on this thing.
11-24-2019 | 03:57 PM
#528
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Joined: Sep 2019
Posts: 339
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From: B777 CA
Couple of things. 1. The MAX-10 will not and was never planned to have MCAS. Fuselage plug forward of the wing means engines are closer to CG then MAX 8/9/7.
2. How do you propose sim training? We have like 4 MAX simulators coming but none here yet and even if we did have one you’d have to program a scenario into the simulator that simulates a tragic but now irrelevant scenario as soon as the new software is loaded in the aircraft, which will probably take place in early 2020 when said simulator training would begin.
Even if we were to conduct simulator training where the IP ran crews through upsets and stab trim runaways over and over it would be redundant for UAL as both initial qualification training and continuing qualification training have had stab trim runaway training. I’m fine with a CBT. Of course, nobody has or will ask me....
2. How do you propose sim training? We have like 4 MAX simulators coming but none here yet and even if we did have one you’d have to program a scenario into the simulator that simulates a tragic but now irrelevant scenario as soon as the new software is loaded in the aircraft, which will probably take place in early 2020 when said simulator training would begin.
Even if we were to conduct simulator training where the IP ran crews through upsets and stab trim runaways over and over it would be redundant for UAL as both initial qualification training and continuing qualification training have had stab trim runaway training. I’m fine with a CBT. Of course, nobody has or will ask me....
11-24-2019 | 04:19 PM
#529
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Joined: Apr 2010
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Why not just KEEP the airplane in-trim, through the use of the primary electric trim, each time MCAS fires and until reaching the STAB TRIM CUTOFF switches ... CUTOFF item on the RUNAWAY STABILIZER checklist?
That way you're never significantly out of trim and manual trimming should not be difficult.
That way you're never significantly out of trim and manual trimming should not be difficult.
11-24-2019 | 07:20 PM
#530
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Joined: Dec 2018
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I have been away for a while now and I'm sorry it takes a couple tragedies to bring out such great discussions (and a couple great articles from the New York(er)).
I do have to say that while these are indeed tragedies; as usual, we will end up learning from them.
I am sorry it took this to make Boeing sit up and listen but thats the best thing to happen to aviation in the last 25 years.
I have been dreading where this is all heading since the late 60's.
For me it all begins with the word "Redundancy"; winds through this strange land of "fly by wire" and "laws". All the while getting further and further away from "flying the airplane" on the pilots side and lost in the techno babble of the manufacturers. How in God's name could a company like Boeing go from edge of Engineering greatness to somehow thinking it's OK to have a single point decision (single AOA input) in that tree.
Unbelievable.
One interesting side note (at least for me). So this article in the New York Times by Langeweische brings back very old memories from his fathers book (Stick and Rudder). I could swear somewhere in that book Wolfgang says something like "of course we can make flying seem safe; by simply attaching a silver chain between the "stick" and the instrument panel, such that we can't ever maneuver the airplane in to trouble. In otherwords we can design an airplane to be so stable it can't hardly get in to trouble but it won't be maneuverable enough to get out of trouble if the pilot lets it wander in. Little did we know the manufacturers would become so powerful AND ignorant that they could put one in an airplane and the pilots are supposed to work around it.
I do have to say that while these are indeed tragedies; as usual, we will end up learning from them.
I am sorry it took this to make Boeing sit up and listen but thats the best thing to happen to aviation in the last 25 years.
I have been dreading where this is all heading since the late 60's.
For me it all begins with the word "Redundancy"; winds through this strange land of "fly by wire" and "laws". All the while getting further and further away from "flying the airplane" on the pilots side and lost in the techno babble of the manufacturers. How in God's name could a company like Boeing go from edge of Engineering greatness to somehow thinking it's OK to have a single point decision (single AOA input) in that tree.
Unbelievable.
One interesting side note (at least for me). So this article in the New York Times by Langeweische brings back very old memories from his fathers book (Stick and Rudder). I could swear somewhere in that book Wolfgang says something like "of course we can make flying seem safe; by simply attaching a silver chain between the "stick" and the instrument panel, such that we can't ever maneuver the airplane in to trouble. In otherwords we can design an airplane to be so stable it can't hardly get in to trouble but it won't be maneuverable enough to get out of trouble if the pilot lets it wander in. Little did we know the manufacturers would become so powerful AND ignorant that they could put one in an airplane and the pilots are supposed to work around it.
Last edited by graybeard; 11-24-2019 at 07:23 PM. Reason: Add which single point I was referring to
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