Boeing 737 Max 8 failures..an explanation ?

As a former small plane pilot I have always been leery of computer commanded stability, but this 737 Max issue where *one sensor* going off can apparently result in pilot overpowering flight "corrections" is just nuts. Grounding them seems to have been the right call until this is all sorted out.
 
Lionair''s flight data released..
It looks to me like the plane first tried to nose dive within 90 secs of take off !??
kqSOEG.png

https://www.adelaidenow.com.au/travel/travel-news/report-reveals-final-moments-in-the-cockpit-of-crashed-lion-air-plane/news-story/ae43933a125c57361dac65cb60405715?utm_source=The%20Advertiser&utm_medium=email&utm_campaign=editorial
After two minutes, the first officer reported a “flight control problem” to air traffic control. The captain asked the first officer to check the quick reference handbook that contained checklists for abnormal events, the first source told Reuters.

For the next nine minutes, “the jet warned pilots it was in a stall and pushed the nose down in response”, according to the report.

The captain tried to get the plane to climb upwards, but the jet’s computer system kept pushing the nose down. It appeared the system was incorrectly sensing a stall.

“They didn’t seem to know the trim was moving down,” the third source told Reuters.

“They thought only about airspeed and altitude. That was the only thing they talked about.”

The pilots — the captain, 31, and the first officer, 41 — remained calm for most of the flight.

It was right before the crash the captain asked the first officer to check the manual as he struggled to control the plane..
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Hillhater said:
Lionair''s flight data released..It looks to me like the plane first tried to nose dive within 90 secs of take off !
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Yeah, that's been out for a few months now. The DFDR data shows exactly what happened when. The first MCAS down trim happens 1:40 into the flight, right after they retract the flaps. (Flaps-down disables the system.) As the system adds more and more nose-down trim eventually it overpowers the pilot.

The data shows the pilots trying to debug the problem, including lowering the flaps again - which temporarily solves the problem because that disables the MCAS. They then raise the flaps and the problem recurs. For quite a while the pilot fights it by trimming up every time the MCAS trims it down, then he loses the fight (distracted? misled as to the problem?) and the aircraft goes into an unrecoverable descent.

Also note that the AOA signals are divergent from the time the takeoff roll starts. It's likely that an optional (more $$) indicator, the AOA DISAGREE warning light, would have alerted them to the problem. The Lion Air aircraft did not have it.

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So what was the planned contingency in the system for a faulty AoA sensor? I can't believe that when the avionics were developed everyone somehow forgot to ask the question of "what happens if this sensor, with complete authority over the aircraft, goes bad?" It's FMEA 101. It's making me think there must be more to this tale, that it can't be this disastrously simple?
 
Punx0r said:
So what was the planned contingency in the system for a faulty AoA sensor?
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Shut down both pitch trim motors.

Normally the pitch trim motors are controlled by a switch on the yoke during hand flying. (There's also a backup wheel next to the throttles.) The pilot regularly uses these to trim the aircraft for the desired speed. There have been failures of the switch causing one of the motors to run continuously, trimming the nose up or down. To get around this the pilot can shut down the bad motor via one of those previously mentioned disconnect switches.

Boeing has been claiming that since pilots (theoretically) already know how to do that for a switch failure, expecting them to do it for an MCAS failure isn't unreasonable.
 
Punx0r said:
...It's making me think there must be more to this tale, that it can't be this disastrously simple?
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One possible simple reason: the Trump administration gave an implicit green light to anyone who was concerned about those "pesky" regulations -- as they made it patently clear from day one that there would be limited-to-no-oversight by any Federal department going forward. And that is no exaggeration. This is what "success" looks like as long as these clowns are in office.
 
I didn't see a "like" button so will post it in a message. Like. But not just this administration. This began in earnest with W... coal ash pond failures, mountain top blast mining, killing new source rules for power plants... etc, etc. This airline "self-certification" problem is just a more dramatic example, and far less harmful that the ones I listed.

MJSfoto1956 said:
One possible simple reason: the Trump administration gave an implicit green light to anyone who was concerned about those "pesky" regulations -- as they made it patently clear from day one that there would be limited-to-no-oversight by any Federal department going forward. And that is no exaggeration. This is what "success" looks like as long as these clowns are in office.
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Thanks for explaining that, Bill. So the pilot would detect a change in attitude of the plane, automatically realise the problem can only (or most likely) be with the pitch trim system and kill power to it with an easily accessible switch? Is there any indicator that pitch trim is currently applied to assist the pilot in diagnosing the problem?
 
It will be interesting to see how much Boeing and the airline company will have to shell out for the victims of these tragedies.
 
WestJet says its sticking with Boeing 737 Max 8 planes once they're certified to fly
https://business.financialpost.com/transportation/airlines/westjet-sticking-with-boeing-737-max-8-once-planes-certified-to-fly




Canadian airlines fly 41 planes of the type that crashed in Ethiopia
https://globalnews.ca/news/5040742/air-canada-westjet-boeing-737-max-8/
And one of those airlines added four more after a separate fatal crash in Indonesia took 189 lives in October.
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Air Canada has 24 Boeing 737 MAX 8s, WestJet Airlines Ltd. had 13 and Sunwing Airlines flies four, according to Transport Canada’s civil aircraft register.
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WestJet confirmed that it has 13 Boeing 737 MAX planes in its fleet — and that’s four more than it had in November when a Lion Air flight crashed in the Java Sea.

Those planes represent just over 10 per cent of the Boeing 737s that it flies in total.

Asked why it added more of those planes following such a devastating crash, WestJet said it has an order for “50 MAX aircraft and have ongoing deliveries.”
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Punx0r said:
Thanks for explaining that, Bill. So the pilot would detect a change in attitude of the plane, automatically realise the problem can only (or most likely) be with the pitch trim system and kill power to it with an easily accessible switch? Is there any indicator that pitch trim is currently applied to assist the pilot in diagnosing the problem?
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Good question. I don't know of a physical indicator that illuminates - and since it's a normal part of most flights, a warning or caution indication (via a master caution indication) would not make sense. However:

1) When the motor runs, the pitch trim wheel spins, and that's a pretty concrete indication. It even has a white stripe on it so you can see that it's spinning.

2) Pilots will automatically use those aforementioned pitch trim switches to trim the plane up when hand flying, and continually having to do that (i.e. fighting the MCAS) would become evident because you'd have to do it every few seconds.

3) Boeing does offer that "AOA DISAGREE" indicator light that tells the pilot the MCAS is getting bad information - but that's not standard on 737 MAX aircraft.

So there's at least one direct indication and one indirect indication that there's a problem - and that's likely what Boeing is referring to when they say pilots already have training to solve this problem. There's also the optional warning light.

(Slight correction - you have to flip two switches to completely disconnect the pitch trim motors.)
 
Ah, OK. So in theory, as long as the pilot is familiar/trained with the system and thinking clearly & logically when the MCAS fault occurs he should be able to cope with it and retain control of the plane.
 
Updates -

So there's a software fix out that Boeing wants approved on a fast track. It does two things; it uses input from two AOA sensors instead of one, and it times out after a little while - meaning that as long as the pilot keeps trimming up every time the MCAS trims down, eventually the MCAS will stop trying.

Meanwhile early results from DFDR data from the second flight indicates that it was the same problem in both crashes. (There's been no official statement yet, but officials who have seen the data says it looks like the same problem, and the CVR records one of the pilots telling the other one to get the nose up.)

The question now - will the FAA be OK with another software fix?
 
Looks like Boeing's commercial interests won out as FAA management bypassed their own safety engineers:

https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/
 
Boeing actually just said this about their new software fix for the 737 MAX:

It “took until now because we wanted to get it right. Rushing it is the wrong thing to do.”

Right. Because they would never rush something to market, and go with a kludge instead of a redesign, just to beat Airbus.
 
Well the first report is out on the Ethopian crash: http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+%2C%28ET-AVJ%29.pdf/4c65422d-5e4f-4689-9c58-d7af1ee17f3e

Some reporters are claiming the pilots followed all the correct procedures provided by Boeing but were unable to control the aircraft, with Boeing now admiting there is a fault with the MCAS system: https://www.bbc.co.uk/news/business-47812225

Reuters claim the problem originated with a bird strike just after takeoff damaging the Angle of Attach sensor, causing the MCAS fault and the pilots were ultimately unable to control the plane due to their own mistake of having kept the engines at full throttle since takeoff: https://uk.reuters.com/article/uk-ethiopia-airplane-reconstruction-insi/how-excess-speed-hasty-commands-and-flawed-software-doomed-an-ethiopian-airlines-737-max-idUKKCN1RH0FG
 
Punx0r said:
Well the first report is out on the Ethopian crash: http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+%2C%28ET-AVJ%29.pdf/4c65422d-5e4f-4689-9c58-d7af1ee17f3e

Some reporters are claiming the pilots followed all the correct procedures provided by Boeing but were unable to control the aircraft, with Boeing now admiting there is a fault with the MCAS system: https://www.bbc.co.uk/news/business-47812225

Reuters claim the problem originated with a bird strike just after takeoff damaging the Angle of Attach sensor, causing the MCAS fault and the pilots were ultimately unable to control the plane due to their own mistake of having kept the engines at full throttle since takeoff: https://uk.reuters.com/article/uk-ethiopia-airplane-reconstruction-insi/how-excess-speed-hasty-commands-and-flawed-software-doomed-an-ethiopian-airlines-737-max-idUKKCN1RH0FG
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Yep. From the DFDR data, the pilots did everything that Boeing suggested - and still couldn't control the aircraft. Not throttling back was definitely an error, but it's also understandable - airspeed and altitude are somewhat interchangeable, and there's a natural desire to not slow down needlessly when you are at low altitudes.

In addition, a second problem has been identified. There's not too many details on it yet, but it has to do with control of flaps/slats which are considered primary flight control surfaces, so by definition it's not a minor problem.

Needless to say this is not good news for Boeing. Industry analysts are predicting a two month grounding minimum as the new fix is evaluated.
 
Yes, good analysis and answers. But what will happen next? Boeing will not give up his idea so quickly. There will be patching holes. But really scary to fly on such planes
 
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