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aerolimani
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 8:51 pm

Revelation wrote:
aerolimani wrote:
Somewhere in this thread, somebody shared a procedure for operating the hand-crank manual trim. I believe it was from the operating manual of a 737 classic. It had to do with the situation where the wheels were near to impossible to turn by hand. I believe the advised procedure in the manual was push the yoke forward to to relieve some pressure on the stabilizer, and to allow the trim wheels to be more easily turned by hand. So, it would seem that the issue (of the the manual trim being difficult to operate) goes back a long ways in the design of the 737, if not to the very beginning.

Of course, the problem gets even worse if an erroneous MCAS activation starts flying you into the ground at a relatively low altitude. Add to that the airspeed disagree, and its corrective procedure which apparently results in flying the plane faster, thus increasing the difficulty of operating the trim by hand. I'm guessing there's an altitude below which one cannot even hope to use the above described procedure for allowing the operation of the manual trim.

So… I come to two questions:
1) Is this procedure for operating the manual trim still in the MAX manual?
2) Have all the previous generations of 737 simply been fortunate enough not to need to need to operate trim manually, at a low altitude, to recover from a nose-down, out-of-trim situation?

The ST article I linked above, Seattle Times: Why Boeing’s emergency directions may have failed to save 737 MAX, has the answer to both your questions.

Here's some relevant fair-use quotes from the article:

His scenario is backed up by extracts from a 1982 Boeing 737-200 Pilot Training Manual posted to an online pilot forum a month ago by an Australian pilot.

That old 737 pilot manual lays out a scenario where a much more elaborate pilot response is required than the one that Boeing outlined in November and has reiterated ever since. The explanation in that manual from nearly 40 years ago is no longer detailed in the current flight manual.

Hmm, wonder which forum Dominic is reading for clues (or which ones he isn't, lol!).

It goes on to say:

More detailed instructions that conceivably could have saved the Ethiopian plane are provided in the 1982 pilot manual for the old 737. As described in the extract posted by the Australian pilot, they require the pilot to do something counterintuitive: to let go of the control column for a brief moment.

As Lemme explains, this “will make the nose drop a bit,” but it will relax the force on the elevator and on the jackscrew, allowing the pilot to crank the stabilizer trim wheel. The instructions in the old manual say that the pilot should repeatedly do this: Release the control column and crank the stabilizer wheel, release and crank, release and crank, until the stabilizer is swiveled back to where it should be.

The 1982 manual refers to this as “the ‘roller coaster’ technique” to trim the airplane, which means to get it back on the required flight path with no force pushing it away from that path.

“If nose-up trim is required, raise the nose well above the horizon with elevator control. Then slowly relax the control column pressure and manually trim nose-up. Allow the nose to drop below the horizon while trimming (manually). Repeat this sequence until the airplane is trim,” the manual states.

Like I wrote above, it's a darn good summary of the current situation, perhaps with some inspiration from this forum, and perhaps even from this thread, but in any case, a lot better written.

It has even more info related to your questions, so go give it a read. And no, I am not Domenic...

Thanks for that. Somehow, I skipped past this article, despite having followed this thread all the way through.

It seems like Boeing's procedures for runaway trim may be inadequate, as it was stated in manuals from the classic series onwards. The roller-coaster technique could still be necessary, in the event of a "normal" runaway trim scenario, and yet, the technique has not been published in a manual, or trained for, since the Jurassic series.

If everything in this article is true, it seems like a matter of mere good fortune that a runaway stab trim didn't cause a serious problem on any 737-300 through 900 series aircraft, with a crew being unable to operate the manual trim wheel. Of course, with ET302, the final nail in their coffin was reactivating the electric trim, and thus MCAS, after most likely being unable to turn the trim wheels manually. Even so, given their relatively low altitude, I wonder if the roller coaster technique would have been possible.

So… will the roller coaster technique have to be added to the Classic, NG, and MAX manuals? If there are possible scenarios where manual trim could be required, then I would think that this technique may be needed. In other words, Boeing's troubles could go a lot further than just the MAX series. If airlines were required to do additional training for all their Classic and NG pilots, that could be quite an expensive undertaking. Would Boeing end up having some responsibility for that cost?

I'm of the belief that this will all get straightened out, and that the MAX will be ungrounded. I believe that the plane will be safe to fly, eventually. However, it seems unfortunate that this manual trim problem is not something which was ever improved upon from the original design, apart from the electrical systems simply becoming more reliable. Especially, it is shocking that this problem was not corrected (or anticipated) in light of the fact that manual trim became the de facto cure for trim problems caused by MCAS.
 
StTim
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 8:51 pm

Some people may read my posts and think I am anti Boeing and the MAX. I am not. I truly believe two things:

1. Boeing right royally effed up the MAX with an astoundingly poorly implemented MCAS solution.

2. Boeing have lots of incredibly competent and clever engineers who will given time and suport find a workable supportable and safe solution.

My worry is the higher paid help get too much in the way.
 
planecane
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 9:12 pm

Richard28 wrote:
planecane wrote:
Most of what you list here is unneccessary. First of all, with respect to the number of AoA sensors, two is sufficient. For a FBW aircraft, triple redundancy is necessary because the flight control computer needs valid data in order for the plane to fly. In the case of MCAS, it just needs to recognize a failed sensor and shut off. If two sensors simultaneously fail with similar invalid measurements, it is likely that a 3rd or 10th would fail as well.


With only two sensors, and a single failure, how would the MAX know which one has failed?

three sensors gives some back up and checks for data consistency... four sensors even more so.


It wouldn't know but it doesn't matter. It just needs to know one is failed and disable MCAS. MCAS is not critical to keep the plane in the air like the flight control system on a FBW aircraft.
 
smartplane
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 9:58 pm

Aesma wrote:
MCAS means Maneuvering Characteristics Augmentation System.

Are we certain its only purpose it to trim down the aircraft in situations it deems dangerous ?

I seem to recall that Airbus FBW aircraft are similar to fly from the pilots' POV, because Airbus makes the controls that way. However the 737 isn't FBW so Boeing can't make the MAX feel like the NG the same way ; when I see what MCAS stands for, I'm left wondering if it's not constantly doing something so that the MAX feels as close to the NG as possible.

Likely MCAS will turn out to have three settings - OFF (procedure yet to be disclosed by Boeing), ON and BACKGROUND (what is currently described as OFF). In certain flight conditions, MCAS can be provoked from BACKGROUND to ON, even intruding in conditions where it shouldn't, like flaps extended and autopilot on.
 
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scbriml
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 10:03 pm

planecane wrote:
It wouldn't know but it doesn't matter. It just needs to know one is failed and disable MCAS.


How does it know one has failed when both are still providing data?
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Jetty
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 10:19 pm

scbriml wrote:
planecane wrote:
It wouldn't know but it doesn't matter. It just needs to know one is failed and disable MCAS.


How does it know one has failed when both are still providing data?

The output of 1 sensor of the Ethiopian plane was that the AoA changed more than 30 degrees within 1 second. A scenario like that would make it easy: one provides impossible outputs and the other does not.

It’s astonishing that Boeing did nothing to prevent such impossible values to trigger the activation of MCAS regardless if there were 1 or 4 AoA sensors on the plane.
 
planecane
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 10:41 pm

scbriml wrote:
planecane wrote:
It wouldn't know but it doesn't matter. It just needs to know one is failed and disable MCAS.


How does it know one has failed when both are still providing data?


When they disagree with each other by more than a few degrees.
 
RickNRoll
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 10:43 pm

Do you want it fast, cheap and reliable. Pick any two.
 
dk1967
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 10:47 pm

An easy an obvious fix to a system designed to keep the operator out of trouble in normal mode is to disable that system if the operator is already in non-normal mode. If any sensor fails causing AOA or IAS disagree, or whatever, MCAS should not engage. The user, in this case a pilot, already knows they’re in non-normal and is troubleshooting other items.

It’s basic engineering. Boeing isn’t evil. They just made a horrific engineering mistake.
 
D L X
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 10:47 pm

planecane wrote:
scbriml wrote:
planecane wrote:
It wouldn't know but it doesn't matter. It just needs to know one is failed and disable MCAS.


How does it know one has failed when both are still providing data?


When they disagree with each other by more than a few degrees.

I guess the next question is, when they disagree, which one does the system trust?
 
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scbriml
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 10:56 pm

D L X wrote:
planecane wrote:
scbriml wrote:

How does it know one has failed when both are still providing data?


When they disagree with each other by more than a few degrees.

I guess the next question is, when they disagree, which one does the system trust?


Well mine would have been: Define "more than a few degrees".

But in fairness to planecane, he did say to disable MCAS at that point, so the decision as to which one to trust wouldn't arise.
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Jetty
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 11:01 pm

scbriml wrote:
D L X wrote:
planecane wrote:

When they disagree with each other by more than a few degrees.

I guess the next question is, when they disagree, which one does the system trust?


Well mine would have been: Define "more than a few degrees".

If you have access to flight data of valid AoA outputs it would be relatively easy to define which outputs are impossible to be valid, including which differences indicate a failure.
 
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Finn350
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 11:18 pm

Here are the MCAS changes as explained by Boeing
https://www.boeing.com/commercial/737ma ... dates.page
 
F9Animal
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 11:26 pm

I hope some heads roll at the top of the food chain at Boeing. That is all I am going to say, but this is absolutely horrific.
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MrBretz
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 11:26 pm

Finn350 wrote:
Here are the MCAS changes as explained by Boeing
https://www.boeing.com/commercial/737ma ... dates.page


Is this the update the FAA recently said needed more work? Or is being considered for approval right now?
 
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Finn350
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 11:30 pm

MrBretz wrote:
Finn350 wrote:
Here are the MCAS changes as explained by Boeing
https://www.boeing.com/commercial/737ma ... dates.page


Is this the update the FAA recently said needed more work? Or is being considered for approval right now?


I would guess that at the level explained there the update won’t change.
 
speedking
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Re: B737MAX Grounded Worldwide

Thu Apr 04, 2019 11:50 pm

What else they didn't know to do properly or saved money from? Pylons made from balsa? Can you trust anything in this plane?
 
barney captain
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 12:15 am

scbriml wrote:
D L X wrote:
planecane wrote:

When they disagree with each other by more than a few degrees.

I guess the next question is, when they disagree, which one does the system trust?


Well mine would have been: Define "more than a few degrees".

But in fairness to planecane, he did say to disable MCAS at that point, so the decision as to which one to trust wouldn't arise.


If there is a disparity, mcas will not trigger. It won't have to figure out which one is correct.
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Exeiowa
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 12:22 am

Anyone think they did the wrong thing by grounding this plane now?
 
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Revelation
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 12:34 am

Finn350 wrote:
Here are the MCAS changes as explained by Boeing
https://www.boeing.com/commercial/737ma ... dates.page

I smell lawyers..

For instance,

All primary flight information required to safely and efficiently operate the 737 MAX is included on the baseline primary flight display. This is true of all our commercial products. Boeing doesn’t put a price on required safety features.

And:

There are no pilot actions or procedures during flight which require knowledge of angle of attack.

So, yeah, we did all we were required to do, and we weren't required to provide a visual clue that the AoA sensors were providing grossly different values even while the aircraft was taxiing.

scbriml wrote:
D L X wrote:
planecane wrote:
When they disagree with each other by more than a few degrees.

I guess the next question is, when they disagree, which one does the system trust?

Well mine would have been: Define "more than a few degrees".
But in fairness to planecane, he did say to disable MCAS at that point, so the decision as to which one to trust wouldn't arise.

FWIW, Boeing defined it as:

If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate.
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abies111
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 12:44 am

Don't know if already mentioned that maybe another problems contribute to the aircraft control issues:

https://www.washingtonpost.com/world/af ... 4a71104515

"Additional software problem detected in Boeing 737 Max flight control system, officials say"
 
RogerMurdock
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 1:15 am

Revelation wrote:
There are no pilot actions or procedures during flight which require knowledge of angle of attack.

So, yeah, we did all we were required to do, and we weren't required to provide a visual clue that the AoA sensors were providing grossly different values even while the aircraft was taxiing.


AoA display and AoA Disagree warning are two different features. There is reasonable debate as to whether display of raw or scaled AoA values is useful to commercial transport pilots. (Military is a different story). I'm pretty sure that everyone at this point has realized that the AoA Disagree warning should be standard, however.
 
juliuswong
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 1:42 am

Read this article in local news: Between Two Boeing Crashes, Days of Silence and Mistrust

https://www.nytimes.com/2019/04/02/worl ... n-air.html

Sickening behaviour by Boeing and FAA. They have blood on their hand! These double tragedies, entirely predictable and entirely preventable (at least for ET flight if information are shared earlier), are in fact crimes committed by Boeing leadership, who gambled with innocent souls as they placed profit above safety.

I hope Boeing is edged out of NB for good, really don't mind Airbus being the sole supplier. Boeing corporate leadership should be held accountable, prosecuted and convicted. The Boeing board members should also be held accountable and prosecuted accordingly. Just sickening!
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dragon6172
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 1:47 am

Revelation wrote:

There are no pilot actions or procedures during flight which require knowledge of angle of attack.

So, yeah, we did all we were required to do, and we weren't required to provide a visual clue that the AoA sensors were providing grossly different values even while the aircraft was taxiing.

AoA indicators reading different on the ground is somewhat normal.
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MildBlueYonder
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 2:34 am

kalvado wrote:
787Driver wrote:
Damn Boeing is in deep shit if indeed the pilots used the stab trim cutout but were still unable to control the aircraft. I wonder how many lawsuits are waiting and how much compensation Boeing will end up having to pay?

And how it would affect the cash position for 797 development.
737 used to be a cash cow to carry Boeing through 787 turbulent development. I wonder if 787 has enough potential to fill that role, while 777 is in transit as well.


From a business perspective, these latest developments probably represent good news for Boeing as they suggest the same set of software problems led to both crashes rather than multiple separate issues being involved, even worse had the much more expensive and far less modifiable aero structures been implicated.

The software bugs can be fixed relatively on the cheap, and the total payouts to families—even if they are generous—will have a ceiling (and may even come in under the $280 million they would have owed WN if additional transitions training had been required). I actually think Boeing, its shareholders, and Max customers are all breathing a sigh of relief from the latest news as it means their investments will likely be protected. Call me jaded, but I don’t think Muilenberg, et al., feel all that panicked by today’s preliminary findings.
 
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Aesma
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 2:42 am

planecane wrote:
Most of what you list here is unnecessary. First of all, with respect to the number of AoA sensors, two is sufficient. For a FBW aircraft, triple redundancy is necessary because the flight control computer needs valid data in order for the plane to fly. In the case of MCAS, it just needs to recognize a failed sensor and shut off. If two sensors simultaneously fail with similar invalid measurements, it is likely that a 3rd or 10th would fail as well..


FBW or not doesn't make a difference. With Airbus aircraft, you lose one sensor, the aircraft throws some warnings but continues to work as usual, because it trusts the remaining sensors. If it wasn't a FBW aircraft, then it would be the pilots who would be looking at sensor data and choosing (of course in practice AoA isn't usually displayed). If two sensors go awry (supercooled water in pitot tubes for AF447 for example) then the aircraft changes its flying laws, letting the pilots decide, and deactivating the envelope protections. You could have the same philosophy with only two sensors, but of course the situation would then happen more often. The logical thing to do is to deactivate envelope protections (and warn the pilots) if sensors are unreliable.

So far I've not seen anything suggesting Boeing plans to do that (deactivate MCAS in case of AoA disagree), which I find quite concerning. Now I'd like to have more info about the 777 and 787 FBW philosophies...
New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
 
planecane
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 3:04 am

Aesma wrote:
planecane wrote:
Most of what you list here is unnecessary. First of all, with respect to the number of AoA sensors, two is sufficient. For a FBW aircraft, triple redundancy is necessary because the flight control computer needs valid data in order for the plane to fly. In the case of MCAS, it just needs to recognize a failed sensor and shut off. If two sensors simultaneously fail with similar invalid measurements, it is likely that a 3rd or 10th would fail as well..


FBW or not doesn't make a difference. With Airbus aircraft, you lose one sensor, the aircraft throws some warnings but continues to work as usual, because it trusts the remaining sensors. If it wasn't a FBW aircraft, then it would be the pilots who would be looking at sensor data and choosing (of course in practice AoA isn't usually displayed). If two sensors go awry (supercooled water in pitot tubes for AF447 for example) then the aircraft changes its flying laws, letting the pilots decide, and deactivating the envelope protections. You could have the same philosophy with only two sensors, but of course the situation would then happen more often. The logical thing to do is to deactivate envelope protections (and warn the pilots) if sensors are unreliable.

So far I've not seen anything suggesting Boeing plans to do that (deactivate MCAS in case of AoA disagree), which I find quite concerning. Now I'd like to have more info about the 777 and 787 FBW philosophies...

I'm pretty sure that I read that Boeing plans to do exactly that in the MCAS software update and disable the system on an AoA disagreement if more than 5.5 degrees.

As for the 777 and 787 I'm sure they have triple redundancy on critical sensors. The 777 is among the safest aircraft every built. If there was a fatal flaw in the FBW design philosophy it would have appeared in over 20 years. The 787 wouldn't have gone backwards in design. I'm sure it is an evolution of the same system.
 
oschkosch
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 5:45 am

it goes from bad to worse, a little more every day!

https://www.smh.com.au/business/compani ... 51b1w.html

The parents of Samya Stumo, 24, alleged Boeing was "blinded by its greed" and rushed the 737 Max 8 to market with the "knowledge and tacit approval" of the FAA, while hiding defects in its automated flight-control system. The suit also cites a similar flaw in the Lion Air flight of a 737 Max 8 jet that crashed into the Java Sea on October 29, killing 189.

https://www.buzzfeednews.com/article/cl ... ashes-that

Boeing's CEO admitted on Thursday that a failure of its software was one of the causes in the recent deadly 737 Max jet crashes.
Dennis Muilenburg said a new software update would prevent future incidents.
"It's our responsibility to eliminate this risk," Muilenburg said in a video message on Thursday. "We own it, and we know how to do it."

Muilenburg's acknowledgement of Boeing's responsibility came after the release earlier Thursday of a preliminary report on the March 10 crash of Ethiopian Airlines Flight 302, which killed all 157 people on board. In the report, Ethiopian investigators said the jet's pilots followed all safety procedures before the crash.

http://www.globaldomainsnews.com/plane- ... re-problem

The newspaper wrote, citing two of the FAA investigation, familiar sources, that the Problem will be classified as critical for flight safety. Boeing described it, however, as a “relatively minor matter” that will fix the group along with the MCAS-Update. “We already have a solution in work”, – was stated in the opinion of the group. In the “coming weeks” will be the Update to the extent that it could be submitted to the FAA for certification. Boeing was pursuing a “comprehensive, disciplined approach, to do it right”.

https://www.rt.com/news/455598-boeing-7 ... e-problem/

‘Minor’ critical problem? Boeing admits ANOTHER glitch in 737 MAX software
 
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Jouhou
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 6:34 am

https://www.msn.com/en-us/news/us/addit ... ar-BBVBQQo

But later Thursday, Boeing confirmed to The Washington Post that it had found a second software problem that the Federal Aviation Administration has ordered fixed — separate from the anti-stall system that is under investigation in the two crashes and is involved in the worldwide grounding of the aircraft.

That additional problem pertains to software affecting flaps and other flight-control hardware and is therefore classified as critical to flight safety, said two officials with knowledge of the investigation.


It'd be nice If it didn't take a crisis to prompt Boeing to get around to debugging their flight control software.
 
smartplane
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 6:49 am

abies111 wrote:
Don't know if already mentioned that maybe another problems contribute to the aircraft control issues:

https://www.washingtonpost.com/world/af ... 4a71104515

"Additional software problem detected in Boeing 737 Max flight control system, officials say"

Additional software, namely that related to flaps and autopilot, in certain instances being able to counter pilot attempts to defeat MCAS.
 
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seahawk
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 6:56 am

And that ignores the problem of the manual trim not being able to overcome the forces on the stabilizer and pilots being unable to move the stab quickly enough.

But in the end it is always bad when a firm calls something a critical but minor problem. It usually means "we made a big blunder".
 
excalibur
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 7:24 am

Jouhou wrote:
https://www.msn.com/en-us/news/us/additional-software-problem-detected-in-boeing-737-max-flight-control-system-officials-say/ar-BBVBQQo

But later Thursday, Boeing confirmed to The Washington Post that it had found a second software problem that the Federal Aviation Administration has ordered fixed — separate from the anti-stall system that is under investigation in the two crashes and is involved in the worldwide grounding of the aircraft.

That additional problem pertains to software affecting flaps and other flight-control hardware and is therefore classified as critical to flight safety, said two officials with knowledge of the investigation.


It'd be nice If it didn't take a crisis to prompt Boeing to get around to debugging their flight control software.


That's what you get when you rush things desperately trying to catch your competitor. A messy plane out of a 60 years old design. Clearly not the Boeing company I remember... Truely hope they will recover from this. Boeing employees and costumers deserve better.
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scbriml
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 7:40 am

abies111 wrote:
Don't know if already mentioned that maybe another problems contribute to the aircraft control issues:

https://www.washingtonpost.com/world/af ... 4a71104515

"Additional software problem detected in Boeing 737 Max flight control system, officials say"


It's OK, Boeing says it's a minor issue (that just happens to be classified as critical to flight safety). :banghead:


So, anyone want to take part in the a.net "When will the MAX be ungrounded" sweepstake?
Time flies like an arrow. Fruit flies like a banana!
There are 10 types of people in the World - those that understand binary and those that don't.
 
XRAYretired
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 7:57 am

smartplane wrote:
abies111 wrote:
Don't know if already mentioned that maybe another problems contribute to the aircraft control issues:

https://www.washingtonpost.com/world/af ... 4a71104515

"Additional software problem detected in Boeing 737 Max flight control system, officials say"

Additional software, namely that related to flaps and autopilot, in certain instances being able to counter pilot attempts to defeat MCAS.


Paywall probs. Can you post the bit that relates the new problem MCAS pls.

Ray
 
marcelh
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:04 am

MildBlueYonder wrote:
kalvado wrote:
787Driver wrote:
Damn Boeing is in deep shit if indeed the pilots used the stab trim cutout but were still unable to control the aircraft. I wonder how many lawsuits are waiting and how much compensation Boeing will end up having to pay?

And how it would affect the cash position for 797 development.
737 used to be a cash cow to carry Boeing through 787 turbulent development. I wonder if 787 has enough potential to fill that role, while 777 is in transit as well.


From a business perspective, these latest developments probably represent good news for Boeing as they suggest the same set of software problems led to both crashes rather than multiple separate issues being involved, even worse had the much more expensive and far less modifiable aero structures been implicated.

The software bugs can be fixed relatively on the cheap, and the total payouts to families—even if they are generous—will have a ceiling (and may even come in under the $280 million they would have owed WN if additional transitions training had been required). I actually think Boeing, its shareholders, and Max customers are all breathing a sigh of relief from the latest news as it means their investments will likely be protected. Call me jaded, but I don’t think Muilenberg, et al., feel all that panicked by today’s preliminary findings.


From a corporate view you are right, but it also shows the inhumanity of the corporate world we are living in. A human life is just a liability.
 
XRAYretired
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:04 am

scbriml wrote:
abies111 wrote:
Don't know if already mentioned that maybe another problems contribute to the aircraft control issues:

https://www.washingtonpost.com/world/af ... 4a71104515

"Additional software problem detected in Boeing 737 Max flight control system, officials say"


It's OK, Boeing says it's a minor issue (that just happens to be classified as critical to flight safety). :banghead:


So, anyone want to take part in the a.net "When will the MAX be ungrounded" sweepstake?



We may be mixing things a little here. The system is safety critical, so a problem with it so classed. The fix may be simple to implement and therefore minor in that aspect.

Ray
 
xmp125a
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:07 am

scbriml wrote:
D L X wrote:
planecane wrote:

When they disagree with each other by more than a few degrees.

I guess the next question is, when they disagree, which one does the system trust?


Well mine would have been: Define "more than a few degrees".

But in fairness to planecane, he did say to disable MCAS at that point, so the decision as to which one to trust wouldn't arise.


But MCAS was condition for certification of the 737MAX as an upgrade (not entirely new design that would require more elaborate pilot retraining) as I understand?! I personally believe that is the reason there is no "MCAS off" switch and the reason why MCAS was not mentioned in the manual. It was planned to be never visible to pilots, unlike AP. Of course, safety-wise that is terrible choice.

But, as soon as you switch MCAS off, the plane and/or the pilot are not certified anymore, right? Because aerodyamics characteristics at high pitch have been changed and suddenly the pilot is sitting on a airframe+engine combo he did not train for. Indeed, if MCAS is needed to avoid stall due to different placement of engines then disabling MCAS can cause crash due to stall, right?
 
WIederling
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:13 am

oschkosch wrote:
‘Minor’ critical problem? Boeing admits ANOTHER glitch in 737 MAX software


Same thing they did for the 787 batteries grounding.
Introduce that Boom Box with great fanfare and
change charging behavior and a choice selection of other issues
in the background "dum di dum di dum, trala, nothing to be seen, ha ha".
Murphy is an optimist
 
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scbriml
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:15 am

XRAYretired wrote:
We may be mixing things a little here. The system is safety critical, so a problem with it so classed. The fix may be simple to implement and therefore minor in that aspect.


Yes, I do understand that. The head banging is more about the fact that this error was only discovered now while looking into the MCAS issues and not prior to certification.
Time flies like an arrow. Fruit flies like a banana!
There are 10 types of people in the World - those that understand binary and those that don't.
 
mjoelnir
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:21 am

I still do not understand people being so blase about manual trim not working, when you come to that point in the checklist.

There is also this point. In the 737-200 operating manual, there is a procedure to help you trim, because it was know that manual trim was sometimes very difficult to move.

Since than this description is no included in the operating manual anymore and on the way to the MAX the trim wheels were reduced in size to make it still more difficult to trim manually.
 
xmp125a
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:24 am

morrisond wrote:

You are making my argument for me. If 80 per cent of crashes are due to human error - shouldn't we be focusing on the 80 percent vs the 20 percent?

MCAS was a design issue falling in the 20 per cent bucket.

Training standards have fallen since 2002 as clearly evidenced that a FO with only 300 hours was given control of aCommercial airplane with over 150 souls onboard.


First, selling point of 737MAX series is that it does not need additional pilot training.
Second, the voice recording clearly documents that FO was calling out proper procedure, that is disabling trim motors per Boeing's procedure to handling erroneous MCAS invocation. So that FO, 300 hours or not (I believe it was close to 400) was up to date with protocols. Those were not two clowns flying "modern american plane", but trained pilots who reacted as expected.

Third, I would be very wary of blaming "third world pilots", let alone "third world birds" (for potentially damaging AoA sensor) for those two crashes. If Boeing made an airplane that could only safely fly in USA and part of the Europe, then Airbus will be extremely concerned - you know, concerned with how to handle all that orders that will come in after 737max cancellations! Imagine being the owner of the low cost asian airline with standing order for 737MAX and hearing all this blaming of "3rd world pilots". Well, 3rd world has its problems (most people there don't own a car, let alone a hobby airplane, unlike on the west - which allows western airlines to cherrypick pilots with 1000s of hours flying hobby airplanes for airline pilot's job), but Boeing should know this and design aircraft AND THE TRAINING REQUIREMENTS to take this into the account!

FO with 400 hours not good to fly 737MAX? 1000 Hours needed minimum? Ok, just put that in official plane requirements and see what happens with your orders across the world!
 
XRAYretired
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:26 am

scbriml wrote:
XRAYretired wrote:
We may be mixing things a little here. The system is safety critical, so a problem with it so classed. The fix may be simple to implement and therefore minor in that aspect.


Yes, I do understand that. The head banging is more about the fact that this error was only discovered now while looking into the MCAS issues and not prior to certification.


Not intended to be critical, apologies if it read that way, just wanted to get the point out there.

Ray
 
XRAYretired
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:58 am

mjoelnir wrote:
I still do not understand people being so blase about manual trim not working, when you come to that point in the checklist.

There is also this point. In the 737-200 operating manual, there is a procedure to help you trim, because it was know that manual trim was sometimes very difficult to move.

Since than this description is no included in the operating manual anymore and on the way to the MAX the trim wheels were reduced in size to make it still more difficult to trim manually.

I think the nub of the question is if the manual trim is operable at 'normal speeds' or not. Remember, with the MCAS fixed you should not end up in the situation where this checklist is needed when in overspeed with no electric trim (not needed at all in fact). So if you are in overspeed for any other reason the overspeed checklist applies and you have electric trim to manage trim.
I'm sure knowledgible posters can come up with complicated scenarios that may contradict but, no one has indicated this has been a problem on NG?

Ray
 
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speedbored
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 8:59 am

XRAYretired wrote:
Paywall probs. Can you post the bit that relates the new problem MCAS pls.

Simple workaround - sign up for the free trial and, whenever you hit the free article limit, delete the site cookies and sign up again.
 
ei146
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 9:18 am

A stupid question regarding the manual trim wheels from a layman:
As I understood it it may be possible that after the cut out of automatic trim (MCAS or whatever) the pilots may have to deal with a completly untrimmed plane, requiering countersteering. Depending on the situation this might result in strong forces to the control surfaces, making it difficult or impossible to manually use the trim wheels, so the pilots can not manually correct the trim, or they can not do it fast enough. This seems to be a known problem as old training manuals talked about it. And this might be a contributing factor in the last crash.
If this is known, why is there no system to support the pilots in these situations to support trim wheel operation? In our cars we have power steering and power brakes. Could such systems help here?
 
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speedbored
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 9:32 am

ei146 wrote:
A stupid question regarding the manual trim wheels from a layman:
As I understood it it may be possible that after the cut out of automatic trim (MCAS or whatever) the pilots may have to deal with a completly untrimmed plane, requiering countersteering. Depending on the situation this might result in strong forces to the control surfaces, making it difficult or impossible to manually use the trim wheels, so the pilots can not manually correct the trim, or they can not do it fast enough. This seems to be a known problem as old training manuals talked about it. And this might be a contributing factor in the last crash.
If this is known, why is there no system to support the pilots in these situations to support trim wheel operation? In our cars we have power steering and power brakes. Could such systems help here?

They do have such a system. Unfortunately, it uses the same actuators that MCAS does, so it had to be disabled in order to disable MCAS.
 
mjoelnir
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 9:37 am

ei146 wrote:
A stupid question regarding the manual trim wheels from a layman:
As I understood it it may be possible that after the cut out of automatic trim (MCAS or whatever) the pilots may have to deal with a completly untrimmed plane, requiering countersteering. Depending on the situation this might result in strong forces to the control surfaces, making it difficult or impossible to manually use the trim wheels, so the pilots can not manually correct the trim, or they can not do it fast enough. This seems to be a known problem as old training manuals talked about it. And this might be a contributing factor in the last crash.
If this is known, why is there no system to support the pilots in these situations to support trim wheel operation? In our cars we have power steering and power brakes. Could such systems help here?


You just switched of the power assist to stop the automatic trim from trying to kill you. There is electric trim, but both you and the automatic can use it. There is no switch to switch off the automatic only.

Just think the situation those pilots are in. There are several faults and several checklists to follow. You have unreliable airspeed, so that checklist tells you to keep up the speed. You have MCAS trying to kill you, so you switch of the electrical trim. Now you can not manual trim because you fly at a rather high speed. And that are only two of the many problems coming down on you at the same time. Catch 22 at its best or worst.

Boeing should be banned from writing in its checklists: and now you use the wheels to trim the frame manually. Boeing would need to find a different solution for these problems, but that would lead to a redesign, end of grandfathering, perhaps new type and more training for pilots to move between frames. A catastrophic event for bean counters.
 
aleka
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 9:53 am

Please can anyone tell me why an anti stall system can be triggered if you are already over speeding? That makes no sense to me...
 
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seahawk
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 9:55 am

Because the AoA sensor is not working correctly.
 
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Jouhou
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Re: B737MAX Grounded Worldwide

Fri Apr 05, 2019 10:07 am

XRAYretired wrote:
mjoelnir wrote:
I still do not understand people being so blase about manual trim not working, when you come to that point in the checklist.

There is also this point. In the 737-200 operating manual, there is a procedure to help you trim, because it was know that manual trim was sometimes very difficult to move.

Since than this description is no included in the operating manual anymore and on the way to the MAX the trim wheels were reduced in size to make it still more difficult to trim manually.

I think the nub of the question is if the manual trim is operable at 'normal speeds' or not. Remember, with the MCAS fixed you should not end up in the situation where this checklist is needed when in overspeed with no electric trim (not needed at all in fact). So if you are in overspeed for any other reason the overspeed checklist applies and you have electric trim to manage trim.
I'm sure knowledgible posters can come up with complicated scenarios that may contradict but, no one has indicated this has been a problem on NG?

Ray


The flight before JT610 was able to manually trim. I'd say yes, it can be. (answering the first question you posed)

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