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glideslope
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 5:18 pm

phollingsworth wrote:
glideslope wrote:
planecane wrote:
MCAS, when operating properly, does not "force the plane to dive." In introduces a mis-trim to cause it to take more force to lift the nose more. MCAS, operating properly, would never have caused a plane to dive or even for a pilot to notice it existed. The issue with MCAS was the botched fault tree analysis and allowing a single sensor failure to cause a potentially catastrophic runaway.

The need for and inclusion of MCAS is not the issue. Especially since it is only need for edge cases that aren't entered into very often, if at all, in normal service. As long as MCAS is fixed to only operate when and how it was originally intended, there is no issue with it.

STS on the NG is doing something similar. It just didn't have the authority and lack of a simple cutout (the column switches for STS) to cause a problem. Actually, STS activates in normal operation all the time so it is far more active than a properly functioning MCAS would ever be.


Correct. The Max is not an inherently unstable design. It was the implementation of MCAS with poorly written code from outsourcing, lack of training, lack of communication with pilots and companies, and Boeings unwillingness to to own up and fix things. Personally I don't see how the Max can fly again if MCAS is retained without a new Type Rating. The Max simply flys different enough from an NG to warrant this.

I'm starting to agree however that it is approaching the point where Boeing may need to think about cutting the program, ask for some Govt. assistance as other companies do ( :box: ) and design a new NB. It's the only way to truly recover from this.


Except that all the evidence says that for the Normal and Operating flight envelope the MAX flies substantially the same as the NG. AS Planecane points out the NG, at the behest of the JAA (now EASA), has an AoA driven function in the Speed Trim System to force the aircraft nose-down in certain situations. This looks to operate in a continuous fashion driving the stab to the limits at a constant rate. Further, the Elevator feel mechanism is designed to make it quite hard for the pilot to reach the aft-cutout limit. This is systems is provided by two simplex systems in an active-monitor setting with a warning light if active disagrees with monitor. Note this disagree activated in the MTC log on the two JT flights, but for some reason the indicators in the cockpit didn't work.

MCAS in its original incarnation was to add manoeuvre stability (stick force per g), as such you don't want the elevator feel mechanism making it impossible to pull back as this makes the aircraft less/un-manoueverable. So Boeing disabled the aft column cutout. However, when Boeing moved it to the 1g case with the increased rates. The fact is that the rates for MCAS are the same as those in the flaps down condition. So what is the problem.
1. Boeing removed the aft-column cutout from the 1g STS/MCAS case. Given that the authority is faster and has a greater range this will delay countering and put the aircraft into a more severe miss-trim.
2. Boeing converted the continuous STS/AoA run to a cyclical one, further delaying the ID.

My guess is the higher rate and range have to do with the fact that the stall is even less identifiable in the MAX compared to the NG. There will be less buffet and the aircraft will have less nose-down tendency. Note: stab trim does not fix the control force issue, it makes it somewhat worse. This is done by the elevator feel system. The problem here is this seems to be solely driven the airspeed. So reasonable for column force to airspeed stability, but no good for column force to AoA stability near stall (this isn't required for anything other than stall ID).


Agreed. Great overview. Thank you. :checkmark:
To know your Enemy, you must become your Enemy.” Sun Tzu
 
2175301
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 5:45 pm

Revelation wrote:
phollingsworth wrote:
Boeing is currently paying the price for trying to retrofit safety criticality into an avionics suite that is not design to be safety critical. It is something that can be done, but basically requires rewriting the entire software stack to accomplish. Had Boeing gone for a rebuild of the underlying avionics on 737MAX in the first instance this would have been a much larger task upfront but would have made RTS a much simpler prospect, FBW or no FBW.

As per earlier posts, the stuff Boeing is doing now (going from active-standby pair to active-active pair) is not a rewrite of the entire stack, it's largely done so you do not have to rewrite the entire stack! The software stack itself is largely preserved, just some comparators are added around the edges, and just some more triggers for disengagement are added. In theory since you already have an active-standby pair the software already has some robustness with respect to rapid failover. The main issue becomes one of testing, and as we've seen with the issue reported last week about activating displays at start up time you often find some places where the software needs more hardening.

It's interesting to see the software audits being held in Cedar Rapids. It's as clear an indication one can get that the center of expertise with regard to the flight control software is at a vendor's site, which IMHO is an absurd position for Boeing to have put itself into.


If I may point out... Boeing is indeed rewriting some of the programs in the "stack" as you refer to it. They announced as part of the change to the flight computers that they would be changing some things to simplify operation and for other reasons. So some of the existing programs remain with verifying output with the other computer checks added where appropriate. Other programs are being rewritten or replaced.

The checking between the computers to verify matches is a lot more complex than most people understand... as you also have to be able to determine the course of action if they disagree... how does the computers keep the aircraft flying?... When does a computer shut down and how does it turn over to the other computer. Those are not simple things. Now Boeing has done that for other more modern aircraft so it's not a new exercise. But, it is highly complex.

Also, I disagree with your concept that somehow Boeing should have all knowledge and expertise in-house. Where else do you do most testing than at the manufacturer who is responsible for the item? That is actually the best place to do most validation testing. They can fix things fastest (and perhaps in less than a day) if they see a problem.

Now certain kinds of testing are shopped out to specialized testing labs (vibration testing goes to test labs with shaker/vibration tables, etc.) Flammability goes to another lab, etc.

Have a great day,
 
hivue
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 5:47 pm

PixelFlight wrote:
It's an ongoing debate if it really could lead to a stall just because MCAS is disabled.


It's an ongoing debate in the sense that whether the Earth is flat or not is an ongoing debate. A pilot can stall the MAX with or without MCAS active. He can stall it with MCAS 1.0, MCAS 2.0, MCAS x.0. A pilot cannot stall a FBW airplane with envelope protection operating in normal law. None of this is as complicated as we're trying to make it.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
2175301
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 6:16 pm

Hindsight Engineering:

Many are stating what is now obvious after the event and after the JTAR and NTSB reports. Also a number of people seem not to understand that there are no perfectly designed aircraft.

While the above mentioned report do mention that Boeing only tested one failure at a time.... There was no requirement for them to do more... and if you read the reports you will find a recombination that "all" international certification agencies need to ensure that multiple failure scenarios are tested at once to determine the workload on the pilots. My conclusion. Boeing was not the only company just testing single failures.

Both reports indicate that Boeing essentially followed the certification process and requirement; even if some things were debatable.

Both reports aim to improve practices by both manufactures and regulators to change and improve the process and standards.

There are other things as well in those reports that are "suggestions" for all international regulators.

Putting larger engines on aircraft has caused similar problems with certain Airbus "NEO" aircraft. Right now there are a bunch of them flying with limitations on the number and locations of passengers for "Center of Gravity" issues for rare edge of envelope flight conditions while Airbus develops appropriate changes to their FBW software to properly address the issue. I note that Airbus discovered the issue after reviewing their own aircraft for similar issues as the 737MAX flight profile issues.

A reality is that it appears that the Boeing design team (not the simulator/training development team) were in fact following decades of established procedures using standard assumptions.

The fact that some of those procedures and assumptions were wrong... is not something so easily seen before they fail (that is the nature of things). They had apparently worked for decades up to that point.

Many improvements to aircraft design, testing, and certification will flow from this tragedy. But, please recognize that what many people are presenting as issues... were only identified as an issue by the messed up safety analysis of MCAS V1. Also, the clear implications of both the JATR and NTSB reports are that a number of those procedures and assumptions were occurring elsewhere in the world as well.

Have a great day,
 
asdf
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 6:43 pm

2175301 wrote:
Hindsight Engineering:

Many are stating what is now obvious after the event and after the JTAR and NTSB reports. Also a number of people seem not to understand that there are no perfectly designed aircraft.



is see what you did here

and what you want us to believe is simply wrong

there is a huge difference between a generally flawed aerodynamical concept of a plane
and some minor adjustments on new developed models which are really common in that industry
 
kayik
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 6:55 pm

Something happened. Boeing lost over $6 billion value in the last 5 minutes.
 
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:02 pm

morrisond wrote:
Three things.

Runaway Trim NNC is basically common to all aircraft types and the ability to run this should not be considered abnormal or requiring test pilot skills. This is why I keep beating a dead horse as this is not MAX specific.


And we keep beating the same dead horse that recognizing an intermittent thing (= non-continuous) does not jive with the wording of the NNC: the NNC clearly calls out CONTINUOUSLY.

Another dead horse, and probably even the bigger issue at hand: how to recognize the correct NNC in a timely fashion under camouflage of a) non-continuous, b) a plethora of other warnings and alerts, c) some of them perhaps even more important/urgent, d) some of them even conflicting with nose up commands, and e) none of this ever being required/recommended to be trained for.



Second, the odds of converting the MAX to FBW or adding an additional system are about O - it would be a lot easier just to train the pilots.

I think you will find that most regulators may consider the unaugmented stall characteristics unsuitable for coping by training only. While we have no evidence of such, there are various indications for such:
• JATR Report writes that MCAS could be considered as stall identification systems or stall protection systems, depending on the natural (unaugmented) stall characteristics of the aircraft;
• It seems to take ages for this specific test (unaugmented stall characteristics) to be performed;
• This test is in the grand scheme of things probably the mosty simple procedure of the Return-to-Flight (RtF) effort, it could have been done immediately after the JATR report;
• If the unaugmented stall characteristics were really as benign as some (Boeing?) want us to believe, surely Boeing would have thrown/leaked some hard data showing the opposite;
• MCAS received heavy authority at low speed regime, both in terms of trim rate (higher than manual electric trimming), and trim amplitude in one single cycle (never mind the repeating authority on MCAS 1.0);
• We have no signs that Boeing ever explored the path of non-MCAS, nor that it is exploring it now for RtF effort. That would be the easy way out, especially since we have now learned Boeing will recommend additional training for MCAS 2.0;
• Boeing is going through a monumental effort for RtF, including MCAS 2.0, cross-comms between FCC, training, and who knows what. All that effort is still seems to be easier than ”just to train the pilots”. I'm inclined to believe there must be good reasons for that . . .




However on the above even if you still have electric trim available it may have not made a difference on the ET flight as even it may not be effective in all corners of the envelope or beyond the normal envelope - which is normal.

It is absolutely *not normal* for any flight control function (including trim) to not work in any part of the (approved) operational flight envelope. Or do you have evidence that the trim does work all the way upto Vmo?
BTW, I believe I have read on here that trim should even be effective upto Vd, which is even higher than Vmo. Admittedly, I do not know if this is correct, or if I have read that correctly.



So you still have to know that leaving Autothrottle engaged at TOGA thrust is a bad idea.

We have no evidence *why* the crew left the throttle were it is. You suggest more or less that they panicked, or did not know/understand how autothrottle works. It may just as well be that as they were having greatful trouble keeping the nose up, and that they did not want to introduce another nosedown moment by reducing throttle. At this stage, your suggestion is nothing more than an assumption (as is mine . . . ).
Not to mention that reducing thrust with stick shaker and/or stall warning active usually is a bad idea . . .



One of the theories on why ET did not bring the plane back into trim when they turned the electric trim back on is that it caused violent effects on the frame and in the cabin due to the excessive high speed - basically trying to throw the pilots to the ceiling and hence why they only used it briefly twice.

Another wild theory/baseless assumption.
Surely, letting somewhat loose of the pulling force of the control column in response to ANU trimming would mostly balance out supposedly violent actions. Your assumptions are not supported by the DFDR graph of control column force.

They made several ANU manual electric trim inputs after MCAS became alive (so they knew quite well fow trim works . . . ). In fact, there were no less than four attempts. All four ended at exactly the same stabilizer pitch angle. While the last two were in Vmo region, the first two were well below Vmo. Yet all four ended at the same stabilizer pitch angle. Even if one wanted to do such on purpose, one would find itself hard-pressed to achieve the exact same angle at all four attempts. There must be more to it than “they forgot to -, or did not understand how to bring back the plane into trim”.



It could have made a difference earlier in the flight right after first and second MCAS activation before they exceeded Vmo - but then they still had electric trim available and could have simply returned it to in-trim before turning it off - just like there Company procedures told them to do so.
As far as we know it still worked and as evidenced later in the flight it still did when they turned it back on.

See above.
Also, As far as we know, it did not work as evidenced by the two manual electric ANU trimming stopping prematurely immediately after MCAS ran-away. They did try to bring it back into trim, but the system/plane did not allow them to do so.
There is just as much fact in this statement as yours, but probably closer to the truth . . .
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Dieuwer
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:13 pm

Boeing stock sinks 5% on more delays. No FAA sign-off in sight.
 
ShamrockBoi330
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:18 pm

Dieuwer wrote:
Boeing stock sinks 5% on more delays. No FAA sign-off in sight.


Further to your point, the CNBC report.

https://www.cnbc.com/2020/01/21/boeing- ... -july.html
 
MSPNWA
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:19 pm

PW100 wrote:
And we keep beating the same dead horse that recognizing an intermittent thing (= non-continuous) does not jive with the wording of the NNC: the NNC clearly calls out CONTINUOUSLY.

Another dead horse, and probably even the bigger issue at hand: how to recognize the correct NNC in a timely fashion under camouflage of a) non-continuous, b) a plethora of other warnings and alerts, c) some of them perhaps even more important/urgent, d) some of them even conflicting with nose up commands, and e) none of this ever being required/recommended to be trained for.


It keeps getting beaten because some here simply don't want to accept the fact that a runaway stab in a 737 shouldn't be a life-ending issue. But the industry as whole has allowed a greater possibility of that, and that's one of the reasons the MAX is grounded and the public (not Boeing, not the airlines) is paying the price.

By continuing to repeat the unsubstantiated and illogical claim that the NNC was insufficient, you're exhibiting the very behavior you're supposedly correcting. To prove this again, to confirm your claim that the the word "continuously" was insufficient in these cases, it must be assumed that the pilots were extremely proficient on the language of the NNC, so proficient that in the "chaos" of the emergency they knew the literal dictionary definitions of the words and voluntarily decided that the NNC didn't apply to this situation because it didn't perfectly fit the plane's behavior. So it must be implied that their failure to use the NNC was actually because they knew the NNC so well. It also must be implied that the crew of JT43 made a mistake in interpreting the language that way, and that mistake is what saved them. To put it mildly, it's an absurd belief.
Last edited by MSPNWA on Tue Jan 21, 2020 7:23 pm, edited 1 time in total.
 
Dieuwer
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:22 pm

I suppose the Chinese and European regulators are shaking their heads when watching the MAX Soap Opera.
I would not be surprised if they already decided - behind closed doors - to not let the MAX fly, ever.
 
asdf
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:23 pm

i dont understand those guys

correct the aerodynamical flaw
no more need for MCAS
accept the higher fuel consumption
and compensate it to the airlines

as soon as that MAX are up in the air
build that NSA

if you are able to deliver the NSA
offer a trade in on the 737MAX to stop compensation

it is not so hard to do that calculation and I am convinced its the cheapest way to get out of this drama
 
MSPNWA
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:24 pm

ShamrockBoi330 wrote:
Further to your point, the CNBC report.

https://www.cnbc.com/2020/01/21/boeing- ... -july.html


In my opinion it's long past time for the public to rise up and demand the FAA put an end to this charade and clear the MAX with MCAS 2.0.
 
ShamrockBoi330
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:26 pm

MSPNWA wrote:
ShamrockBoi330 wrote:
Further to your point, the CNBC report.

https://www.cnbc.com/2020/01/21/boeing- ... -july.html


In my opinion it's long past time for the public to rise up and demand the FAA put an end to this charade and clear the MAX with MCAS 2.0.


Sorry, think you're wrong on that! there's at least 350 relations to those who perished out there that never want see this plane fly again.
 
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:31 pm

MSPNWA wrote:
PW100 wrote:
And we keep beating the same dead horse that recognizing an intermittent thing (= non-continuous) does not jive with the wording of the NNC: the NNC clearly calls out CONTINUOUSLY.

Another dead horse, and probably even the bigger issue at hand: how to recognize the correct NNC in a timely fashion under camouflage of a) non-continuous, b) a plethora of other warnings and alerts, c) some of them perhaps even more important/urgent, d) some of them even conflicting with nose up commands, and e) none of this ever being required/recommended to be trained for.


It keeps getting beaten because some here simply don't want to accept the fact that a runaway stab in a 737 shouldn't be a life-threatening issue. But the industry has allowed it to be one, and that's one of the reasons the MAX is grounded and the public (not Boeing, not the airlines) is paying the price.

By continuing to repeat the unsubstantiated and illogical claim that the NNC was insufficient, you're exhibiting the very behavior you're supposedly correcting. To prove this again, to confirm your claim that the the word "continuously" was insufficient in these cases, it must be assumed that the pilots were extremely proficient on the language of the NNC, so proficient that in the "chaos" of the emergency they knew the literal dictionary definitions of the words and voluntarily decided that the NNC didn't apply to this situation because it didn't perfectly fit the plane's behavior. So it must be implied that their failure to use the NNC was actually because they knew the NNC so well. It also must be implied that the crew of JT43 made a mistake in interpreting the language that way, and that mistake is what saved them. To put it mildly, it's an absurd belief.


I'm honestly struggling to understand what is "extremely proficient on the language" with respect to the word CONTINUOUSLY???


If one crew (with the benefit of an additional member in an observer role) can find the right solution in the correct time frame, what guarantees would that give that all crews could/should to that as well?
The fact that I can successfully type my own name without typing errors, does not mean I will do just that every single time. And that is about the simplest task for a human being. A million times easier than recognizing MCAS run-away.

Why would Boeing design MCAS for a 10 second cycle duration, when you expect them to shut it down after three seconds (because that in Boeings mind would constitute to a trim runaway). Let alone design it for multiple 10 second cycles (MCAS 1.0 that is). By designing in the 10 second MCAS cycle, Boeing shot down their own rather ridiculous 3 second assumption. And with that their MCAS FMEA went totally down the drain.
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tobsw
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:31 pm

Will this flying tin ever fly again? :whiteflag:
 
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:33 pm

asdf wrote:
i dont understand those guys

correct the aerodynamical flaw
no more need for MCAS
accept the higher fuel consumption
and compensate it to the airlines


You mean this . . . :

Image
Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
 
asdf
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:36 pm

PW100 wrote:
Why would Boeing design MCAS for a 10 second cycle duration, when you expect them to shut it down after three seconds (because that in Boeings mind would constitute to a trim runaway). Let alone design it for multiple 10 second cycles (MCAS 1.0 that is). By designing in the 10 second MCAS cycle, Boeing shot down their own rather ridiculous 3 second assumption. And with that their MCAS FMEA went totally down the drain.


could please someone pin that in the news and reference thread .....
 
StTim
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:40 pm

MSPNWA wrote:
ShamrockBoi330 wrote:
Further to your point, the CNBC report.

https://www.cnbc.com/2020/01/21/boeing- ... -july.html


In my opinion it's long past time for the public to rise up and demand the FAA put an end to this charade and clear the MAX with MCAS 2.0.


What clue does the public have? More will be concerned about getting on a MAX.
 
hivue
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:44 pm

ShamrockBoi330 wrote:
Dieuwer wrote:
Boeing stock sinks 5% on more delays. No FAA sign-off in sight.


Further to your point, the CNBC report.

https://www.cnbc.com/2020/01/21/boeing- ... -july.html


I thought Boeing was out of the business of speculating on RTS dates.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
asdf
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:46 pm

PW100 wrote:
asdf wrote:
i dont understand those guys

correct the aerodynamical flaw
no more need for MCAS
accept the higher fuel consumption
and compensate it to the airlines


You mean this . . . :


i dont know

but I know they had hundreds if not thousand REAL test flights between 2013 and 2015 to find a way to correct the aerodynamical flaws of that 737MAX

i am sure the found a few possible solutions
but could not use them because that hits the economic goals

maybe its so easy to fix a ballast weight in the nose
or block three rows in the back
i dont know
maybe they even try it that way to cheat EASA in the TestFlight these days ;-) LOL

but the compensation to the airlines for the worser economy can never be so high than the compensation for not delivering at all
if you can deliver a NSA within lets say 6 years ... someone needs to do his numbers now ... it is way cheaper this way .... I am sure
 
RossW
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:47 pm

hivue wrote:
ShamrockBoi330 wrote:
Dieuwer wrote:
Boeing stock sinks 5% on more delays. No FAA sign-off in sight.


Further to your point, the CNBC report.

https://www.cnbc.com/2020/01/21/boeing- ... -july.html


I thought Boeing was out of the business of speculating on RTS dates.


They probably received new information that they have to disclose to the market
 
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flyingphil
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:49 pm

From Dominic Gates
It's now official from Boeing:

"We are informing our customers and suppliers that we are currently estimating that the ungrounding of the 737 MAX will begin during mid-2020."

So June/July 2020 for the FAA green light.. then the work begins ..
What about the other regulators? China? etc
Pilot training can then start?
737MAX simulators available?

So.. realistically maybe some limited return to service by Q1 2021 ?

Restarting production.. .. sometime / never ?

How can customers have any faith in Boeings guesstimates..
 
MSPNWA
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:50 pm

PW100 wrote:
I'm honestly struggling to understand what is "extremely proficient on the language" with respect to the word CONTINUOUSLY???

If one crew (with the benefit of an additional member in an observer role) can find the right solution in the correct time frame, what guarantees would that give that all crews could/should to that as well?
The fact that I can successfully type my own name without typing errors, does not mean I will do just that every single time. And that is about the simplest task for a human being. A million times easier than recognizing MCAS run-away.

Why would Boeing design MCAS for a 10 second cycle duration, when you expect them to shut it down after three seconds (because that in Boeings mind would constitute to a trim runaway). Let alone design it for multiple 10 second cycles (MCAS 1.0 that is). By designing in the 10 second MCAS cycle, Boeing shot down their own rather ridiculous 3 second assumption. And with that their MCAS FMEA went totally down the drain.


Because the root of your belief is that the word "continually" applies and "continuously" doesn't. Do you know the difference off the top of your head without consulting a dictionary? And now try to imagine remembering in the cockpit of a malfunctioning airliner.

How long MCAS operates is a red herring. That's not going to work in this debate.
Last edited by MSPNWA on Tue Jan 21, 2020 7:51 pm, edited 1 time in total.
 
oschkosch
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:50 pm

There seems to be a Boeing announcement coming asap on this.
And Airlease boss has recommended a name change for the max.

https://www.investors.com/news/boeing-s ... ed-demand/

Boeing (BA) stock fell on a report that the company now sees getting regulator clearance for the 737 Max's return well into the summer. Trading was later halted, pending an announcement.

Before trading was halted, shares sank 5.5% to 306.27 on the stock market today, hitting the lowest level in a year.

Meanwhile, Air Lease (AL) Chairman Steven Udvar-Hazy has said the Dow Jones stock may have to drop the 737 Max name completely to regain confidence.

"We've asked Boeing to get rid of that word Max. I think that word Max should go down in the history books as a bad name for an aircraft," he said at an aviation finance conference in Dublin. "The Max brand is damaged and there is really no reason for it."


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MSPNWA
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:53 pm

StTim wrote:
What clue does the public have? More will be concerned about getting on a MAX.


What the FAA said and did this summer. Or is what the FAA said and did not good enough?
 
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scbriml
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 7:58 pm

MSPNWA wrote:
ShamrockBoi330 wrote:
Further to your point, the CNBC report.

https://www.cnbc.com/2020/01/21/boeing- ... -july.html


In my opinion it's long past time for the public to rise up and demand the FAA put an end to this charade and clear the MAX with MCAS 2.0.


Why? In what way is "the public" sufficiently hurt or harmed by the grounding of MAX that would cause them to "rise up"?
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:00 pm

scbriml wrote:
Why? In what way is "the public" sufficiently hurt or harmed by the grounding of MAX that would cause them to "rise up"?


Do you think we're not ultimately paying for the grounding?
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:06 pm

MSPNWA wrote:
scbriml wrote:
Why? In what way is "the public" sufficiently hurt or harmed by the grounding of MAX that would cause them to "rise up"?


Do you think we're not ultimately paying for the grounding?
well I'm not paying for it. Are you?



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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:07 pm

PW100 wrote:
Why would Boeing design MCAS for a 10 second cycle duration, when you expect them to shut it down after three seconds (because that in Boeings mind would constitute to a trim runaway). Let alone design it for multiple 10 second cycles (MCAS 1.0 that is). By designing in the 10 second MCAS cycle, Boeing shot down their own rather ridiculous 3 second assumption. And with that their MCAS FMEA went totally down the drain.


Bravo. I did not expect to see a brilliant argument like this to settle this question once and for all after almost full year of back and forth about this subject.

The whole design and operation of MCAS v1.0 relied on the assumption that pilots would NOT react to if as a runaway trim. If the pilots would react it would completely prevent the MCAS from ever achieving the thing it was built to do.

MSPNWA wrote:
How long MCAS operates is a red herring. That's not going to work in this debate.


Oh the contrary. The whole argument is now put completely to rest with one clean sweep as far as I can understand.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:10 pm

MSPNWA wrote:
scbriml wrote:
Why? In what way is "the public" sufficiently hurt or harmed by the grounding of MAX that would cause them to "rise up"?


Do you think we're not ultimately paying for the grounding?


Not really, but Boeing is to the tune of tens of billions. How does that directly affect you and me (unless you have Boeing shares right now, even then they’ll likely recover).
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:10 pm

2175301 wrote:
The checking between the computers to verify matches is a lot more complex than most people understand... as you also have to be able to determine the course of action if they disagree... how does the computers keep the aircraft flying?... When does a computer shut down and how does it turn over to the other computer. Those are not simple things. Now Boeing has done that for other more modern aircraft so it's not a new exercise. But, it is highly complex.

Earlier reports suggested it really was as simple as just disconnecting the automation and raising alerts upon disagreement. Keep in mind this is not FBW, computers are just there for "augmentation", plane can be flown with cables/hydraulics.

2175301 wrote:
Also, I disagree with your concept that somehow Boeing should have all knowledge and expertise in-house. Where else do you do most testing than at the manufacturer who is responsible for the item? That is actually the best place to do most validation testing. They can fix things fastest (and perhaps in less than a day) if they see a problem.

I guess I should have made my statement more clearly. What I'm trying to say is I'm surprised the FCC software is done by the vendor, not in-house. Maybe I'm prejudiced after decades of being a software engineer, but I'd think that's something so important as to want to keep that tech in house.
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:14 pm

2175301 wrote:
Hindsight Engineering:

Many are stating what is now obvious after the event and after the JTAR and NTSB reports. Also a number of people seem not to understand that there are no perfectly designed aircraft.

While the above mentioned report do mention that Boeing only tested one failure at a time.... There was no requirement for them to do more... and if you read the reports you will find a recombination that "all" international certification agencies need to ensure that multiple failure scenarios are tested at once to determine the workload on the pilots. My conclusion. Boeing was not the only company just testing single failures.

Both reports indicate that Boeing essentially followed the certification process and requirement; even if some things were debatable.

Both reports aim to improve practices by both manufactures and regulators to change and improve the process and standards.

There are other things as well in those reports that are "suggestions" for all international regulators.

Putting larger engines on aircraft has caused similar problems with certain Airbus "NEO" aircraft. Right now there are a bunch of them flying with limitations on the number and locations of passengers for "Center of Gravity" issues for rare edge of envelope flight conditions while Airbus develops appropriate changes to their FBW software to properly address the issue. I note that Airbus discovered the issue after reviewing their own aircraft for similar issues as the 737MAX flight profile issues.

A reality is that it appears that the Boeing design team (not the simulator/training development team) were in fact following decades of established procedures using standard assumptions.

The fact that some of those procedures and assumptions were wrong... is not something so easily seen before they fail (that is the nature of things). They had apparently worked for decades up to that point.

Many improvements to aircraft design, testing, and certification will flow from this tragedy. But, please recognize that what many people are presenting as issues... were only identified as an issue by the messed up safety analysis of MCAS V1. Also, the clear implications of both the JATR and NTSB reports are that a number of those procedures and assumptions were occurring elsewhere in the world as well.

Have a great day,

Unfortunately, your description do not includes the now established facts that some peoples inside Boeing did know that something was really wrong with the MCAS certification and the obsession to not provides 737-8/9 MAX simulators nor specific training, and did lie to the FAA. This is not the story of a "honest" mistake.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
beechnut
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:33 pm

scbriml wrote:
MSPNWA wrote:
scbriml wrote:
Why? In what way is "the public" sufficiently hurt or harmed by the grounding of MAX that would cause them to "rise up"?


Do you think we're not ultimately paying for the grounding?


Not really, but Boeing is to the tune of tens of billions. How does that directly affect you and me (unless you have Boeing shares right now, even then they’ll likely recover).


The strain on the narrow-body fleet will ultimately throttle the seat supply and keep airline costs up as they try to stretch the lives of some less-efficient airframes that in many cases are now approaching the geriatric stage (think AC's early-build A320s) with some inevitable retirements with nothing to replace them reducing the overall seat availability. So demand will have to balance against the available supply, and the only way to do that will upward pressure on fares.

Of course if you're lucky enough to live in Europe, or the Northeast Corridor or anywhere else where a decent rail infrastructure is available, you can do like Greta and avoid air travel.

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Re: Boeing 737MAX Grounding News and Reference Thread 2020

Tue Jan 21, 2020 8:38 pm

At this point I don't see how Boeing can be described as other than incompetent as an airframe manufacturer. The adjective is well earned. Do not see this as anything but sad.
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WIederling
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Re: Boeing 737MAX Grounding News and Reference Thread 2020

Tue Jan 21, 2020 8:39 pm

2nd2none wrote:


unsurprising.

They obviously would not have stopped production for a month or two.
This was internal knowledge but not made public?

What kind of stringency/legal relevance is associated with the upcoming
(2019) Year End reports "future outlook" statements ?
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IADFCO
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:40 pm

asdf wrote:
PW100 wrote:
asdf wrote:
i dont understand those guys

correct the aerodynamical flaw
no more need for MCAS
accept the higher fuel consumption
and compensate it to the airlines


You mean this . . . :


i dont know

but I know they had hundreds if not thousand REAL test flights between 2013 and 2015 to find a way to correct the aerodynamical flaws of that 737MAX

i am sure the found a few possible solutions
but could not use them because that hits the economic goals

maybe its so easy to fix a ballast weight in the nose
or block three rows in the back
i dont know
maybe they even try it that way to cheat EASA in the TestFlight these days ;-) LOL

but the compensation to the airlines for the worser economy can never be so high than the compensation for not delivering at all
if you can deliver a NSA within lets say 6 years ... someone needs to do his numbers now ... it is way cheaper this way .... I am sure


With the important caveat that we are all giving at best informed guesses, as there are no hard technical data out in the open about the MAX aerodynamics, no, I don't think that an aerodynamic fix is easy or maybe even possible within the geometric constraints of the engine/pylon/wing coupling. My own speculation is that they saw the problem in CFD, wind tunnel test, or both, but someone decided that they didn't want to spend the time and money to explore it and understand it further, especially since a software-only fix seemed possible. This is my interpretation of the leaks saying that when they did the flight tests they had to increase the amount of movement of the stabilizer, and that they missed one of the flight regimes where bad things would happen. They didn't understand the phenomenon well enough.

I think that understanding exactly what is going on aerodynamically at the engine/wing interface is key. Depending on how bad post-stall behavior is, MCAS may (or may not) have to work as an envelope limiting controller. Of course Boeing knows, but it won't say.
 
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Re: Boeing 737MAX Grounding News and Reference Thread 2020

Tue Jan 21, 2020 8:49 pm

WIederling wrote:
What kind of stringency/legal relevance is associated with the upcoming (2019) Year End reports "future outlook" statements?


Per a company spokesman, Boeing prepared the estimate on when the Max would be approved for its own financial planning in advance of the company’s report on quarterly earnings next week.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:52 pm

MSPNWA wrote:
It keeps getting beaten because some here simply don't want to accept the fact that a runaway stab in a 737 shouldn't be a life-ending issue. But the industry as whole has allowed a greater possibility of that, and that's one of the reasons the MAX is grounded and the public (not Boeing, not the airlines) is paying the price.



We're drowning in people who have no idea in this place.

Firstly, logic test - would an aircraft be grounded for a year if it was simply a question of a few foreigners being unable to follow an NNC? I'll help you with the answer - almost certainly not. This, in itself is a hint that there are serious issues.

Secondly, look at the evidence - two aircraft crashed in very similar circumstances. The fact is that the MCAS "system" (not the function) contained catastrophic failure modes. This is a failure of the system architecture and was alluded to in the email from Mr Marko.

For the point about non-application of the NNC - in normal circumstances, when a fault occurs, there is an unambiguous indication. Think "engine fire" - nice red light and a clear idea of what to do. What we have heard about MCAS failures is a combination of overspeed and stall warnings along with a nose dive and GPWS warnings as well.

There have been all sorts of leaks, most without context so it is hard to really know what's happening but during a simulator session, half the pilots (who cannot be unaware of MCAS) were still using the wrong procedure. I would guess that it is proving difficult to get the "now modified (two AoA vanes + cross-comparison)" architecture sufficiently robust. A substantial change to the system architecture, if that is what is needed, is a big job.

If I'm wrong and it is just a software qualification problem, documenting what you've already done is very difficult. If I remember correctly, Airbus had to write the A400M FADEC software from scratch because of missing justification.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:54 pm

PW100 wrote:
morrisond wrote:
Three things.

Runaway Trim NNC is basically common to all aircraft types and the ability to run this should not be considered abnormal or requiring test pilot skills. This is why I keep beating a dead horse as this is not MAX specific.


And we keep beating the same dead horse that recognizing an intermittent thing (= non-continuous) does not jive with the wording of the NNC: the NNC clearly calls out CONTINUOUSLY.

Another dead horse, and probably even the bigger issue at hand: how to recognize the correct NNC in a timely fashion under camouflage of a) non-continuous, b) a plethora of other warnings and alerts, c) some of them perhaps even more important/urgent, d) some of them even conflicting with nose up commands, and e) none of this ever being required/recommended to be trained for.



Second, the odds of converting the MAX to FBW or adding an additional system are about O - it would be a lot easier just to train the pilots.

I think you will find that most regulators may consider the unaugmented stall characteristics unsuitable for coping by training only. While we have no evidence of such, there are various indications for such:
• JATR Report writes that MCAS could be considered as stall identification systems or stall protection systems, depending on the natural (unaugmented) stall characteristics of the aircraft;
• It seems to take ages for this specific test (unaugmented stall characteristics) to be performed;
• This test is in the grand scheme of things probably the mosty simple procedure of the Return-to-Flight (RtF) effort, it could have been done immediately after the JATR report;
• If the unaugmented stall characteristics were really as benign as some (Boeing?) want us to believe, surely Boeing would have thrown/leaked some hard data showing the opposite;
• MCAS received heavy authority at low speed regime, both in terms of trim rate (higher than manual electric trimming), and trim amplitude in one single cycle (never mind the repeating authority on MCAS 1.0);
• We have no signs that Boeing ever explored the path of non-MCAS, nor that it is exploring it now for RtF effort. That would be the easy way out, especially since we have now learned Boeing will recommend additional training for MCAS 2.0;
• Boeing is going through a monumental effort for RtF, including MCAS 2.0, cross-comms between FCC, training, and who knows what. All that effort is still seems to be easier than ”just to train the pilots”. I'm inclined to believe there must be good reasons for that . . .




However on the above even if you still have electric trim available it may have not made a difference on the ET flight as even it may not be effective in all corners of the envelope or beyond the normal envelope - which is normal.

It is absolutely *not normal* for any flight control function (including trim) to not work in any part of the (approved) operational flight envelope. Or do you have evidence that the trim does work all the way upto Vmo?
BTW, I believe I have read on here that trim should even be effective upto Vd, which is even higher than Vmo. Admittedly, I do not know if this is correct, or if I have read that correctly.



So you still have to know that leaving Autothrottle engaged at TOGA thrust is a bad idea.

We have no evidence *why* the crew left the throttle were it is. You suggest more or less that they panicked, or did not know/understand how autothrottle works. It may just as well be that as they were having greatful trouble keeping the nose up, and that they did not want to introduce another nosedown moment by reducing throttle. At this stage, your suggestion is nothing more than an assumption (as is mine . . . ).
Not to mention that reducing thrust with stick shaker and/or stall warning active usually is a bad idea . . .



One of the theories on why ET did not bring the plane back into trim when they turned the electric trim back on is that it caused violent effects on the frame and in the cabin due to the excessive high speed - basically trying to throw the pilots to the ceiling and hence why they only used it briefly twice.

Another wild theory/baseless assumption.
Surely, letting somewhat loose of the pulling force of the control column in response to ANU trimming would mostly balance out supposedly violent actions. Your assumptions are not supported by the DFDR graph of control column force.

They made several ANU manual electric trim inputs after MCAS became alive (so they knew quite well fow trim works . . . ). In fact, there were no less than four attempts. All four ended at exactly the same stabilizer pitch angle. While the last two were in Vmo region, the first two were well below Vmo. Yet all four ended at the same stabilizer pitch angle. Even if one wanted to do such on purpose, one would find itself hard-pressed to achieve the exact same angle at all four attempts. There must be more to it than “they forgot to -, or did not understand how to bring back the plane into trim”.



It could have made a difference earlier in the flight right after first and second MCAS activation before they exceeded Vmo - but then they still had electric trim available and could have simply returned it to in-trim before turning it off - just like there Company procedures told them to do so.
As far as we know it still worked and as evidenced later in the flight it still did when they turned it back on.

See above.
Also, As far as we know, it did not work as evidenced by the two manual electric ANU trimming stopping prematurely immediately after MCAS ran-away. They did try to bring it back into trim, but the system/plane did not allow them to do so.
There is just as much fact in this statement as yours, but probably closer to the truth . . .


Go read pages 28-33 of the preliminary report with ET's own description of the issue - what to look for and what to do - run the Runaway trim NNC.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:54 pm

MSPNWA wrote:
I see some common misconceptions. One that punishing "Boeing" isolates the punishment to Boeing...


Stop right here. Are you really convinced the grounding was done to "punish Boeing"? A grounding is never done to punish an airline or a producer. It's done to protect the public, airlines and ultimately producers from further damage. The Max will get ungrounded once it can convince the FAA the issue is solved and the plane safe to fly. The damage to society would be much bigger should there be more Maxes falling out of the sky.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 8:54 pm

PW100 wrote:

Why would Boeing design MCAS for a 10 second cycle duration, when you expect them to shut it down after three seconds (because that in Boeings mind would constitute to a trim runaway). Let alone design it for multiple 10 second cycles (MCAS 1.0 that is). By designing in the 10 second MCAS cycle, Boeing shot down their own rather ridiculous 3 second assumption. And with that their MCAS FMEA went totally down the drain.


Wow! So either:
1. Boeing didn’t realise the requirements of their own systems.
2. Boeing knew that pilots wouldn’t stop a runaway trim and so leave the MCAS to do its thing.
3. Boeing thought the pilots would perform the runaway trim procedures and thus the MCAS system was not required.

I think that surely means that if Boeing are able to make MCAS available through the full 3 x AOA sensor system then the above still applies...

I had thought the solution was as ‘simple’ as the redundancy in the system. Seems maybe not.

Fred



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WillyEckers
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 9:01 pm

MSPNWA wrote:

In my opinion it's long past time for the public to rise up and demand the FAA put an end to this charade and clear the MAX with MCAS 2.0.


It's not a charade. It just needs to be a solution that's compliant along with the proof that it is compliant. I doubt very much that it's the FAA sitting on things. I would guess that they have a list of required deliverables and will check them off the list as they arrive.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 9:04 pm

mileduets wrote:
MSPNWA wrote:
I see some common misconceptions. One that punishing "Boeing" isolates the punishment to Boeing...


Stop right here. Are you really convinced the grounding was done to "punish Boeing"? A grounding is never done to punish an airline or a producer. It's done to protect the public, airlines and ultimately producers from further damage. The Max will get ungrounded once it can convince the FAA the issue is solved and the plane safe to fly. The damage to society would be much bigger should there be more Maxes falling out of the sky.


Spot on

Let's not in ANY way pretend Boeing is some kind of victim here

Seriously any decision makers in the Boeing organisation should feel grateful to still have a job and livelihood. They personally should be punished. It's a crying shame that Boeing are going to bring down many much better managed and well run businesses around them by their abysmal approach to business and safety etc.
Last edited by Interested on Tue Jan 21, 2020 9:08 pm, edited 1 time in total.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 9:06 pm

MSPNWA wrote:
PixelFlight wrote:
Unfortunately, your description do not includes the now established facts that some peoples inside Boeing did know that something was really wrong with the MCAS certification and the obsession to not provides 737-8/9 MAX simulators nor specific training, and did lie to the FAA. This is not the story of a "honest" mistake.

Those are not facts. You have just stated a lie.

Those are facts released by Boeing itself.

"Boeing Co has released hundreds of internal messages that show attempts to duck regulatory scrutiny in the development of the 737 MAX, as well as employees disparaging the plane, the company and aviation regulators."
https://www.reuters.com/article/us-boei ... SKBN1Z90NP

In brief:
https://www.theguardian.com/business/2020/jan/10/737-max-scandal-the-internal-boeing-messages-and-emails
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
hivue
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 9:30 pm

PW100 wrote:
Why would Boeing design MCAS for a 10 second cycle duration, when you expect them to shut it down after three seconds (because that in Boeings mind would constitute to a trim runaway). Let alone design it for multiple 10 second cycles (MCAS 1.0 that is). By designing in the 10 second MCAS cycle, Boeing shot down their own rather ridiculous 3 second assumption. And with that their MCAS FMEA went totally down the drain.


I think what Boeing assumed was pilots would take 3 sec to recognize a runaway pitch trim situation. What makes you think Boeing, or anyone else, would consider 3 sec or less of trim activity to constitute runaway pitch trim?
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Ertro
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 9:44 pm

hivue wrote:
PW100 wrote:
Why would Boeing design MCAS for a 10 second cycle duration, when you expect them to shut it down after three seconds (because that in Boeings mind would constitute to a trim runaway). Let alone design it for multiple 10 second cycles (MCAS 1.0 that is). By designing in the 10 second MCAS cycle, Boeing shot down their own rather ridiculous 3 second assumption. And with that their MCAS FMEA went totally down the drain.


I think what Boeing assumed was pilots would take 3 sec to recognize a runaway pitch trim situation. What makes you think Boeing, or anyone else, would consider 3 sec or less of trim activity to constitute runaway pitch trim?


For the original MCAS design to make any sense and achieve what is was built to do in the real intended activation situation Boeing would have had to assume pilots would not notice at all what is going on for at least 10 seconds or many multiples of the 10 seconds.
 
giblets
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 9:48 pm

How is the Max delivery schedule looking now?! My understanding is they will prioritise the completed airframes first, that could be 6-9months if deliveries. Then they have to re-start production and then ramp that up...

So how long after RTS will ‘new build’ planes start getting delivered.
What’s the effect on the tail end of deliveries?! (IAG were expecting in ‘23 but hoping for ‘22, were they at the tail end?). Or should I ask when the earliest delivery window is for a potential new order? (How does that compare to the NEO? It was one of the advantages Boeing still had)


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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 9:53 pm

Revelation said “I guess I should have made my statement more clearly. What I'm trying to say is I'm surprised the FCC software is done by the vendor, not in-house. Maybe I'm prejudiced after decades of being a software engineer, but I'd think that's something so important as to want to keep that tech in house.”

That surprises me too. But, I presume, Rockwell Collins is pretty experienced in this area and had been producing the FCC all along? And I keep questioning the comments about Indian programmers doing MCAS since it resides in the FCC.
 
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Tue Jan 21, 2020 9:55 pm

Ertro wrote:
hivue wrote:
PW100 wrote:
Why would Boeing design MCAS for a 10 second cycle duration, when you expect them to shut it down after three seconds (because that in Boeings mind would constitute to a trim runaway). Let alone design it for multiple 10 second cycles (MCAS 1.0 that is). By designing in the 10 second MCAS cycle, Boeing shot down their own rather ridiculous 3 second assumption. And with that their MCAS FMEA went totally down the drain.


I think what Boeing assumed was pilots would take 3 sec to recognize a runaway pitch trim situation. What makes you think Boeing, or anyone else, would consider 3 sec or less of trim activity to constitute runaway pitch trim?


For the original MCAS design to make any sense and achieve what is was built to do in the real intended activation situation Boeing would have had to assume pilots would not notice at all what is going on for at least 10 seconds or many multiples of the 10 seconds.


if the pilot is not assumed to take action if the trimwheels spins for ten second .... the discussion about pilot faults (not taking action against a (kinda) "trim runaway) in the two accidents are completely silly

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