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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 11:41 am

AvWeek ( https://aviationweek.com/commercial-avi ... ax-testing ) has a pretty concise description of the situation:

The issue came to light within the last week during tests in Boeing’s MAX engineering flight simulator, or e-cab, a source with knowledge of the situation confirmed. The pilots were simulating a runaway stabilizer scenario and running through the requisite emergency-response checklist. A key early step is to use control column-mounted electric-trim switches to command horizontal stabilizer movement to counter the runaway. A subsequent step, if needed, is to toggle cutout switches that disable the trim motors.

According to the source, the FAA pilots found response to the electric-trim inputs took too long. “They had a difficult time quickly resolving the situation,” the source explained.

The issue has been traced to how quickly a specific flight control computer chip is processing data, the source said. What is not clear: whether the chip itself needs to be changed, or if a software update will address the issue. A second industry source said that a software fix is possible—and certainly would be preferable for Boeing, which suggested in a statement that a software modification will be sufficient. Changing chips could further delay the MAX’s return to service, as it would likely require new chip architecture as well as changing chips on nearly more than 500 MAXs in airline fleets or ready to be delivered.

Seems Boeing's suggestion that it can be fixed via software is yet another opportunity for Boeing to disappoint should it not be fixable via software.

If it is not fixable by software and a new chip with a new architecture is needed then this already enormous tragedy will go off the scales, and we'd be in that place where even Airbus didn't want to go, which is a total melt down of the 737 product line with dreadful knock on effects for world aviation.

The newly discovered issue came up during a very specific failure scenario, and it is not clear whether it has any link to either MAX accident sequence, the first source emphasized.

I don't know if this is a blessing (i.e. not related to MCAS) or a curse (a lack of processing resources needed to be addressed via software redesign or new hardware).

The software redesign is manageable especially if such was already begun eight months ago as hinted at by the Bloomberg piece.

A new processor chip would be an enormous increase in scope, especially if no ground work was already in progress for one. The hardware itself would need massive amounts of testing (for things like electromagnetic interference, power consumption under load, performance when blazing hot or freezing cold, etc) and then all the software from beginning to end would need to be retested. It would be a grounding measured in years rather than months.
Last edited by Revelation on Thu Jun 27, 2019 11:47 am, edited 1 time in total.
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SteinarN
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 11:46 am

From Aviation Week

It seems in fact like the latest problem is related to FCC overload. The article says the THS is slow to react to manual trim inputs from the thumb switches when simulating a trim runaway. Thereby forcing the aircraft into a steep dive before the THS finally starts reacting to the thumb switches. It is not clear if this problem can be fixed by a software update or if it requires time consuming hardware changes.

WASHINGTON—FAA test pilots have flagged a new issue in the Boeing 737 MAX flight control system that must be addressed as part of changes being made to get the aircraft back into service, Aviation Week has learned.The issue came to light within the last week during tests in Boeing’s MAX engineering flight simulator, or e-cab, a source with knowledge of the situation confirmed.

The pilots were simulating a runaway stabilizer scenario and running through the requisite emergency-response checklist. A key early step is to use control column-mounted electric-trim switches to command horizontal stabilizer movement to counter the runaway. A subsequent step, if needed, is to toggle cutout switches that disable the trim motors. According to the source, the FAA pilots found response to the electric-trim inputs took too long. “They had a difficult time quickly resolving the situation,” the source explained. The issue has been traced to how quickly a specific flight control computer chip is processing data, the source said. What is not clear: whether the chip itself needs to be changed, or if a software update will address the issue. A second industry source said that a software fix is possible—and certainly would be preferable for Boeing, which suggested in a statement that a software modification will be sufficient.

It seems in fact like the latest problem is related to FCC overload. The article says the THS is slow to react to manual trim inputs from the thumb switches when simulating a trim runaway. Thereby forcing the aircraft into a steep dive before the THS finally starts reacting to the thumb switches. It is not clear if this problem can be fixed by a software update or if it requires time consuming hardware changes.


Changing chips could further delay the MAX’s return to service, as it would likely require new chip architecture as well as changing chips on nearly more than 500 MAXs in airline fleets or ready to be delivered.“The FAA is following a thorough process, not a prescribed timeline, for returning the Boeing 737 MAX to passenger service,” the agency said in a statement. “The FAA recently found a potential risk that Boeing must mitigate. ”Boeing said the issue is “an additional requirement” that the FAA “has asked the company to address through the software changes that the company has been developing” for the MAX. “Boeing agrees with the FAA’s decision and request and is working on the required software to address the FAA’s request. Addressing this condition will reduce pilot workload by accounting for a potential source of uncommanded stabilizer motion,” it added.

The MAX has been grounded since mid-March following two fatal accidents in five months. Boeing has been working on changes to the MAX’s flight control system, specifically the maneuvering characteristics augmentation system (MCAS) flight control law. MCAS commands automatic horizontal stabilizer inputs in certain flight scenarios, and it activated erroneously in both accident sequences. Its failure can result in a runaway stabilizer scenario, which pilots are supposed to mitigate by following the “stabilizer runaway” checklist. Trimming the aircraft using the control-column switches is a key first step meant to stabilize the aircraft and enable the pilots to safely de-power horizontal stabilizer trim motors using cutout switches mounted on the aircraft’s center console. In both accident sequences—the October 2018 crash of Lion Air Flight 610 and Mar. 10 crash of Ethiopian Airlines Flight 302—the crews used the column-mounted switches to counter MCAS. Neither followed the runaway stabilizer checklist step-by-step, and were overcome by MCAS’s repeated inputs that forced the aircraft’s nose down due to erroneous angle-of-attack data being fed to the flight control computer. Both accident sequences ended with uncontrollable dives. The newly discovered issue came up during a very specific failure scenario, and it is not clear whether it has any link to either MAX accident sequence, the first source emphasized.


Edit;
Revelation was quicker than me to find the AW article....
 
Lewton
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 11:55 am

Revelation wrote:
Seems Boeing's suggestion that it can be fixed via software is yet another opportunity for Boeing to disappoint should it not be fixable via software.

If it is not fixable by software and a new chip with a new architecture is needed then this already enormous tragedy will go off the scales, and we'd be in that place where even Airbus didn't want to go, which is a total melt down of the 737 product line with dreadful knock on effects for world aviation.

It is obvious to everybody with a bit of a brain that Airbus wants this issue with the MAX grounding to be resolved asap.
A bit of bad PR for your biggest competitor is always welcome, but a continuous nightmare that puts the whole industry under scrutiny is not welcome at all.
Additionally, if the worst case scenario for Boeing happens, and the MAX is never again allowed to fly, then Boeing will obviously build an amazing new modern small aircraft from scratch, which will crash the A230neo and will force Airbus too to spend billions in order to develop a really new modern small aircraft.

This would suck for both companies, but would be awesome news for everybody else and most importantly for the planet, as a new generation of small aircraft would do the same flights with a much smaller economical footprint.
So here is hope that the 737 MAX will never be allowed to fly again.
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 11:59 am

xmp125a wrote:
crimsonchin wrote:
Basically another potentially fatal fault was discovered unrelated to the MCAS issue that was being tested for and this fault has also been there from the start?


Apparently, the bug was in the NEW code, which was developed as a fix for MCAS!

https://www.theregister.co.uk/2019/06/2 ... bug_found/

The US manufacturer on Wednesday confirmed that, during simulator tests on the embattled jetliners, the 737 Max's new control software would lock up a microprocessor resulting in the plane automatically entering a dangerous nosedive. It's understood the code that knackered the hardware was part of a firmware update to address deadly flaws in MCAS,

This means exactly I was saying 2 months ago. It is not MCAS problem, it is a Boeing problem, they simply cannot develop safety critical code up to standards. Whether this is due to lack of experienced engineers (who left, retired, or have been forced out because they were pesky enough with safety issues), we don't know. But FAA should really look at the processes inside Boeing now.
I don't know if I believe theregister. The complaint was that response from the flight system was slow. A hard loop would cause no response.
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:04 pm

Lewton wrote:
Revelation wrote:
Seems Boeing's suggestion that it can be fixed via software is yet another opportunity for Boeing to disappoint should it not be fixable via software.

If it is not fixable by software and a new chip with a new architecture is needed then this already enormous tragedy will go off the scales, and we'd be in that place where even Airbus didn't want to go, which is a total melt down of the 737 product line with dreadful knock on effects for world aviation.

It is obvious to everybody with a bit of a brain that Airbus wants this issue with the MAX grounding to be resolved asap.
A bit of bad PR for your biggest competitor is always welcome, but a continuous nightmare that puts the whole industry under scrutiny is not welcome at all.
Additionally, if the worst case scenario for Boeing happens, and the MAX is never again allowed to fly, then Boeing will obviously build an amazing new modern small aircraft from scratch, which will crash the A230neo and will force Airbus too to spend billions in order to develop a really new modern small aircraft.

This would suck for both companies, but would be awesome news for everybody else and most importantly for the planet, as a new generation of small aircraft would do the same flights with a much smaller economical footprint.
So here is hope that the 737 MAX will never be allowed to fly again.


It's about time the duopoly was broken

Let's not limit this to Boeing and Airbus - just having the two competing clearly doesn't work
 
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BobMUC
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:05 pm

Very bad news and we should be prepared to have additional threads for Q3 AND Q4. Nobody wants this but I don't see a chance how the grounding will be lifted within the next three month.
 
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SomebodyInTLS
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:19 pm

lightsaber wrote:
trini81 wrote:
https://edition.cnn.com/2019/06/26/politics/boeing-737-max-flaw/index.html

Havent seen it posted before... it seems a New flaw discovered on Boeing 737 Max.
"In simulator tests, government pilots discovered that a microprocessor failure could push the nose of the plane toward the ground. It is not known whether the microprocessor played a role in either crash.
When testing the potential failure of the microprocessor in the simulators, "it was difficult for the test pilots to recover in a matter of seconds," one of the sources said. "And if you can't recover in a matter of seconds, that's an unreasonable risk."

Rhoo rhoo

Fault testing is interesting. Double faults must be tested in the lab/flight simulator. It sounds like one was found.

That's ok, I know if worse found in the lab (that is why software with real hardware is tested).

This will add 30 to 60 days to the grounding (my opinion). Possibly longer due to politics.

Lightsaber


This might be interesting... I was always suspicious that the AoA vane might not have been the root cause of the spurious readings...

(I'm a bit late to the thread today, so this may have been addressed already)
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:24 pm

My question now is are those pilots and the FAA also conducting that same test in the NG simulator?
The article states they were simulating a runaway stabilizer scenario, so in my mind also MCAS related, but runaway stabilizer can also occur on the NG no matter how small a probability, indeed the MCAS fault tree includes the pilots using the same procedure to correct the issue.
So if they are now stating the microprocessor is an issue, I would first like to know if the same hardware is in the NG and if so, do that same test and see if the slow response is the same, if it is, we have a hardware issue that predates MCAS, so what to do.
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:30 pm

According to google the CPU is a Motorola 68040 running at 60 MHz. A fine CPU back in its day but possibly not up to coping with a complex situation such as an MCAS event.

Modern CPUs for control systems such as this run at about 2000 MHz. (Give our take).

The A320 would have a CPU with a similar vintage but must have been more capable as it was designed to run full FBW from the start.
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:45 pm

par13del wrote:
My question now is are those pilots and the FAA also conducting that same test in the NG simulator?
The article states they were simulating a runaway stabilizer scenario, so in my mind also MCAS related, but runaway stabilizer can also occur on the NG no matter how small a probability, indeed the MCAS fault tree includes the pilots using the same procedure to correct the issue.
So if they are now stating the microprocessor is an issue, I would first like to know if the same hardware is in the NG and if so, do that same test and see if the slow response is the same, if it is, we have a hardware issue that predates MCAS, so what to do.


Hopefully even on the rare occasions it's ever needed on the NG it's not dealing with the more complex issues that MCAS brings and can handle what's needed in a timely manner?
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:49 pm

If the deceased pilots were trained on how to deal with manual trim on NG and on Max it doesn't react quick enough to the same commands then their checklist fails them doesn't it?

They even assume manual trim isn't working ?

Which of course it isn't working (properly)
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:51 pm

LJ wrote:
LDRA wrote:
Who did the worst case analysis for computation resources? Why is this scenario not covered by worst case analysis?


Let's be realistic. It's very difficult to predict each possible worst case which could arise and thus no test will ever cover 100% of all possible (worst) cases. That's why we have somebody else look at it from a different perspective and thus increase the likelihood that the test covers more situations. Yes, Boeing needs to analyse why they didn't discover this issue, but we shouldn't demand the impossible from Boeing. We must be glad that the issue was discovered by the FAA and thus that the safety system worked. Moreover, I'm sure the regulators will also ask Boeing to explain why they missed this and asses if this is an issue. Then again, some on this board will never trust the regulators and thus will always be very skeptical should the MAX be approved to fly one day.


Nope. It is unreasonable to rely on testing to uncover 100% all possible worst cases, that is why it is done from design. Worst analysis often makes conservative assumptions that are worse than actual worst case for that reason
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 12:53 pm

goosebayguy wrote:
Apparently the latest testing has failed. Boeing have accused the test pilot on trying too hard to get MCAS to fail and it has. Only in the sense that it took too long to recover. So AA And Southwest have put back introduction for another month.

Beoing has to appreciate that they have to get this right. A further crash will destroy Boeing. Why are they not taking safety seriously?


What are you talking about? Please cite where Boeing has accused the test pilot of trying too hard to get MCAS to fail. In the CNN article, it was their source that said that it was difficult for the test pilots to recover in a matter of seconds which made it too high of a risk.
 
LightningZ71
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:10 pm

I wasn't aware that they had released versions of the 68040 in excess of 40Mhz. If they are hitting a performance wall with it, the 68EC060 is fully instruction compatible with it (in its embedded form, like the embedded 040 is), is more efficient with respect to instructions per clock that can be processed, and is available at up to 75Mhz speed. It's also a few dollars more expensive per unit, but, given the price of these birds, that seems like a manageable expense.
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:11 pm

planecane wrote:
goosebayguy wrote:
Apparently the latest testing has failed. Boeing have accused the test pilot on trying too hard to get MCAS to fail and it has. Only in the sense that it took too long to recover. So AA And Southwest have put back introduction for another month.

Beoing has to appreciate that they have to get this right. A further crash will destroy Boeing. Why are they not taking safety seriously?


What are you talking about? Please cite where Boeing has accused the test pilot of trying too hard to get MCAS to fail. In the CNN article, it was their source that said that it was difficult for the test pilots to recover in a matter of seconds which made it too high of a risk.


There was a report last week that Boeing safety analysis for Max relied on pilots being able to deal with MCAS within 3 seconds

Which at the time seemed incredibly ambitious and optimistic and risky to me for them to expect and plan for that?

Your post above is written in a way that kind of suggests that not being able to deal with stuff in seconds might not be considered a risk?

Ie you've written it to try and make it sound not that important?

But what we read suggested last week that the speed with which Boeing needed pilots to be able to deal with MCAS for it to be safe was extremely important?

3 seconds important!!

Now test pilots saying the microprocessor isn't quick enough to deal with MCAS safely

Thankfully for the test pilots they werent facing a real emergency

Are you getting ready to change your view on blaming pilots for the two crashes (yet)?

You appear to be one of the few hangers on to that theory left on here?

TBF to you _ until now you weren't aware of the issues test pilots were experiencing of course?

Time to change your view do you think?
Last edited by Interested on Thu Jun 27, 2019 1:14 pm, edited 2 times in total.
 
ArgentoSystems
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:13 pm

xmp125a wrote:
I would say this has become Pandora's box. After MCAS 1.0 all the code was subject to review, either by FAA or internally by Boeing. The only explanation for the long delay in releasing the MCAS 2.0 could be that code is a mess (not Toyota-level mess, but nevertheless a mess regarding the strict safety requirements for airplanes) so far untestable. So perhaps large swaths of the code have to be written from scratch before it could even be properly tested. In that scenario I would not be surprised if someone at Boeing got the idea to invite "government pilots" to test the plane with the old code with some kind of quick fix, for the PR purposes. Obviously it backfired.

I mean i HOPE that was the old code. Not the code for which Boeing said "there, this has been tested now".

Rewriting a bunch of code in a hurry is no way to get a reliable system. Even if we are talking about relative hurry only. I don't think that is what's going on. I think BA is still in a 'quickfix' mode - minimum changes to get passable result to get back in the air asap. I mean, I find it extremely embarrassing to deliver a system, and let the customer discover a bug. And here we have Boeing, supposedly pinnacle of engineering brilliance, letting FAA discover a flaw. I'm speechless. Seems like 'good enough' attitude is prevalent at Boeing. While the standard goal should be 'impeccable'.

At this point in time there is no need for them to hurry. Market has already swallowed multi-month grounding and dismal sales and profits for the year. So take your time, because obviously nobody is rushing to approve the plane back into the air. Also, don't they see that another crash, for whatever reasons, will set back them so badly, that they might not recover for another 10 years.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:14 pm

Lewton wrote:

This would suck for both companies, but would be awesome news for everybody else and most importantly for the planet, as a new generation of small aircraft would do the same flights with a much smaller economical footprint.
So here is hope that the 737 MAX will never be allowed to fly again.


You are obviously not an engineer. A new generation of small aircraft will not be that much more effiicient than the A320NEO or 737MAX. That is why Boeing did the MAX instead of a clean sheet. They stated at the time that the engines to get a step change in efficiency (which you are suggesting is possible now) would not be available until 2030 or later.

Your hope is misguided at best. If the MAX was never allowed to fly again, airlines that need aircraft would be foreced to fly older, less efficient, aircraft longer. They would need something between now and 2030 to replace retired aircraft and grow. Even if Airbus could produce enough A320 series to cover the need, the A320NEO is only silghtly more efficient than the 737MAX in certain missions. What would also happen is that Boeing would be forced to restart production of the NG and give huge discounts to keep customers. They can't have no narrowbody to sell for a decade and remain in the commercial aviation business.
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:18 pm

planecane wrote:
Lewton wrote:

This would suck for both companies, but would be awesome news for everybody else and most importantly for the planet, as a new generation of small aircraft would do the same flights with a much smaller economical footprint.
So here is hope that the 737 MAX will never be allowed to fly again.


You are obviously not an engineer. A new generation of small aircraft will not be that much more effiicient than the A320NEO or 737MAX. That is why Boeing did the MAX instead of a clean sheet. They stated at the time that the engines to get a step change in efficiency (which you are suggesting is possible now) would not be available until 2030 or later.

Your hope is misguided at best. If the MAX was never allowed to fly again, airlines that need aircraft would be foreced to fly older, less efficient, aircraft longer. They would need something between now and 2030 to replace retired aircraft and grow. Even if Airbus could produce enough A320 series to cover the need, the A320NEO is only silghtly more efficient than the 737MAX in certain missions. What would also happen is that Boeing would be forced to restart production of the NG and give huge discounts to keep customers. They can't have no narrowbody to sell for a decade and remain in the commercial aviation business.


Great - get the NG back in production and everybody can feel safe again

Will cost the shareholders at Boeing billions. But hopefully some strong lessons will have been learnt
 
ArgentoSystems
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:21 pm

Revelation wrote:
What is not clear: whether the chip itself needs to be changed, or if a software update will address the issue. A second industry source said that a software fix is possible—and certainly would be preferable for Boeing, which suggested in a statement that a software modification will be sufficient. Changing chips could further delay the MAX’s return to service, as it would likely require new chip architecture as well as changing chips on nearly more than 500 MAXs in airline fleets or ready to be delivered.

Boeing and 'software fix' don't mix well :)
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:32 pm

Interested wrote:
planecane wrote:
goosebayguy wrote:
Apparently the latest testing has failed. Boeing have accused the test pilot on trying too hard to get MCAS to fail and it has. Only in the sense that it took too long to recover. So AA And Southwest have put back introduction for another month.

Beoing has to appreciate that they have to get this right. A further crash will destroy Boeing. Why are they not taking safety seriously?


What are you talking about? Please cite where Boeing has accused the test pilot of trying too hard to get MCAS to fail. In the CNN article, it was their source that said that it was difficult for the test pilots to recover in a matter of seconds which made it too high of a risk.


There was a report last week that Boeing safety analysis for Max relied on pilots being able to deal with MCAS within 3 seconds

Which at the time seemed incredibly ambitious and optimistic and risky to me for them to expect and plan for that?

Your post above is written in a way that kind of suggests that not being able to deal with stuff in seconds might not be considered a risk?

Ie you've written it to try and make it sound not that important?

But what we read suggested last week that the speed with which Boeing needed pilots to be able to deal with MCAS for it to be safe was extremely important?

3 seconds important!!

Now test pilots saying the microprocessor isn't quick enough to deal with MCAS safely

Thankfully for the test pilots they werent facing a real emergency

Are you getting ready to change your view on blaming pilots for the two crashes (yet)?

You appear to be one of the few hangers on to that theory left on here?

TBF to you _ until now you weren't aware of the issues test pilots were experiencing of course?

Time to change your view do you think?


I think you are imagining things I am saying just to argue with me. Where did I suggest anything that you just said in my post? The post I responded to accused Boeing of trying to blame the test pilots for creating a failure in an unreasonable manner. The post said, "Boeing have accused the test pilot on trying too hard to get MCAS to fail."

I was reponding to the fact that they didn't do anything of the sort. I posted the fact of what the CNN article said about what the test pilots determined to counter the original post's accusation of Boeing trying to blame the test pilots. The CNN article (or any other report I've seen) says nothing of the sort. Next time, I'll just reply with a blank message so you can use your imagination to fill in what I said.

And for the 1000th time, I don't blame the pilots for the crashes. I said that they COULD have recovered if they had recognized the runaway stabilizer and followed the NNC exactly as intended. Lion Air 043 did recover from the exact same situation. I blamed lack of documentation from Boeing and lack of training on runaway stabilizer for the pilots not being prepared to recognize the problem and react. I have also said about a million times that the original MCAS design was terrible. Yet, somehow you convince yourself that I work for Boeing or something and am trying to use the "influential" a.net forum to counteract dozens of media outlets writing negative articles. I don't work for Boeing, I don't currently own (directly at least) any Boeing stock. The only remote connection I have to Boeing is that my wife's cousin that I've never met and that she hasn't seen or communicated with in at least 20 years either works or used to work at Boeing in St. Louis on the military side.

My only "defense" of Boeing has been my belief that they didn't purposely disregard safety for cost savings. Of course the goal of any design is to minimize costs (and maintain as much similarity to the NG as possible in this case). Yes, MCAS was designed to be as simple as possible but those involved in the decision making and design didn't think it was unsafe and include it anyway.
 
hivue
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:34 pm

CNBC were emphasizing this morning that the fact that the FAA chose to leak the microprocessor issue is very significant (sorry, no link to that story yet). I have to agree.
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kalvado
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:34 pm

ArgentoSystems wrote:
At this point in time there is no need for them to hurry. Market has already swallowed multi-month grounding and dismal sales and profits for the year. So take your time, because obviously nobody is rushing to approve the plane back into the air. Also, don't they see that another crash, for whatever reasons, will set back them so badly, that they might not recover for another 10 years.

They should be approaching 200 planes in inventory, that is $10B or so. Partially paid for, but with limited new orders (1 LOI with unclear down payment) and possibly reduced progress payments. Compensations. $10B cash were reported at the beginning of the mess, probably mostly depleted.
Their market cap is $200B - but going down, and that can accelerate any day. They can borrow quite a bit to keep things going, but there will be painful and costly decisions - production MAX cuts, possibly 777X freeze. Probably personell cuts left and right - not to mention people probably running away from nightmare.
It is not rosy at Boeing, this is a fight for survival.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:34 pm

Interested wrote:

Great - get the NG back in production and everybody can feel safe again



Will you feel that way if it is determined that the same potential cause of runaway stabilizer (a microprocessor failure) exists on the NG as well?
 
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sassiciai
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:35 pm

Revelation wrote:
AvWeek ( https://aviationweek.com/commercial-avi ... ax-testing ) has a pretty concise description of the situation:

The issue came to light within the last week during tests in Boeing’s MAX engineering flight simulator, or e-cab, a source with knowledge of the situation confirmed. The pilots were simulating a runaway stabilizer scenario and running through the requisite emergency-response checklist. A key early step is to use control column-mounted electric-trim switches to command horizontal stabilizer movement to counter the runaway. A subsequent step, if needed, is to toggle cutout switches that disable the trim motors.

According to the source, the FAA pilots found response to the electric-trim inputs took too long. “They had a difficult time quickly resolving the situation,” the source explained.

The issue has been traced to how quickly a specific flight control computer chip is processing data, the source said. What is not clear: whether the chip itself needs to be changed, or if a software update will address the issue. A second industry source said that a software fix is possible—and certainly would be preferable for Boeing, which suggested in a statement that a software modification will be sufficient. Changing chips could further delay the MAX’s return to service, as it would likely require new chip architecture as well as changing chips on nearly more than 500 MAXs in airline fleets or ready to be delivered.

Seems Boeing's suggestion that it can be fixed via software is yet another opportunity for Boeing to disappoint should it not be fixable via software.

If it is not fixable by software and a new chip with a new architecture is needed then this already enormous tragedy will go off the scales, and we'd be in that place where even Airbus didn't want to go, which is a total melt down of the 737 product line with dreadful knock on effects for world aviation.

The newly discovered issue came up during a very specific failure scenario, and it is not clear whether it has any link to either MAX accident sequence, the first source emphasized.

I don't know if this is a blessing (i.e. not related to MCAS) or a curse (a lack of processing resources needed to be addressed via software redesign or new hardware).

The software redesign is manageable especially if such was already begun eight months ago as hinted at by the Bloomberg piece.

A new processor chip would be an enormous increase in scope, especially if no ground work was already in progress for one. The hardware itself would need massive amounts of testing (for things like electromagnetic interference, power consumption under load, performance when blazing hot or freezing cold, etc) and then all the software from beginning to end would need to be retested. It would be a grounding measured in years rather than months.

Mr Revelation, I am also a graduate in Computer Science, now retired from the industry!

In the simplistic case where there is "too much software" in a "wee processor", then trying to rewrite the software to somehow reduce the instruction count, optimise the code, or drop some checks that "are not really necessary" is, IMO, a recipe for disaster. The overpowering aroma of corner cutting in "unlikely areas" might cut down on the processing. Just imagine having to prove that the system still functions as specified!

Squeezing a litre into a pint pot is always a failed business. Maybe the processor in the NG is already working at 99.9% sometimes, and if you add another iterative function to that load, you enter into unpredictable areas where things misbehave! When those areas are aircraft flight control software, OMG!!!!

Someone above indicates that if the processor has to be swapped for something more modern and/or powerful, then everything has to retested from zero, and it would take years! I am not sure that I agree with this argument. There are processors on many aircraft types that were developed and proven much more recently that that of the 737 NG. Surely some processor that has several million flight hours proven on a 777, for example, could serve as a platform onto which to port and prove the 737 NG software, and then (re)apply the Max updates. (Would it physically fit?)
 
memphiX
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:36 pm

Revelation wrote:
I don't know if this is a blessing (i.e. not related to MCAS) or a curse (a lack of processing resources needed to be addressed via software redesign or new hardware).


Imho, it actually opens up a different can of worms. The FAA ran into this while testing an "unlikely" scenario, that makes me think if there is any other "unlikely" scenario where the response time/delay is less than optimal?

After all, the crashes happened in "unlikely" scenarios that weren't simulated/tested by Boeing.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:38 pm

planecane wrote:
What would also happen is that Boeing would be forced to restart production of the NG and give huge discounts to keep customers. They can't have no narrowbody to sell for a decade and remain in the commercial aviation business.

Hmmm... they may also be able to charge a premium or same price, after all, how long would it take Airbus to provide alternative a/c?
We are still talking about a supply and demand process right, the fact that supply is limited could override the need to provide a discount for a less efficient frame.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:42 pm

kalvado wrote:
ArgentoSystems wrote:
At this point in time there is no need for them to hurry. Market has already swallowed multi-month grounding and dismal sales and profits for the year. So take your time, because obviously nobody is rushing to approve the plane back into the air. Also, don't they see that another crash, for whatever reasons, will set back them so badly, that they might not recover for another 10 years.

They should be approaching 200 planes in inventory, that is $10B or so. Partially paid for, but with limited new orders (1 LOI with unclear down payment) and possibly reduced progress payments. Compensations. $10B cash were reported at the beginning of the mess, probably mostly depleted.
Their market cap is $200B - but going down, and that can accelerate any day. They can borrow quite a bit to keep things going, but there will be painful and costly decisions - production MAX cuts, possibly 777X freeze. Probably personell cuts left and right - not to mention people probably running away from nightmare.
It is not rosy at Boeing, this is a fight for survival.

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planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:42 pm

RickNRoll wrote:
The problem is that the processor is an old one that does not appear to have enough power to run more complex time critical calculations. The processor cannot be easily changed. The process to do so would take years since they are tested so thoroughly.


What would preclude them from using a more powerful processor that is already certified and used on the 787 or 787? There would still be time required to port the software but that would eliminate the need to certify the hardware.
 
xmp125a
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:48 pm

sassiciai wrote:

Someone above indicates that if the processor has to be swapped for something more modern and/or powerful, then everything has to retested from zero, and it would take years! I am not sure that I agree with this argument. There are processors on many aircraft types that were developed and proven much more recently that that of the 737 NG. Surely some processor that has several million flight hours proven on a 777, for example, could serve as a platform onto which to port and prove the 737 NG software, and then (re)apply the Max updates. (Would it physically fit?)


This would mean changing the flight computer(s). If you use ancient M68XXX, you cannot just plug in a cpu that is currently in 777/787.Would be helluva of an engineering job to use FBW computing hardware developed for newer airplanes in 737, plus you break grandfathering certifications...
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:48 pm

RickNRoll wrote:
According to google the CPU is a Motorola 68040 running at 60 MHz. A fine CPU back in its day but possibly not up to coping with a complex situation such as an MCAS event.

Modern CPUs for control systems such as this run at about 2000 MHz. (Give our take).

The 2000 MHz figure is pretty meaningless. The processor only runs at that rate once data is stored in registers. If it has to reach out to the first level cache for either instructions or data there is a four cycle penalty i.e. it runs at 500 MHz. If it has to wait for things in the 2nd level cache or main memory it gets far worse. This is why there is such a focus on multi threading and multi core processors: there is a need to find other things to do so often.

The bottleneck may be something other than the rate at which the CPU can execute instructions. It could be that the cost of accessing the 2nd AOA sensor is the straw breaking the camel's back. It may be that tuning the access rate of that and other sensors could be a fix. None of us know enough to say.

RickNRoll wrote:
The A320 would have a CPU with a similar vintage but must have been more capable as it was designed to run full FBW from the start.

Last time I googled, the A320 flight computer was rocking 80186 processors, a fine choice for an embedded control processor in 1988, and (sarcasm alert) as we all know, technology hasn't moved on since then, so all is good.

ArgentoSystems wrote:
Rewriting a bunch of code in a hurry is no way to get a reliable system. Even if we are talking about relative hurry only. I don't think that is what's going on. I think BA is still in a 'quickfix' mode - minimum changes to get passable result to get back in the air asap. I mean, I find it extremely embarrassing to deliver a system, and let the customer discover a bug.

Embarrassing for sure but anyone who works in software knows it can and does happen far more often than desired.

ArgentoSystems wrote:
And here we have Boeing, supposedly pinnacle of engineering brilliance, letting FAA discover a flaw. I'm speechless. Seems like 'good enough' attitude is prevalent at Boeing. While the standard goal should be 'impeccable'.

I doubt any sane engineer or engineering organization would describe themselves as the "pinnacle of engineering brilliance".

Anyone who is an actual engineer and not blinded by arrogance is aware of how difficult if not impossible "impeccable" is.

Interestingly enough the CEO said he owned putting the right people on to the job.

He may be providing the rope needed to hang himself.

ArgentoSystems wrote:
Boeing and 'software fix' don't mix well :)

Guess you're another one who will never fly on a Boeing ever again, since they all use "software" for lots of key functions.
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:50 pm

kayik wrote:
Would you be surprised if this was a PR effort staging how effective FAA is and not rubber stamping at all?

And Boeing provided ammo
 
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 1:56 pm

hivue wrote:
CNBC were emphasizing this morning that the fact that the FAA chose to leak the microprocessor issue is very significant (sorry, no link to that story yet). I have to agree.

Leak? Boeing itself made a statement to the capital markets which is not a leak but is the whole dam busting!

planecane wrote:
RickNRoll wrote:
The problem is that the processor is an old one that does not appear to have enough power to run more complex time critical calculations. The processor cannot be easily changed. The process to do so would take years since they are tested so thoroughly.


What would preclude them from using a more powerful processor that is already certified and used on the 787 or 787? There would still be time required to port the software but that would eliminate the need to certify the hardware.

In addition to what was posted above by xmp125a above, you have to consider things like the newer processor may demand more power than you can (reliably) supply, or generate more heat than you can get rid of, or generate more electrical noise than you can block, or have different physical layer characteristics (i.e. voltage levels, bit rates, etc) than the old one.
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Agrajag
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 2:04 pm

How easily can NG production be ramped up again and how much of a discount will they have to give? Buy one get 2 free and free oil changes for life?
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SomebodyInTLS
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 2:10 pm

xmp125a wrote:
Amiga500 wrote:
2. Boeing cannot realistically change the computing hardware within 24 months. They would have to re-certify the whole architecture (S/W and H/W). That would be an absolute nightmare scenario.


Let's take a step back.Remember when everyone were shaking their heads how on Earth MCAS V1.0 found its way to production?

A bit of conspiracy teory, but plausible one: what if "proper" MCAS design was tested during MAX development but found to be too demanding for the flight computer? And then MCAS 1.0 with its fatal flaws was born, and seemingly stupid design decisions, like use 1 sensor only, alternate sensor between the flights?

Is that really out of the question?


That sounds quite plausible and does go some way to explaining the inexplicable...
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Elementalism
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 2:23 pm

Lewton wrote:
Revelation wrote:
Seems Boeing's suggestion that it can be fixed via software is yet another opportunity for Boeing to disappoint should it not be fixable via software.

If it is not fixable by software and a new chip with a new architecture is needed then this already enormous tragedy will go off the scales, and we'd be in that place where even Airbus didn't want to go, which is a total melt down of the 737 product line with dreadful knock on effects for world aviation.

It is obvious to everybody with a bit of a brain that Airbus wants this issue with the MAX grounding to be resolved asap.
A bit of bad PR for your biggest competitor is always welcome, but a continuous nightmare that puts the whole industry under scrutiny is not welcome at all.
Additionally, if the worst case scenario for Boeing happens, and the MAX is never again allowed to fly, then Boeing will obviously build an amazing new modern small aircraft from scratch, which will crash the A230neo and will force Airbus too to spend billions in order to develop a really new modern small aircraft.

This would suck for both companies, but would be awesome news for everybody else and most importantly for the planet, as a new generation of small aircraft would do the same flights with a much smaller economical footprint.
So here is hope that the 737 MAX will never be allowed to fly again.


Wish I could share your optimism. If the 737 MAX line fails. I think Boeing has the potential to fail. And then no new aircraft. The question would become, will the US Govt allow Boeing to fail?
Last edited by Elementalism on Thu Jun 27, 2019 2:27 pm, edited 1 time in total.
 
Amiga500
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 2:23 pm

sassiciai wrote:
Someone above indicates that if the processor has to be swapped for something more modern and/or powerful, then everything has to retested from zero, and it would take years! I am not sure that I agree with this argument. There are processors on many aircraft types that were developed and proven much more recently that that of the 737 NG. Surely some processor that has several million flight hours proven on a 777, for example, could serve as a platform onto which to port and prove the 737 NG software, and then (re)apply the Max updates. (Would it physically fit?)


I'm working on DAL A software right now - and there are others in this office sitting literally a few feet away doing just such a hardware change for a particular aerospace application.

It is not finding hardware that is certified for use in aerospace and has sufficient capacity - there are loads of options around the world for that - it is in ensuring that all the interfaces, all the signals, all the resets, all the redundancies - all the timings - still follow the philosophy of the original architecture. They would likely be quicker re-writing the whole software stack from top to bottom than try and port it over to new hardware.

Be in absolutely no doubt - it would take years.
 
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 2:36 pm

kalvado wrote:
They should be approaching 200 planes in inventory, that is $10B or so. Partially paid for, but with limited new orders (1 LOI with unclear down payment) and possibly reduced progress payments. Compensations. $10B cash were reported at the beginning of the mess, probably mostly depleted.
Their market cap is $200B - but going down, and that can accelerate any day. They can borrow quite a bit to keep things going, but there will be painful and costly decisions - production MAX cuts, possibly 777X freeze. Probably personell cuts left and right - not to mention people probably running away from nightmare.
It is not rosy at Boeing, this is a fight for survival.

Finances are not my area of expertise, but I've been told that running out of cash for Boeing is not really a concern. Assuming MAX gets back into air at the end of the year, all of these costs will be forgot and forgiven as they a drop in the ocean of money that BA is set make in coming years. And so far it seems that market strongly believes that MAX will fly again this year.How it is going to play out is yet to be seen. In March I thought we are looking at least 4 month grounding, but now it is hard to tell. I think end of the year is the best they could hope for. And even then, simultaneous worldwide ungrounding will require some kind of miracle.
 
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 2:38 pm

Guys, BA will not fail even if MAX is forever banned from flying. It will be a decade long setback, but it is not enough to break BA. Remember they also have space and military. MAX is only ~30% of their sales.
 
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 2:47 pm

planecane wrote:
And for the 1000th time, I don't blame the pilots for the crashes. I said that they COULD have recovered if they had recognized the runaway stabilizer and followed the NNC exactly as intended. Lion Air 043 did recover from the exact same situation. I blamed lack of documentation from Boeing and lack of training on runaway stabilizer for the pilots not being prepared to recognize the problem and react. .


Sorry for the selective quoting, but could perhaps this recent software/microprocessor issue be related to with the fact that all four uptrim actions of the ET crew (after MCAS became alive) stopped at 2.4 units stabilizer trim? Could that perhaps have been an issue preventing those pilots from using electric uptrimming?

And one step further, thinking aloud, could that also have been the case with the JT accident, that somehow the copilot electric uptrim also did not work?

Lots of questions we will not get definite answers on for some time, but for me sufficient reason to hold back judgement on crew actions . . .
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ArgentoSystems
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:24 pm

Southwest canceled flights till Oct 1.

https://www.usatoday.com/story/travel/f ... 582494001/
 
Lewton
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:34 pm

Elementalism wrote:
Lewton wrote:
Additionally, if the worst case scenario for Boeing happens, and the MAX is never again allowed to fly, then Boeing will obviously build an amazing new modern small aircraft from scratch, which will crash the A230neo and will force Airbus too to spend billions in order to develop a really new modern small aircraft.

This would suck for both companies, but would be awesome news for everybody else and most importantly for the planet, as a new generation of small aircraft would do the same flights with a much smaller economical footprint.
So here is hope that the 737 MAX will never be allowed to fly again.


Wish I could share your optimism. If the 737 MAX line fails. I think Boeing has the potential to fail. And then no new aircraft. The question would become, will the US Govt allow Boeing to fail?

Being has way too much money and some very good money making businesses to fail due to the MAX crisis.
 
AirwayBill
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:39 pm

Lewton wrote:
Being has way too much money and some very good money making businesses to fail due to the MAX crisis.


Ah, the famous "too-big-to-fail".

Never say never, no company is immune to anything.
 
OldAeroGuy
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:40 pm

Interested wrote:
There was a report last week that Boeing safety analysis for Max relied on pilots being able to deal with MCAS within 3 seconds

Which at the time seemed incredibly ambitious and optimistic and risky to me for them to expect and plan for that?

Your post above is written in a way that kind of suggests that not being able to deal with stuff in seconds might not be considered a risk?


Both the FAA and EASA use 3 seconds as a standard pilot recognition time for a changing situation. See AC25-7C, pages 151 - 154. https://www.faa.gov/documentLibrary/med ... -7C%20.pdf

Boeing safety analyses use of 3 seconds is consistent with regulatory agency practice used for all Part 25 airplanes.
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:47 pm

SomebodyInTLS wrote:
xmp125a wrote:
Amiga500 wrote:
2. Boeing cannot realistically change the computing hardware within 24 months. They would have to re-certify the whole architecture (S/W and H/W). That would be an absolute nightmare scenario.


Let's take a step back.Remember when everyone were shaking their heads how on Earth MCAS V1.0 found its way to production?

A bit of conspiracy teory, but plausible one: what if "proper" MCAS design was tested during MAX development but found to be too demanding for the flight computer? And then MCAS 1.0 with its fatal flaws was born, and seemingly stupid design decisions, like use 1 sensor only, alternate sensor between the flights?
Is that really out of the question?


That sounds quite plausible and does go some way to explaining the inexplicable...


Reminds me a bit of Ariane 5 failure:
https://www.slideshare.net/sommerville-videos/ariane-5-launcher-failure-30036896?next_slideshow=1

If you read those slides, then one could form a mental picture where this software/hardware interaction issue was already present on the NG, but never surfaced as in the older version the system would never reach its limitations. Now that MCAS and associated testing forced the system to its extremes, it exposed this software/hardware interaction issue?
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planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:48 pm

PW100 wrote:
planecane wrote:
And for the 1000th time, I don't blame the pilots for the crashes. I said that they COULD have recovered if they had recognized the runaway stabilizer and followed the NNC exactly as intended. Lion Air 043 did recover from the exact same situation. I blamed lack of documentation from Boeing and lack of training on runaway stabilizer for the pilots not being prepared to recognize the problem and react. .


Sorry for the selective quoting, but could perhaps this recent software/microprocessor issue be related to with the fact that all four uptrim actions of the ET crew (after MCAS became alive) stopped at 2.4 units stabilizer trim? Could that perhaps have been an issue preventing those pilots from using electric uptrimming?

And one step further, thinking aloud, could that also have been the case with the JT accident, that somehow the copilot electric uptrim also did not work?

Lots of questions we will not get definite answers on for some time, but for me sufficient reason to hold back judgement on crew actions . . .


No worries on the selective quoting. I don't have enough information about the microprocessor issue to speculate one way or the other. I'm not going to say that it couldn't have been an issue. The information about the microprocessor issue is a little conflicting at the moment. The official statements from Boeing and the FAA as well as the reporting by CNN seem to indicate that the microprocessor issue is an additional possible cause of runaway stabilizer that was discovered. Other reports indicate that the issue is the manual electric trim not responding fast enough.

I don't understand from the reports if the response time issue only happens when this new failure mode that was discovered happens. It is also unclear if the new failure mode was introduced because of the MCAS 2.0 software needing more processing power of it it always existed (possibly even on the NG) and was just now discovered. If it is something introduced by MCAS 2.0 then I don't think it had anything to do with the crashes. If it was always there, there is a possibility.
 
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PW100
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:56 pm

OldAeroGuy wrote:
Interested wrote:
There was a report last week that Boeing safety analysis for Max relied on pilots being able to deal with MCAS within 3 seconds

Which at the time seemed incredibly ambitious and optimistic and risky to me for them to expect and plan for that?

Your post above is written in a way that kind of suggests that not being able to deal with stuff in seconds might not be considered a risk?


Both the FAA and EASA use 3 seconds as a standard pilot recognition time for a changing situation. See AC25-7C, pages 151 - 154. https://www.faa.gov/documentLibrary/med ... -7C%20.pdf

Boeing safety analyses use of 3 seconds is consistent with regulatory agency practice used for all Part 25 airplanes.


Is 3 seconds sufficient to recognize a runaway trim in a stand-alone failure scenario (leaving aside that usually other issues be present at the same time)?
If we look at MCAS, it has a 9 second cycle. Should pilots be expected to disable MCAS after only 3 seconds, or should they allow at least a full MCAS cyce, and take action at the next cycle (after 3 seconds)?
Leaving aside the question whether the intermittent behaviour of MCAS would be recognizable as runaway trim (prior to the accidents).
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StTim
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:56 pm

planecane wrote:
PW100 wrote:
planecane wrote:
And for the 1000th time, I don't blame the pilots for the crashes. I said that they COULD have recovered if they had recognized the runaway stabilizer and followed the NNC exactly as intended. Lion Air 043 did recover from the exact same situation. I blamed lack of documentation from Boeing and lack of training on runaway stabilizer for the pilots not being prepared to recognize the problem and react. .


Sorry for the selective quoting, but could perhaps this recent software/microprocessor issue be related to with the fact that all four uptrim actions of the ET crew (after MCAS became alive) stopped at 2.4 units stabilizer trim? Could that perhaps have been an issue preventing those pilots from using electric uptrimming?

And one step further, thinking aloud, could that also have been the case with the JT accident, that somehow the copilot electric uptrim also did not work?

Lots of questions we will not get definite answers on for some time, but for me sufficient reason to hold back judgement on crew actions . . .


No worries on the selective quoting. I don't have enough information about the microprocessor issue to speculate one way or the other. I'm not going to say that it couldn't have been an issue. The information about the microprocessor issue is a little conflicting at the moment. The official statements from Boeing and the FAA as well as the reporting by CNN seem to indicate that the microprocessor issue is an additional possible cause of runaway stabilizer that was discovered. Other reports indicate that the issue is the manual electric trim not responding fast enough.

I don't understand from the reports if the response time issue only happens when this new failure mode that was discovered happens. It is also unclear if the new failure mode was introduced because of the MCAS 2.0 software needing more processing power of it it always existed (possibly even on the NG) and was just now discovered. If it is something introduced by MCAS 2.0 then I don't think it had anything to do with the crashes. If it was always there, there is a possibility.


I agree - there is far too little publicly available information on exactly what this new issue is to reliably comment.

I would say those speculating that the 737MAX will never fly again are still at the very outer edge of what is likely. The timeline to get the bird back in operation is certainly extended by this news. How long? Who knows - certainly not Boeing. Each new push back of operational date by the airlines is just them planning for best case scenario. There was an interesting article on Leeham on how the lessors are not happy at rolling extensions. It must be giving them a lot of headaches (and profits as rates go up).
 
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BoeingVista
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 3:57 pm

Revelation wrote:
It could be that the cost of accessing the 2nd AOA sensor is the straw breaking the camel's back. It may be that tuning the access rate of that and other sensors could be a fix. None of us know enough to say.



Its more likely that the issue is having only 2 rather than 3 sensors Boeing have had to add a whole bunch of processing logic to determine which one is good / bad (are they both bad?) and are doing this by comparing with other instruments / processes. This iterative process has to run often and is highest priority & time critical that needs to produce a data point as part of the control loop before trim is actioned. This data is also only good for a limited period of time so programmers face the problem of what to do if you don't get an answer in a prescribed time, do you wait, drop the data point, guess, use last data point etc, all of those choices have inferences. Late delivery, where data comes after the condition has changed could be worse than inaction i.e no trim change which is what we seem to have here.

The system designers have not budgeted any hardware resources for this additional high level process so chip could be crashing / shedding processes / locking up / lagging. If they are lucky its just sloppy coding but I doubt it, this is a can or worms.
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planecane
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Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 4:09 pm

BoeingVista wrote:
Revelation wrote:
It could be that the cost of accessing the 2nd AOA sensor is the straw breaking the camel's back. It may be that tuning the access rate of that and other sensors could be a fix. None of us know enough to say.



Its more likely that the issue is having only 2 rather than 3 sensors Boeing have had to add a whole bunch of processing logic to determine which one is good / bad (are they both bad?) and are doing this by comparing with other instruments / processes. This iterative process has to run often and is highest priority & time critical that needs to produce a data point as part of the control loop before trim is actioned. This data is also only good for a limited period of time so programmers face the problem of what to do if you don't get an answer in a prescribed time, do you wait, drop the data point, guess, use last data point etc, all of those choices have inferences. Late delivery, where data comes after the condition has changed could be worse than inaction i.e no trim change which is what we seem to have here.

The system designers have not budgeted any hardware resources for this additional high level process so chip could be crashing / shedding processes / locking up / lagging. If they are lucky its just sloppy coding but I doubt it, this is a can or worms.


Nothing in Boeing's official statements on the software update indicate that they are trying to figure out which sensor is the good one. Everything they said indicates that when the two sensors disagree by more than 5 degrees MCAS is disabled.
 
Exeiowa
Posts: 147
Joined: Fri Jul 06, 2018 4:49 pm

Re: Boeing 737MAX Grounded Worldwide Q2 2019

Thu Jun 27, 2019 4:18 pm

3 seconds might be how long it takes you to say "what the hell" when suddenly the plane does something you do not expect, let alone figure out which systems is the cause, and then turn it off.

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