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7BOEING7
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 12:25 am

par13del wrote:
So EASA asking for a fix for a trim wheel function that is present on hundreds of NG's operating in Europe to allow the MAX back in the air while not grounding the NG passes the sniff test?


If the exact issue is present on both the NG and the MAX unrelated to MCAS, based on the NG’s safety record I could see it being an IOU rather than a continued grounding issue for the MAX, with appropriate work around.
 
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7BOEING7
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 12:31 am

Relative to the back in service date, I believe Boeing indicated after they got dinged by the FAA, they said September would be the date for providing paperwork to the FAA, so in service would be 2-3 months after that if all went well.
 
Absynth
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 12:34 am

par13del wrote:
Absynth wrote:
If that list doesn't concern you I doubt what list will. A lot of them are hardware issues. The heavy trim wheel, how to address that? Unreliable AoA sensors? I read that as 2 = not enough, not issues with the AoA sensor itself. And all these software and hardware issues will be addressed in two months?

By all accounts everyone is free to believe what they want. But that statement doesn't even remotely pass the sniff test.

So EASA asking for a fix for a trim wheel function that is present on hundreds of NG's operating in Europe to allow the MAX back in the air while not grounding the NG passes the sniff test?


So are you saying Bloomberg made that list up?

Maybe the trim wheel is not seen as crucial to the safety of the NG and earlier versions, but I can see why they might think different on the MAX. There might be other reasons, and it might be that the MCAS v2 solution is enough. But yes, let's just ignore it's on the EASA list.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 12:58 am

smartplane wrote:
Aren't investigators already testing NG simulators and checking certification documentation, the latter presumably for 'names' linked to MAX defects to see what they 'touched' on the NG?

Poster was talking about the list of items EASA wants cleared before the MAX can be returned to service, the trim wheel is among the items.
Per his sniff test, the trim wheel difficulty also exist on the NG, so if clearing that must be accomplished the NG would have to be grounded if that is the sniff test.
Last edited by par13del on Sun Jul 07, 2019 1:05 am, edited 1 time in total.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 12:59 am

7BOEING7 wrote:
par13del wrote:
So EASA asking for a fix for a trim wheel function that is present on hundreds of NG's operating in Europe to allow the MAX back in the air while not grounding the NG passes the sniff test?


If the exact issue is present on both the NG and the MAX unrelated to MCAS, based on the NG’s safety record I could see it being an IOU rather than a continued grounding issue for the MAX, with appropriate work around.

Totally agree.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 1:04 am

Absynth wrote:
So are you saying Bloomberg made that list up?

Maybe the trim wheel is not seen as crucial to the safety of the NG and earlier versions, but I can see why they might think different on the MAX. There might be other reasons, and it might be that the MCAS v2 solution is enough. But yes, let's just ignore it's on the EASA list.

Unless you found the sniff test in the article, I did not, that is what I was responding to.
The trim wheel is on the list, but if EASA attempts to use that functionality which is the same as on the NG then yeah, your sniff test will smell funny.

As for going along with the other line of ignoring the EASA list, if you want to do that to continue the activity on this thread fine.
As I said earlier, I will go along with the reporting which stated that the FAA and Boeing agreed on the items to be corrected and were working to resolve the items to each others mutual satisfaction.
But yeah, let's just ignore that part of the reporting.
 
Absynth
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 1:19 am

par13del wrote:
Absynth wrote:
So are you saying Bloomberg made that list up?

Maybe the trim wheel is not seen as crucial to the safety of the NG and earlier versions, but I can see why they might think different on the MAX. There might be other reasons, and it might be that the MCAS v2 solution is enough. But yes, let's just ignore it's on the EASA list.

Unless you found the sniff test in the article, I did not, that is what I was responding to.
The trim wheel is on the list, but if EASA attempts to use that functionality which is the same as on the NG then yeah, your sniff test will smell funny.


If the Max needs the trim wheel ~100x more often then no, this is a completely different situation. That is why it's on the list. You are again stating EASA made a nonsense bucket list.

As for going along with the other line of ignoring the EASA list, if you want to do that to continue the activity on this thread fine.
As I said earlier, I will go along with the reporting which stated that the FAA and Boeing agreed on the items to be corrected and were working to resolve the items to each others mutual satisfaction.
But yeah, let's just ignore that part of the reporting.



It seems you are the one ignoring crucial parts of the article:

Both the FAA and EASA along with Canada and Brazil, have meanwhile come together in tentative agreement that the return to service should be closely coordinated in an effort to help restore public trust in the global aviation safety system, people familiar with the matter have said, though they cautioned that EASA may still make additional requests and lag behind the FAA.



Good luck on that strategy of ignoring EASA. We know FAA & Boeing are a great team, they achieve the most efficient results without outside interference.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 1:40 am

So where exactly is the line stating that Boeing and the FAA are ignoring the EASA list and concerns of the other regulators?
Is that another A.Net myth?
 
Absynth
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 1:43 am

par13del wrote:
7BOEING7 wrote:
par13del wrote:
So EASA asking for a fix for a trim wheel function that is present on hundreds of NG's operating in Europe to allow the MAX back in the air while not grounding the NG passes the sniff test?


If the exact issue is present on both the NG and the MAX unrelated to MCAS, based on the NG’s safety record I could see it being an IOU rather than a continued grounding issue for the MAX, with appropriate work around.

Totally agree.


Good to read the both of you have seen the full MCAS FMEA and that of all other MAX specific flight control software. Now please share it with the rest of us.

Or it could be you are just making things up.

We already know MCAS v1 needs the trim wheel in failure modes that do not exist on the NG. And I wouldn't be surprised if the FCC delay necessites trim wheel usage as well.

The both of you seem to lack basic understanding how the same trim wheel may be an issue for certification authorities on one plane yet not the other.
 
mwmav8r01
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 1:54 am

par13del wrote:
Absynth wrote:
If that list doesn't concern you I doubt what list will. A lot of them are hardware issues. The heavy trim wheel, how to address that? Unreliable AoA sensors? I read that as 2 = not enough, not issues with the AoA sensor itself. And all these software and hardware issues will be addressed in two months?

By all accounts everyone is free to believe what they want. But that statement doesn't even remotely pass the sniff test.

So EASA asking for a fix for a trim wheel function that is present on hundreds of NG's operating in Europe to allow the MAX back in the air while not grounding the NG passes the sniff test?



Exactly what I was thinking. This whole thing is a spectacle now. Now EASA is playing games, seems pretty clear by this. The trim wheel is the same as its been. Whats the new AP issue? Wierd how airplanes havent been hrounded much ever but now ALL of these issues are deal breakers.

Ill be the first to admit that Boeing needs to change MCAS logic and a short term grounding was needed. ADs happen which cause operators to change the way we operate airplanes. Sometimes they are short term until a fix is implemented, others stay forever. There needs to be a plan. This is just getting silly. Or are we just gunna ground airplanes always now?
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 2:00 am

The article below is on multiple sites, but as it relates to the latest issue with the microprocessor, Boeing ultimately agreed with the FAA.
Also posted eralier in this thread.
https://theaircurrent.com/aviation-safe ... re-glitch/

As for ignoring the EASA list, everything we read says Boeing is working with the FAA and the FAA is working with all and sundry, so..
https://www.ft.com/content/b98ccbfa-9f2 ... 459ed04726
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 2:04 am

Absynth wrote:
Good to read the both of you have seen the full MCAS FMEA and that of all other MAX specific flight control software. Now please share it with the rest of us.
Or it could be you are just making things up.

Since no official reports of either crash has been released, we are all making things up, but....will leave well enough alone.
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 2:07 am

Trim wheel issue is likely Max only. Appearantly Max electrical trim " does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts." So trim wheel is needed to meet trim related regulations

STATEMENT OF ISSUE
The aisle stand trim switches can be used to trim the airplane throughout the flight envelope and fully complies with the reference regulation Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.In those cases, longitudinal trim is achieved by using the manual stabilizer trim wheel to position the stabilizer. The trim wheel can be used to trim the airplane throughout the entire flight envelope.In addition, the autopilot has the authority to trim the airplane in these conditions.The reference regulation and policy do not specify the method of trim, nor do they state that when multiple pilot trim control paths exist that they must each independently be able to trim the airplane throughout the flight envelope.Boeing did not initially consider this to be a compliance issue because trim could always be achieved, even during the conditions where use of the aisle stand trim switch was required.Subsequent to flight testing, the FAA-TAD expressed concern with compliance to the reference regulation based on an interpretation of the intent behind “trim”. The main issue being that longitudinal trim cannot be achieved throughout the flight envelope using thumb switch trim only.

EASA POSITION
Boeing set the thumb switch limits in order to increase the level of safety for out-of-trim dive characteristics(CS 25.255(a)(1)). The resulting thumb switch limits require an alternative trim method to meet CS 25.161trim requirements in certain corners of the operational envelope. The need to use the trim wheel is considered unusual, as it is only required for manual flight in those corners of the envelope.The increased safety provided by the Boeing design limits on the thumb switches (for out-of-trim dive characteristics) provides a compensating factor for the inability to use the thumb switches throughout the entire flight envelope. Furthermore, the additional crew procedures and training material will clearly explain to pilots the situations where use of the trim wheel may be needed due to lack of trim authority with the wheel mounted switches.The trim systems on the 737Max provide an appropriate level of safety relative to longitudinal trim capability.
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 2:12 am

Revelation wrote:
Absynth wrote:
You present Boeing PR fluff as fact to dismiss statements by the EASA Revelation. That's pretty improper if you ask me.

Actually it does not dismiss statements by the EASA, that's just the spin you are applying. It's quite possible Boeing fully understands what EASA is requesting and still feels it can return the aircraft to service in September. Both Boeing and EASA say they've had frequent communications so none of this should be a surprise to Boeing.

ArgentoSystems wrote:
SPEEA engineer breaks silence on Boeing's MAX 737. Read this letter

https://www.kuow.org/stories/boeing-eng ... his-letter

What silence is being broken? There's been nothing silent about this entire situation. It should be no surprise a union leader should not like cost cutting measures and would paint a rosy picture of days gone by. While I'm generally pro-union, some of the stuff Boeing's unions have been doing over the years to pad their membership numbers with make work jobs are absurd.
The unions area in competition with management for remuneration. Stu far I don't see any unionists with anything like pay the senior management is giving itself.
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 2:18 am

LDRA wrote:
Trim wheel issue is likely Max only. Appearantly Max electrical trim " does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts." So trim wheel is needed to meet trim related regulations

STATEMENT OF ISSUE
The aisle stand trim switches can be used to trim the airplane throughout the flight envelope and fully complies with the reference regulation Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.In those cases, longitudinal trim is achieved by using the manual stabilizer trim wheel to position the stabilizer. The trim wheel can be used to trim the airplane throughout the entire flight envelope.In addition, the autopilot has the authority to trim the airplane in these conditions.The reference regulation and policy do not specify the method of trim, nor do they state that when multiple pilot trim control paths exist that they must each independently be able to trim the airplane throughout the flight envelope.Boeing did not initially consider this to be a compliance issue because trim could always be achieved, even during the conditions where use of the aisle stand trim switch was required.Subsequent to flight testing, the FAA-TAD expressed concern with compliance to the reference regulation based on an interpretation of the intent behind “trim”. The main issue being that longitudinal trim cannot be achieved throughout the flight envelope using thumb switch trim only.

EASA POSITION
Boeing set the thumb switch limits in order to increase the level of safety for out-of-trim dive characteristics(CS 25.255(a)(1)). The resulting thumb switch limits require an alternative trim method to meet CS 25.161trim requirements in certain corners of the operational envelope. The need to use the trim wheel is considered unusual, as it is only required for manual flight in those corners of the envelope.The increased safety provided by the Boeing design limits on the thumb switches (for out-of-trim dive characteristics) provides a compensating factor for the inability to use the thumb switches throughout the entire flight envelope. Furthermore, the additional crew procedures and training material will clearly explain to pilots the situations where use of the trim wheel may be needed due to lack of trim authority with the wheel mounted switches.The trim systems on the 737Max provide an appropriate level of safety relative to longitudinal trim capability.
So this is a third issue then? It is possible to get a situation where the electric trim won't work? I honestly thought MCAS would be it, but Boeing has been making multiple compromises in it's effort to get the MAX out the door.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 2:27 am

7BOEING7 wrote:
par13del wrote:
So EASA asking for a fix for a trim wheel function that is present on hundreds of NG's operating in Europe to allow the MAX back in the air while not grounding the NG passes the sniff test?


If the exact issue is present on both the NG and the MAX unrelated to MCAS, based on the NG’s safety record I could see it being an IOU rather than a continued grounding issue for the MAX, with appropriate work around.

One can argue, that MAX is architecturally more reliant on trim, so problems with backup are more critical in MAX than in NG.
A second argument is that NG has an in-service record to show, so more relaxed approach is warranted - while MAX has a horrible record directly related to trim functionality, and there is a full reason to go by the book to ensure there are at least 2 layers of cheese added to past crash scenarios.
Last, but not the least, this is bureaucratic action vs inaction thing: action requires taking responsibility, inaction is less so.
Grounding NG is an action, keeping it in the air is inaction. The other way around for MAX
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 2:37 am

RickNRoll wrote:
LDRA wrote:
Trim wheel issue is likely Max only. Appearantly Max electrical trim " does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts." So trim wheel is needed to meet trim related regulations

STATEMENT OF ISSUE
The aisle stand trim switches can be used to trim the airplane throughout the flight envelope and fully complies with the reference regulation Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.In those cases, longitudinal trim is achieved by using the manual stabilizer trim wheel to position the stabilizer. The trim wheel can be used to trim the airplane throughout the entire flight envelope.In addition, the autopilot has the authority to trim the airplane in these conditions.The reference regulation and policy do not specify the method of trim, nor do they state that when multiple pilot trim control paths exist that they must each independently be able to trim the airplane throughout the flight envelope.Boeing did not initially consider this to be a compliance issue because trim could always be achieved, even during the conditions where use of the aisle stand trim switch was required.Subsequent to flight testing, the FAA-TAD expressed concern with compliance to the reference regulation based on an interpretation of the intent behind “trim”. The main issue being that longitudinal trim cannot be achieved throughout the flight envelope using thumb switch trim only.

EASA POSITION
Boeing set the thumb switch limits in order to increase the level of safety for out-of-trim dive characteristics(CS 25.255(a)(1)). The resulting thumb switch limits require an alternative trim method to meet CS 25.161trim requirements in certain corners of the operational envelope. The need to use the trim wheel is considered unusual, as it is only required for manual flight in those corners of the envelope.The increased safety provided by the Boeing design limits on the thumb switches (for out-of-trim dive characteristics) provides a compensating factor for the inability to use the thumb switches throughout the entire flight envelope. Furthermore, the additional crew procedures and training material will clearly explain to pilots the situations where use of the trim wheel may be needed due to lack of trim authority with the wheel mounted switches.The trim systems on the 737Max provide an appropriate level of safety relative to longitudinal trim capability.
So this is a third issue then? It is possible to get a situation where the electric trim won't work? I honestly thought MCAS would be it, but Boeing has been making multiple compromises in it's effort to get the MAX out the door.


I first read this before manual trim wheel force issue was public. At the time, I was shocked EASA let this one slid, not knowing manual trim wheel wouldn't work near Vmo also!
 
IADFCO
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 4:37 am

7BOEING7 wrote:

I thought this had been put to bed a while back. Every time I read this I think about replying but don't, just hoping it will go away.

Throw out other big airplanes (everybody has TCAS) and terrain (all the MAX's have EGWPS). Also anything ATC sees that you don't will be done within the normal operating limit.

That said, if you're trying to dodge something small (drones, birds, etc) or a light airplane (non-TCAS) that just came into view and you make a turn using an excessive bank angle the "event" would be over in seconds -- it's a hit or a miss -- at which point you'd return to normal stable flight. 737's ae not F-16's. They do respond nicely in roll but they don't slow down that rapidly (unless you help by pulling the thrust levers to idle) and even at has high a bank angle as any commercial pilot would go to the stick shaker speed would still take a while to get to. I think most pilots would add power in this case realizing they were going into a higher than normal bank turn.

In other words within seconds of starting the maneuver you'd be recovering long before the MCAS went off.


I'm sorry I reduced your signal-to-noise ratio. Unfortunately in every forum there are a few bad apples. You can always hope that we won't post frequently or you can simply ignore us.

Any maneuver on the MAX that takes the angle of attack above the MCAS activation threshold, and holds it there for more than 10 seconds, is potentially dangerous, regardless of failures. I filed a comment form with the FAA describing this during last May's public comment period, so that this issue would be brought up officially at least once. They have access to aircraft and hard engineering data, which I don't. If they decide that my concern is unjustified, for whatever reason, that's fantastic! I probably have Boeing stocks in my retirement account.
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 5:50 am

PixelFlight wrote:
tenHangar wrote:
MrBretz wrote:

I agree with this. That’s what we did years ago. They are probably reprogramming some C or C+ routines/objects in assembly language to get more speed. It is labor intensive but easy to check for errors with software simulations.

One of my first thoughts when I heard about the "slow response time" and $9/hour programmer issues was inappropriate programming language. Indian programmers are known for/strong in Java which is arguably slower than C or C++. (Note, I don't know what languages are actually used in 737MAX systems).

It's not the programmer that decide the programming language used in a safety critical flight computer. This is part of the high level planning per DO-178. I think it's very unlikely that the 737-8/9 MAX flight computer contain any Java code. You can certainly find a lot of competent Indian engineers in any programming language.


And the reason it most likely not in Java is because Java is an interpretive language. It runs on any processor with a processor dependent runtime engine. It’s transportable but slow. We are all just guessing because none of know anything about the software architecture or how it is implemented. All here remind me of high level managers I used to work for that were mostly clueless. And that includes me.
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 6:16 am

LDRA wrote:
RickNRoll wrote:
LDRA wrote:
Trim wheel issue is likely Max only. Appearantly Max electrical trim " does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts." So trim wheel is needed to meet trim related regulations

So this is a third issue then? It is possible to get a situation where the electric trim won't work? I honestly thought MCAS would be it, but Boeing has been making multiple compromises in it's effort to get the MAX out the door.


I first read this before manual trim wheel force issue was public. At the time, I was shocked EASA let this one slid, not knowing manual trim wheel wouldn't work near Vmo also!


I don't think it is established that the trim wheel won't work near Vmo. It's been established that it won't work near Vmo AND severely out of trim. It would seem from the EASA position that it does work near Vmo when starting close to "in trim."
 
PStechPaul
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 7:54 am

I thought I had read that the trim wheels for the 737MAX were smaller than for the NG, thus requiring greater force. But apparently that happened during the changes from the 737-200 Classic to the 737NG. It is not clear if the gearing of the manual actuators was changed to compensate, but in light of the cost-cutting environment in place of good engineering at Boeing, I would bet that they chose the cheapest option, and minimized any changes on a system that was probably thought to be extraneous anyway.

https://www.moonofalabama.org/2019/05/b ... 7-ngs.html
 
xmp125a
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 10:11 am

planecane wrote:
keesje wrote:
Let's keep ignoring the EASA found Boeing 737 Max's Autopilot Has Problem. Maybe it 'll go away..

Until they release details of exactly what they found it's hard to know how much of an "issue" it is. From what I've read, there isn't an issue "with" the autopilot (which would imply a problem with autopilot function) but rather that it fails to disengage in certain emergencies.

It isn't clear if failure to disengage means failure to do so automatically or failure to do so manually. The former might not be a big issue if the "certain" emergencies are very low likelihood..


More importantly, it is very likely that this is 100% software problem and can be addressed as such.
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 11:31 am

Absynth wrote:
Revelation wrote:
Absynth wrote:
I'm just not so sure this particular fix will cut it for EASA. I think they have significant extra work ahead of them after the FCC fix. The MAX return to flight may be ultra long haul.

The most interesting thing about the article being discussed is that EASA has provided a list of things Boeing needs to address. Up to this point their concerns were open ended if not nebulous. From my point of view this probably bounds the amount of time that 737 will be grounded. Their list of concerns may be changed with time, but as an engineer I'd rather have a list of things to address than to just be looking at various things wondering if that's what the regulator is concerned about.

If that list doesn't concern you I doubt what list will. A lot of them are hardware issues. The heavy trim wheel, how to address that? Unreliable AoA sensors? I read that as 2 = not enough, not issues with the AoA sensor itself. And all these software and hardware issues will be addressed in two months?

Please read without embellishing: I'd rather have a list of things to do rather than no list and finding myself spending my time trying to guess what the regulator thinks I need to do.

We're reading this list for the first time now, we have no idea how long Boeing has had this list in full or in part. We do know that all involved claim they have been working together all along. As much as some here want to see the regulators drop the hammer on Boeing, we do know there is a steady flow of questions and answers going back and forth.

The Bloomberg piece offers some perspective that seems to be lacking here:

“Any of these could significantly affect the return to service, but we don’t know if they are actually going to become requirements or are they just items for discussion,’’ said John Cox, a former 737 pilot who is president of the aviation consulting company Safety Operating Systems.

Cox said that such questions between regulators are the norm during aircraft certification work and may not pose new risks for Boeing.

People here seem to be assuming some worse case scenarios without knowing what the letter says. I am a systems software expert and I know that some of the suggestions here relative to my area of expertise are laughable. I am not an avionics or flight control specialist but I can imagine the same may be true in those spaces.

7BOEING7 wrote:
Relative to the back in service date, I believe Boeing indicated after they got dinged by the FAA, they said September would be the date for providing paperwork to the FAA, so in service would be 2-3 months after that if all went well.

That may be, but that is not what the Bloomberg report says, which is:

Boeing has been telling customers and others in the industry that it expects the plane will be returned to service by September. That timetable includes fixing the software implicated in the two crashes as well as the latest flaw identified with the microprocessor, said a person familiar with the company’s guidance.

Ref: https://www.bloomberg.com/news/articles ... -fly-again
Wake up to find out that you are the eyes of the world
The heart has its beaches, its homeland and thoughts of its own
Wake now, discover that you are the song that the morning brings
The heart has its seasons, its evenings and songs of its own
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 12:52 pm

PStechPaul wrote:
I thought I had read that the trim wheels for the 737MAX were smaller than for the NG, thus requiring greater force. But apparently that happened during the changes from the 737-200 Classic to the 737NG. It is not clear if the gearing of the manual actuators was changed to compensate, but in light of the cost-cutting environment in place of good engineering at Boeing, I would bet that they chose the cheapest option, and minimized any changes on a system that was probably thought to be extraneous anyway.

https://www.moonofalabama.org/2019/05/b ... 7-ngs.html


The classic is the 737-400 vintage. The NG is the 737-800 vintage. The MAX is the 737-8.

The change is from the classic to the NG. It changed the gearing that made it harder to turn the trim and also had to add dampers to stop backlash, which also made the trim wheel harder to turn.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 12:56 pm

So was that deliberate to prevent accidental manipulation of the wheels in flight?
 
Absynth
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 12:58 pm

Revelation wrote:
7BOEING7 wrote:
Relative to the back in service date, I believe Boeing indicated after they got dinged by the FAA, they said September would be the date for providing paperwork to the FAA, so in service would be 2-3 months after that if all went well.

That may be, but that is not what the Bloomberg report says, which is:

Boeing has been telling customers and others in the industry that it expects the plane will be returned to service by September. That timetable includes fixing the software implicated in the two crashes as well as the latest flaw identified with the microprocessor, said a person familiar with the company’s guidance.

Ref: https://www.bloomberg.com/news/articles ... -fly-again


That would mean the fix (or all fixes) should be ready about now. How realistic is that Revelation?

You sound like someone hunting that pot of gold near that rainbow that is just a few 100m from where you are standing.

I'm wondering how long it'll take you to reassess that september timeframe internally. Absent any news or developments I'm thinking around september 28-29 you'll start to worry Boeing won't stick to it's estimate.
 
kalvado
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 1:04 pm

par13del wrote:
So was that deliberate to prevent accidental manipulation of the wheels in flight?

Changes in flight deck instrumentation encroached in trim wheel space, so the wheel had to be reduced.
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 1:30 pm

Revelation wrote:
Absynth wrote:
Revelation wrote:
The most interesting thing about the article being discussed is that EASA has provided a list of things Boeing needs to address. Up to this point their concerns were open ended if not nebulous. From my point of view this probably bounds the amount of time that 737 will be grounded. Their list of concerns may be changed with time, but as an engineer I'd rather have a list of things to address than to just be looking at various things wondering if that's what the regulator is concerned about.

If that list doesn't concern you I doubt what list will. A lot of them are hardware issues. The heavy trim wheel, how to address that? Unreliable AoA sensors? I read that as 2 = not enough, not issues with the AoA sensor itself. And all these software and hardware issues will be addressed in two months?

Please read without embellishing: I'd rather have a list of things to do rather than no list and finding myself spending my time trying to guess what the regulator thinks I need to do.

We're reading this list for the first time now, we have no idea how long Boeing has had this list in full or in part. We do know that all involved claim they have been working together all along. As much as some here want to see the regulators drop the hammer on Boeing, we do know there is a steady flow of questions and answers going back and forth.

The Bloomberg piece offers some perspective that seems to be lacking here:

“Any of these could significantly affect the return to service, but we don’t know if they are actually going to become requirements or are they just items for discussion,’’ said John Cox, a former 737 pilot who is president of the aviation consulting company Safety Operating Systems.

Cox said that such questions between regulators are the norm during aircraft certification work and may not pose new risks for Boeing.

People here seem to be assuming some worse case scenarios without knowing what the letter says. I am a systems software expert and I know that some of the suggestions here relative to my area of expertise are laughable. I am not an avionics or flight control specialist but I can imagine the same may be true in those spaces.

7BOEING7 wrote:
Relative to the back in service date, I believe Boeing indicated after they got dinged by the FAA, they said September would be the date for providing paperwork to the FAA, so in service would be 2-3 months after that if all went well.

That may be, but that is not what the Bloomberg report says, which is:

Boeing has been telling customers and others in the industry that it expects the plane will be returned to service by September. That timetable includes fixing the software implicated in the two crashes as well as the latest flaw identified with the microprocessor, said a person familiar with the company’s guidance.

Ref: https://www.bloomberg.com/news/articles ... -fly-again


A very fair assessment.

The way this works, I believe, is that the letter will be formalisation of the known position arrived at over the past months of discussion and analysis. Nothing in it will be new to FAA or Boeing.

Just a little embellishment - All potentially good news for the MAX - The 'Critical' list does not include MCAS or Flap System and would likley imply that both EASA and FAA probably consider these resolved. The EASA letter being issued may well indicate that the EASA review of the flight control system has been completed and so there will nothing else to come (not withstanding another ball from left field).

Ray
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 2:45 pm

It is not rare for some safety issues to be given as long as two years (?) to be fully implemented. Safety is a statistical thing. The trick is to have proper statistics. Some of those items EASA raised may have a 6-E, and Europe wants a 7 (don't know the proper grammar for that, correction invited).
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 3:00 pm

Absynth wrote:
Revelation wrote:
7BOEING7 wrote:
Relative to the back in service date, I believe Boeing indicated after they got dinged by the FAA, they said September would be the date for providing paperwork to the FAA, so in service would be 2-3 months after that if all went well.

That may be, but that is not what the Bloomberg report says, which is:

Boeing has been telling customers and others in the industry that it expects the plane will be returned to service by September. That timetable includes fixing the software implicated in the two crashes as well as the latest flaw identified with the microprocessor, said a person familiar with the company’s guidance.

Ref: https://www.bloomberg.com/news/articles ... -fly-again


That would mean the fix (or all fixes) should be ready about now. How realistic is that Revelation?

You sound like someone hunting that pot of gold near that rainbow that is just a few 100m from where you are standing.

I'm wondering how long it'll take you to reassess that september timeframe internally. Absent any news or developments I'm thinking around september 28-29 you'll start to worry Boeing won't stick to it's estimate.

Again, I'm just posting what Bloomberg is reporting that Boeing is telling its customers. Please stop embellishing, it's childish. I have no way of saying how close or how far Boeing is from meeting such a timeline, neither do you.
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MrBren
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 4:15 pm

The MAX will be the worst aeronautic industrial nightmare financially speaking.
 
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sergegva
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 6:17 pm

par13del wrote:
The article below is on multiple sites, but as it relates to the latest issue with the microprocessor, Boeing ultimately agreed with the FAA.
Also posted eralier in this thread.
https://theaircurrent.com/aviation-safe ... re-glitch/


I am not sure I fully understand the implications of this article. As I understand it, it seems to say that, in some cases, the automatic trim button controlled by the pilots does not react quickly enough to counter the MCAS effect. Correct?

However, one of the main mysteries of the two crashes is precisely: why did the pilots suddenly stop counter-triming every MCAS imput, when the strategy had worked so far (Lion Air case), and why didn't the pilots completely compensate the nose-down impulses of the MCAS with the auto-trim button before hitting the cutout switch (Ethiopian)?

Is it possible that the auto-trim worked too slowly to compensate the MCAS imputs (Ethiopian), or even stopped working completely after a while, due to successive activations that saturated the microprocessor? (Lion Air)
 
WPvsMW
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 6:27 pm

It's puzzling that Boeing's proposed fix is to use multiple processors instead of a higher throughput processor. If 2 cores isn't enough, use 4 cores, or 6 cores, or 8 cores, or 10 cores. Multiple CPUs add overhead. For redundancy, a second x-core processor, rather than four, 2-core processors.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 7:06 pm

WPvsMW wrote:
It's puzzling that Boeing's proposed fix is to use multiple processors instead of a higher throughput processor. If 2 cores isn't enough, use 4 cores, or 6 cores, or 8 cores, or 10 cores. Multiple CPUs add overhead. For redundancy, a second x-core processor, rather than four, 2-core processors.

737-8/9 MAX flight computer processor is likely to be a 80286. Single core.
https://www.moonofalabama.org/2019/06/b ... .html#more
https://en.wikipedia.org/wiki/Boeing_73 ... sing_issue
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 7:59 pm

PixelFlight wrote:
WPvsMW wrote:
It's puzzling that Boeing's proposed fix is to use multiple processors instead of a higher throughput processor. If 2 cores isn't enough, use 4 cores, or 6 cores, or 8 cores, or 10 cores. Multiple CPUs add overhead. For redundancy, a second x-core processor, rather than four, 2-core processors.

737-8/9 MAX flight computer processor is likely to be a 80286. Single core.
https://www.moonofalabama.org/2019/06/b ... .html#more
https://en.wikipedia.org/wiki/Boeing_73 ... sing_issue

Satcom Guru has as a diagram notated 737NG that has CPU1 as 'SDP-185' (I believe is a Honeywell design) and CPU2 as 'Z16C02' No indication of age, so may suggest there has been a processor change at some point.
https://www.satcom.guru/2018/11/stabilizer-trim.html

The point I was going to make was any hardware change would require at least a 12 month programme to implement, so its not really an option if you can move functions from one CPU to the other in a months timescale.

Ray
 
WPvsMW
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 8:27 pm

The SDP-185 is a minor upgrade of the Sperry (acquired by Honeywell) SDP-175. 1980's era CPU. :roll: :shock: :shock:
Easy to see why the stack would overflow.
viewtopic.php?f=3&t=1426007&p=21494277#p21494277

It gets worse. Remember Zilog and UARTs ...from from the 80's? ZIlog had a chunk of the serial i/o and small RISC market, including the Z16C01, -02,....
https://www.zilog.com/index.php?option= ... tId=Z16C02
https://en.wikipedia.org/wiki/Zilog_Z16C01

Sad, really, that the semiconductor designs date from the Classics, and some from the Jurassics.

The Jurassic to Classic upgrade was probably as big a jump as the NG to MAX, and Boeing didn't skimp on the gen1 to gen2 change. Different story from gen3 to gen 4.
 
Chemist
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 9:11 pm

MrBren wrote:
The MAX will be the worst aeronautic industrial nightmare financially speaking.


I doubt it.
If they are back on the market and sell thousands it will be financially extremely profitable.

This isn't the thread to talk A380, so....
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 9:40 pm

XRAYretired wrote:
Satcom Guru has as a diagram notated 737NG that has CPU1 as 'SDP-185' (I believe is a Honeywell design) and CPU2 as 'Z16C02' No indication of age, so may suggest there has been a processor change at some point.
https://www.satcom.guru/2018/11/stabilizer-trim.html
:checkmark: :thumbsup: Good catch !
I have found in his document: https://ntrs.nasa.gov/archive/nasa/casi ... 023534.pdf on page 157 (noted 6-10):
"The SDP-185 is a custom Honeywell-developed 2901-based processor circuit"
So it seem that we are talking about something like this: https://en.wikipedia.org/wiki/AMD_Am2900

Edit:
This document https://ntrs.nasa.gov/archive/nasa/casi ... 005742.pdf page 92 (noted 79) list the specification of an older SDP-175:
Weight: 7Kg, (15 pounds)
Power Dissipation: 40 Watts
Memory: 24K ROM, 2K RAM by 16 bit Expandable to 64K
Processor: General Purpose, 16-bits data and instructions
Instruction times:
0.5 µsec add, substract
5.5 µsec multiply
12.0 µsec divide
0.75 µsec test, set bit
800 KOPS for standard airborne mix
Software: Assembly, Floppy disk operating system
I/O: Input 4 AC, 20 DC, 16 28V Discrete, 48 5V Discrete; Output 0 AC, 20 DC, 16 28V Discrete, 56 5V Discrete.
Functions: Airborne remote terminal bus, control avionics processing.

There is even a picture (poor quality) of the Sperry SDP-175 Digital Computer Figure 31 on page 116 (noted 103)
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 10:42 pm

Just got to wondering, what exactly would take in terms of a hardware upgrade for Boeing to ditch the MCAS software entirely, and build planes that actually fly, rather than depending on computer software that can fail.

I assume first it would:

1) be expensive for the MAX program
2) need to entirely new MAX recertification
3) may or may not have a common pilot type rating with the NG
4) Instill public confidence in the MAX again
5) Not be as carbon neutral friendly as the MAX
6) Potentially a safer approach
7) Enable Boeing to continue with a NSA 10/11/12 with the basic 737 design
8) Orphans the MAX 10
9) New higher landing gear common for the NSA 10/11/12 and MAX
10) Round Engine Nacelles
11)) Modified wing and pylons
Aesthetically the A 340 got it right!
 
f1restate
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 10:44 pm

WPvsMW wrote:

Easy to see why the stack would overflow.


Why are you assuming that this latest issue is actually a stack overflow ?

Sent from my SM-G975F using Tapatalk
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 10:54 pm

Also found this document about the Am2900 familly:
https://en.wikichip.org/w/images/c/c4/T ... 979%29.pdf
I will not be surprised that the SDP-175/185 is based on a typical 16-bits micocomputer design like the one on the page 265
This is pre-1980 electronics, with gate geometry greater than 1 µm !
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Sun Jul 07, 2019 10:59 pm

KlimaBXsst wrote:
Just got to wondering, what exactly would take in terms of a hardware upgrade for Boeing to ditch the MCAS software entirely, and build planes that actually fly, rather than depending on computer software that can fail.

I assume first it would:

1) be expensive for the MAX program
2) need to entirely new MAX recertification
3) may or may not have a common pilot type rating with the NG
4) Instill public confidence in the MAX again
5) Not be as carbon neutral friendly as the MAX
6) Potentially a safer approach
7) Enable Boeing to continue with a NSA 10/11/12 with the basic 737 design
8) Orphans the MAX 10
9) New higher landing gear common for the NSA 10/11/12 and MAX
10) Round Engine Nacelles
11)) Modified wing and pylons


Super easy, ballast in the nose to shift CoG, so after CoG limit can be moved forward. Will probably solve some other issues related to trim
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 12:30 am

PixelFlight wrote:
Also found this document about the Am2900 familly:
https://en.wikichip.org/w/images/c/c4/T ... 979%29.pdf
I will not be surprised that the SDP-175/185 is based on a typical 16-bits micocomputer design like the one on the page 265
This is pre-1980 electronics, with gate geometry greater than 1 µm !


I find this surprising if not shocking. I wonder what the 787 uses.
 
GalaxyFlyer
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 12:54 am

KlimaBXsst wrote:
Just got to wondering, what exactly would take in terms of a hardware upgrade for Boeing to ditch the MCAS software entirely, and build planes that actually fly, rather than depending on computer software that can fail.

I assume first it would:

1) be expensive for the MAX program
2) need to entirely new MAX recertification
3) may or may not have a common pilot type rating with the NG
4) Instill public confidence in the MAX again
5) Not be as carbon neutral friendly as the MAX
6) Potentially a safer approach
7) Enable Boeing to continue with a NSA 10/11/12 with the basic 737 design
8) Orphans the MAX 10
9) New higher landing gear common for the NSA 10/11/12 and MAX
10) Round Engine Nacelles
11)) Modified wing and pylons


It’s a new design, 5-7 years and another $12-$14 billion. It’s only time and money.

GF
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 1:01 am

MrBretz wrote:
PixelFlight wrote:
Also found this document about the Am2900 familly:
https://en.wikichip.org/w/images/c/c4/T ... 979%29.pdf
I will not be surprised that the SDP-175/185 is based on a typical 16-bits micocomputer design like the one on the page 265
This is pre-1980 electronics, with gate geometry greater than 1 µm !


I find this surprising if not shocking. I wonder what the 787 uses.

The 787 use ARNIC 664 aka AFDX (Avionic Full Duplex Ethernet) network and CCS (Common Core System) Freescale (probably e500 cores) processing cluster. It's similar technology than into the A380.
https://www.greencarcongress.com/2011/1 ... 11028.html
https://nari.arc.nasa.gov/sites/default ... _LEARN.pdf

It's clear than Boeing have all the competences and experiences to upgrade a 737-8/9 frame to AFDX+CCS+FBW actuators. Later or sooner, Airbus will need to do that move too on the A320 family.
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 1:30 am

Thanks, PixelFlight. I found similar articles. I wonder if the OS is VxWorks?

However, to move to that is what BA should have done. You don’t upgrade; you build a new plane.
 
WPvsMW
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 3:55 am

f1restate wrote:
WPvsMW wrote:

Easy to see why the stack would overflow.


Why are you assuming that this latest issue is actually a stack overflow ?

Sent from my SM-G975F using Tapatalk


Just a guess.
 
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keesje
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 6:18 am

PixelFlight wrote:
WPvsMW wrote:
It's puzzling that Boeing's proposed fix is to use multiple processors instead of a higher throughput processor. If 2 cores isn't enough, use 4 cores, or 6 cores, or 8 cores, or 10 cores. Multiple CPUs add overhead. For redundancy, a second x-core processor, rather than four, 2-core processors.

737-8/9 MAX flight computer processor is likely to be a 80286. Single core.
https://www.moonofalabama.org/2019/06/b ... .html#more
https://en.wikipedia.org/wiki/Boeing_73 ... sing_issue


I and my friends bought 80286s (AT's) around 1988, so that one was already aging when the NG showed up. Using it for the MAX is typical grandfathered design and requirements to reduce costs on certification.
"Never mistake motion for action." Ernest Hemingway
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 6:25 am

Keesje, what kind of computers are used on A320’s? Were they upgraded for the NEO?
 
xmp125a
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 7:33 am

MrBretz wrote:
And the reason it most likely not in Java is because Java is an interpretive language. It runs on any processor with a processor dependent runtime engine. It’s transportable but slow. We are all just guessing because none of know anything about the software architecture or how it is implemented. All here remind me of high level managers I used to work for that were mostly clueless. And that includes me.


Why are we even talking about this? It is pretty clear that the software running on M68XXX inside the FCC is not Java or any other newfangled language made to increase the productivity of IT code monkeys. Embedded control systems are mostly programmed in C (NOT C++) or even lower languages (assembly). Given that this is safety critical system it needs to have predictable timings, so most likely those processors don't even run any kind of mainstream OS that would support java... I would be extremely surprised if there is OS in usual sense at all (even realtime OS).

For christ sake, FCC of a modern airliner is not your Android phone!

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