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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 8:07 am

MrBretz wrote:
However, to move to that is what BA should have done. You don’t upgrade; you build a new plane.
It was AB until now, but ABC is expected soon and C have full IMA (CCS+ADFX+FBW) for it C919.
https://leehamnews.com/2018/01/03/unite ... es-flying/

keesje wrote:
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.
xmp125a wrote:
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.
Based on the last analysis, the 737-8/9 MAX FCC is likely to run the same processors as on the 737-800/900 NG: a Am2901 slice based processor called SDP-185 and a Z16C02:
https://www.satcom.guru/2018/11/stabilizer-trim.html
https://4.bp.blogspot.com/-P4p43sc-X1Y/ ... 3%2BAM.png

MrBretz wrote:
Keesje, what kind of computers are used on A320’s? Were they upgraded for the NEO?
Still the original 80186 and 68000 combo according to viewtopic.php?t=1362007
 
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MrBren
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 8:39 am

Chemist wrote:
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....


The cost to make it fly again will be huge. The cost to cancel the whole program will be huge. This will be obviously a financial and industrial disaster.
 
ELBOB
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 8:49 am

PixelFlight wrote:
MrBretz wrote:
Keesje, what kind of computers are used on A320’s? Were they upgraded for the NEO?
Still the original 80186 and 68000 combo according to viewtopic.php?t=1362007


68010 and Intel 8086 and 80186. No 68000.
 
xmp125a
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 9:20 am

keesje wrote:
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.


NO. As the article above describes (one of them) this is a very special hardware. It is nothing wrong with using M68XXX or i286 processor even in modern embedded designs, provided that they satisfy all requirements. Please don't compare these to your android phone or windows PC! They may have limited computing power, but this is not the main constraint - it is safety, which comes from predictability, which comes from the hardware design that is simple enough to analyze in a deterministic way.

If Boeing overloaded the CPU with his bandage-on-bandage approach to fix self-made problems, they don't have their SW development under control.
 
XRAYretired
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 9:24 am

xmp125a wrote:
keesje wrote:
PixelFlight wrote:
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.


NO. As the article above describes (one of them) this is a very special hardware. It is nothing wrong with using M68XXX or i286 processor even in modern embedded designs, provided that they satisfy all requirements. Please don't compare these to your android phone or windows PC! They may have limited computing power, but this is not the main constraint - it is safety, which comes from predictability, which comes from the hardware design that is simple enough to analyze in a deterministic way.

If Boeing overloaded the CPU with his bandage-on-bandage approach to fix self-made problems, they don't have their SW development under control.

:checkmark:
Deterministic is the watchword for safety critical flight and engine control.

Ray
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 10:28 am

xmp125a wrote:
NO. As the article above describes (one of them) this is a very special hardware. It is nothing wrong with using M68XXX or i286 processor even in modern embedded designs, provided that they satisfy all requirements. Please don't compare these to your android phone or windows PC! They may have limited computing power, but this is not the main constraint - it is safety, which comes from predictability, which comes from the hardware design that is simple enough to analyze in a deterministic way.

If Boeing overloaded the CPU with his bandage-on-bandage approach to fix self-made problems, they don't have their SW development under control.

For sure deterministic is critically important for flight safety, but today IMA technology allow to safety flight far more processing resources and redundancies. The 787 and A350 flight computers have certainly more than 100 time the processing power than in a 737 and there are still using deterministic processing, software and communication.
 
peterinlisbon
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 10:57 am

It seems to me that the FAA just trusted Boeing to get things right and now that they're actually looking at the aircraft properly they're finding all kinds of problems. Let's hope they don't find anything else.
 
LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 11:11 am

xmp125a wrote:
LDRA wrote:
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


Center of gravity has very little to do with MCAS issue. It is centre of thrust that matters (in relation to all surfaces that provide aerodynamic drag that opposes the thrust). Not doable without redesigning the aerodynamics.


The handling characteristic problem that drives MCAS only occurs with after CoG configuration. No after CoG configuration => no need for MCAS
 
uta999
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 11:24 am

What did the two affected (crash) aircraft do in service, that Boeing failed to do in the 18-month long MAX flight test program? If they had to create MCAS in a hurry, then they knew there was a serious problem. I don't believe it was put in simply to make it fly similar to the NG.
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keesje
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 11:25 am

peterinlisbon wrote:
It seems to me that the FAA just trusted Boeing to get things right and now that they're actually looking at the aircraft properly they're finding all kinds of problems. Let's hope they don't find anything else.


Boeing lobbied congress to get the goals of FAA more clearly towards supporting the national aerospace industry & speed up the process by allowing more self certification. In recent successive Acts, Congress directed FAA to streamline certification, including increased delegation to Organization Designation Authorizations (ODAs).

FAA says the use of delegation is similar to organizational programs used in Europe and other countries and it helps the United States maintain a level playing field with foreign competitors. But they where pushed by Congress and congress by Boeing. Yes, a circle.

https://www.faa.gov/licenses_certificates/aircraft_certification/airworthiness_certification/

Congress wasn't on the side line here & will do damage control behind the curtains.. Looking tough but greasing. National interest collided with flight safety.
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 12:33 pm

PixelFlight wrote:
keesje wrote:
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.

MrBretz wrote:
Keesje, what kind of computers are used on A320’s? Were they upgraded for the NEO?

Still the original 80186 and 68000 combo according to viewtopic.php?t=1362007

I and my friends bought 80186s and 68000s around 1988, so that was already aging when the A320 showed up. Using it for the A320NEO is typical grandfathered design and requirements to reduce costs on certification. Airbus had the chance to prove virtue matters more than euros and cents, they chose euros and cents. Besides, as we all know, technology hasn't improved since 1988 so it's all good.
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 1:26 pm

Revelation wrote:
I and my friends bought 80186s and 68000s around 1988, so that was already aging when the A320 showed up. Using it for the A320NEO is typical grandfathered design and requirements to reduce costs on certification. Airbus had the chance to prove virtue matters more than euros and cents, they chose euros and cents. Besides, as we all know, technology hasn't improved since 1988 so it's all good.

Technology have vastly improved since 1988. Just see the IMA avionic in the A350, or in the B787, or in the near ready C919. Someday Airbus and Boeing inevitably will have to update the avionic of there cash cow products.
 
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keesje
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 2:03 pm

It think redundancy requirements of the FBW concept let to Intel and Motorallo bases systems, each seperately programmed, that could each "fly" the aircraft if one messed up & warm the pilots if the systems disagree. Together with flight enveloppe protection, the 1988 A320 still seems a steps up from the 737MAX in terms of build in flight safety
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ArgentoSystems
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 2:58 pm

The speculations about FCC CPUs here on the last couple pages are beyond ridiculous.

Judging embedded avionics CPU the same way you evaluate desktop PC (more than 5 five years old == antiquated trash) is just stupid, I'm sorry. The older the better, I say. It does not need latest and greatest, that always come out with pages of errata that takes year or two to iron out. And CPU revision change always trigger full retest. You want want very stable very mature CPU, and never change it unless you really have to.

Suggestions "to just replace CPU" with a more powerful one are laughable. It's not like they come with a USB plug, so you can unplug the old one and have instant upgrade. Maybe try remove a drivers door from your car and try to "just replace" it with a bigger door from another car. Amount of work involved might give you an idea how much pain it is to replace a CPU.

And obviously it does not run Java. That idea is so crazy I'm shocked it even had to mentioned.
Last edited by ArgentoSystems on Mon Jul 08, 2019 3:01 pm, edited 1 time in total.
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 3:24 pm

xmp125a wrote:
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!


Agree completely. But someone else brought it up. Unlike apparently everyone else, many, many years ago, I actually programmed on a flight computer for military aircraft. The “OS” was a completely predictable “executive” costume written. Everything was written in assembly language. I suspect that the 737 and most likely the A320 have similar architectures. I believe that later avionics packages for the 777, 787, A???, etc. use a RT OS that is available from, I believe, Wind River. This allows the same “predictable” timing but at a lower priority allows the incorporation of industry standard interfaces. I know this has nothing to do with the MAX crash. Sorry for the digression.
 
FlyHossD
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 3:52 pm

PW100 wrote:
ArgentoSystems wrote:
Amiga500 wrote:
It'd be a nightmare if it emerges that they all need hardware rework!

I'm guessing that is where things are going. No technical basis for this guess, of course. It's just in the past their estimation for s/w fix was "a couple of weeks". Now it was immediately 3-4 months, and later CEO is afraid to give any estimates at all.


The CEO now only says: “It’s important we take the time necessary to make these updates.”

That sounds awfully like CEO talk for this is going to take more than just a couple of months . . .

https://www.flightglobal.com/news/articles/boeing-ceo-addresses-new-737-max-issue-459465/


According to a quote from that article, Boeing still thinks it can be solved with a software update:

"we must take action on this [issue], and we are already working on the required software."

While it seems obvious that a software update would be quicker than a software and hardware update, I hope for Boeing's sake that Mullenburg is correct. But in any case, Boeing needs to get this right, no matter how long it takes.
My statements do not represent my former employer or my current employer and are my opinions only.
 
asdf
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 3:53 pm

MrBretz wrote:
...Everything was written in assembly language. I suspect that the 737 and most likely the A320 have similar architectures.....


as far as i have heard:
A320 uses two different OS, programmed by two different teams
to avoid indidents caused by OS bugs

because if the two OS are complete different it is impossible to "fall" into the same bug on both computers
 
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Spiderguy252
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 4:09 pm

How feasible is it for Boeing to just offer 737NGs to all pending customers, cull the MAX program and start over with a clean sheet design which they should have done so to start with?
Vahroone
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 4:16 pm

Spiderguy252 wrote:
How feasible is it for Boeing to just offer 737NGs to all pending customers, cull the MAX program and start over with a clean sheet design which they should have done so to start with?

This one has come up several times already.

See Post #112 and related posts for a recent instance.
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WPvsMW
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 6:54 pm

xmp125a wrote:
If Boeing overloaded the CPU with his bandage-on-bandage approach to fix self-made problems, they don't have their SW development under control.


I don't think any posters disagree with that assessment.
 
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seahawk
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 6:55 pm

Revelation wrote:
PixelFlight wrote:
keesje wrote:
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.

MrBretz wrote:
Keesje, what kind of computers are used on A320’s? Were they upgraded for the NEO?

Still the original 80186 and 68000 combo according to viewtopic.php?t=1362007

I and my friends bought 80186s and 68000s around 1988, so that was already aging when the A320 showed up. Using it for the A320NEO is typical grandfathered design and requirements to reduce costs on certification. Airbus had the chance to prove virtue matters more than euros and cents, they chose euros and cents. Besides, as we all know, technology hasn't improved since 1988 so it's all good.


Any comparison to the A320 system would net be favourable for the 737, as they could really redo everything to just match the A320. Considering the level of redundancy in the the A320 systems. If Boeing would be forced to match that system in the 737, the grounding would last a very long time.
 
WPvsMW
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 6:59 pm

Spiderguy252 wrote:
How feasible is it for Boeing to just offer 737NGs to all pending customers, cull the MAX program and start over with a clean sheet design which they should have done so to start with?


"clean sheet design" = B797
 
Absynth
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 7:20 pm

I think now would be the time for Airbus to open a design centre near Seattle. I wonder how many Boeing engineers would jump ship.

Not sure Airbus would need the extra hands and brains but I'm sure there are some areas of expertise left where they could add value to the company.
 
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 9:17 pm

Absynth wrote:
I think now would be the time for Airbus to open a design centre near Seattle. I wonder how many Boeing engineers would jump ship.

Not sure Airbus would need the extra hands and brains but I'm sure there are some areas of expertise left where they could add value to the company.

Airbus and Boeing both have top notch IMA avionic in there recent designs (A350, B787), proving that both have the required competences and experiences.
And a lot of the implementation is actually done by subcontractors like Rockwell Collins, Honywell, Thales, etc..
 
747megatop
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 9:19 pm

EUASA has outlined 5 MUST FIX items for the 737 MAX - https://www.bloomberg.com/news/articles ... -fly-again
 
RickNRoll
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 9:19 pm

I think there were some people in the FAA who were not happy with what Boeing were doing and suspected or knew that the flight computers were in danger of being overloaded if a full failure tree was investigated.
 
Absynth
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 9:38 pm

PixelFlight wrote:
Absynth wrote:
I think now would be the time for Airbus to open a design centre near Seattle. I wonder how many Boeing engineers would jump ship.

Not sure Airbus would need the extra hands and brains but I'm sure there are some areas of expertise left where they could add value to the company.

Airbus and Boeing both have top notch IMA avionic in there recent designs (A350, B787), proving that both have the required competences and experiences.
And a lot of the implementation is actually done by subcontractors like Rockwell Collins, Honywell, Thales, etc..



I'm not so much doubting the competence itself but added value vs expense and logistics of opening an additional design centre.

Boeing with its stockholders-first ethos just seems to have become a rather hostile environment for engineers to work at. On top of that, the moral impact of the crashes, public outcry over the MAX design, and stressful aftermath must put a tremendous damper on spirits.
 
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Dieuwer
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 10:25 pm

What would the financial hit to Boeing be if the MAX never ever flies again?
 
asdf
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 10:30 pm

Dieuwer wrote:
What would the financial hit to Boeing be if the MAX never ever flies again?


they would not be able to move a significant amount of orders to the NG because the gap to the 320NEO is to big
you cant make that difference in economics up with a lower price
they need tht MAX

if it never flies again ....
well
maybe potus will start a war somewhere in the world to safe B through the orders on the military side ...
 
MSPNWA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 10:54 pm

Dieuwer wrote:
What would the financial hit to Boeing be if the MAX never ever flies again?

Don't limit it to Boeing. Airlines and the flying public will ultimately pay more. To put it simply, the impact would be so great that the MAX can't be grounded for long, let alone forever. Time to end the crazy talk.
 
Checklist787
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Mon Jul 08, 2019 11:02 pm

asdf wrote:
Dieuwer wrote:
What would the financial hit to Boeing be if the MAX never ever flies again?


they would not be able to move a significant amount of orders to the NG because the gap to the 320NEO is to big
you cant make that difference in economics up with a lower price
they need tht MAX

if it never flies again ....
well
maybe potus will start a war somewhere in the world to safe B through the orders on the military side ...


Or propose to the airlines to change their orders 737MAX in 797X ... :roll:
 
crjflyboy
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 12:56 am

I understand Boeing has set aside 100 million to compensate those that perished on the 2 crashes, but are they also helping the airlines with the planes being grounded ?

If not … this is some serious dead weight for the airlines to cover.
 
frmrCapCadet
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 1:10 am

The $100 million is to compensate survivors of those who died. It is, as I understand, being offered without conditions.
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LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 1:20 am

Boeing stock down today
 
WPvsMW
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 3:54 am

Withheld info (from pilots flying the MAX and from certification authorities), kludge (as distinct from grandfathered) engineering, and "we 'just' realized that optional feature is actually mandatory".... the MAX is the safety nadir of BCA as a company.

Concurrently...
"Boeing is also looking to improve the systems which allow digital information to be transmitted between air traffic control, the pilots, and an airline’s operations crew to optimize routing efficiency and safety."
https://airwaysmag.com/manufacturer/boe ... r-testbed/
is the other side of the Boeing coin.
 
Thorkel
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 5:01 am

f1restate 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).
No mission critical embedded system will run Java code. It is either C or C++ . Judging by the architecture used, it would be C, with some portions written in assembly.

Sent from my SM-G975F using Tapatalk


High SIL systems (such as Flight Control Systems) have rarely been written in C or C++. C has many problematic characteristics (pointers, no strict separation of data and commands, signals, etc). C++ has plenty of ‘determined at runtime’ behaviours (e.g. polymorphism) which make them difficult to statically analyse. Higher integrity variants exist (e.g. MISRA), but then you run into problems with libraries (boost, SDL, etc) which you can’t use as they are rarely written for the higher integrity standard.

Whilst I don’t know what was used in the 737, ADA has often been the language of choice. I believe most of the 777 FCS was written in ADA (and likely SPARK ADA, for higher integrity, which allows the specification of formal pre/post conditions to procedures). Typhoon is ADA. JSF is the only plane I’ve heard that has a lot of C++ in high integrity systems, and that caused a bit of a hoo-ha with some customers who typically wouldn’t accept C++ in critical systems.
 
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seahawk
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 5:14 am

Grandfathering is not a problem, the problem of the 737MAX is, that it really is a mix and match of new systems and old systems. Not really a manual plane any more but also not the same level of redundancy and safety like a fly-by-wire plane. Just look at the trim system. It started with a simple electric solution and a simple manual back-up. Then they decided to add the speedtrim on top of the electrical system to improve efficiency, then they added MCAS with is much more relevant for the safety of the plane.So over time they went from full manual to something that very much acts like a fly-by-wire systems with automatic trim inputs and some form on envelope protection. Just that it lacked the redundancy of a fly-by-wire and also lacks the integrated flight control system.
 
MrBretz
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 6:23 am

Thorkel, thanks for the informative post. Ada slipped my thought process since I never used it. Assuming you are right about Ada on the 777, what OS do you think was used on that project? Or maybe Ada comes with it’s own runtime environment to do periodic scheduling? As far as the 737, my guess is assembly language and a custom runtime executive/scheduler.
P.S. I was just doing some quick reading. I bet the 777 and 787 systems are written in Ada. Now I know this has nothing to do with the 737, but thank you.
Last edited by MrBretz on Tue Jul 09, 2019 6:29 am, edited 1 time in total.
 
AAflyguy
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 6:23 am

Has anyone seen an update stating how many additional MAX aircraft carriers would have taken delivery of by now? I’ve seen these same months old numbers of 34 / 24 / 14 grounded aircraft for the U.S. carriers and it seems like no one is asking the question of how many more each of them would be operating since the grounding. Boeing has continued building 40-50 monthly and surely a few are for those U.S. carriers, plus AS. I’m thinking the WN number is closing in on 50 by now. Just curious if I’ve missed some updated numbers per media coverage. Thanks in advance.

AAFlyGuy
 
Thorkel
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 7:46 am

MrBretz wrote:
Thorkel, thanks for the informative post. Ada slipped my thought process since I never used it. Assuming you are right about Ada on the 777, what OS do you think was used on that project? Or maybe Ada comes with it’s own runtime environment to do periodic scheduling? As far as the 737, my guess is assembly language and a custom runtime executive/scheduler.
P.S. I was just doing some quick reading. I bet the 777 and 787 systems are written in Ada. Now I know this has nothing to do with the 737, but thank you.


As far as I’m aware, most of the aircraft of the 737 and 777 era don’t use off the shelf OS. They’ll be custom runtimes that do cyclic scheduling (with maybe some priority based stuff within the set cycle periods - Integrated Modular Avionic style architecture). It might be that something newer like a 787 does - that I don’t know.

You’d never use assembler for anything safety related or critical. ADA has much less ambiguous semantics (and SPARK ADA even more so). That means it is much easier to analyse statically and is more predictable. If MCAS has been assessed as hazardous in the HAZOP or whatever, I cannot see assembler being allowed as an implementation language. The problem with MCAS from a functional safety perspective in my view is not one of implementation (verification) but validation and change management. Basically it’s been built to the requirements, but the requirements were wrong and poorly managed by the looks of things.

Even C is more analysable and predictable than assembler. MISRA C is a restricted subset of C more common in automotive - it’s basically C with anything threatening taken out. No recursion, dynamic memory allocation, use of pointers, signals, assignments within comparisons, etc. ADA doesn’t allow most of those things by default and SPARK takes it to the extreme.
 
asdf
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 8:24 am

Checklist787 wrote:
asdf wrote:
Dieuwer wrote:
What would the financial hit to Boeing be if the MAX never ever flies again?


they would not be able to move a significant amount of orders to the NG because the gap to the 320NEO is to big
you cant make that difference in economics up with a lower price
they need tht MAX

if it never flies again ....
well
maybe potus will start a war somewhere in the world to safe B through the orders on the military side ...


Or propose to the airlines to change their orders 737MAX in 797X ... :roll:


the MAX is doomed anyway

the initial problem is the much to large engine diameter
its the reason
its the key
its the problem
they need it to get the economics in the NEO level
they cant change it away
the safe use of a plane with engines that much out of COD is only possible with full FBW

but even at the MAX BA didnt upgrade the MAX to a full FBW plane
they only used patches here and patches there since decades on that model
and sold it as "give the pilots all authority and not the computers"

you can NOT make a safe plane from a model with inherent instable aerodynamic properties
you can make it as safe as possible, but it is never ever as safe as a plane with contemporary aerodynamical properties

aviation is all about statistics
you can blend the customer
you can safe yourself for a few months
but statistics will catch you up

if the MAX (with MCAS v2, v3, v4 or whatever) is less safe than normal planes, it will crash more often
its not an option
its all statistic


they can push it through the FAA and the ESA and whom ever withing days
the can lift the grounding now and then
with whatever changes to the flight controlls
it will not change a lot how they fix the MCAS

because MCAS is only the symptom, its not the problem
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 11:27 am

Let's be honest

Max 737 has so many different things happening than 737 NG it shouldn't have been classed as grandfathering

Hence the crashes and the issues everyone is now scrambling to deal with

Putting new size engines on a plane and adding MCAS is a new plane IMO
 
asdf
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 11:55 am

Interested wrote:
Putting new size engines on a plane and adding MCAS is a new plane IMO


yes and no

they put new wings on that animal and it worked well
they stretched the hull and it worked well

i dont think the grandfathering - based on experience with that type - is bad at all
but you need to follow normal mind to make grandfathering work

no one ever moved that engines so far forward and up to make them fit
there is NO experience

you can NOT fix the engines in a way no one did befor on a transport category aircraft and then think you can "grandfather" that
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 12:32 pm

Seems to me the case on Boeing and the FAA was that with the underfunded FAA they trusted Boeing to ensure their aircraft was safe as they couldn't do a thorough testing campaign in the time that OEMs need or want. So until a issue like MCAS comes up the OEM has credit with the regulator. Once the crap hits the fan then all bets are off and this relates to all aspects of certification of a model for an OEM, this generation or previous.

If the issue is the underfunded FAA rather than "grandfathering" itself, how can they be trusted to certificate the clean sheet that so many here want to replace 737?

In my experience fitting stuff in to a mature design has its challenges, but the resulting reviews are easier to do than a clean sheet where everything has to be reviewed from scratch.
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 12:38 pm

Thorkel, thanks for the informative post. Ada slipped my thought process since I never used it. Assuming you are right about Ada on the 777, what OS do you think was used on that project? Or maybe Ada comes with it’s own runtime environment to do periodic scheduling? As far as the 737, my guess is assembly language and a custom runtime executive/scheduler.
P.S. I was just doing some quick reading. I bet the 777 and 787 systems are written in Ada. Now I know this has nothing to do with the 737, but thank you.

Someone posted http://archive.adaic.com/projects/atwork/boeing.html recently which confirms the major 777 systems (flight control computers, power management, brake controllers) are programmed in Ada. No real mention of schedulers or operating systems, though. https://en.wikipedia.org/wiki/VxWorks#Notable_uses says 787 used VxWorks for an OS. I wonder if they regret that decision. VxWorks parent was run by a bunch of greedy SOBs that make Boeing look like a non-profit organization.

As far as I’m aware, most of the aircraft of the 737 and 777 era don’t use off the shelf OS. They’ll be custom runtimes that do cyclic scheduling (with maybe some priority based stuff within the set cycle periods - Integrated Modular Avionic style architecture). It might be that something newer like a 787 does - that I don’t know.

You’d never use assembler for anything safety related or critical. ADA has much less ambiguous semantics (and SPARK ADA even more so). That means it is much easier to analyse statically and is more predictable. If MCAS has been assessed as hazardous in the HAZOP or whatever, I cannot see assembler being allowed as an implementation language. The problem with MCAS from a functional safety perspective in my view is not one of implementation (verification) but validation and change management. Basically it’s been built to the requirements, but the requirements were wrong and poorly managed by the looks of things.

Even C is more analysable and predictable than assembler. MISRA C is a restricted subset of C more common in automotive - it’s basically C with anything threatening taken out. No recursion, dynamic memory allocation, use of pointers, signals, assignments within comparisons, etc. ADA doesn’t allow most of those things by default and SPARK takes it to the extreme.

Not if you were starting from scratch today, however if your main computer was a SDP-185 as described over the last few pages you will be seeing nothing but assembly.

It's 70s vintage tech, a bit more advanced than Apollo's Guidance Computer, but not enough to support a high level language.

AMD 29xx bit slice technology isn't even a microprocessor, it's a set of parts to put together to get a functional equivalent of a microprocessor.

It's kind of funny that googling this stuff leads one to a a.net thread from 2001!
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
 
ArgentoSystems
Posts: 237
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 12:55 pm

Revelation wrote:
Not if you were starting from scratch today, however if your main computer was a SDP-185 as described over the last few pages you will be seeing nothing but assembly. It's 70s vintage tech, a bit more advanced than Apollo's Guidance Computer, but not enough to support a high level language.


I have my doubts about asm. C is very compiler friendly and has zero overhead. Notion that some CPU is not enough to support C is not valid. Carefully written C with a good compiler can get you very close (performance wise) to the same code written in Asm completely.

It should be also understood that only small portion of the entire application is performance critical, so writing everything in ASM makes no sense at all.
 
Interested
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 1:12 pm

Revelation wrote:
Seems to me the case on Boeing and the FAA was that with the underfunded FAA they trusted Boeing to ensure their aircraft was safe as they couldn't do a thorough testing campaign in the time that OEMs need or want. So until a issue like MCAS comes up the OEM has credit with the regulator. Once the crap hits the fan then all bets are off and this relates to all aspects of certification of a model for an OEM, this generation or previous.

If the issue is the underfunded FAA rather than "grandfathering" itself, how can they be trusted to certificate the clean sheet that so many here want to replace 737?

In my experience fitting stuff in to a mature design has its challenges, but the resulting reviews are easier to do than a clean sheet where everything has to be reviewed from scratch.


This is a fair point

It's going to be hard to trust a clean sheet plane from any combination of Boeing or FAA right now

I have no idea on Airbus and FAA combination?

But at least a clean sheet plane wouldn't give Boeing so many constraints to work with?

And you have to think Boeing can build a safe plane still from scratch?

Even if you can't trust FAA to oversee it all

Surely?
 
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ACCS300
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 1:18 pm

Without reading through 8 million posts, how hard would it be for Boeing to convert the already built or nearly built MAXs to NGs should the MAX program be cancelled or severely postponed?... then market them to airlines with existing MAX orders at further discounts.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 1:39 pm

ACCS300 wrote:
Without reading through 8 million posts, how hard would it be for Boeing to convert the already built or nearly built MAXs to NGs should the MAX program be cancelled or severely postponed?... then market them to airlines with existing MAX orders at further discounts.

I wish more of this thread was filled with such questions, would make for more interesting reading.
One big issue taking place now is certification, this is critical for a/c production.
Certification for both a/c is different, a lot of hardware is different, the nose of the MAX was slightly raised, the engines are different thus the computers related to the engines have different software loaded, as with the 787 debacle, it would be cheaper to build from scratch versus attempting to convert existing MAX frames to NG. Irrespective of all the talk about grandfathering and the fact that the MAX looks somewhat similar to the NG, there are major differences under the hood.
Now the fact that they are continuing to produce the MAX at 40+ or so per month does add another financial pressure point which the 787 did not have, VOLUME, this however can have the effect of pressuring all and sundry to get the a/c back in service even if it is under the mandate that it is the last 737 that will ever be certified.
 
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DL717
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 1:46 pm

ACCS300 wrote:
Without reading through 8 million posts, how hard would it be for Boeing to convert the already built or nearly built MAXs to NGs should the MAX program be cancelled or severely postponed?... then market them to airlines with existing MAX orders at further discounts.


If I’m not mistaken, they’d need to pull the whole wing. The pylons are completely different which if I recall, changed the internals of the wing significantly for both the mounting of the engine further forward and the additional engine weight. Not sure what kind of tube mods were made to support this either. I could be wrong though. Also, I don’t believe the -10 works at all. I don’t thing the older gen engines have the thrust. They could probably no doubt use the new glass in the cockpit. Cabin is probably a non-issue.
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