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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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Thorkel
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 2:27 pm

Revelation wrote:
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.


Yeah, I developed on VxWorks for several years. We had a POSIX compliant set of base libraries which, when ported to VxWorks POSIX compliant abstraction later showed it was anything but.

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.


But we’re talking about MCAS and that is starting from scratch very recently. Even if you’re generous and talking about automated speed trim, didn’t that come in with the NG? I can’t see how either of those systems would be allowed, under current standards, to be developed in assembly. I don’t know the SDP-185, but I don’t think it’s confirmed that’s what the MAX uses.

The regulators that I’ve worked with would have had a fit if we proposed something with a ‘Hazardous’ (SIL 2 or 3) classification being written in assembly when there are clearly more appropriate options today.
 
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Revelation
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 2:27 pm

ArgentoSystems wrote:
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.

Clearly you aren't putting yourself into the 1970s mind set, before "C" even left Bell Labs.

"C" was a creature of the R&D side of the main telco provider "Ma Bell" in the US, and was leading-edge stuff.

You didn't do leading edge stuff on a flight control computer, you went with tried and true.

Go back to #443 and read the specs:

PixelFlight wrote:
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)

This is the SDP-175 but even if SDP-185 is 100% better you are still very resource constrained.

Back then, entire operating systems were written in assembly. So was the ATC software. So was the SABRE reservation system.

You wrote in assembly because every clock cycle mattered, every byte mattered, compilers were not very trusted when it came to performance or correctness, and programmers were cheaper than computers.

Nerd note: assembly is the language, assembler is the tool! :thumbsup:
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LDRA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 2:52 pm

DO-178 came out in 80s or early 90s right?
 
asdf
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 2:52 pm

.....Floppy disk operating system...


just WOW ...
 
Vladex
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 2:53 pm

MSPNWA wrote:
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.


It would open the competition to other players as the duopoly had gotten stale.
 
f1restate
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 3:17 pm

Thorkel wrote:
f1restate wrote:
tenHangar wrote:
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.
Yeah I am pretty sure that C++ is mostly NOT used in these oldish systems . You need a certain performance level from cpu & cache to "eat" the overhead that you get there.

However , C is one level above assembly and in my opinion ideal for such tasks. You may not use dynamic allocations at all, and just stick to static memory / overlaid buffers. There were C coding guidelines from JPL I believe that laid this and other things in detail.

ADA is a good shout. Had forgotten that such language existed. Ages ago I knew I guy who worked in GHS and now I remember he was complaining that he had to learn it.

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FluidFlow
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 3:45 pm

They should use Fortran instead of whatever language they use now. The Voyagers are still flying... ;-)
 
hivue
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 6:12 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.


Boeing likely would end up with an "NG" that would require certification separate from the "current" NG. Engine pylons, nose gear, and a host of other things would be different between the two versions of the "NG."
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 6:35 pm

Thorkel wrote:
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.


f1restate wrote:
Yeah I am pretty sure that C++ is mostly NOT used in these oldish systems . You need a certain performance level from cpu & cache to "eat" the overhead that you get there.

However , C is one level above assembly and in my opinion ideal for such tasks. You may not use dynamic allocations at all, and just stick to static memory / overlaid buffers. There were C coding guidelines from JPL I believe that laid this and other things in detail.

ADA is a good shout. Had forgotten that such language existed. Ages ago I knew I guy who worked in GHS and now I remember he was complaining that he had to learn it.

Sent from my SM-G975F using Tapatalk

Ada was pushed by some big players at some point in the past (with VHDL for the hardware) but there is not so much new engineers willing to beat on learning it due to the few opportunities on the market. And it's a very formal language near the boring level for some.

C has a very long history on embedded systems, including safety critical systems. There exists compilers audited for safety application as well as coding rules compliance check to established rules set for safety application. There are still enough engineers learning C but I observe a significant decrease in interest since the rise of the web and mobiles, not counting that only a few learn how to code safety applications.

C++ is on the rise on the safety area. New engineers don't take significant risk to learn it. The usual subset for safety application is fairly limited compared to the (too) large languages possibilities, see MISRA C++ as an example. In that context the virtual tables overhead are minimal.
 
rheinwaldner
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 6:53 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?

NGs is what they have...
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enzo011
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 8:13 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.


Well you must have missed the part where I said, in the time that OEMs need or want. I am sure the FAA can do it but seeing as they have passed on a lot of work to Boeing and are seemingly just ticking boxes if they would do this themselves it would be done but not as quickly. This would cause problems for Boeing as they have set out a timescale for test flights but if this is delayed it delays deliveries which delays cash coming in.

Who knows, you may be better placed to tell me that the FAA is not underfunded?* You could also confirm if they have allowed a lot of the certification work to be done by Boeing as well.* Now I know you could answer that EASA and Airbus, but until the A320 kills more than 300 people in a few months due to features of the aircraft that is not a valid answer.

*The Boeing 737 Max Story Shows That Deregulation Is Dangerous
The FAA has handed an increasing amount of authority over to Boeing to certify the safety of its own planes.


The FAA, citing lack of funding and resources, has over the years delegated increasing authority to Boeing to take on more of the work of certifying the safety of its own airplanes. Early on in certification of the 737 MAX, the FAA safety engineering team divided up the technical assessments that would be delegated to Boeing versus those they considered more critical and would be retained within the FAA.

But several FAA technical experts said in interviews that as certification proceeded, managers prodded them to speed the process. Development of the MAX was lagging nine months behind the rival Airbus A320neo. Time was of the essence for Boeing. A former FAA safety engineer who was directly involved in certifying the MAX said that halfway through the certification process, “we were asked by management to re-evaluate what would be delegated. Management thought we had retained too much at the FAA.”


So is it a problem with grandfathering or FAA funding? It is both most likely. The grandfathering of certification allowed for a truncated timescale in certifying the 737MAX and an underfunded FAA was under pressure to pass even more work on to Boeing. If you are a fan of Boeing you should actually hoped that all certification was done by the FAA, that way you would wash your hands from any problems that were not discovered. Now it is a double whammy, Boeing did a lot of the certification which seems to have failed (346 dead) and the FAA is still not properly funded.
 
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par13del
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 8:30 pm

enzo011 wrote:
So is it a problem with grandfathering or FAA funding? It is both most likely. The grandfathering of certification allowed for a truncated timescale in certifying the 737MAX and an underfunded FAA was under pressure to pass even more work on to Boeing. If you are a fan of Boeing you should actually hoped that all certification was done by the FAA, that way you would wash your hands from any problems that were not discovered. Now it is a double whammy, Boeing did a lot of the certification which seems to have failed (346 dead) and the FAA is still not properly funded.

Well since it is Boeing's reputation at stake when an a/c crashes, I would say it is in Boeing interest to ensure that their planes are safe regardless of whether they or the FAA are doing the certification. The Federal Government collects a lot of taxes from the airlines and pax travelling, they are funding the improvements to ATC throughout the country and that has been a project that has taken a lot of twist and turn, perhaps in hindsight, some of those funds should have been diverted to maintain resource levels for certification?
 
Virtual737
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 8:45 pm

Revelation wrote:
You wrote in assembly because every clock cycle mattered


This, and the fact that writing in "machine code" (assembly) you have pretty much direct control over the clock cycles. ie it is very clear how many clock cycles each instruction will take - knowing this is often more important than writing the fastest code.

Then you need to factor in readability / maintenance. C code benefits in that it is much easier to debug than raw machine code. It is one level up from pure geek.

However, as C is a compiled language, different compilers can produce different results. Unless you know the compiler inside out and upside down you don't fully know what the output will be and, if that output needs to be fully vetted you might as well have written it in assembly to start with.

Welcome to my world. What might appear to be the best tool and the best language at first glance might in fact not be. I fondly remember the days of 6502 assembly and, sadly enough, can still read much of it from memory.
 
MSPNWA
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 9:05 pm

Vladex wrote:
It would open the competition to other players as the duopoly had gotten stale.


It would more likely push it closer to a monopoly than a triopoly. The ever higher barriers to entry and shrinking technological gains of the mature industry don't lend itself well to the success of a third company.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 9:20 pm

Virtual737 wrote:
Revelation wrote:
You wrote in assembly because every clock cycle mattered


This, and the fact that writing in "machine code" (assembly) you have pretty much direct control over the clock cycles. ie it is very clear how many clock cycles each instruction will take - knowing this is often more important than writing the fastest code.

Then you need to factor in readability / maintenance. C code benefits in that it is much easier to debug than raw machine code. It is one level up from pure geek.

However, as C is a compiled language, different compilers can produce different results. Unless you know the compiler inside out and upside down you don't fully know what the output will be and, if that output needs to be fully vetted you might as well have written it in assembly to start with.

Welcome to my world. What might appear to be the best tool and the best language at first glance might in fact not be. I fondly remember the days of 6502 assembly and, sadly enough, can still read much of it from memory.

In a system designed using the top-down approach, coding in opcode assembly is mostly like doing manually the C compiler work, because the specifications are at some point usually expressed as a pseudo language often not so distant than how a equivalent C code look like. Doing the translation from the pseudo code to opcode assembly manually is more error prone than with a C compiler. The difference between compilers is not an argument on a project than will use the same compiler over and over again.
 
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PixelFlight
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Tue Jul 09, 2019 9:23 pm

MSPNWA wrote:
Vladex wrote:
It would open the competition to other players as the duopoly had gotten stale.


It would more likely push it closer to a monopoly than a triopoly. The ever higher barriers to entry and shrinking technological gains of the mature industry don't lend itself well to the success of a third company.

I am certain that Boeing and Airbus will monitor the C919 to see when it could set a triopoly.
 
jplatts
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 11:20 am

Boeing should add a safety mechanism to the 737 MAX that will disable MCAS if the plane is descending too quickly in order to avoid another tragedy similar to JT 610 or ET 302. This safety mechanism should be designed at safety level A (catastrophic failure condition), and this safety mechanism should measure parameters such as altitude, rate of descent, and airspeed. There also should be enough redundancy in this safety mechanism to reduce the likelihood of another tragedy such as JT 610 or ET 302 happening again.
 
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SomebodyInTLS
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 12:02 pm

asdf wrote:
.....Floppy disk operating system...


just WOW ...


Errr.... why?

I remember hard disks arriving for IBM PC clones *late 1980s / early 1990s* and they were expensive, heavy pieces of bolt-on kit. Everything before the 90s booted up from floppy, tape or punch-card (except for ROM-based home computers).

I presume you've heard of Microsoft Disk Operating System, aka MS-DOS or just DOS?
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KlimaBXsst
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 4:32 pm

I really prefer the reliability of a virtual reality airplane, rather than those that actually fly without a computer. NOT. I can really see the circular loop thinking the computer crowd is in to by the latest posts in this thread. Wow the MAX fix is really problematic with this looped thinking. Brilliant people here, just a bit complex to think about when 400 feet off the ground on take off and at the edge of the stall envelope, or in a trim configuration not making sense if things do not go quite according to AI plan.

AI is not the way to build an airplane to stabilize it for flight before it actually leaves the ground in civilian commercial passenger ops.
Aesthetically the A 340 got it right!
 
hivue
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 5:16 pm

jplatts wrote:
Boeing should add a safety mechanism to the 737 MAX that will disable MCAS if the plane is descending too quickly in order to avoid another tragedy similar to JT 610 or ET 302. This safety mechanism should be designed at safety level A (catastrophic failure condition), and this safety mechanism should measure parameters such as altitude, rate of descent, and airspeed. There also should be enough redundancy in this safety mechanism to reduce the likelihood of another tragedy such as JT 610 or ET 302 happening again.


So MCAS gets disabled in the case of an emergency decent for a depressurization accident? The airplane likely would not be certifiable with such a feature.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
KlimaBXsst
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 5:45 pm

PW100 wrote:
Revelation wrote:
Also seems hypocritical to me for people here who railed against criticism of "third world pilots" (that was not actually made!) to now be silent while the ability of "third world engineers" to code to Boeing's specifications is being openly criticized.

Perhaps those posters decided to stay sort of within their field of expertise.
For my part I have zero knowledge on software engineering, and will stay away commenting on this subject I have no experience in.



They do seem rather brilliant
Aesthetically the A 340 got it right!
 
planecane
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 5:49 pm

jplatts wrote:
Boeing should add a safety mechanism to the 737 MAX that will disable MCAS if the plane is descending too quickly in order to avoid another tragedy similar to JT 610 or ET 302. This safety mechanism should be designed at safety level A (catastrophic failure condition), and this safety mechanism should measure parameters such as altitude, rate of descent, and airspeed. There also should be enough redundancy in this safety mechanism to reduce the likelihood of another tragedy such as JT 610 or ET 302 happening again.

I can only assume you are not an engineer. This makes absolutely no sense at all. If you have followed the MCAS fix at all, you'd know that after the new software, MCAS will not be able to cause an uncontrollable dive. Even if both AoA sensors fail reading too high and MCAS activates, the new software will not allow it to move the trim past the point where the elevator loses authority to keep the aircraft level.

If Boeing had included that simple restriction of authority from the beginning the MAX would still be flying with MCAS 1.0 and the MCAS 2.0 improvements would be rolling out in a few months as an improvement after the data about a few minor incidents made its way to Boeing/FAA.
 
jplatts
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 6:00 pm

hivue wrote:
So MCAS gets disabled in the case of an emergency decent for a depressurization accident? The airplane likely would not be certifiable with such a feature.


I meant to say that the MCAS disabling mechanism is intended to apply in cases where there is rapid descent due to incorrect activation of MCAS arising from faulty or incorrect AOA readings, but not in cases such as emergency descent for a depressurization incident where the altimeter, airspeed indicator, and AOA sensors are all working correctly.
 
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767333ER
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 7:14 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.

But that is always the thing with cleansheets, can it be trusted? That question is what gives the neutered regulatory bodies a little more power as that question warrants it, they can’t just say “oh it’s a 737, it’s the same as it has been so don’t worry about it” even when it isn’t.
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aden23
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 10:15 pm

MSPNWA wrote:
Airlines and the flying public will ultimately pay more.



The flying public will pay a LOT more to avoid flying on the MAX, that's for sure.

At this point, I'd be surprised if you could find anyone in the general public that would willingly fly on a MAX, regardless of what they "fix."

The damage is done.
 
maint123
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Wed Jul 10, 2019 11:38 pm

Governments would be negligent if they allow the max to fly in their airspaces, after all this confused patch work being done on them.
No point in blaming FAA, it's just a industry wise fall in competence in American aerospace industry. Look at max or the neo engines.
The Europeans have maintained their standards with solid engineering, not relying on half baked products to remain competitive.
Scrap the max and concentrate on NG for the short term. In another decade or so, Boeing would have a property engineered new plane, with no safety concerns.
And if financially Boeing can't stay afloat from its civilian sales, like always the US government can subsidize it with billions in airforce contracts.
This is the only honest path.
 
wingman
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 12:00 am

aden23 wrote:
MSPNWA wrote:
Airlines and the flying public will ultimately pay more.



The flying public will pay a LOT more to avoid flying on the MAX, that's for sure.

At this point, I'd be surprised if you could find anyone in the general public that would willingly fly on a MAX, regardless of what they "fix."

The damage is done.


Prepare yourself to be very surprised. I’d probably sit down. I wouldn’t go near a MAX with someone else’s boarding pass right now but once this plane is back in the air it’ll probably be the safest, most inspected, most thoroughly certified and most rigorously trained for commercial aircraft in history. It’s still a horrible price for 300 dead but I’d happily get on one after five regulatory agencies have inspected every last nut, bolt, aileron and algorithm that goes into it.
 
maint123
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 12:04 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.

Crux of the issue. Being ignored by most here.
Boeing has made a aerodynamically unstable passenger plane, which it keeps level by incorporating MCAS. Good for fighter planes, with their inherent need for fast response but not so great for heavy, bulky civilian planes.
All the best software in the world can't save a mechanically bad product, speaking from personal experience. Electronics will fail and this plane will again be in the news. This is the hard truth.
 
TTailedTiger
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 12:18 am

aden23 wrote:
MSPNWA wrote:
Airlines and the flying public will ultimately pay more.



The flying public will pay a LOT more to avoid flying on the MAX, that's for sure.

At this point, I'd be surprised if you could find anyone in the general public that would willingly fly on a MAX, regardless of what they "fix."

The damage is done.


No they won't pay more. And outside of the couple of friends who know anything about aviation, none of my family or friends have any idea of what a 737 Max is.

But maybe you just made that post for a little humor. I really hope you wouldn't be that naive.
 
maint123
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Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 12:20 am

WPvsMW wrote:
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.

The more I read the experts here the more I get confused.
So whats the latest consensus on the max MCAS issue, is the problem due to wrong logic (flowchart) or the logic given was OK but was wrongly programmed?
 
planecane
Posts: 1022
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 1:12 am

maint123 wrote:
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.

Crux of the issue. Being ignored by most here.
Boeing has made a aerodynamically unstable passenger plane, which it keeps level by incorporating MCAS. Good for fighter planes, with their inherent need for fast response but not so great for heavy, bulky civilian planes.
All the best software in the world can't save a mechanically bad product, speaking from personal experience. Electronics will fail and this plane will again be in the news. This is the hard truth.

Stop posting this garbage. It isn't true. MCAS does not keep the plane level. It is intended to activate in a part of the flight envelope that will rarely, if ever be entered into in service.

Lion Air 043 flew without MCAS for over an hour. If the MAX was so unstable how were they able to have an uneventful rest of the flight?
 
smartplane
Posts: 1024
Joined: Fri Aug 03, 2018 9:23 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 2:32 am

Apparently a certain EASA workshop scheduled for late August may be re-purposed.
 
maint123
Posts: 172
Joined: Sun Nov 04, 2018 4:18 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 2:32 am

planecane wrote:
maint123 wrote:
xmp125a wrote:

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.

Crux of the issue. Being ignored by most here.
Boeing has made a aerodynamically unstable passenger plane, which it keeps level by incorporating MCAS. Good for fighter planes, with their inherent need for fast response but not so great for heavy, bulky civilian planes.
All the best software in the world can't save a mechanically bad product, speaking from personal experience. Electronics will fail and this plane will again be in the news. This is the hard truth.

Stop posting this garbage. It isn't true. MCAS does not keep the plane level. It is intended to activate in a part of the flight envelope that will rarely, if ever be entered into in service.

Lion Air 043 flew without MCAS for over an hour. If the MAX was so unstable how were they able to have an uneventful rest of the flight?

I understand your distress as a American, but 2 crashes with 350 dead within 6 months, does not point to a rarely entered envelope.
MCAS does keep the plane level in manual mode, when all inputs are OK. But as we have seen, the inputs get compromised very easily.
And I find it hilarious when ppl like you discuss lower standards in non Western organisations, when the collaboration between FAA and Boeing stands so badly exposed.
Remember usa was the last country to ban max flights, insisting till the end that Max was a perfect plane.
Now we know what value that assessment has.
 
User avatar
DocLightning
Posts: 21480
Joined: Wed Nov 16, 2005 8:51 am

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 2:53 am

maint123 wrote:
I understand your distress as a American, but 2 crashes with 350 dead within 6 months, does not point to a rarely entered envelope.


They did not enter the relevant envelope. A broken AOA vane told MCAS that they were in that envelope when they weren't.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
-Carl Sagan
 
planecane
Posts: 1022
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 2:55 am

maint123 wrote:
planecane wrote:
maint123 wrote:
Crux of the issue. Being ignored by most here.
Boeing has made a aerodynamically unstable passenger plane, which it keeps level by incorporating MCAS. Good for fighter planes, with their inherent need for fast response but not so great for heavy, bulky civilian planes.
All the best software in the world can't save a mechanically bad product, speaking from personal experience. Electronics will fail and this plane will again be in the news. This is the hard truth.

Stop posting this garbage. It isn't true. MCAS does not keep the plane level. It is intended to activate in a part of the flight envelope that will rarely, if ever be entered into in service.

Lion Air 043 flew without MCAS for over an hour. If the MAX was so unstable how were they able to have an uneventful rest of the flight?

I understand your distress as a American, but 2 crashes with 350 dead within 6 months, does not point to a rarely entered envelope.
MCAS does keep the plane level in manual mode, when all inputs are OK. But as we have seen, the inputs get compromised very easily.
And I find it hilarious when ppl like you discuss lower standards in non Western organisations, when the collaboration between FAA and Boeing stands so badly exposed.
Remember usa was the last country to ban max flights, insisting till the end that Max was a perfect plane.
Now we know what value that assessment has.

Your post is full of wrong information. Stop posting BS
 
sgrow787
Posts: 158
Joined: Fri May 16, 2014 8:12 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 3:32 am

planecane wrote:
Stop posting this garbage. It isn't true. MCAS does not keep the plane level. It is intended to activate in a part of the flight envelope that will rarely, if ever be entered into in service.


MCAS was intended to keep the Max from getting NEAR both corners of the flight envelope. 0.6 deg per cycle for the high speed corner, 2.5 deg for the low.
So in effect, Boeing is using more software inside of the flight envelope where real aerodynamic design should be used. And they're trying to stick that software on hardware that's already maxed out.

In fact it looks like the only engineering Boeing did was to reverse engineer the certification process starting with how do we get a MAX certified under a 737 type certificate.
 
User avatar
tenHangar
Posts: 15
Joined: Tue Jul 11, 2017 2:39 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 4:09 am

aden23 wrote:
MSPNWA wrote:
Airlines and the flying public will ultimately pay more.



The flying public will pay a LOT more to avoid flying on the MAX, that's for sure.

At this point, I'd be surprised if you could find anyone in the general public that would willingly fly on a MAX, regardless of what they "fix."

The damage is done.
I'd fly on it, but wouldn't put my family on one.
 
Chemist
Posts: 540
Joined: Tue Oct 20, 2015 4:46 am

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 4:14 am

maint123 wrote:
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.

Crux of the issue. Being ignored by most here.
Boeing has made a aerodynamically unstable passenger plane, which it keeps level by incorporating MCAS. Good for fighter planes, with their inherent need for fast response but not so great for heavy, bulky civilian planes.
All the best software in the world can't save a mechanically bad product, speaking from personal experience. Electronics will fail and this plane will again be in the news. This is the hard truth.


It's not unstable and MCAS is not a stability system. Cut the ridiculous hyperbole.
 
sgrow787
Posts: 158
Joined: Fri May 16, 2014 8:12 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 4:32 am

Chemist wrote:
It's not unstable and MCAS is not a stability system. Cut the ridiculous hyperbole.


MCAS my ass. It's a stall prevention system given an alternative innocent sounding name so they could assign it a lower safety classification, so the FAA wouldn't ask questions.

In fact I'm going to go ahead and say it. Because everyone I've listened to in the aerospace industry agrees it's ludicrous for a one-sensor design to have ended up in the Max.

The recent FCC processor "data flow" issue may have been the real reason Boeing went forward with a Max with a one-sensor MCAS system. Everything else that happened follows logically from there.
- the lowering of the safety classification
- the deletion of MCAS information from pilots' FCOM
- the (intentional) failure to notify the FAA of the increased MCAS authority

I'm thinking the G + AOA worked because both sensors are onside. But two AOAs means the offside AOA may have to come from the offside FCC, and that would be through something like a SPI bus or other FCC-to-FCC communication, which would be more resource intensive.

You could call a babysitter an MCASer. All they do is maneuver the baby's sleeping position so they don't cry all night.
 
Interested
Posts: 647
Joined: Thu May 19, 2016 12:19 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 5:54 am

planecane wrote:
maint123 wrote:
xmp125a wrote:

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.

Crux of the issue. Being ignored by most here.
Boeing has made a aerodynamically unstable passenger plane, which it keeps level by incorporating MCAS. Good for fighter planes, with their inherent need for fast response but not so great for heavy, bulky civilian planes.
All the best software in the world can't save a mechanically bad product, speaking from personal experience. Electronics will fail and this plane will again be in the news. This is the hard truth.

Stop posting this garbage. It isn't true. MCAS does not keep the plane level. It is intended to activate in a part of the flight envelope that will rarely, if ever be entered into in service.

Lion Air 043 flew without MCAS for over an hour. If the MAX was so unstable how were they able to have an uneventful rest of the flight?


Because they didn't have to avoid anything with a quick manoeuvre the rest of the flight?

Like the vast majority of flights

Maybe they should just scrap the rules about flight envelopes as they aren't needed very often at all?

Would you be happy with that?

Another step backwards for public safety to help Boeing get a plane back in the air?
Last edited by Interested on Thu Jul 11, 2019 6:05 am, edited 1 time in total.
 
planecane
Posts: 1022
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 6:04 am

Interested wrote:
planecane wrote:
maint123 wrote:
Crux of the issue. Being ignored by most here.
Boeing has made a aerodynamically unstable passenger plane, which it keeps level by incorporating MCAS. Good for fighter planes, with their inherent need for fast response but not so great for heavy, bulky civilian planes.
All the best software in the world can't save a mechanically bad product, speaking from personal experience. Electronics will fail and this plane will again be in the news. This is the hard truth.

Stop posting this garbage. It isn't true. MCAS does not keep the plane level. It is intended to activate in a part of the flight envelope that will rarely, if ever be entered into in service.

Lion Air 043 flew without MCAS for over an hour. If the MAX was so unstable how were they able to have an uneventful rest of the flight?


Because they didn't have to avoid anything with a quick manoeuvre the rest of the flight?


These arguments are getting so tiresome with you anti-Boeing posters. The post I replied to stated that MCAS was needed to keep the aircraft level because it is unstable.

These quick maneuvers are also speculation. The "old school" test pilot was ok with MCAS because he thought it would almost never activate. If the maneuvers that activate it are somewhat common his opinion would have been different.
 
planecane
Posts: 1022
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 6:10 am

sgrow787 wrote:
Chemist wrote:
It's not unstable and MCAS is not a stability system. Cut the ridiculous hyperbole.


MCAS my ass. It's a stall prevention system given an alternative innocent sounding name so they could assign it a lower safety classification, so the FAA wouldn't ask questions.

In fact I'm going to go ahead and say it. Because everyone I've listened to in the aerospace industry agrees it's ludicrous for a one-sensor design to have ended up in the Max.

The recent FCC processor "data flow" issue may have been the real reason Boeing went forward with a Max with a one-sensor MCAS system. Everything else that happened follows logically from there.
- the lowering of the safety classification
- the deletion of MCAS information from pilots' FCOM
- the (intentional) failure to notify the FAA of the increased MCAS authority

I'm thinking the G + AOA worked because both sensors are onside. But two AOAs means the offside AOA may have to come from the offside FCC, and that would be through something like a SPI bus or other FCC-to-FCC communication, which would be more resource intensive.

You could call a babysitter an MCASer. All they do is maneuver the baby's sleeping position so they don't cry all night.


Can we all stop making things up that are contradicted by facts?

The investigative reports said that the single sensor was chosen for dispatch reliability. Had they already coded a 2 sensor algorithm and found the FCC issue it would have taken about 2 days after the Lion Air crash to submit MCAS 2.0 to the FAA since it was already done according to your speculation.
 
User avatar
seahawk
Posts: 8516
Joined: Fri May 27, 2005 1:29 am

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 6:21 am

The dispatch reliability is not an argument imho, as the 2 sensors are flight critical anyway, as they supply the flight computers for captain and co-pilot.
 
User avatar
PixelFlight
Posts: 507
Joined: Thu Nov 08, 2018 11:09 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 6:56 am

sgrow787 wrote:
In fact it looks like the only engineering Boeing did was to reverse engineer the certification process starting with how do we get a MAX certified under a 737 type certificate.
LOL, but sadly true to some extend. Well, there did a lot of others engineering, but there should not have do that one.

sgrow787 wrote:
Chemist wrote:
It's not unstable and MCAS is not a stability system. Cut the ridiculous hyperbole.


MCAS my ass. It's a stall prevention system given an alternative innocent sounding name so they could assign it a lower safety classification, so the FAA wouldn't ask questions.

In fact I'm going to go ahead and say it. Because everyone I've listened to in the aerospace industry agrees it's ludicrous for a one-sensor design to have ended up in the Max.

The recent FCC processor "data flow" issue may have been the real reason Boeing went forward with a Max with a one-sensor MCAS system. Everything else that happened follows logically from there.
- the lowering of the safety classification
- the deletion of MCAS information from pilots' FCOM
- the (intentional) failure to notify the FAA of the increased MCAS authority

I'm thinking the G + AOA worked because both sensors are onside. But two AOAs means the offside AOA may have to come from the offside FCC, and that would be through something like a SPI bus or other FCC-to-FCC communication, which would be more resource intensive.

You could call a babysitter an MCASer. All they do is maneuver the baby's sleeping position so they don't cry all night.
The raw processor capability issue is still a speculation a this time, there are so many way to overload a processor and there no real detail available. Fact is that Boeing say there expect to fix this by software (no hardware). Time will tell if it's possible or not.

I don't think that the raw processor capability can be the reason Boeing went forward with a Max with a one-sensor MCAS system. The same type rating and same training was already critical goals when the project was started for evaluation, long long before there have identified the non-compliance while doing a test flight and consequently modified the MCAS to use a single sensor.

Each FCCs are already exchanging data together as shows the two figures in the middle of this blog: https://www.satcom.guru/2018/11/737-fcc ... mmand.html The same article say:
"While engaged, even single channel, the FCC uses inputs from both ADIRUs to avoid a potential issue if one ADIRU produces false data." The resources to exchange the extra AoA value, if not already done, should be just one byte or two in each directions. What worry me in the schematic is that the FCC, contrary to the SMYD, don't seem to have each independent input of the two ADIRU. It look like there need to pass trough the other side FCC to get the other side ADIRU data. I see this fragile principle as more likely a source of issue. For example, there could need the SDP-185 processor running to copy the ADIRU values from the ADIRU link input buffer to the other FCC link output buffer. If that processor fail, the other FCC no longer get the updated ADIRU values of that side, including the AoA value.
 
planecane
Posts: 1022
Joined: Thu Feb 09, 2017 4:58 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 7:01 am

seahawk wrote:
The dispatch reliability is not an argument imho, as the 2 sensors are flight critical anyway, as they supply the flight computers for captain and co-pilot.

The reasoning was flawed but the anonymous insider told a reporter that it was the reason. Perhaps the MCAS software team didn't know that both sensors needed to be functional for dispatch.
 
User avatar
PixelFlight
Posts: 507
Joined: Thu Nov 08, 2018 11:09 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 7:57 am

planecane wrote:
The investigative reports said that the single sensor was chosen for dispatch reliability.
Really ? Please give a link on that.
I don't see how a software change could have anything to do with the dispatch reliability of two AoA sensors that are already mounted anyway on the previous model.
Last edited by PixelFlight on Thu Jul 11, 2019 8:05 am, edited 1 time in total.
 
User avatar
seahawk
Posts: 8516
Joined: Fri May 27, 2005 1:29 am

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 8:02 am

planecane wrote:
seahawk wrote:
The dispatch reliability is not an argument imho, as the 2 sensors are flight critical anyway, as they supply the flight computers for captain and co-pilot.

The reasoning was flawed but the anonymous insider told a reporter that it was the reason. Perhaps the MCAS software team didn't know that both sensors needed to be functional for dispatch.


I can see how a risk analysis might go wrong, I can even see commercial interests playing a role, but such basic lack of knowledge about the 737 avionics by people developing a system for that plane would be outright scary for me.
 
Interested
Posts: 647
Joined: Thu May 19, 2016 12:19 pm

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 8:35 am

planecane wrote:
Interested wrote:
planecane wrote:
Stop posting this garbage. It isn't true. MCAS does not keep the plane level. It is intended to activate in a part of the flight envelope that will rarely, if ever be entered into in service.

Lion Air 043 flew without MCAS for over an hour. If the MAX was so unstable how were they able to have an uneventful rest of the flight?


Because they didn't have to avoid anything with a quick manoeuvre the rest of the flight?


These arguments are getting so tiresome with you anti-Boeing posters. The post I replied to stated that MCAS was needed to keep the aircraft level because it is unstable.

These quick maneuvers are also speculation. The "old school" test pilot was ok with MCAS because he thought it would almost never activate. If the maneuvers that activate it are somewhat common his opinion would have been different.


So like I say - your preference is to go with the view that because the maneuvers aren't common that we can ignore them?

Is that your solution?

The claim that because the Lion air flight had no problems with MCAS after it was turned off and all is ok without MCAS isnt that convincing to me as an outsider looking in?

Being honest

It seems that everything about Max 737 is a compromise?
 
asdf
Posts: 324
Joined: Tue Mar 18, 2014 12:03 am

Re: Boeing 737MAX Grounded Worldwide Q3 2019

Thu Jul 11, 2019 11:07 am

planecane wrote:
.......The "old school" test pilot was ok with MCAS because he thought it would almost never activate. If the maneuvers that activate it are somewhat common his opinion would have been different.


i dont know waht the "old school test pilot said" but the boeing testpilots wasn´t OK with the test flight result, because they tuned up MCAS to counteract the unusual behavior of the MAX much more as it was initialy planed and initialy reportet to the FAA
that alone is a big red hering that the whole case of the very unusual engine position is not that simple and that harmless

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