There is no way Boeing can salvage the situation in a short time. The managers have fired good engineers, and sublet jobs elsewhere -- and especially software, to low cost Indian engineers that pays a few dollar an hour.

Right now, the managers got to go back India, and ask these software engineers to debug millions of lines of codes. Good luck.

...and all these problems just because of the short main landing gear?

It has been the common truth now for so long that the landing gear for the 737 cannot be lengthened. Can someone please explain why that is so impossible to do?

14ccKemiskt wrote:

...and all these problems just because of the short main landing gear?

It has been the common truth now for so long that the landing gear for the 737 cannot be lengthened. Can someone please explain why that is so impossible to do?

Would probably involve a new wing box, which might likely involve a new wing, at which point it is already better for a clean sheet design.

14ccKemiskt wrote:

...and all these problems just because of the short main landing gear?

It has been the common truth now for so long that the landing gear for the 737 cannot be lengthened. Can someone please explain why that is so impossible to do?

The -10's telescopic MLG is basically an artificially lengthened gear, due to longer fuselage and tail strike hazard. The "telescopic" feature allows for no changes of the gear bay, which would be extensive if the longer MLG was "non retractable".

Probably the design of such MLG wasn't ready for the design freeze of the -8/-9 (which, as reminder, was under very high deadline pressure to counter the neo), so they opted for a quicker/cheaper option of mounting the engines more fwd/above the wing, and only a higher nose wheel?

In reality, everything can be done, it depends on capabilities of the engineering team.

747 went from drawing board to the sky in 1968, a time span just 3 years. Today, with all these software modelling tools, super fast PCs, the Boeing engineers come back and say nothing can be fixed.

Scotron12 wrote:

BoeingVista wrote:

From the last Dominic Gates article https://www.seattletimes.com/business/b ... -controls/

It has specifically rejected Boeing’s assumption that the plane’s pilots can be relied upon as the backstop safeguard in scenarios such as the uncommanded movement of the horizontal tail involved in both the Indonesian and Ethiopian crashes. That notion was ruled out by FAA pilots in June when, during testing of the effect of a glitch in the computer hardware, one out of three pilots in a simulation failed to save the aircraft.

One of the FAA pilots crashed the simulator while trying to recover, I think that this is new information? We assume that they would consider themselves above "average" pilots so you can imagine how pissed the FAA were with Boeing throwing this mess at line pilots.

My understanding is that of the three test pilots, two were FAA and one was an airline pilot. The airline pilot was the one that lost the frame.

That makes sense but I think thats worse for Boeing in that 100% of line pilots crashed the plane using a fix that Boeing had signed off. FAA get to wonder if an 'average' pilot can handle a MAX under emergency conditions.

14ccKemiskt wrote:

...and all these problems just because of the short main landing gear?

It has been the common truth now for so long that the landing gear for the 737 cannot be lengthened. Can someone please explain why that is so impossible to do?

There are a lot of reasons, but in case of emergency on the 737 you have to jump from the wing... if you lengthen the MLG the B737 would need to have slides from the wing exits to comply with the regulations. Thus preventing longer MLGs without a re-design.

EDIT: If the "jump" is higher than 1.8m then you have to have slides (Source: https://www.aerosociety.com/media/8534/emergency-evacuation-of-commercial-passenger-aeroplanes-paper.pdf; section 8.9 points to the related EASA regulation CS 25).

So if you are not in the mood to jump from the wing in an emergency better be seated in the front or back of the B737.

14ccKemiskt wrote:

...and all these problems just because of the short main landing gear?

It has been the common truth now for so long that the landing gear for the 737 cannot be lengthened. Can someone please explain why that is so impossible to do?

The overwing exits on 737 have no slides. You crawl out and slide down the wing itself. It still involves quite significant drop to the tarmac, unless the pilot adjusts the spoilers and other surfaces to let you slide down more gracefully (but even then it is quite a drop). This is what you can get away as airplane manufacturer due to grandfathering. I would be very anxious evacuating via this route if I would be normally functioning 70-80 year old. Certainly more than a few broken bones.

Now, increasing THAT height - impossible. Image is here: https://aviationweek.com/site-files/avi ... .Large.jpg

BoeingVista wrote:

Scotron12 wrote:

BoeingVista wrote:

From the last Dominic Gates article https://www.seattletimes.com/business/b ... -controls/



One of the FAA pilots crashed the simulator while trying to recover, I think that this is new information? We assume that they would consider themselves above "average" pilots so you can imagine how pissed the FAA were with Boeing throwing this mess at line pilots.

My understanding is that of the three test pilots, two were FAA and one was an airline pilot. The airline pilot was the one that lost the frame.

That makes sense but I think thats worse for Boeing in that 100% of line pilots crashed the plane using a fix that Boeing had signed off. FAA get to wonder if an 'average' pilot can handle a MAX under emergency conditions.

No, No. The guy was probably culturally not pre-disposed to handling technology and wasn't properly trained by his airline and didn't have a copy the latest FCOM in his pocket. It was basic memory items that should have been applied and all would have been simple and good. He should have been following the procedures and NNCs to the letter, except when the same a.net experts say he shouldn't and apply basic airmanship like you do in a Cessna. Train him up, get him to do 1500hrs in a crop-duster, slip an AD in his hand re-enforce the seat of his pants and all's well. No need for this ridiculous design modification nanny state stuff, its all fine as it is. And fancy driving a simulator at such a low altitude with AP engaged anyway, tsch, should never happen. Oh and why did the previous guy in the simulator not tell him how to do it is the biggest question.

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.

Not to dispute this, but in modern processors (e.g. Intel PC processor families for the past 15 years or so) you actually don't know this even if you write directly in the machine code. This is another reason to stick to ancient architectures that are now decades old.

oOfredOo wrote:

ArgentoSystems wrote:

oOfredOo wrote:

I’ve read the article and as another embedded software engineer I find it plausible as well. I also think that the probability of this specific combination of bit flips occurring is very low

h

Cosmic rays is nonsense. It should be obvious that whatever problem the FAA identified and Boeing is fixing has nothing at all to do with cosmic rays. For starters, this kind of events are exceptionally rare. Second, it is not very hard to write software in a way that makes it immune to random bit flips.

No it is not. With large amounts of memory, it approaches 100%. At 10km chances are 10^2 higher than at sea level. However, this is old tech with very limited amounts of memory. And you fix it in HW first with ECC. As there are more locations where bit flips can occur, e.g. buses or caches, and more types of failures, you checksum in SW as well. Only then you compare between CPUs

100%? Are you making stuff up as you go? You would know this is BS if you just tried to apply a bit of common sense.

Have you ever tried to use a laptop on the airplane? Play a game or music on cellphone? Each have GBs of RAM, 100000s times more than needed for flight computers, and NONE of the fancy tech you mentioned. My laptop certainly does not have ECC memory and I doubt cellphones do. And it is bleeding edge COMMERCIAL equipment. Not radiation hardened, 30 year old chip with HUGE transistors that simply can't (ok orders of magnitude less likely than modern chips) be flipped by a single cosmic ray event.

Point is, normal commercial equipment operates just fine at 10Km. It is only 10KM, you know. Still tons of air on top. With just a bit of foresight you can design dedicated avionics hardware and s/w in way that makes it immune to cosmic rays events. Suggestion that Boeing is just now addressing that is patently absurd.

FluidFlow wrote:

14ccKemiskt wrote:

...and all these problems just because of the short main landing gear?

It has been the common truth now for so long that the landing gear for the 737 cannot be lengthened. Can someone please explain why that is so impossible to do?

There are a lot of reasons, but in case of emergency on the 737 you have to jump from the wing... if you lengthen the MLG the B737 would need to have slides from the wing exits to comply with the regulations. Thus preventing longer MLGs without a re-design.

EDIT: If the "jump" is higher than 1.8m then you have to have slides (Source: https://www.aerosociety.com/media/8534/emergency-evacuation-of-commercial-passenger-aeroplanes-paper.pdf; section 8.9 points to the related EASA regulation CS 25).

So if you are not in the mood to jump from the wing in an emergency better be seated in the front or back of the B737.

Yeah. 1.8 metre jump is not safe. I am guessing that height just happens to be the height you have to jump off a 737. Boeing should have been made to put slides on the exits when the NG came into service.

mmo wrote:

This must be a really great place for Non-Boeing fans.

I’m not a Boeing fan (or Airbus), and to me this isn’t a “great place”. There are 346 people dead.

The 320,321 NEO and 350 now have new loading advice, read restrictions which must be adheared to. Boeing should have done the same thing and this thread wouldn't exist.

You may ask yourself why Boeing haven’t acted the way Airbus does, at least not with the 737MAX. IMO, because Boeing was aware that a quick fix didn’t do the job. OTOH, Airbus is working on a software update to mitigate the said restrictions (at least for the A321neo).

xmp125a wrote:

The overwing exits on 737 have no slides. You crawl out and slide down the wing itself. It still involves quite significant drop to the tarmac, unless the pilot adjusts the spoilers and other surfaces to let you slide down more gracefully (but even then it is quite a drop). This is what you can get away as airplane manufacturer due to grandfathering. I would be very anxious evacuating via this route if I would be normally functioning 70-80 year old. Certainly more than a few broken bones.

Now, increasing THAT height - impossible. Image is here: https://aviationweek.com/site-files/avi ... .Large.jpg

Wow, it never even crossed my mind that latest and greatest 21st century airplane, designed to operates for at least another 30 years, does not come with wing slides.

FluidFlow wrote:

14ccKemiskt wrote:

...and all these problems just because of the short main landing gear?

It has been the common truth now for so long that the landing gear for the 737 cannot be lengthened. Can someone please explain why that is so impossible to do?

There are a lot of reasons, but in case of emergency on the 737 you have to jump from the wing... if you lengthen the MLG the B737 would need to have slides from the wing exits to comply with the regulations. Thus preventing longer MLGs without a re-design.

EDIT: If the "jump" is higher than 1.8m then you have to have slides (Source: https://www.aerosociety.com/media/8534/emergency-evacuation-of-commercial-passenger-aeroplanes-paper.pdf; section 8.9 points to the related EASA regulation CS 25).

So if you are not in the mood to jump from the wing in an emergency better be seated in the front or back of the B737.

All right, I had forgotten about the evacuation issue. Thanks for a well written answer.

I once jumped down a slide from the front door of some 737 (NG) for training purposes. It's high enough to appreciate a slide there. Especially with hard surfaces or possible debris waiting to be hit downstairs.

xmp125a wrote:

is what you can get away as airplane manufacturer due to grandfathering. I would be very anxious evacuating via this route if I would be normally functioning 70-80 year old. Certainly more than a few broken bones.

Now, increasing THAT height - impossible. Image is here: https://aviationweek.com/site-files/avi ... .Large.jpg

Yes, the picture show a frightening height for anybody not super fit.

Are you suggesting that this height would not have been allowed, had it not been for the continous need for backward compability of the 738?

ArgentoSystems wrote:

oOfredOo wrote:

ArgentoSystems wrote:

h

Cosmic rays is nonsense. It should be obvious that whatever problem the FAA identified and Boeing is fixing has nothing at all to do with cosmic rays. For starters, this kind of events are exceptionally rare. Second, it is not very hard to write software in a way that makes it immune to random bit flips.

No it is not. With large amounts of memory, it approaches 100%. At 10km chances are 10^2 higher than at sea level. However, this is old tech with very limited amounts of memory. And you fix it in HW first with ECC. As there are more locations where bit flips can occur, e.g. buses or caches, and more types of failures, you checksum in SW as well. Only then you compare between CPUs

100%? Are you making stuff up as you go? You would know this is BS if you just tried to apply a bit of common sense.

Have you ever tried to use a laptop on the airplane? Play a game or music on cellphone? Each have GBs of RAM, 100000s times more than needed for flight computers, and NONE of the fancy tech you mentioned. My laptop certainly does not have ECC memory and I doubt cellphones do. And it is bleeding edge COMMERCIAL equipment. Not radiation hardened, 30 year old chip with HUGE transistors that simply can't (ok orders of magnitude less likely than modern chips) be flipped by a single cosmic ray event.

Point is, normal commercial equipment operates just fine at 10Km. It is only 10KM, you know. Still tons of air on top. With just a bit of foresight you can design dedicated avionics hardware and s/w in way that makes it immune to cosmic rays events. Suggestion that Boeing is just now addressing that is patently absurd.

The flux density of high energy neutrons at 30Kft, particularly over the poles, is high enough to engender concern as to the long term health of frequent flyers. It is also a reality for causing 'single event upsets' in avionics.

In a previous existence, I was aware of several instances where single event upset was the only plausible cause of the events (none with serious consequence fortunately). On one of these occasions, the track of the particle was actually found in the substrate and could be viewed under very high magnification.

The linked item is useful for a rough guide as to the frequency of impacts.
https://spacemath.gsfc.nasa.gov/weekly/3Page6.pdf

Ray

ArgentoSystems wrote:

Point is, normal commercial equipment operates just fine at 10Km. It is only 10KM, you know. Still tons of air on top.

Not really.

From Wikipedia (and I am sure there are other sources):
The atmosphere has a mass of about 5.15×10 18 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface.

https://en.m.wikipedia.org/wiki/Atmosphere_of_Earth

So the vast majority of air is below 10 km.

MartijnNL wrote:

ArgentoSystems wrote:

Point is, normal commercial equipment operates just fine at 10Km. It is only 10KM, you know. Still tons of air on top.

Not really.

Not really what? 3/4 of air is below 10K, so? 3/4 is not a "vast majority". 1/4 is still above 10K. Which is still not an insignificant amount.

mmo wrote:

The rule of thumb about runaway trim that I grew up with, is if it moves and you didn't command it and you're hand-flying it, the first place you go is the red guarded switches and you never reset them.

Aren't the trim wheels spinning on their own quite frequently thanks to STS? I don't think your rule of thumb would work in 737.

ArgentoSystems wrote:

Not really what? 3/4 of air is below 10K, so? 3/4 is not a "vast majority". 1/4 is still above 10K. Which is still not an insignificant amount.

Not really tons of air on top. Just a quarter.

3/4 is not a vast majority? Then what is it? A small majority?

XRAYretired wrote:

The flux density of high energy neutrons at 30Kft, particularly over the poles, is high enough to engender concern as to the long term health of frequent flyers. It is also a reality for causing 'single event upsets' in avionics.

Let's not gt distracted and stay on point. Which is physics of the problem has been know forever, and ways to mitigate it, both s/w and hardware, has been around for half a century. Surely Boeing did something right and took care of it?

sillystrings wrote:

mmo wrote:

The rule of thumb about runaway trim that I grew up with, is if it moves and you didn't command it and you're hand-flying it, the first place you go is the red guarded switches and you never reset them.

Aren't the trim wheels spinning on their own quite frequently thanks to STS? I don't think your rule of thumb would work in 737.

But you would expect that, wouldn't you? Or when the aircraft is on autopilot, the trim wheel will spin. However, in these cases, the power was at climb, a normal pitch attitude. and you get a massive trim from the MCAS, stick shaker or not, the airplane is not in a stall! The trim would be unexpected and the guarded switches would be turned off, which would turn off the MCAS. Now you just have to listen to the stick shaker.

ArgentoSystems wrote:

XRAYretired wrote:

The flux density of high energy neutrons at 30Kft, particularly over the poles, is high enough to engender concern as to the long term health of frequent flyers. It is also a reality for causing 'single event upsets' in avionics.

Let's not gt distracted and stay on point. Which is physics of the problem has been know forever, and ways to mitigate it, both s/w and hardware, has been around for half a century. Surely Boeing did something right and took care of it?

Your distraction I believe. Perhaps consider that maybe the significantly increased automation of MAX and consequentially increased propensity for hazardous outcomes due to SEU is such that the existing protections are no longer considered adequate.

Ray

MSPNWA wrote:

SomebodyInTLS wrote:

Fair enough. But you have to wonder why it's been used here almost exclusively by people promoting a certain viewpoint...

And when that viewpoint has been pretty much discredited in the meantime, it's annoying to see someone spouting the same tired old stuff again.

It's only "discredited" by those that need to discredit it because they can't accept the facts that don't fit their viewpoint.

The website is a valuable resource that simply lays out facts. It's up to us to consume the facts.

Boeing and the FAA have discredited the viewpoint I'm talking about in their own recent testimonies.

Revelation wrote:

ArgentoSystems wrote:

"A change in software architecture" is not a 100% rewrite. Shall we say 70%?

Without seeing the code or documentation, my educated guess is 10-20% code addition/modification worst case.

Again, in many cases architecture changes are made to preserve the core logic, and this is almost certainly one of those cases.

Agreed that a "total rewrite" is in the ballpark of your estimate (probably even less). That said...while I am not a developer myself, I have hired lots of developers over the last 20 years and in my experience, the problem with projects like this is NOT how much code is actually rewritten, but the QA required to make sure all the bugs are addressed before they make it to certification. Even the best developers can sometimes not predict what architecture changes will do to every line of code which I assume in this case is MASSIVE. So that September timeframe could easily slip if more bugs than expected show up after the initial required code changes. Only time can tell.

qf789 wrote:

There are currently around 35 737MAX fuselage in storage at Wichita by Spirit



https://twitter.com/ICTBiz_dmccoy/statu ... 98784?s=20

Impressive line-up. Better pray they are not hit by one of those after-summer storms . . .

https://www.kansas.com/news/business/aviation/article1090370.html

SEU wrote:

This is so bad now, 1 in 3 test pilots couldnt save the plane. How did Boeing get away with this? I dont buy that they didnt know there was flaws. They did, they just thought "what are the chances of it actually crashing?" and saw $$$.

We already etsablsihed that two of three crews could not save the plane when MCAS misfired. Some put that down to "poorly trained / incompetent pilots".

Now FAA enigneered several sim test scenarios, following the line of action of MCAS failure results, and one in three American (American as in the country, not the airline) pilots could not save the plane. Wonder if the third one is now also considered to be "poorly trained / incompetent". And what level of training would be required to safely operate the MAX.
Yet, Boeing deemed that no sim time was required to expand a pilot from NG to MAX.

RickNRoll wrote:

A fundamental software redesign is the equivalent of changing the foundations of a building. That would surely require some intensive testing.

Yes, and no.

The main area to be tested is: do the software modules that comprise each flight control computer stop/start themselves correctly when errors are detected by the comparison logic?

That is the main area to test, and you do also test that the modules function correctly after restart, but it's not like you have to retest every edge condition of every software module.

I don't know anything about the internals of these systems, but I think it's fair to say avionics flight control software is a lot more robust than the stuff on your laptop or phone and probably has much if not all of the restart logic built in to it already and it's mostly a matter of perhaps some changes to harden the software and a lot of testing.

FluidFlow wrote:

It is a completely new architecture never seen on a 737 before and to be safe everything that was ever tested and certified on the single FCC design should be retested and re-certified on the double FCC input design and I can not believe that the FAA nor the EASA or CAAC would be able to do this within 4 weeks.

My guess based on the confidence shown by the simultaneous "leaks" is that Boeing is already testing this heavily right now with good initial results. Presumably FAA is participating/observing. Boeing will issue a report whose contents will largely be known by FAA, it will get a thorough review, retests may or may not be required, a final version will be written and go through an approval cycle.

Given that Boeing always gives optimistic dates we should presume "September" means late September and October means late October so it's probably more than four weeks anyway.

SEU wrote:

This is so bad now, 1 in 3 test pilots couldnt save the plane. How did Boeing get away with this? I dont buy that they didnt know there was flaws. They did, they just thought "what are the chances of it actually crashing?" and saw $$$

Seriously, the only way I see the MAX flying pax again, is a complete re-do of the software which will take months, re-certification which will take months, meaning training for pilots like a brand new aircraft, which will take months, then to get round to every max currently built and install the software which will take months, then clear the backlog of undelivered planes back to airlines , which boeing has admitted might take nearly a year.

I can actually see Boeing scrapping the max now, bite the the bullet, deliver NGs and work on a NSA.

You read the entire ST report, or even the bits quoted here, and this is your take away?

The report says:

• The specific fault that showed up has never happened in 200 million flight hours on this same flight-control computer in [older model] 737 NGs.
• They tested 33 different scenarios that might be sparked by a rare, random microprocessor fault in the jet's flight-control computer
• Each of the 33 tests injected a set of five different bit-flip errors into the computer
• These injected errors aren't chosen randomly, they are chosen to generate worst case scenarios
• The test that failed had an error injected to make the computer think MCAS was off when it was on
• This meant that the column mounted horizontal stabilizer cut off switches were inoperative
• That same test also began an uncommanded upward movement to the horizontal stabilizer
• Three other faults were present at the same time
• This test was run two times
• The first time it was run all three pilots recovered the aircraft!
• The second time they decided to let the horizontal stabilizer move for a longer period of time
• How much longer it ran was not specified
• The second time two of three pilots did recover the aircraft!

Basically, the test that failed is far far more unlikely to happen than a two engine failure, which we've seen several times, most notably with Sully at the Hudson.

Even in this very unlikely scenario, all three recovered the aircraft the first time, and two of three did when they waited longer to make it harder to recover.

Above we read:

oOfredOo wrote:

1Kbit of memory already puts this in 10^-14 territory. 5 bit flips due to cosmic rays is in itself already extremely remote. (10^-10 for a single bit to flip per day!)

So we're talking one in ten billion to one in ten trillion odds of this happening once in a day, then those five bit flips have to change something important like the MCAS state rather than some unused data.

Your response:

• How did Boeing get away with this?
• Seriously, the only way I see the MAX flying pax again, is a complete re-do of the software
• Or re-certification which will take months
• I can actually see Boeing scrapping the max now, bite the the bullet, deliver NGs and work on a NSA

It's an interesting point of view, given that FAA just told Congress this week that their process for certifying the MAX was fundamentally sound, and we now have this report showing how far FAA is going to stress test the flight control computers.

It's pretty obvious that Boeing's plan is to just keep dealing with whatever faults the regulators call out, and do their best to get the 737 un-grounded.

It's pretty obvious that this should happen in a small number of months rather than the five plus years a new model will take, and will preserve the majority of the 737 backlog that Boeing, its partners and its customers have invested in.

As for Boeing taking the cheap way out, the ST report says:

Boeing could have just rewritten the software governing what functions are monitored within the flight-control computer to eliminate this failure scenario.

Instead, it’s decided to make a much more radical software redesign, one that will not only fix this problem but make the MAX’s entire flight-control system — including MCAS — more reliable, according to three sources.

They chose to take a more robust approach to the general set of problems rather than applying quick and dirty "point fixes".

They should get some credit for doing so, IMO.

It is the exact opposite of taking the cheap way out.

My suspicion is that the ET accident probably kicked off a deep review of these kinds of scenarios, and that review in turn kicked off the work on the new more robust architecture months ago, so it should be ready for an approval cycle relatively soon.

mmo wrote:

sillystrings wrote:

mmo wrote:

The rule of thumb about runaway trim that I grew up with, is if it moves and you didn't command it and you're hand-flying it, the first place you go is the red guarded switches and you never reset them.

Aren't the trim wheels spinning on their own quite frequently thanks to STS? I don't think your rule of thumb would work in 737.

But you would expect that, wouldn't you? Or when the aircraft is on autopilot, the trim wheel will spin. However, in these cases, the power was at climb, a normal pitch attitude. and you get a massive trim from the MCAS, stick shaker or not, the airplane is not in a stall! The trim would be unexpected and the guarded switches would be turned off, which would turn off the MCAS. Now you just have to listen to the stick shaker.

I don't know. If I remember correctly pilots running simulations of the event had difficulties identifying this as a runaway trim with all the seemingly conflicting indications. Even though some succeeded in solving the problem, it was more difficult than anticipated.

SQ32 wrote:

In reality, everything can be done, it depends on capabilities of the engineering team.

747 went from drawing board to the sky in 1968, a time span just 3 years. Today, with all these software modelling tools, super fast PCs, the Boeing engineers come back and say nothing can be fixed.

Incomparable.

For starters, safety was much much worsen then. If you think that the MAX introduction is bad with two fatal accidents, you might want to look at the 727 introduction. Hint, MAX safety record actually looks very good then compared to the 727.

All that extra enigneering requires time, money and valuable resources. If you would go back to the sixties safety level, MAX would already have been flying within weeks (if grounded at all).

BoeingVista wrote:

That makes sense but I think thats worse for Boeing in that 100% of line pilots crashed the plane using a fix that Boeing had signed off. FAA get to wonder if an 'average' pilot can handle a MAX under emergency conditions.

100% is not accurate, but since no one chose to mention that, I guess folks are just tired, so..........
We had 3 MCAS version 1.0 incidents and 2 crashes, if it was 3 for 3 the death toll would have been higher.

xmp125a wrote:

The overwing exits on 737 have no slides. You crawl out and slide down the wing itself. It still involves quite significant drop to the tarmac, unless the pilot adjusts the spoilers and other surfaces to let you slide down more gracefully (but even then it is quite a drop). This is what you can get away as airplane manufacturer due to grandfathering. I would be very anxious evacuating via this route if I would be normally functioning 70-80 year old. Certainly more than a few broken bones.

I feel the grand fathering thing is usually overblown. Grandfathering means that millions and millions of service hours have proven it to be a safe system. As opposed to new designs, which have to prove their safety through analysis. Nothing beats service experience . . .

Emotions aside, do you have any hard numbers demonstrating that the 737 egress system is less safe than that of any comparable more modern design?

mmo wrote:

sillystrings wrote:

mmo wrote:

The rule of thumb about runaway trim that I grew up with, is if it moves and you didn't command it and you're hand-flying it, the first place you go is the red guarded switches and you never reset them.

Aren't the trim wheels spinning on their own quite frequently thanks to STS? I don't think your rule of thumb would work in 737.

But you would expect that, wouldn't you? Or when the aircraft is on autopilot, the trim wheel will spin. However, in these cases, the power was at climb, a normal pitch attitude. and you get a massive trim from the MCAS, stick shaker or not, the airplane is not in a stall! The trim would be unexpected and the guarded switches would be turned off, which would turn off the MCAS. Now you just have to listen to the stick shaker.

As MCAS was not teached to pilots, the stick shaker and stall remark is irrelevant.

As far as the pilots were concerned, it just STS, Auto pilot, and Thump trim switch commanding electric trim motor. Also, STS is not related to stall function.
I believe that the one of the crews piror to the Lionair accident flight, actually made a log book write up of STS behaving unusual, when it was in fact MCAS doing he work, not STS.

SelseyBill wrote:

TTailedTiger wrote:

The court of public opinion will have no bearing on whether the 73M returns to service.

Interesting viewpoint. Airlines around the world are very conscious of the views of their customers and public, and that problem will be focussed onto their national authorities. If they then refuse to book on MAX flights in the future en-masse, it'll be a bigger problem for Boeing than you seem to think.......

TTailedTiger wrote:

..........they have no voice on any other civil or criminal proceeding.

.....ill be sure to let the families of the 346 dead know they have no voice in court. Im sure they'll be pleased to hear from you......

TTailedTiger wrote:

I don't know how you do things in your country but in the US do not allow kangaroo courts or mob rule.

.......thats correct, you don't. English Common Law and the laws you enjoy in the USA have more in common than you might think, and indeed they both do not feature 'kangaroo courts' or 'mob-rule'. They do both, however, have the ability for regular citizens to take to court organisations who may have acted with negligence.

TTailedTiger wrote:

If Boeing is able to satisfy all established FAA requirements then the FAA will have no choice but to put it back on the air. What you or anyone else thinks is immaterial.

Im afraid you have that the wrong way round. Boeing will not be permitted to get the MAX back into public service until the FAA is absolutely satisfied Boeing has satisfactorily met their requirements. Even then, the FAA might not then even permit MAX flight operations until other authorities have given unified worldwide clearance.

Sorry, but no.

The whole thing from the FAA right now (and EACH of the other regulatory bodies) is that EACH one will make the best decision available, beholden to noone.

We all read that as meanIng that Boeing will not be allowed to lean on the FAA - or any other one of the regulatory bodies.

Just as it should be.



But then flip it - how would it even be remotely just if the FAA (or any other regulatory body) had decided that MCAS 2.0 was in fact safe & certifiable (yeah, I get it, OK???) yet still wilfully withheld that clearance and so incurred further losses to Boeing???? On the basis that the FAA (or whoever) judged 2.0 to be OK - but they were afraid to move without concurrence from everyone else?

Sorry, major civil-law penalty time lurking in that seemingly innocent statement.

Not to mention the (predictably) volcanic reaction from POTUS when informed that the FAA had cleared 2.0 internally - but the FAA`was afraid to declare their decision without support from other regulatory agencies (read EU)..
And so the FAA breezily, wilfully incurred Boeing/the USA trade balance even further losses.

Be a few senior bureaucrats fighting for what was left of their (early) pension, IMHO.


On another note, Dominic Gates at the Seattle Times (free - google it!) has a long piece on MCAS 2.0 today.

It is now much more ambitious & comprehensive than previously. Hence the further delay.

But absolutely no mention of engine disintegration/flight-control system issues.

cheers

PW100 wrote:

xmp125a wrote:

The overwing exits on 737 have no slides. You crawl out and slide down the wing itself. It still involves quite significant drop to the tarmac, unless the pilot adjusts the spoilers and other surfaces to let you slide down more gracefully (but even then it is quite a drop). This is what you can get away as airplane manufacturer due to grandfathering. I would be very anxious evacuating via this route if I would be normally functioning 70-80 year old. Certainly more than a few broken bones.

I feel the grand fathering thing is usually overblown. Grandfathering means that millions and millions of service hours have proven it to be a safe system. As opposed to new designs, which have to prove their safety through analysis. Nothing beats service experience . . .

Emotions aside, do you have any hard numbers demonstrating that the 737 egress system is less safe than that of any comparable more modern design?

I actually tried to look this up but it is a hard research to find good results and I have no time to go full on into it.

Statistics for incidents usually just go for deceased, injured or unharmed. While for most accidents there is a map of where people of the three categories were seated but it is really hard to figure out if the injured passengers got injured during the incident or during evacuation.

I know there are always injuries during the actual evacuation but I could not find reports that gave me information how this injuries happened. It might be possible to look at incidents where all injuries happened during evacuation and compare them between different airliners (A320 vs B737) and see if one has a relatively higher rate of injuries. But still if people would have died falling from the wing or being pushed from the wing they would have changed it long time ago.

ArgentoSystems wrote:

"fundamental software redesign of 737 MAX flight controls"
I don't get it. They are talking about fundamental s/w redesign, and at the same time insist on completion is September. Are they nuts?

https://www.seattletimes.com/business/b ... -controls/

Going back to his surpising articel. I am surpised to read the following:

www.seattletimes.com wrote:

In one scenario, the bits chosen first told the computer that MCAS was engaged when it wasn’t. This had the effect of disabling the cut-off switches inside the pilot-control column, which normally stop any uncommanded movement of the horizontal tail if the pilot pulls in the opposite direction. MCAS cannot work with those cut-off switches active and so the computer, fooled into thinking MCAS was operating, disabled them.

In one of the previous threads, it was argued that a.net analysis the wiring diagram proved that there was no computer/processor functionality between thump trim switch and trim motor. However the above quoted part shows that the trim input was interrupted/slowed down by the clipped bits in the FCC. How does that jive. Does that mean that trim switch signal is first processed by FCC before being send to trim motor?

Reason I ask is because, as I put forward previously, that I find the ET FDR manual electric uptrim graph behaviour very suspicious. The FDR traces show a total of four electric up-trims after MCAS became alive. And ALL FOUR of them stopped at exactly the same pitch trim: 2.3 degrees. Coincidence? Can any crew do such a thing on purpose? I'm having a hard time accepting that.
It must be noted that after take-off, electric trimming was applied several times (both up and down) resulting in a balanced control column. So the crew clearly knew how that works. Why didn't/couldn't they do that after MCAS became alive?
If the trim signal first goes through FCC, the that could change the scope of how the pilots reacted dramatically. Perhaps they did command the uptrim further, but the system somehow did not allow that.

Then the next question would be: could the same thing have been happening with the Lionair accident, when control was handed over to the co-pilot? Perhaps for the same reason, did his uptrim actions not pass through the FCC somehow?

PW100 wrote:

SQ32 wrote:

In reality, everything can be done, it depends on capabilities of the engineering team.

747 went from drawing board to the sky in 1968, a time span just 3 years. Today, with all these software modelling tools, super fast PCs, the Boeing engineers come back and say nothing can be fixed.

Incomparable.

For starters, safety was much much worsen then. If you think that the MAX introduction is bad with two fatal accidents, you might want to look at the 727 introduction. Hint, MAX safety record actually looks very good then compared to the 727.

All that extra enigneering requires time, money and valuable resources. If you would go back to the sixties safety level, MAX would already have been flying within weeks (if grounded at all).

This is the truth. We have better tools but these planes are also much more complex. It is partly why the F35 and F22 had 20 year development cycles while the P51, P47,F6F and F4U took a couple years back in the 40s. But look at losses of frames from WWII and see how many were due to failures of the plane vs combat. Pretty shocking. The other part of why the F35\22 took so long is general incompetence\corruption of govt, and feature creep by the brass.

brindabella wrote:

But then flip it - how would it even be remotely just if the FAA (or any other regulatory body) had decided that MCAS 2.0 was in fact safe & certifiable (yeah, I get it, OK???) yet still wilfully withheld that clearance and so incurred further losses to Boeing???? On the basis that the FAA (or whoever) judged 2.0 to be OK - but they were afraid to move without concurrence from everyone else?

Sorry, major civil-law penalty time lurking in that seemingly innocent statement.

A civil suit against whom, or what organization? Boeing could sue the FAA to compel approval - and then the FAA could cite uncertainties by other boards as reason for not proceeding. The Courts probably won't insert themselves in technical matters and will side with the FAA.

Elementalism wrote:

PW100 wrote:

SQ32 wrote:

In reality, everything can be done, it depends on capabilities of the engineering team.

747 went from drawing board to the sky in 1968, a time span just 3 years. Today, with all these software modelling tools, super fast PCs, the Boeing engineers come back and say nothing can be fixed.

Incomparable.

For starters, safety was much much worsen then. If you think that the MAX introduction is bad with two fatal accidents, you might want to look at the 727 introduction. Hint, MAX safety record actually looks very good then compared to the 727.

All that extra enigneering requires time, money and valuable resources. If you would go back to the sixties safety level, MAX would already have been flying within weeks (if grounded at all).

This is the truth. We have better tools but these planes are also much more complex. It is partly why the F35 and F22 had 20 year development cycles while the P51, P47,F6F and F4U took a couple years back in the 40s. But look at losses of frames from WWII and see how many were due to failures of the plane vs combat. Pretty shocking. The other part of why the F35\22 took so long is general incompetence\corruption of govt, and feature creep by the brass.

It's mostly political - look at some of the most incredible engineering achievements in modern aerospace history; Apollo program, SR-71/A-12 (2 years from contract to first flight!!) to the XB-70... probably the most extreme aircraft we'll ever see, was in the air in about 6 years.

We could have absolutely done it if *if we had to* - but from here on out, you'll see these drawn-out programs that take decades.

I guess we also have the issue of necessity; Apollo, SR-71, XB-70, etc were all born out of this requirement (as were the WWII fighters you mentioned).

PW100 wrote:

ArgentoSystems wrote:

"fundamental software redesign of 737 MAX flight controls"
I don't get it. They are talking about fundamental s/w redesign, and at the same time insist on completion is September. Are they nuts?

https://www.seattletimes.com/business/b ... -controls/

Going back to his surpising articel. I am surpised to read the following:

www.seattletimes.com wrote:

In one scenario, the bits chosen first told the computer that MCAS was engaged when it wasn’t. This had the effect of disabling the cut-off switches inside the pilot-control column, which normally stop any uncommanded movement of the horizontal tail if the pilot pulls in the opposite direction. MCAS cannot work with those cut-off switches active and so the computer, fooled into thinking MCAS was operating, disabled them.

In one of the previous threads, it was argued that a.net analysis the wiring diagram proved that there was no computer/processor functionality between thump trim switch and trim motor. However the above quoted part shows that the trim input was interrupted/slowed down by the clipped bits in the FCC. How does that jive. Does that mean that trim switch signal is first processed by FCC before being send to trim motor?

Reason I ask is because, as I put forward previously, that I find the ET FDR manual electric uptrim graph behaviour very suspicious. The FDR traces show a total of four electric up-trims after MCAS became alive. And ALL FOUR of them stopped at exactly the same pitch trim: 2.3 degrees. Coincidence? Can any crew do such a thing on purpose? I'm having a hard time accepting that.
It must be noted that after take-off, electric trimming was applied several times (both up and down) resulting in a balanced control column. So the crew clearly knew how that works. Why didn't/couldn't they do that after MCAS became alive?
If the trim signal first goes through FCC, the that could change the scope of how the pilots reacted dramatically. Perhaps they did command the uptrim further, but the system somehow did not allow that.

Then the next question would be: could the same thing have been happening with the Lionair accident, when control was handed over to the co-pilot? Perhaps for the same reason, did his uptrim actions not pass through the FCC somehow?

The article is referring to the yoke mcroswitches not the thumb switches.

My recall was that the Trim drive command is through the FCC?

Ray

AirwayBill wrote:

Probably the design of such MLG wasn't ready for the design freeze of the -8/-9 (which, as reminder, was under very high deadline pressure to counter the neo), so they opted for a quicker/cheaper option of mounting the engines more fwd/above the wing, and only a higher nose wheel?

The -10 gear design has the same static clearance that the regular 737MAX frames have.
What it provides is an effective softer spring constant that allows the sprung gearlegs to
extend before lift generated goes beyond aircraft weight.
Result: in the moment of rotation the fuselage is 10..15 inches further up giving more
clearance at the tail for the desired rotation angle.

As far as I understand, the MCAS system was first designed for KC-767 and KC-46 tankers. The tankers needed this feature to augment pitch during refueling operations.

It was also proposed for the original commercial 767 back in the 80s, but was dropped because vortex generators provided adequate control.

This suggests that the pitch up problem in the MAX is larger than what vortex generators could handle on their own.

https://www.mro-network.com/airframe/bo ... tch-system

JetBuddy wrote:

As far as I understand, the MCAS system was first designed for KC-767 and KC-46 tankers. The tankers needed this feature to augment pitch during refueling operations.

It was also proposed for the original commercial 767 back in the 80s, but was dropped because vortex generators provided adequate control.

This suggests that the pitch up problem in the MAX is larger than what vortex generators could handle on their own.

https://www.mro-network.com/airframe/bo ... tch-system

Vortex generators reduce efficiency and the more they are needed the more negative the effect is on the efficiency. There is no gain for Boeing to build an aircraft with fancy new engines if you slap drag generators on them. Thats why you go for the software solution. You just better not go for the cheaply developed and quickly implemented „it will be alright version“.

oOfredOo wrote:

I’ve read the article and as another embedded software engineer I find it plausible as well. I also thin,k that the probability of this specific combination of bit flips occurring is very low. 1Kbit of memory already puts this in 10^-14 territory. 5 bit flips due to cosmic rays is in itself already extremely remote. (10^-10 for a single bit to flip per day!)

So we are rewriting 20% of the code of the FCC for something that will never ever occur in reality. The probability that some major new bugs are introduced approaches 100%. Oh boy, I really hope they put this bird through full flight tests and system tests again.

I read the article too. When they got to cosmic rays and bit flipping, I laughed. The writer is clueless. It’s really laughable. But I buy that Boeing is using both computers now. What is actually happening in the logic is what we don’t know.

BoeingVista wrote:

From the last Dominic Gates article https://www.seattletimes.com/business/b ... -controls/

It has specifically rejected Boeing’s assumption that the plane’s pilots can be relied upon as the backstop safeguard in scenarios such as the uncommanded movement of the horizontal tail involved in both the Indonesian and Ethiopian crashes. That notion was ruled out by FAA pilots in June when, during testing of the effect of a glitch in the computer hardware, one out of three pilots in a simulation failed to save the aircraft.

One of the FAA pilots crashed the simulator while trying to recover, I think that this is new information? We assume that they would consider themselves above "average" pilots so you can imagine how pissed the FAA were with Boeing throwing this mess at line pilots.

I think there had been some allusions to this before. And these are pilots who knew what was coming and didn't have the added stress of their lives being on the line, so its a much easier situation.

It should put to rest all the nonsense about how this only happens to foreign pilots and would never happen to Americans. But I bet it won't.

A stat that bad - 33% - also shows why whatever Boeing wanted and was telling the public, and despite its blatant efforts, still afer everything, to put pressure on the regulator, there was no way this plane as going to fly again soon. The FAA screwed up but at least they seem to have learned from it. I dont get the impression anyone in Boeing management has learned a thing. Both those facts make me suspect the 777X certification is going to take a lot longer than Boeing wants as well.

SomebodyInTLS wrote:

Boeing and the FAA have discredited the viewpoint I'm talking about in their own recent testimonies.

Care to share those testimonies and explain how they discredit them?

FluidFlow wrote:

Happy to hear Boeing is confident it can address the software "problems" by using dual input. One question arising from the Seattle Times article (https://www.seattletimes.com/business/boeing-aerospace/newly-stringent-faa-tests-spur-a-fundamental-software-redesign-of-737-max-flight-controls/)

According to a third person familiar with the details, Boeing expects to have this new software architecture ready for testing toward the end of September. Meanwhile, it will continue certification activities in parallel so that it can stick to its announced schedule and hope for clearance from the FAA and other regulators in October.

It is a rather big change to have a new software architecture for the flight controls. Can this really be tested and approved withing 4 weeks (End of September till End of October)?

It is a completely new architecture never seen on a 737 before and to be safe everything that was ever tested and certified on the single FCC design should be retested and re-certified on the double FCC input design and I can not believe that the FAA nor the EASA or CAAC would be able to do this within 4 weeks.

Unless we’re talking apples and oranges. Boeing is continuing to perform the work required to get the airplane back in the air around the world and also working on a further improvement that will be incorporated at a later date. If the double FCC input is a significant software change I also think it won’t be a quick certification but maybe it’s not that big a deal.