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kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 8:51 pm

MSPNWA wrote:
kalvado wrote:
Because this is about permitting to start operation for a previously problematic design - vs continuing operations for situations where problems are known to be managable.


Nice try moving the goalposts, and no, I'm not talking about "manageable" issues. You implied real-world safety is having no issues (which in real-life is wrong - the world doesn't work that way). You didn't imply that real-word safety means you can't start (in this case restart) operations with an issue. But even if true, that logic proves that there's a cost/benefit angle to safety. If you have thousands in the air? More leniency.

Of course there is cost-benefit, and of course there is statistics. You need to come out clean for certification, but everyone expects teething issues.
This time teething issues are so severe, that certification review is warranted, not just a patch on a problem. Simple as that.
 
Interested
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 8:52 pm

kalvado wrote:
MSPNWA wrote:
kalvado wrote:
You're thinking Boeingish safety. Real world safety works different - MAX remains grounded until proven to have no issues.


"No issues" is incorrect. That's not real-world safety. Thousands of aircraft are flying today with known, potentially dangerous issues (and airlines too, but that's another avenue).

It begs the question as to why the MAX must be held to a different standard. Real-world safety has a cost angle to analyze. So much for Boeing being the only perpetrator of toeing that line.

Because this is about permitting to start operation for a previously problematic design - vs continuing operations for situations where problems are known to be managable.


Exactly

For a new plane due to be a huge part of aviation for the foreseeable future. At least that was the plan.

Boeing themselves may have blown the plan and the cash cow they thought they were designing
 
Interested
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 8:57 pm

MSPNWA wrote:
kalvado wrote:
Because this is about permitting to start operation for a previously problematic design - vs continuing operations for situations where problems are known to be managable.


Nice try moving the goalposts, and no, I'm not talking about "manageable" issues. You implied real-world safety is having no issues (which in real-life is wrong - the world doesn't work that way). You didn't imply that real-word safety means you can't start (in this case restart) operations with an issue. But even if true (the real-world says it's not), that logic proves that there's a cost/benefit angle to safety. If you have thousands in the air? More leniency. Safety isn't worth it. Illogical, but it's the route you've praised with the MAX.


Any of these unsafe planes crash they too will be investigated and potentially grounded etc.

We know how unsafe Max is and how important the plane is

And we know that Boeing have cynically and deliberately confused and covered up numerous aspects just to get it in the air

It's touch and go whether this plane will ever fly again IMO. Too many people on the case now for Boeing to get a fudge through.
 
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flyingturtle
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 8:59 pm

morrisond wrote:

I have flown an 172 in Turbulence where the controls go negative - it's not that hard to counter and all training tells you to not rely on feel - rely on your instruments and outside visual reference.


I remember having read these words one or two months ago... maybe we're discussing in loops...
Reading accident reports is what calms me down
 
Interested
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 9:13 pm

morrisond wrote:
kalvado wrote:
morrisond wrote:

From what I saw in this forum way back when but has now been deleted it really was a stick force issue (from a Boeing insider who should not have been publishing the information in public) and not weird stall characteristics - the data showed that the stick force which was about 6lbs fell to 4 instead of increasing to 7.

If the MAX does have really weird Stall Characteristics then it should be scrapped. I hope EASA makes public the results of it's test flights without MCAS.

Problem is - this is exactly describing ugly stall characteristics.
The way things work, arm controls force rather than position. Did you ever try non-spring loaded joysticks? Nightmare...
So, the way trouble goes is: pilot pulls stick to what would be 10 deg AoA from 8 deg AoA, force goes down; arm moves further to 12 deg AoA, force goes down, arm moves to 15 - and plane stalls before pilot realizes what goes wrong. You need to train some very counterintuitve muscle memory to avoid that.


I have flown an 172 in Turbulence where the controls go negative - it's not that hard to counter and all training tells you to not rely on feel - rely on your instruments and outside visual reference.

.


Great to know Morrison. Let's keep those thoughts for pilots and small planes and let's not start bringing in feel and outside visual references into flight safety for newly designed commercial planes with hundreds of lives at stake.

We really don't need to go down that route. In this day and age.

We shouldn't even be having to discuss stuff like the above for a newly designed Boeing plane.

It just shows the level the Max has dragged us down to discussing. Ridiculous really. Micky mouse stuff.
 
speedbird52
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 10:11 pm

I am really perplexed at why people still blame the ET pilots. There is no circumstance where an airplane should attempt to fly itself into the ground. End of story. Pilot training is beyond the point, because this shouldn't be something that happens period.
 
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par13del
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 10:23 pm

Interested wrote:
Great to know Morrison. Let's keep those thoughts for pilots and small planes and let's not start bringing in feel and outside visual references into flight safety for newly designed commercial planes with hundreds of lives at stake.

We really don't need to go down that route. In this day and age.

We shouldn't even be having to discuss stuff like the above for a newly designed Boeing plane.

It just shows the level the Max has dragged us down to discussing. Ridiculous really. Micky mouse stuff.

Ok, help me to understand the train of thought, is the MAX a 737 a/c from the 60's with old technology using grandfathering or a newly designed plane as you state? I am honestly having a hard time following the principles of some of the arguments.
 
beechnut
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 10:43 pm

morrisond wrote:
kalvado wrote:
morrisond wrote:
I have flown an 172 in Turbulence where the controls go negative - it's not that hard to counter and all training tells you to not rely on feel - rely on your instruments and outside visual reference.

It takes probably a good 15-20 seconds on an 737 beyond the point where the controls get a little light to get into an actual stall - it's not as dramatic as you are making out.


I have owned for 14 years and several hundred hours a Beech Sundowner and done aerobatics in it, one of the rare examples with the aerobatic kit and certified for aerobatics.

Having the controls go light, momentarily, in turbulence or an upset, and having the controls get lighter as you approach stall, are two completely different things. A counter-intuitive and progressive reversal in control force is not something to be trifled with. Look up "hinge moment reversal" and "ATR-72" in a Google search.

Once, in my Sundowner due to an error by the maintenance shop, the actuator became detached from the anti-servo tab on the stabilator resulting in zero feedback on stabilator position. The aircraft became a handful to fly, in clear, calm VFR waather.

Beech
Last edited by beechnut on Sun Jan 12, 2020 10:47 pm, edited 1 time in total.
 
kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 10:46 pm

par13del wrote:
Interested wrote:
Great to know Morrison. Let's keep those thoughts for pilots and small planes and let's not start bringing in feel and outside visual references into flight safety for newly designed commercial planes with hundreds of lives at stake.

We really don't need to go down that route. In this day and age.

We shouldn't even be having to discuss stuff like the above for a newly designed Boeing plane.

It just shows the level the Max has dragged us down to discussing. Ridiculous really. Micky mouse stuff.

Ok, help me to understand the train of thought, is the MAX a 737 a/c from the 60's with old technology using grandfathering or a newly designed plane as you state? I am honestly having a hard time following the principles of some of the arguments.

I am not the one being asked, but I'll offer my perspective:
we're dealing with unhappy marriage of different generations of technology. In particular, control system has an FBW-type approach - MCAS - stapled to Wright brothers style direct control via mechanical links, with mid-20th century hydrolics added to deal with larger jet - including hydrolic stick force immitating computer. Could this be done properly? Yes, by someone having at least some idea about all three design approaches. Apparently, Boeing didn't have a proper person, though... They ended up with disadvantages of FBW being able to crash the plane despite pilot's efforts, without getting full advantage of FBW due to ancient hardware.
Boeing is working hard on their Ruby Goldberg machine. Frankly speaking, they did a great job for RG machine. Problem is that even very good RG doesn't really work in high reliability applications
 
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 10:48 pm

MildBlueYonder wrote:
wingman wrote:
I've been on this site for 20 years backing and supporting Boeing in most debates. When I fly now, and it's it's every other week at minimum on AS, I breathe a sigh of relief every time I see it's an ex-Virgin bird and not a 737. I don't care what version it is, I know it's designed by a company that lost its way so badly it ended up abandoning every core principle that ever mattered. The whole place needs to be gutted and rebooted.


Feel exactly the same way. My interest in aviation started with Boeing and the 21st Century Jet documentary in the late 90s; really admired them as a kid and would have firmly been in the B-supporter camp in recent A vs. B conversations. Not now though. Sad to see how far the company has fallen since the Alan Mulally + 777 heyday. As someone who flies GA regularly out of RNT, I don't see Boeing when I look across the ramp these days...I see McD.

I have no sweat with the 737 NG. Why? Because, unlike the Max, it has proven to be reliable and very safe plane, even in the hands of Lionair and other so claimed "third world operators".

And in my book, there is only one thing better than proven safety through analysis and testing (= type certification) and that is proven safety through actual flight hours. Not hundred thousand flight hours (like Max), but hundreds of millions of flight hours (NG). And that is also the main reason why I'm not having issues with grandfathering.

I wonder why Alan Mulally is used as a poster child CEO? Wasn't it under his watch that Boeing went nuts on RONA, resulting in excessive outsourcing, resulting in basically loss of control over supplier interfaces, and eventually significant loss of configuration control on 787 terrible teens?
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 10:52 pm

MSPNWA wrote:
kalvado wrote:
You're thinking Boeingish safety. Real world safety works different - MAX remains grounded until proven to have no issues.


"No issues" is incorrect. That's not real-world safety. Thousands of aircraft are flying today with known, potentially dangerous issues (and airlines too, but that's another avenue).

It begs the question as to why the MAX must be held to a different standard. Real-world safety has a cost angle to analyze. So much for Boeing being the only perpetrator of toeing that line.


I suspect that you are using a different definition of "issues" than subject poster.

However, you are certainly correct that Max issues find them selves under a bigger microscope now.
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zippy
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 10:53 pm

PW100 wrote:
I wonder why Alan Mulally is used as a poster child CEO? Wasn't it under his watch that Boeing went nuts on RONA, resulting in excessive outsourcing, resulting in basically loss of control over supplier interfaces, and eventually significant loss of configuration control on 787 terrible teens?


Me too considering Mullally was never CEO of Boeing.
 
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 11:02 pm

morrisond wrote:
kalvado wrote:
Problem is - this is exactly describing ugly stall characteristics.
The way things work, arm controls force rather than position. Did you ever try non-spring loaded joysticks? Nightmare...
So, the way trouble goes is: pilot pulls stick to what would be 10 deg AoA from 8 deg AoA, force goes down; arm moves further to 12 deg AoA, force goes down, arm moves to 15 - and plane stalls before pilot realizes what goes wrong. You need to train some very counterintuitve muscle memory to avoid that.


I have flown an 172 in Turbulence where the controls go negative - it's not that hard to counter and all training tells you to not rely on feel - rely on your instruments and outside visual reference.


Where your controls went negative was not a function of the plane, but a function of atmospheric conditions.

I wonder how your plane would have felt if it ALSO had controls going light by design (which is just a different way of saying there isn't enough stability margin) ON TOP of the atmospheric conditions you experienced.

It may not have been hard to counter, but that is by design of the plane. The 172 is a very stable and predictable platform (the jury is still out for that on the unaugmented MAX).

You may have felt is was not that hard to counter, but that was on a very stable and forgiving platform. If that part of the design is insufficient, you may find that to be very hard and unsuitable for airline ops. I suspect that may be an important reason why this FAR exists today.
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 11:03 pm

zippy wrote:
PW100 wrote:
I wonder why Alan Mulally is used as a poster child CEO? Wasn't it under his watch that Boeing went nuts on RONA, resulting in excessive outsourcing, resulting in basically loss of control over supplier interfaces, and eventually significant loss of configuration control on 787 terrible teens?


Me too considering Mullally was never CEO of Boeing.


Right. President of Boeing Commercial.
Thanks.
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PW100
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 11:15 pm

oschkosch wrote:
morrisond wrote:
........ as I believe EASA flew the MAX last week if there is- but as there were no reports of MAX crashes last week - if there was Catastrophic Instability - they were able to recover.


Nope. The test flights are expected to happen from 15th January onwards - maybe.

https://www.livemint.com/news/india/faa ... 04853.html

Gesendet von meinem SM-G950F mit Tapatalk


Funny, we have been reading since last July that those test flights will happen ". . . within a few weeks . . ".

I would expect that if the problem is so benign as some would like to portray it, surely Boieng would have put such a test flight must right on top of their milestone list. It would be extremely helpful in getting the regulators mind set that they are dealing with a benign problem, rather than something catastrophic. And surely they would have made sure the whole world would know.
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morrisond
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 11:34 pm

PW100 wrote:
MSPNWA wrote:
kalvado wrote:
You're thinking Boeingish safety. Real world safety works different - MAX remains grounded until proven to have no issues.


"No issues" is incorrect. That's not real-world safety. Thousands of aircraft are flying today with known, potentially dangerous issues (and airlines too, but that's another avenue).

It begs the question as to why the MAX must be held to a different standard. Real-world safety has a cost angle to analyze. So much for Boeing being the only perpetrator of toeing that line.


I suspect that you are using a different definition of "issues" than subject poster.

However, you are certainly correct that Max issues find them selves under a bigger microscope now.


I think if you spend some time on the FAA and EASA AD websites you will get a better appreciation of what some of those issues are that MSPNWA is talking about.

Many have Catastrophic consequences but the planes are allowed to fly and not grounded immediately to be corrected.

Aviation is not about perfection - it’s about compromise and good enough - If airplanes were perfect they would be too heavy to leave the ground.
 
MildBlueYonder
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 11:41 pm

PW100 wrote:
MildBlueYonder wrote:
wingman wrote:
I've been on this site for 20 years backing and supporting Boeing in most debates. When I fly now, and it's it's every other week at minimum on AS, I breathe a sigh of relief every time I see it's an ex-Virgin bird and not a 737. I don't care what version it is, I know it's designed by a company that lost its way so badly it ended up abandoning every core principle that ever mattered. The whole place needs to be gutted and rebooted.


Feel exactly the same way. My interest in aviation started with Boeing and the 21st Century Jet documentary in the late 90s; really admired them as a kid and would have firmly been in the B-supporter camp in recent A vs. B conversations. Not now though. Sad to see how far the company has fallen since the Alan Mulally + 777 heyday. As someone who flies GA regularly out of RNT, I don't see Boeing when I look across the ramp these days...I see McD.

I have no sweat with the 737 NG. Why? Because, unlike the Max, it has proven to be reliable and very safe plane, even in the hands of Lionair and other so claimed "third world operators".

And in my book, there is only one thing better than proven safety through analysis and testing (= type certification) and that is proven safety through actual flight hours. Not hundred thousand flight hours (like Max), but hundreds of millions of flight hours (NG). And that is also the main reason why I'm not having issues with grandfathering.

I wonder why Alan Mulally is used as a poster child CEO? Wasn't it under his watch that Boeing went nuts on RONA, resulting in excessive outsourcing, resulting in basically loss of control over supplier interfaces, and eventually significant loss of configuration control on 787 terrible teens?


I don't have any issues with the NG, either, but see that as a pre-merger project contemporaneous with the 777. BCA executed both rather well. Since then, however, you've got the 787 which is, what, at least $24 billion over initial estimates, entered service three years late effectively killing the whole Yellowstone strategy, and suffered a safety grounding over the lithium ion batteries. Admittedly, the Dreamliner was an ambitious project with a lot of new and untested tech, so maybe Boeing gets a partial pass there. But now you have the MAX, which was supposed to be a simple derivative, that ends up being a bigger program disaster than the 787.

I agree that the RONA fixation probably started Boeing on its downward spiral. I guess I'm less clear on who in management decided to take this path. This was around the time that Condit was ousted and Stonecipher installed as interim..before he was ousted as well. Mulally left for Ford in 2006; don't know if he jumped only because he was passed over for CEO or there was some simmering discontent about the evolving leadership culture. Would love to hear an insider's take on that period in BCA history. Otherwise, I guess I'll wait for the HBS case study on this massive corporate failure.
 
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PixelFlight
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Sun Jan 12, 2020 11:48 pm

morrisond wrote:
PW100 wrote:
MSPNWA wrote:

"No issues" is incorrect. That's not real-world safety. Thousands of aircraft are flying today with known, potentially dangerous issues (and airlines too, but that's another avenue).

It begs the question as to why the MAX must be held to a different standard. Real-world safety has a cost angle to analyze. So much for Boeing being the only perpetrator of toeing that line.


I suspect that you are using a different definition of "issues" than subject poster.

However, you are certainly correct that Max issues find them selves under a bigger microscope now.


I think if you spend some time on the FAA and EASA AD websites you will get a better appreciation of what some of those issues are that MSPNWA is talking about.

Many have Catastrophic consequences but the planes are allowed to fly and not grounded immediately to be corrected.

Aviation is not about perfection - it’s about compromise and good enough - If airplanes were perfect they would be too heavy to leave the ground.

There are allowed to fly only if the condition that can potentially cause catastrophic consequences can be safely avoided.
And no, civil commercial aviation safety is not about "compromise and good enough". It's a far more rigorous process.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
Thorkel
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 12:31 am

morrisond wrote:
PW100 wrote:
MSPNWA wrote:

"No issues" is incorrect. That's not real-world safety. Thousands of aircraft are flying today with known, potentially dangerous issues (and airlines too, but that's another avenue).

It begs the question as to why the MAX must be held to a different standard. Real-world safety has a cost angle to analyze. So much for Boeing being the only perpetrator of toeing that line.


I suspect that you are using a different definition of "issues" than subject poster.

However, you are certainly correct that Max issues find them selves under a bigger microscope now.


I think if you spend some time on the FAA and EASA AD websites you will get a better appreciation of what some of those issues are that MSPNWA is talking about.

Many have Catastrophic consequences but the planes are allowed to fly and not grounded immediately to be corrected.

Aviation is not about perfection - it’s about compromise and good enough - If airplanes were perfect they would be too heavy to leave the ground.


Consequences mostly don’t change in this sort of safety analysis. If you can eliminate a hazard then great - but all planes, pretty much by definition, have catastrophic consequences as per all the various functional safety standards. You can’t eliminate the catastrophic consequence of a plane crashing unless it never takes off.

The job of the safety work here is to minimise the risk by putting in safety controls. Engineering controls carry greater weight in most of the standards than administrative (human) controls. Basically your job is to get the residual risk at least tolerable, and ideally as low as practicable.

Techniques like FMEA and LOPA are means to calculate residual risks, particularly when you don’t have sufficient real data. Pretty much all the standards say you should update these analyses when real data comes to light.

So, all planes have catastrophic consequences associated with their systems. This is normal. The residual risk will not be zero with any plane/hazard combination but will typically be at least tolerable.

One of the issues with the MAX is the safety analysis did not properly assess the hazard, and the resulting residual risk is not tolerable - as borne out by the real world evidence. That’s the difference compared to other aircraft flying today. The MAX isn’t being held to a different standard - it didn’t meet the tolerability criteria.
 
MSPNWA
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 12:44 am

kalvado wrote:
Of course there is cost-benefit, and of course there is statistics. You need to come out clean for certification, but everyone expects teething issues.
This time teething issues are so severe, that certification review is warranted, not just a patch on a problem. Simple as that.


Good, you understand the the equation. It begs the questions. Is going way beyond MCAS the most pressing safety need when we have many known issues that are allowed to fly? Is costing society (mostly the public that flies or is reliant of flight) billions to keep the MAX grounded for things beyond MCAS worth the benefit? Your subjective belief falls apart into the illogical when subjected to tough questions.

PixelFlight wrote:
And no, civil commercial aviation safety is not about "compromise and good enough". It's a far more rigorous process.


No offense, but I'm smiling at how completely wrong this is. It's absolutely a "good enough" equation. And of course that subjects it to a subjective opinion as to what "good enough" is, in an inverse relationship to the cost of course.

Your excuses for that subjectiveness never end. It's not about "rigorous". It can be "rigorous" and still be "good enough". They are not mutually exclusive as you imply.
Last edited by MSPNWA on Mon Jan 13, 2020 12:51 am, edited 2 times in total.
 
kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 12:48 am

MSPNWA wrote:
PixelFlight wrote:
And no, civil commercial aviation safety is not about "compromise and good enough". It's a far more rigorous process.


No offense, but I'm smiling at how completely wrong this is. It's absolutely a "good enough" equation. And of course that subjects it to a subjective opinion as to what "good enough" is, in an inverse relationship to the cost of course.

Your excuses for that subjectiveness never end. It's not about "rigorous". It can be "rigorous" and still be "good enough". They are not mutually exclusive as you imply.

Depends on what do you mean by "good enough". 1e-9 for crash probability is "good enough" by today's standard. I suspect posters are using a lesser definition, though.
 
MSPNWA
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 12:55 am

kalvado wrote:
Depends on what do you mean by "good enough".


That's the dilemma! If "good enough" strays from facts and reason, as subjective matters often do, it becomes a problem.
 
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PixelFlight
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:14 am

MSPNWA wrote:
kalvado wrote:
Of course there is cost-benefit, and of course there is statistics. You need to come out clean for certification, but everyone expects teething issues.
This time teething issues are so severe, that certification review is warranted, not just a patch on a problem. Simple as that.


Good, you understand the the equation. It begs the questions. Is going way beyond MCAS the most pressing safety need when we have many known issues that are allowed to fly? Is costing society (mostly the public that flies or is reliant of flight) billions to keep the MAX grounded for things beyond MCAS worth the benefit? Your subjective belief falls apart into the illogical when subjected to tough questions.

PixelFlight wrote:
And no, civil commercial aviation safety is not about "compromise and good enough". It's a far more rigorous process.


No offense, but I'm smiling at how completely wrong this is. It's absolutely a "good enough" equation. And of course that subjects it to a subjective opinion as to what "good enough" is, in an inverse relationship to the cost of course.

Your excuses for that subjectiveness never end. It's not about "rigorous". It can be "rigorous" and still be "good enough". They are not mutually exclusive as you imply.


Actually the initial comment was not about "equation" (as in a formal risk assessment) but about "compromise" (as if the required safety level could not be done). I could be wrong on that interpretation. My point is that safety risk analyzing is a rigorous process that was developed precisely to avoid quick and potentially biased evaluation, and to ensure that safety is not a compromise.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:18 am

MSPNWA wrote:
kalvado wrote:
Depends on what do you mean by "good enough".


That's the dilemma! If "good enough" strays from facts and reason, as subjective matters often do, it becomes a problem.

Not even that.... "good enough" for medical applications can mean 99 out of 100 successfull surgeries. Sucks to be the 100th guy, but this is often the best what can be done. Pretty good chance for once in a lifetime, life-saving surgery, I would say.
If 99 out of 100 would be "good enough" for aviation crash rate, planes would crash faster than A and B would be making them... So it has to be numerical after all, not just fact based. And 1e-9 estimates can be pretty counterintuitive, as many posters demonstrated in this thread.
 
mjoelnir
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 2:23 am

MSPNWA wrote:
kalvado wrote:
Of course there is cost-benefit, and of course there is statistics. You need to come out clean for certification, but everyone expects teething issues.
This time teething issues are so severe, that certification review is warranted, not just a patch on a problem. Simple as that.


Good, you understand the the equation. It begs the questions. Is going way beyond MCAS the most pressing safety need when we have many known issues that are allowed to fly? Is costing society (mostly the public that flies or is reliant of flight) billions to keep the MAX grounded for things beyond MCAS worth the benefit? Your subjective belief falls apart into the illogical when subjected to tough questions.

PixelFlight wrote:
And no, civil commercial aviation safety is not about "compromise and good enough". It's a far more rigorous process.


No offense, but I'm smiling at how completely wrong this is. It's absolutely a "good enough" equation. And of course that subjects it to a subjective opinion as to what "good enough" is, in an inverse relationship to the cost of course.

Your excuses for that subjectiveness never end. It's not about "rigorous". It can be "rigorous" and still be "good enough". They are not mutually exclusive as you imply.


The point about the original 737MAX certification is, that it was not about rigorous or god enough, but about what can we conceal and get away with.
 
mjoelnir
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 2:26 am

MSPNWA wrote:
kalvado wrote:
Depends on what do you mean by "good enough".


That's the dilemma! If "good enough" strays from facts and reason, as subjective matters often do, it becomes a problem.


Yes and Boeing with the MAX steered away from facts and reasons, into the realm of what can we get away with.
 
kalvado
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 8:13 am

MSPNWA wrote:
kalvado wrote:
Of course there is cost-benefit, and of course there is statistics. You need to come out clean for certification, but everyone expects teething issues.
This time teething issues are so severe, that certification review is warranted, not just a patch on a problem. Simple as that.


Good, you understand the the equation. It begs the questions. Is going way beyond MCAS the most pressing safety need when we have many known issues that are allowed to fly? Is costing society (mostly the public that flies or is reliant of flight) billions to keep the MAX grounded for things beyond MCAS worth the benefit? Your subjective belief falls apart into the illogical when subjected to tough questions.

Thanks, now lets see if you understand the equation.
There is a certain probability that a given design problem is caught before EIS.
State of the art - 777, 350 - manage to log years before anything catastrophic shows up.
Now MAX managed to get a systematic problem not only overlooked - not even understood after the first crash with all data on hand. What does it tell about the initial review? Nothing good.
So what are the reasons to allow MAX back in service? Hint: "thorough review during certification" is no longer a good answer.

I said it before, I'll repeat it: Boeing lost control over MAX design somewhere in the process. And structured design approaches exist for a reason - so Boeing is facing a very difficult problem of redoing design from scratch to eliminate design issues without actually redoing anything. Good luck, they will need a lot of it.
 
smartplane
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 8:19 am

MSPNWA wrote:
kalvado wrote:
Depends on what do you mean by "good enough".


That's the dilemma! If "good enough" strays from facts and reason, as subjective matters often do, it becomes a problem.

'Good enough' might be a benchmark for aircraft in service, but the MAX is a special case. Will the 'good enough' bar be raised permanently, or as a one off to penalise Boeing? Some would argue Boeing hasn't even met historical 'good enough' standards.

Airworthiness authorities then must decide:

1. Currently built - delivered to airlines - previously in service.
Modifications to be completed before they can re-enter service, plus AD's to be actioned by agreed date.

2. Currently built - not delivered to airlines - never in service.
As for ONE, plus perhaps some of the AD's to be actioned before they can be delivered to customers.

3. Partly built / not built
All modifications and AD's to be actioned during the production process.
 
Interested
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 8:20 am

par13del wrote:
Interested wrote:
Great to know Morrison. Let's keep those thoughts for pilots and small planes and let's not start bringing in feel and outside visual references into flight safety for newly designed commercial planes with hundreds of lives at stake.

We really don't need to go down that route. In this day and age.

We shouldn't even be having to discuss stuff like the above for a newly designed Boeing plane.

It just shows the level the Max has dragged us down to discussing. Ridiculous really. Micky mouse stuff.

Ok, help me to understand the train of thought, is the MAX a 737 a/c from the 60's with old technology using grandfathering or a newly designed plane as you state? I am honestly having a hard time following the principles of some of the arguments.


IMO grandfathering is designed to ensure a previously safe plane is developed to become safer

So many significant changes to the plane. Moving of the engines. Lack of stability or whatever people want to call it and the need for MCAS means we have a huge problem. And the issues introduced are why we are in such a mess now. We've got safety problems we wouldnt have to face on a plane that was genuinely grandfathered.

We know that Boeing have deliberately and cynically hidden changes to get the plane certified. IMO it's a new design and a flawed design.
 
Interested
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 8:23 am

PixelFlight wrote:
morrisond wrote:
PW100 wrote:

I suspect that you are using a different definition of "issues" than subject poster.

However, you are certainly correct that Max issues find them selves under a bigger microscope now.


I think if you spend some time on the FAA and EASA AD websites you will get a better appreciation of what some of those issues are that MSPNWA is talking about.

Many have Catastrophic consequences but the planes are allowed to fly and not grounded immediately to be corrected.

Aviation is not about perfection - it’s about compromise and good enough - If airplanes were perfect they would be too heavy to leave the ground.

There are allowed to fly only if the condition that can potentially cause catastrophic consequences can be safely avoided.
And no, civil commercial aviation safety is not about "compromise and good enough". It's a far more rigorous process.


Rightly so

Boeing are the ones who have tried to bring compromise into it

To their huge failing and they must seriously regret the decisions they made when doing so
 
Interested
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 8:25 am

Thorkel wrote:
morrisond wrote:
PW100 wrote:

I suspect that you are using a different definition of "issues" than subject poster.

However, you are certainly correct that Max issues find them selves under a bigger microscope now.


I think if you spend some time on the FAA and EASA AD websites you will get a better appreciation of what some of those issues are that MSPNWA is talking about.

Many have Catastrophic consequences but the planes are allowed to fly and not grounded immediately to be corrected.

Aviation is not about perfection - it’s about compromise and good enough - If airplanes were perfect they would be too heavy to leave the ground.


Consequences mostly don’t change in this sort of safety analysis. If you can eliminate a hazard then great - but all planes, pretty much by definition, have catastrophic consequences as per all the various functional safety standards. You can’t eliminate the catastrophic consequence of a plane crashing unless it never takes off.

The job of the safety work here is to minimise the risk by putting in safety controls. Engineering controls carry greater weight in most of the standards than administrative (human) controls. Basically your job is to get the residual risk at least tolerable, and ideally as low as practicable.

Techniques like FMEA and LOPA are means to calculate residual risks, particularly when you don’t have sufficient real data. Pretty much all the standards say you should update these analyses when real data comes to light.

So, all planes have catastrophic consequences associated with their systems. This is normal. The residual risk will not be zero with any plane/hazard combination but will typically be at least tolerable.

One of the issues with the MAX is the safety analysis did not properly assess the hazard, and the resulting residual risk is not tolerable - as borne out by the real world evidence. That’s the difference compared to other aircraft flying today. The MAX isn’t being held to a different standard - it didn’t meet the tolerability criteria.


Boeing deliberately hid the and confused the very things they should have been testing the safety of

It's horrendous really. No idea why anyone is trying to defend this? Had the FAA and test pilots and Boeing all made genuine mistakes and miscalculations together it would be understandable.

The fact Boeing have deliberately hidden stuff suggests the plane would not have been certified.

Trust was put in Boeing, They've seriously abused the trust. They've probably all forgotten the reasons Boeing was ever trusted in the first place. And profits have overtaken safe engineering.
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 9:11 am

asdf wrote:
morrisond wrote:
United787 wrote:

This is an oversimplification but: those engines on those wings on that fuselage. There are hundreds of other posts that go into more detail but that is the inherent flaw. Boeing's 1st mistake, of many, was not doing a clean sheet design. Their 2nd mistake was not doing a clean sheet design...



This, exactly!


Yes - but just remember - as REV pointed out it would have been the same clowns designing the clean sheet.

At least it would have been a lot easier to hide any potential Aerodynamic flaws with FBW though.


You do not need to „hide“ a aerodynamical behavior of a FBW Plane.

FBW compensates a behavior. Its Part of the plan. It is Designed for it. It does ist very well.

Pilots dont.
They are Not used to it


Except that aerodynamic behaviour is still there and can come back to bite you if your FBW allows it too. Stall identification is a really issue in modern aircraft, and it has bitten both FBW and non-FBW aircraft. Hence the reason that the FAA is now requiring more stall and post stall sim training. The fact is that a model, irreversible control, FBW aircraft is easier to modify the flight control parameters than an old, reversible control, hydraulically boosted, system. However, there is nothing about the old system that inherently precludes it from producing acceptable handling characteristics. Implementation is the key.
 
Strato2
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 9:26 am

scbriml wrote:
The total cost to Boeing though will be a lot more than just the $$$s ("designed by clowns who are managed by monkeys" comes to mind).


This was the latest blurb to come out and it's a catchy phrase that was plastered all over the news media. The flying public will remember this because it's like an ad only in reverse. I would not be surprised if it led to 737 MAX memes to come out.
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 11:20 am

United787 wrote:
phollingsworth wrote:
However, I do wonder what you believe are the inherent flaws of the 737MAX that are not present on all other modern airliners?


This is an oversimplification but: those engines on those wings on that fuselage. There are hundreds of other posts that go into more detail but that is the inherent flaw. Boeing's 1st mistake, of many, was not doing a clean sheet design. Their 2nd mistake was not doing a clean sheet design...

SteelChair wrote:
I reassert what I said several months ago. Time to stop the MAX program take a $40B charge, fire up the NG program for 4 years, and design an all new airplane. Fire most of the top management, scrap all the MAX frames and totally remake the company. Employees will need to take pay and benefit cuts. Everyone will need to pull together to make it work.


This, exactly!


There is nothing particular about those engines, those wings, or that fuselage in isolation that is at all an issue, or any more than any other airliner out there. A clean sheet design would have very similar engines, wings, and fuselage. The issue, and it is an issue with all modern airliners, is the interaction between the engines and wings. The fact is a clean sheet design would not eliminate either of the two aerodynamic issues displayed by the MAX, ie the shift in effective aerodynamic centre at high AoA and stall identification. I am not privy to Boeing's technology curve and arsenal, but it is entirely reasonable to expect that even a 'clean-sheet' design would have exactly the same aerodynamic 'flaws' as the sweet spot might involve the same nacelle-wing interactions. The one thing a 'clean-sheet' would do is weaken the desire to minimise differences with the current fleet. You could make a new aircraft that flies like a 737NG, but given you will have changed all the failure modes substantially why would you do it. Of course once you break the commonality on the pilot and MTC side, there isn't any specific advantage for a WN to stick with Boeing.

As for walking away from the MAX now and making NGs. That really isn't practical and would probably cost a lot more than $40 billion. Boeing would have to compensate the airlines on fuel cost for the next 20-30 years.
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 11:25 am

PixelFlight wrote:
phollingsworth wrote:
PixelFlight wrote:
Not in all the new cases open by the MCAS on the 737-8/9 MAX: at some points the pilots loss the longitudinal control and this was actively hidden in the safety assessment by using obsolete assumptions that was not asserted and too later found wrong on that aircraft design.


The question is, given the MCAS rates would this have occurred in 3 seconds of MCAS activation from a trimmed condition? If not then the regulations have little to say. Maybe they should. If it does and was 'actively' hidden then there are other issues.

The 3 seconds was part of the obsolete and wrong assumption. The MCAS was designed to trim nose down as long a 9 seconds, and as such was subject to safety critical requirements imposing redundant sensors, redundant flight computers, and redundant actuators.


While the 3-second bit in the regulations may stem from the same assumption as Boeing's safety analysis they are effectively two different things. If the the aircraft can still be controlled after a 3-second trim run, then it satisfies the regulations on controllability, even if it didn't satisfy the original intent because pilots would not catch the runaway in 3-seconds. Of course, if the pilots don't catch the failure and additional runaways occur such the the aircraft becomes uncontrollable other areas of the FAR-25/CS-25 would apply. It also means that maybe the regulation needs to be rewritten so that a more meaningful check of compliance with the intent must be done.
 
beaconinbound
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 11:29 am

phollingsworth wrote:
United787 wrote:
phollingsworth wrote:
However, I do wonder what you believe are the inherent flaws of the 737MAX that are not present on all other modern airliners?


This is an oversimplification but: those engines on those wings on that fuselage. There are hundreds of other posts that go into more detail but that is the inherent flaw. Boeing's 1st mistake, of many, was not doing a clean sheet design. Their 2nd mistake was not doing a clean sheet design...

SteelChair wrote:
I reassert what I said several months ago. Time to stop the MAX program take a $40B charge, fire up the NG program for 4 years, and design an all new airplane. Fire most of the top management, scrap all the MAX frames and totally remake the company. Employees will need to take pay and benefit cuts. Everyone will need to pull together to make it work.


This, exactly!


There is nothing particular about those engines, those wings, or that fuselage in isolation that is at all an issue, or any more than any other airliner out there. A clean sheet design would have very similar engines, wings, and fuselage. The issue, and it is an issue with all modern airliners, is the interaction between the engines and wings. The fact is a clean sheet design would not eliminate either of the two aerodynamic issues displayed by the MAX, ie the shift in effective aerodynamic centre at high AoA and stall identification. I am not privy to Boeing's technology curve and arsenal, but it is entirely reasonable to expect that even a 'clean-sheet' design would have exactly the same aerodynamic 'flaws' as the sweet spot might involve the same nacelle-wing interactions. The one thing a 'clean-sheet' would do is weaken the desire to minimise differences with the current fleet. You could make a new aircraft that flies like a 737NG, but given you will have changed all the failure modes substantially why would you do it. Of course once you break the commonality on the pilot and MTC side, there isn't any specific advantage for a WN to stick with Boeing.

As for walking away from the MAX now and making NGs. That really isn't practical and would probably cost a lot more than $40 billion. Boeing would have to compensate the airlines on fuel cost for the next 20-30 years.


Oh man, have you ever seen CFD results - let alone results of wind tunnel testing - of any existing modern aircraft? I can tell you, "complex" is an underestimation in that context. A clean sheet design could well address these issues. Another hint: A few inches can make a huge difference in aerodynamics...
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 11:56 am

PW100 wrote:
morrisond wrote:
kalvado wrote:
Problem is - this is exactly describing ugly stall characteristics.
The way things work, arm controls force rather than position. Did you ever try non-spring loaded joysticks? Nightmare...
So, the way trouble goes is: pilot pulls stick to what would be 10 deg AoA from 8 deg AoA, force goes down; arm moves further to 12 deg AoA, force goes down, arm moves to 15 - and plane stalls before pilot realizes what goes wrong. You need to train some very counterintuitve muscle memory to avoid that.


I have flown an 172 in Turbulence where the controls go negative - it's not that hard to counter and all training tells you to not rely on feel - rely on your instruments and outside visual reference.


Where your controls went negative was not a function of the plane, but a function of atmospheric conditions.

I wonder how your plane would have felt if it ALSO had controls going light by design (which is just a different way of saying there isn't enough stability margin) ON TOP of the atmospheric conditions you experienced.

It may not have been hard to counter, but that is by design of the plane. The 172 is a very stable and predictable platform (the jury is still out for that on the unaugmented MAX).

You may have felt is was not that hard to counter, but that was on a very stable and forgiving platform. If that part of the design is insufficient, you may find that to be very hard and unsuitable for airline ops. I suspect that may be an important reason why this FAR exists today.


The 172 has very clear stall identification and post-stall behaviour. It is really hard to hold the nose up once the wing stalls. Also it does not have an issue with control lightening on approach to stall as it isn't a swept wing aircraft with a sophisticated aerofoil. The fact that the 737MAX does have these issues is not, in and of itself, a problem. They are present on every other commercial transport being delivered today. The issue is can you create an augmentation system that alleviates these issues and does not present catastrophic new issues?

The fact is any aircraft that uses stab trim to help with stick force and stall identification can present a case where the stabiliser trims nose-down in an inappropriate condition. Just like any aircraft that forces elevator nose down to prevent a stall can do the same. These systems have been and are currently acceptable means of compiling with the letter and intent of the regulations. The questions that need to be answered for 737MAX, and may have been answered already in some cases.
  • Is there are point in the flight envelope where the pilot would have to push the stick forward to counter an AoA upset from a trimmed condition? – Basic static stability
  • Does the trim rate of the stabiliser allow for appropriate stick force gradients through the flight envelope?
  • Is stall, or approach to stall, clearly identifiable by the pilot?
  • If the augmentation system fails what are the failure modes and what can those lead to if handled improperly? A fail passive mode that allows stick force lightening or makes stall identification harder is very different than a fail active that noses the aircraft into the ground
  • If the system fails active can other systems and/or the flight crew take appropriate action to counter said failure, and can they take such action fast enough to prevent catastrophic outcomes

The fact is that 737NG STS is a simplex system with a similar failure rate of the primary sensor to that of MCAS. Boeing assumes that is fails 1E-5 per flight hour. This was deemed fine by the regulator (it was done at the behest of the JAA), and has worked acceptably in practice. The reason for this is that the failure modes don't lead to catastrophic outcomes at a rate that is unacceptable. MCAS, in the stall identification mode, breaks that condition. The combination of increased authority, plus different presentation of failure leads to catastrophic outcomes far too often. The solution to this is:
  • Reduce the fail active rate, if you can move it from 1E-5 to 1E-9 you are good from a purely regulatory point of view
  • Increase the ability of flight crews to counter the failure mode
This is what Boeing is proposing to do with MCAS 2.0. They will then need to ask another question.
  • As MCAS will now be a duplex system will the increase in system unavailability lead to other unacceptable conditions happening too often?
If the answer to that is no, then you should be fine, if the answer is yes, then some form of triplex or psuedo-triplex system would be required

It seems that Boeing has finally acknowledged that simulator training will be required for the NG to MAX conversion. There are a number of reasons why this is likely to be the case. However, they will most likely centre around the behaviour on MCAS failure
  • Since the MCAS system is now likely to be unavailable 2E-5 per flight hour, the reactions of the pilots need to be considered to ensure that a fail passive does not enter the Major or Hazardous realm
  • Pilots reactions to the fail-active condition need to be improved

The potentially good thing for Boeing is that the failure modes are unique to MAX and in addition to the ones shared with the NG, eg both still have the same speed-trim runaway. Further, the actions countering a failure on the MAX would also counter similar conditions on an NG. This makes the training simpler as you can actually just work it into the reoccurring training regime for NG pilots prior to MAX delivery.

PS I still think Boeing would be well served to change the stab trim cutout switches back to one controls auto-trim and the other manual electronic trim. This allows the flight crew to use electric trim in many of the failure modes above, reducing workload.
 
phollingsworth
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 11:59 am

beaconinbound wrote:
phollingsworth wrote:
United787 wrote:

This is an oversimplification but: those engines on those wings on that fuselage. There are hundreds of other posts that go into more detail but that is the inherent flaw. Boeing's 1st mistake, of many, was not doing a clean sheet design. Their 2nd mistake was not doing a clean sheet design...



This, exactly!


There is nothing particular about those engines, those wings, or that fuselage in isolation that is at all an issue, or any more than any other airliner out there. A clean sheet design would have very similar engines, wings, and fuselage. The issue, and it is an issue with all modern airliners, is the interaction between the engines and wings. The fact is a clean sheet design would not eliminate either of the two aerodynamic issues displayed by the MAX, ie the shift in effective aerodynamic centre at high AoA and stall identification. I am not privy to Boeing's technology curve and arsenal, but it is entirely reasonable to expect that even a 'clean-sheet' design would have exactly the same aerodynamic 'flaws' as the sweet spot might involve the same nacelle-wing interactions. The one thing a 'clean-sheet' would do is weaken the desire to minimise differences with the current fleet. You could make a new aircraft that flies like a 737NG, but given you will have changed all the failure modes substantially why would you do it. Of course once you break the commonality on the pilot and MTC side, there isn't any specific advantage for a WN to stick with Boeing.

As for walking away from the MAX now and making NGs. That really isn't practical and would probably cost a lot more than $40 billion. Boeing would have to compensate the airlines on fuel cost for the next 20-30 years.


Oh man, have you ever seen CFD results - let alone results of wind tunnel testing - of any existing modern aircraft? I can tell you, "complex" is an underestimation in that context. A clean sheet design could well address these issues. Another hint: A few inches can make a huge difference in aerodynamics...


I have, you are spot on the "complex". Changing a couple of inches could well address the issues or it might not. It is very hard to know what the behaviour will be for a yet uncontemplated design. The fact is that there is nothing particularly odd about the aerodynamics of the MAX, but it is very hard to know exactly where they lie until you do a lot of testing, so stating with high confidence that a clean-sheet will fix it is a risky proposition.
 
beaconinbound
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 12:40 pm

phollingsworth wrote:

I have, you are spot on the "complex". Changing a couple of inches could well address the issues or it might not. It is very hard to know what the behaviour will be for a yet uncontemplated design. The fact is that there is nothing particularly odd about the aerodynamics of the MAX, but it is very hard to know exactly where they lie until you do a lot of testing, so stating with high confidence that a clean-sheet will fix it is a risky proposition.


Fully agreed. My guess - and thats only a guess because I have not seen anything regarding aerodynamical layout on the MAX - is a violation of the area rule due to the dimensions of the Leaps. That would explain FAAs "unacceptable" as there would be very complex pressure effects between nacelles, fuselage and wing including shifts of GC in an unexpected way. My take has always been that the mere additional upward lift is just a contribution in a more complex situation.
 
uta999
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 12:49 pm

Plan B, back in March last year should have been; Come up with an A320 type long landing gear, and re-position the engines back under the wing. It would likely take much the same time to certify. MCAS would not be needed and it would behave in a normal way in turns.

Ironically, the 787 also has some very short legs, limiting its length and engine choice in the future.
Your computer just got better
 
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SomebodyInTLS
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 12:51 pm

phollingsworth wrote:
The fact is a clean sheet design would not eliminate either of the two aerodynamic issues displayed by the MAX, ie the shift in effective aerodynamic centre at high AoA and stall identification. I am not privy to Boeing's technology curve and arsenal, but it is entirely reasonable to expect that even a 'clean-sheet' design would have exactly the same aerodynamic 'flaws' as the sweet spot might involve the same nacelle-wing interactions.


This entire debacle is down to the short gear preventing Boeing from mounting the engines in a more typical location under the wings.

Even then, the engine fan had to be smaller than that fitted on the A320NEO since the short gear doesn't leave enough runway clearance.

This is *ALL* down to specific MAX issues and none of this would affect a clean sheet design to the same extent.
"As with most things related to aircraft design, it's all about the trade-offs and much more nuanced than A.net likes to make out."
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 12:54 pm

2175301 wrote:
frmrCapCadet wrote:
Another reliable poster suggested that simulator training may be related to issues other than just MCAS. He (and his sources) would not go further. But one could suspect the changes in the computer and something to do with the 3 second discussions. Again he did not say, but Roll difficulties may also be involved. All of this may also relate to my observation that when political winds were favorable, Boeing was often given the benefit of doubt on some issues. No more!


That might have been me; and the post itself was deleted as it was in the "news" thread.

It is my understanding that MCAS V2 is a fairly simple software change (a dozen or two lines of code); and if that was all that was needed that Boeing felt that there would be no need for simulator training.

...

Have a great day,

As a computer scientist myself, that's not surprising. I was listing examples of how you can detect AoA disagreement in another thread, and there are really only 8 cases to test for. All you need is the historical sensor data of the flight and the code comparing that data, the trends in it, and the latest inputs can be written by a novice.

Really what will take time is the new computer designs and the rewiring, especially if the EASA forces the issue on using 3 AoA sensors' input instead of 2 (which would be ridiculous).
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:01 pm

SomebodyInTLS wrote:
phollingsworth wrote:
The fact is a clean sheet design would not eliminate either of the two aerodynamic issues displayed by the MAX, ie the shift in effective aerodynamic centre at high AoA and stall identification. I am not privy to Boeing's technology curve and arsenal, but it is entirely reasonable to expect that even a 'clean-sheet' design would have exactly the same aerodynamic 'flaws' as the sweet spot might involve the same nacelle-wing interactions.


This entire debacle is down to the short gear preventing Boeing from mounting the engines in a more typical location under the wings.

Even then, the engine fan had to be smaller than that fitted on the A320NEO since the short gear doesn't leave enough runway clearance.

This is *ALL* down to specific MAX issues and none of this would affect a clean sheet design to the same extent.

Even so, some of the regulations around requiring slides in the over-wing exit doors after the wing is more than 7 feet off the ground (or however much it is) are draconian. If you're able-bodied enough to fly, you can hang off the wing by your hands/arms and safely drop a full body length without breaking any bones.
 
patrickjp93
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:05 pm

uta999 wrote:
Plan B, back in March last year should have been; Come up with an A320 type long landing gear, and re-position the engines back under the wing. It would likely take much the same time to certify. MCAS would not be needed and it would behave in a normal way in turns.

Ironically, the 787 also has some very short legs, limiting its length and engine choice in the future.

The 787 isn't trying to be shoe-horned into a grandfathered regulation where slides on over-wing exit doors aren't required. The 787 NG can get longer landing gear easily enough if needed.
 
Exeiowa
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:08 pm

patrickjp93 wrote:
SomebodyInTLS wrote:
phollingsworth wrote:
The fact is a clean sheet design would not eliminate either of the two aerodynamic issues displayed by the MAX, ie the shift in effective aerodynamic centre at high AoA and stall identification. I am not privy to Boeing's technology curve and arsenal, but it is entirely reasonable to expect that even a 'clean-sheet' design would have exactly the same aerodynamic 'flaws' as the sweet spot might involve the same nacelle-wing interactions.


This entire debacle is down to the short gear preventing Boeing from mounting the engines in a more typical location under the wings.

Even then, the engine fan had to be smaller than that fitted on the A320NEO since the short gear doesn't leave enough runway clearance.

This is *ALL* down to specific MAX issues and none of this would affect a clean sheet design to the same extent.

Even so, some of the regulations around requiring slides in the over-wing exit doors after the wing is more than 7 feet off the ground (or however much it is) are draconian. If you're able-bodied enough to fly, you can hang off the wing by your hands/arms and safely drop a full body length without breaking any bones.


I would love to see that in an evacuation exercise and if the time requirements will be met or trying it while a plane is on fire and there is pushing and panic.
 
Boeingphan
Posts: 231
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Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:15 pm

SomebodyInTLS wrote:
phollingsworth wrote:
The fact is a clean sheet design would not eliminate either of the two aerodynamic issues displayed by the MAX, ie the shift in effective aerodynamic centre at high AoA and stall identification. I am not privy to Boeing's technology curve and arsenal, but it is entirely reasonable to expect that even a 'clean-sheet' design would have exactly the same aerodynamic 'flaws' as the sweet spot might involve the same nacelle-wing interactions.


This entire debacle is down to the short gear preventing Boeing from mounting the engines in a more typical location under the wings.

Even then, the engine fan had to be smaller than that fitted on the A320NEO since the short gear doesn't leave enough runway clearance.

This is *ALL* down to specific MAX issues and none of this would affect a clean sheet design to the same extent.



The good news is Boeing learned their lesson with the landing gear issue, and promptly configured the 787 trio with a short gear so when it's time to re engine that they will find themselves in the same predicament. Last time I looked fans aren't getting smaller. It's a clown show right now at Boeing and it's hard to watch.
 
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PixelFlight
Posts: 1018
Joined: Thu Nov 08, 2018 11:09 pm

Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:28 pm

patrickjp93 wrote:
As a computer scientist myself, that's not surprising. I was listing examples of how you can detect AoA disagreement in another thread, and there are really only 8 cases to test for. All you need is the historical sensor data of the flight and the code comparing that data, the trends in it, and the latest inputs can be written by a novice.

Really what will take time is the new computer designs and the rewiring, especially if the EASA forces the issue on using 3 AoA sensors' input instead of 2 (which would be ridiculous).

2 AoA sensors are ok only if the function can be disabled while maintaining safety. If the function have still to work with a disagreement between 2 AoA sensors, then 3 AoA sensors will be required, but that one could eventually be a synthetic one. By the way the A350 has no less than 4 AoA sensors.
Last edited by PixelFlight on Mon Jan 13, 2020 1:34 pm, edited 5 times in total.
:stirthepot: 737-8 MAX: "For all speeds higher than 220 Kts and trim set at a value of 2.5 units, the difficulity level of turning the manual trim wheel was level A (trim wheel not movable)." :stirthepot:
 
patrickjp93
Posts: 648
Joined: Thu Aug 22, 2019 12:00 pm

Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:30 pm

Boeingphan wrote:
SomebodyInTLS wrote:
phollingsworth wrote:
The fact is a clean sheet design would not eliminate either of the two aerodynamic issues displayed by the MAX, ie the shift in effective aerodynamic centre at high AoA and stall identification. I am not privy to Boeing's technology curve and arsenal, but it is entirely reasonable to expect that even a 'clean-sheet' design would have exactly the same aerodynamic 'flaws' as the sweet spot might involve the same nacelle-wing interactions.


This entire debacle is down to the short gear preventing Boeing from mounting the engines in a more typical location under the wings.

Even then, the engine fan had to be smaller than that fitted on the A320NEO since the short gear doesn't leave enough runway clearance.

This is *ALL* down to specific MAX issues and none of this would affect a clean sheet design to the same extent.



The good news is Boeing learned their lesson with the landing gear issue, and promptly configured the 787 trio with a short gear so when it's time to re engine that they will find themselves in the same predicament. Last time I looked fans aren't getting smaller. It's a clown show right now at Boeing and it's hard to watch.

As I said above, the 787 isn't trying to meet a grandfathering rule to avoid having slides in the over-wing exits, so when the 787 NG comes along, the landing gear can be extended without issue. Having as short a gear as possible saves in OEW/gives more allowance to fuel/cargo toward MTOW, small allowance as it is.
 
patrickjp93
Posts: 648
Joined: Thu Aug 22, 2019 12:00 pm

Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:32 pm

PixelFlight wrote:
patrickjp93 wrote:
As a computer scientist myself, that's not surprising. I was listing examples of how you can detect AoA disagreement in another thread, and there are really only 8 cases to test for. All you need is the historical sensor data of the flight and the code comparing that data, the trends in it, and the latest inputs can be written by a novice.

Really what will take time is the new computer designs and the rewiring, especially if the EASA forces the issue on using 3 AoA sensors' input instead of 2 (which would be ridiculous).

2 AoA sensors are ok only if the function can be disabled while maintaining safety. If the function have to still work with a failed AoA sensor, 3 AoA sensors will be required, but that one could eventually be a synthetic one.

Incorrect. If an AoA fails and is detected as such, the system can easily run off the working one. If THAT one then fails, MCAS can simply be disabled outright, either automatically or manually. So requiring 3 simultaneous inputs is simply ridiculous when not a single aircraft in the sky today uses 3 for any FBW system.

And given the maximum flight time of the MAX 8 is roughly 8 hours with the diversion allowance included, the chance of both sensors failing mid-flight through the given e-5 per flight hour probability is still well under the tolerable threshold.
Last edited by patrickjp93 on Mon Jan 13, 2020 1:34 pm, edited 1 time in total.
 
morrisond
Posts: 2664
Joined: Thu Jan 07, 2010 12:22 am

Re: Boeing 737MAX Grounding, General Discussion Thread, January 2020

Mon Jan 13, 2020 1:33 pm

flipdewaf wrote:
morrisond wrote:
I have flown an 172 in Turbulence where the controls go negative - it's not that hard to counter and all training tells you to not rely on feel - rely on your instruments and outside visual reference.

(bold added by me)

You are misconstruing the information that is given on training (I, like many others, have had that training). The not relying on 'Feel' and using the instruments only really refers to acceleration and refers to not being able to judge the aircraft attitude and where you shouldn't rely on the seat of your pants and instead use the attitude indicator(s).

The feel as it is referred to by the control force piece is an absolutely vital piece and should be done by feel as human force based proprioception is hugely more accurate and repeatable than displacement based proprioception plus the fact that force/g varies much less than the displacement/g over the speed envelope. This suggests that if you are adding the human in to the open control loop (to close the loop) you want to use reasonable measures of force/g (and its associated derivatives), one DOES NOT rely on instruments for this This is why the regulation exists.....

BTW, I got trained in this piece too....

Your sour grapes smell like Bovine excrement on the way back out.

morrisond wrote:
It takes probably a good 15-20 seconds on an 737 beyond the point where the controls get a little light to get into an actual stall
Cool story, how do you know? sounds a lot like wishful thinking but I'm happy to change my mind when I see evidence...

Fred


And when outside visual reference is not available - how is relying just on feel going to work out for you?

Yes - it's not ideal - and by reports 737 controls don't go negative force - but a slight lightening - plus you have the stick shaker (who can feel the control force with the stick shaker going off anyways) audio alarms, frame buffeting and STS trimming down (I think it's STS on the NG - this is from memory) as well.

Here is the Video of stalls on the NG - the MAX may be different and that is hopefully what the EASA test flights will show.

https://www.youtube.com/watch?v=zCJco59tqoQ

BTW - how much Force Feedback do FBW systems have?

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