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NYT: How Boeing’s Responsibility in a Deadly Crash ‘Got Buried’

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NYT: How Boeing’s Responsibility in a Deadly Crash ‘Got Buried’

Old 24th Jan 2020, 15:53
  #101 (permalink)  
 
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Originally Posted by retired guy View Post
In respect of ungrounding the airplane Boeing remains in the hands of the FAA just as it also does internationally with other global regulators that have followed suit in grounding the airplane.
But that isn't right is it? It was the FAA who "followed suit" in grounding the airplane, after CAAC and EASA and others did so, and after FAA had just said that "Thus far, our review shows no systemic performance issues and provides no basis to order grounding the aircraft".

One might suppose that since the FAA was reluctant to follow the other regulators in grounding the aircraft, the others may also be slower in allowing it to fly again.
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Old 24th Jan 2020, 17:09
  #102 (permalink)  
 
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Originally Posted by Semreh View Post
@MechEngr



Does that mean continuous functions have no meaning?

If you can understand the concept of an expected duration of a process, you can talk meaningfully about the process being continuous if it is not interrupted within the expected duration, or continual if it is interrupted a number of times within the expected duration. If we talk about a 'runaway stabiliser', it would be expected to continue until it reached the end-stops unless a manual cut-out is performed. If a stabiliser movement ceases without manual input, then restarts without manual input later, one can talk about an interruption. If the stabiliser moves in a particular direction, stops, then continues to move again several times, then it is moving continually.

Obviously, but unhelpfully, in the limit, when time goes towards infinity, all processes can be expected to terminate at some point, so yes, in the perspective of unlimited time, no process is continuous. If you limit, or focus your view on a finite subset of time, then a process can be said to be continuous over that segment if there are no discontinuities/interruptions.

I hope that clarifies things sufficiently for you.
The trigger for MCAS to resume is that a pilot made a trim input. Otherwise it was a one-shot. So it only restarted in response to manual input. And it moved continuously over that finite subset interval of time. It did not change speed or direction.

Awaiting a CVR transcript where the pilots are discussing continuous vs continual and that because it was continual, that the 60+ pounds of force required to hold the nose up required no trim to offset it.
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Old 24th Jan 2020, 17:46
  #103 (permalink)  
 
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The trigger for MCAS to resume is that a pilot made a trim input. Otherwise it was a one-shot. So it only restarted in response to manual input. And it moved continuously over that finite subset interval of time. It did not change speed or direction.
So you agree that MCAS is not continuous, and therefore it is entirely reasonable not to characterise its operation as continuous/runaway, so not applying the runaway stabiliser QRH procedure is a reasonable (non) response?

The Runaway Stabiliser QRH characterises 'Runaway Stabiliser' as:

"Condition: Uncommanded stabilizer trim movement occurs continuously."

MCAS can be 'one-shot' or continual, interrupted by Stab Trim operations, and operating again if the MCAS trigger conditions still apply 5 seconds later. It is not, as you point out, continuous, which is enough to put doubt into the mind of a cognitively overloaded pilot whether the Runaway Stab QRH is appropriate.

It doesn't help that STS operates by executing uncommanded stabiliser movements, so pilots regard that as normal operations. Seeing and hearing the trim wheels move is normal flight deck background, which is part of the reason why MCAS was so insidious.
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Old 24th Jan 2020, 19:21
  #104 (permalink)  
 
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Originally Posted by RetiredBA/BY View Post
... the teaching was that if the trim wheel was rotating and not because of manual trim inputs or autopilot trimming, then you had a trim runaway and the IMMEDIATE, RECALL, action was stab trim switches to OFF.
So, think back to that first takeoff you made in the -300. I assume you made AND trim inputs as you accelerated, because that would be normal. Likewise, I assume that the STS made ANU trim inputs, as it was designed to do, as the aircraft accelerated. And since those inputs were not manual, by you, nor were they made by the autopilot, because it was not engaged, you, that very first time the STS made a trim input, uncommanded by either you or the autopilot, did an IMMEDIATE RECALL action, and cut the stab trim switches to OFF. Please tell me that is so.

Last edited by Takwis; 24th Jan 2020 at 19:39.
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Old 24th Jan 2020, 19:30
  #105 (permalink)  
 
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Originally Posted by Semreh View Post
It doesn't help that STS operates by executing uncommanded stabiliser movements, so pilots regard that as normal operations. Seeing and hearing the trim wheels move is normal flight deck background, which is part of the reason why MCAS was so insidious.
This fact has been ignored for too long.

737 pilots have been trained, by constant repetition, to ignore relatively short, uncommanded (by either the pilot or the autopilot) trim inputs.
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Old 24th Jan 2020, 19:37
  #106 (permalink)  
 
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Originally Posted by Semreh View Post
So you agree that MCAS is not continuous, and therefore it is entirely reasonable not to characterise its operation as continuous/runaway, so not applying the runaway stabiliser QRH procedure is a reasonable (non) response?

The Runaway Stabiliser QRH characterises 'Runaway Stabiliser' as:

"Condition: Uncommanded stabilizer trim movement occurs continuously."

MCAS can be 'one-shot' or continual, interrupted by Stab Trim operations, and operating again if the MCAS trigger conditions still apply 5 seconds later. It is not, as you point out, continuous, which is enough to put doubt into the mind of a cognitively overloaded pilot whether the Runaway Stab QRH is appropriate.

It doesn't help that STS operates by executing uncommanded stabiliser movements, so pilots regard that as normal operations. Seeing and hearing the trim wheels move is normal flight deck background, which is part of the reason why MCAS was so insidious.
Does STS require 60 pounds on the control wheel to maintain the desired pitch? I'm confused why you think that STS performance has anything to do with this. Some pilots have commented that they have to unwind some STS inputs via the trim switches; why would they not do the same for MCAS?

At what point should a pilot refuse to make trim inputs while pulling 60 pounds on the wheel when trim is available to them? After how many uncommanded adverse trim inputs should a pilot assume that the trim system has failed?

OTOH MCAS operated continuously long enough that when it was not offset the plane crashed. You would not close your eyes for a full 9 seconds driving on a crowded highway, so pick the amount of time the pilots should ignore an adverse trim increasing the control forces.

I have previously recommended that it change from trim blah-blah-blah to adverse trim forces, but I would have assumed that most pilots would know to trim the plane against high control loads. It turns out that it is a bad assumption and that training allows for pilots who try to overcome such forces with their own musculature.

As you want to be a language pedant you are welcome to it.
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Old 24th Jan 2020, 19:47
  #107 (permalink)  
 
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Originally Posted by MechEngr View Post
After how many uncommanded adverse trim inputs should a pilot assume that the trim system has failed?
Lets see...lets say an average of three per takeoff, and I've done maybe 5000 takeoffs, and watched another 5000, I guess that would mean at least 30,000, in my case. YMMV

As for the wheel trim, the Ethiopian crew tried it, and stated that it didn't work. We still don't know why.
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Old 24th Jan 2020, 20:02
  #108 (permalink)  
 
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Originally Posted by Takwis View Post
Lets see...lets say an average of three per takeoff, and I've done maybe 5000 takeoffs, and watched another 5000, I guess that would mean at least 30,000, in my case. YMMV

As for the wheel trim, the Ethiopian crew tried it, and stated that it didn't work. We still don't know why.
Could be because they let the speed build up so much by not reducing power.
Perhaps they pulled the levers back without disconnecting AT , took their hands off the TLs to pull back on the yoke, but thrust levers then moved back to TOGA because AT was still connected.
Just a theory.
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Old 24th Jan 2020, 20:03
  #109 (permalink)  
 
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Originally Posted by alf5071h View Post
Dr Dekker; please publish similar reports on 737 Max, 777 SFO, AF447, CRJ Sweden.
Who is paying?
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Old 24th Jan 2020, 20:12
  #110 (permalink)  
 
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MechEngr
Thank you for the discussion, which I am sure will be of interest to others, even if we continue to cordially disagree.

I hope you have a good weekend.
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Old 24th Jan 2020, 20:56
  #111 (permalink)  
 
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This is drifting way off-topic. This thread is supposed to be about alleged whitewashing of Boeing's share of responsibility in the cited 2009 AMS crash.

Also, we're in the deja-vu-all-over-again realm where some folks simply insist that the MAX crashes were substantially due to pilot error. It's fine for those who want to believe that to do so, of course -- everyone is entitled to her or his own opinion. However, it should be recognized that virtually everyone and every entity responsible for aircraft certification, around the world, has agreed for nearly a year that the MAX, as it was introduced and initially flown, had engineering/design defects sufficiently serious to justify its grounding, for many months. And grounded is where it is now. The blame-the-pilots narrative has been overwhelmingly rejected.
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Old 24th Jan 2020, 21:06
  #112 (permalink)  
 
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That narrative is still in place from the manufacturer, hopeful operators, and most of their pilots. It has been rejected here, but I don't know if that counts for much.
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Old 24th Jan 2020, 21:47
  #113 (permalink)  
 
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Originally Posted by Takwis View Post
That narrative is still in place from the manufacturer, hopeful operators, and most of their pilots. It has been rejected here, but I don't know if that counts for much.
It has been rejected by the world's CAAs (including, apparently reluctantly, by the FAA). That counts.
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Old 24th Jan 2020, 22:12
  #114 (permalink)  
 
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Originally Posted by OldnGrounded View Post
That counts.
It does. The recent governmental panel shook my faith in that, unfortunately. I could see pressure, threats of economic downturn, loss of a major manufacturer, jobs, suppliers, etc. further eroding my faith in the regulatory bodies. I could also see a "fill the squares" sort of solution getting the plane back into service more quickly than a completely satisfying one. We'll see, I guess.
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Old 24th Jan 2020, 23:42
  #115 (permalink)  
 
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Originally Posted by Takwis View Post
Lets see...lets say an average of three per takeoff, and I've done maybe 5000 takeoffs, and watched another 5000, I guess that would mean at least 30,000, in my case. YMMV

As for the wheel trim, the Ethiopian crew tried it, and stated that it didn't work. We still don't know why.
Sorry, I should have emphasized how many trim events added 30 pounds of pull for each one in quick succession on a single flight.

But if you feel STS is adverse and compromising your ability to control the plane, perhaps you should write that up.
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Old 25th Jan 2020, 00:12
  #116 (permalink)  
 
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Originally Posted by OldnGrounded View Post
This is drifting way off-topic. This thread is supposed to be about alleged whitewashing of Boeing's share of responsibility in the cited 2009 AMS crash.

Also, we're in the deja-vu-all-over-again realm where some folks simply insist that the MAX crashes were substantially due to pilot error. It's fine for those who want to believe that to do so, of course -- everyone is entitled to her or his own opinion. However, it should be recognized that virtually everyone and every entity responsible for aircraft certification, around the world, has agreed for nearly a year that the MAX, as it was introduced and initially flown, had engineering/design defects sufficiently serious to justify its grounding, for many months. And grounded is where it is now. The blame-the-pilots narrative has been overwhelmingly rejected.
You will note that I've started the blame for the pilot side with the airline, the relevant CAA, and finally with the pilots who rejected training for the Ethiopian crash. I just remain puzzled and saddened that in the case of Lion Air, one pilot repeatedly responded to adverse trim by eliminating the trim problem and keeping the plane on speed and altitude while the other pilot seems to have been transfixed with the idea that making the ever increasing amount of trim stop was sufficient. As if he didn't notice the trim position was changing and instead just wanted to keep the trim wheel from moving all while the control loads were going up.

As to whitewashing, that is a bad thing. OTOH airlines failing to perform due diligence is also a bad thing. They had access to all 737 accident reports and could certainly quiz the maker about their approach to avoiding similar accidents.

So why did the Dutch Safety board give in? They are independent of the FAA and the US NTSB and not obligated to Boeing. In no way does the NY Times article explain how the Dekker report got buried.

The human factors concept for alerting pilots or training them, in this case, is flawed. Had either system gone with dual sensors or some other scheme to prevent an adverse result there would have been zero benefit to a distracting alert of the pilots to the discrepancy and therefore no human factor to be considered. It's far better to avoid involving humans in performance decisions. This appears to be what Boeing's software changes did and there were no more RA failure related crashes. LIke MCAS, the manufacturer problem isn't failing to train or alert pilots, it's not recognizing the potential combination leading to a bad outcome.

Let's face it - there are human factors engineers at Boeing. Bunches of them. Yet not a peep from them complaining that MCAS ran on a single sensor and that pilots would certainly crash the plane if that sensor misreported. At least so far - maybe there are more emails, but my experience with human factors engineers is they are outspoken on all sorts of things.

What it really was was a failure of Systems Architects, a relatively new and somewhat toxic addition to engineering. This bunch of hand wavers sit between management and promises made to customers and the actual engineers and are responsible for creating the performance specifications for the hardware and software. Which is exactly where flawed software like MCAS gets born. The good SAs are great - Kelly Johnson of the Skunk Works was one. Anyone living in PowerPoint land? View with great skepticism.
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Old 25th Jan 2020, 01:52
  #117 (permalink)  
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Some pilots have commented that they have to unwind some STS inputs via the trim switches; why would they not do the same for MCAS?
The call, "It's like STS is working in reverse!" is a clue. They noticed it was an anomaly but that's the point, the knowledge it was wrong left them bewildered.
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Old 25th Jan 2020, 08:11
  #118 (permalink)  
 
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Originally Posted by Takwis View Post
Got an answer for this one, RetiredBA/BY?
No I dont.

Perhaps I have an early onset of something but I have no memory of a STS on our very early -300s, which even had round instruments, and absolutely no memory of anything about it in the sim. Mach trim yes STS no. This worries me a little as the technicalities of my aircraft of all types were always of deep interest. No recall of ever seeing uncommanded trim movement, either.

Our - 300 “course”. Was very simple really just the FMS and autopilot operation, the rest we pretty much made up in the belief -300 airframe was pretty much as a - 200 with some tweaks.

My FO on my first -300 trip is coming on Friday, I will discuss his knowledge of the STS.

Just looked at my Boeing training notes. Runaway stab was practised on 7 sorties, manual trim operation alone on 2 and no discussion or even mention of the Yo Yo procedure, never heard of it on my time on the 73.

Intersting to see my ppl now shows my former types include all 737s up upto 900, never even sat in one !
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Old 25th Jan 2020, 09:34
  #119 (permalink)  
 
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Originally Posted by RetiredBA/BY View Post
No I dont.

Perhaps I have an early onset of something but I have no memory of a STS on our very early -300s, which even had round instruments, and absolutely no memory of anything about it in the sim. Mach trim yes STS no. This worries me a little as the technicalities of my aircraft of all types were always of deep interest. No recall of ever seeing uncommanded trim movement, either.

Our - 300 “course”. Was very simple really just the FMS and autopilot operation, the rest we pretty much made up in the belief -300 airframe was pretty much as a - 200 with some tweaks.

My FO on my first -300 trip is coming on Friday, I will discuss his knowledge of the STS.

Just looked at my Boeing training notes. Runaway stab was practised on 7 sorties, manual trim operation alone on 2 and no discussion or even mention of the Yo Yo procedure, never heard of it on my time on the 73.

Intersting to see my ppl now shows my former types include all 737s up upto 900, never even sat in one !
No guarantee of accuracy, but see https://aviation.stackexchange.com/q...the-boeing-737

>Was the Speed Trim System implemented on the original Boeing 737 or just the Boeing 737 NG series?

Boeing's patent (US4676460A) for the STS was filed on 1984-11-28, the same day of the 737 Classic (3/4/500 series) entering service.

So since the addition of the bigger engines on the Classic, it's been there.

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Old 25th Jan 2020, 10:15
  #120 (permalink)  
 
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Originally Posted by MechEngr View Post
What it really was was a failure of Systems Architects, a relatively new and somewhat toxic addition to engineering. This bunch of hand wavers sit between management and promises made to customers and the actual engineers and are responsible for creating the performance specifications for the hardware and software. Which is exactly where flawed software like MCAS gets born. The good SAs are great - Kelly Johnson of the Skunk Works was one. Anyone living in PowerPoint land? View with great skepticism.
As a long-time systems guy, I certainly won't argue with that. In recent years, those slots have increasingly been filled by people who are better at impressing the suits than they are at real engineering -- and whose mission in life is to find easy jobs. But the good ones are invaluable.

There are, of course, HF people at Boeing, as there are at other aircraft manufacturers. There's a lot of evidence, however, that the products, in the end, often don't reflect the best current understanding of the discipline. If I design a system with the expectation that operators will act and react in particular ways, within some stated time frames, and that doesn't happen in the real world, it's not only the behavior of the operators that needs careful examination.
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