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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

Old 12th Jul 2019, 08:47
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Originally Posted by john_tullamarine
I am sure that, at day's end, the company, the regulators, and so forth, will sort the problems out and the aircraft will go on to greater things.
I'm not sure yet I find it very probable that given the way things are (or not) developing, the only great thing Max is destined for is "beyond".
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Old 12th Jul 2019, 09:20
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Originally Posted by DIBO
Boeing leader at Renton 737 MAX plant retires
https://www.seattletimes.com/busines...plant-retires/
Interesting article, but nobody (that I know of) is questioning the manufacturing of the B737 MAX. The design is a different story, and done by another team of people...



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Old 12th Jul 2019, 09:45
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Originally Posted by GordonR_Cape
The design is a different story, and done by another team of people...
Precisely.
...People who do not retire, resign, get fired, admit any wrong doing...

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Old 12th Jul 2019, 10:46
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Originally Posted by gums
Somehow the Airbus 320 and following are certified and those suckers have zero feel as the plane approaches a high AoA or low AoA or any damned AoA. The sticks provide no feedback to the pilot WRT control surface deflection or aero forces, nor any trim requirement if speed is changed, nor ........ "there must be fifty ways"

So my main question is why did FAA squawk about the column force? I have not seen a technical description of a commercial airliner built after 1950 that did not have some kinda "artificial feel" add-on to the ropes, levers, pulleys and tubes. Prolly 99% of every military "light" since 1950 had zero direct mechanical feedback from the control surfaces.

So how did the latest bus get certified, but the 737 had to add the MCAS?
All (civilian) fbw a/c with neutral stability control laws (C*) are certified under special conditions starting with A320 (actually arguably with Concorde but that was such a different beast it must have been all special conditions), those SCs, or at least the rationale, have more or less carried over since then (all later buses and other makers too now). I think even today (30+ yrs after A320 and much longer after the birds you flew) fbw is still referred to as "novel or unusual design feature" in certification The rationale is that the control force cues for heading towards the edge of the envelope are not required if the edge of envelope is protected by hard limits / fences instead (similarly MCAS is not needed on autopilot because the autopilot is fenced/limited). Pretty sure this was well covered on the 447 threads, mind you so was everything...

Boeing took a different approach with 777/787, inventing C*U and providing a completely artificial feel on conventional controls, which I think allows them to meet the normal control force / stability reqs of part 25 without special conditions.

All these approaches fail in some way when stuff breaks and the a/c doesn't know (accurately) where it is in the envelope, AF477 ended up in a C* law without protection, C*U will inevitably reduce to C* if U is unknown (or deemed unreliable). There is a general principle (which turns into a requirement somewhere in the regs. I think) that any degradation of handling qualities must be inversely related to probability of occurrence and seriousness of failure consequences - that is the bit of the design and approvals process that MCAS seems to have got fatally wrong.
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Old 12th Jul 2019, 15:23
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Here's an interesting new line.

https://www.forbes.com/sites/lorenth.../#1e2f1d3b521b

Thompson is a reliable supporter of his clients, and one may assume that he doesn't write a word without consulting with them. But what's the message here? That the FAA needs to get on with return-to-flight, and lean on the naysaying foreigners? And what "orgy of negative reporting"? I believe that even here, where journalists are seldom the flavor of the month, the work by Dominic Gates and by the WSJ team has been well regarded.

Is the message, then, that this is too important to be left to the engineering nerds?
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Old 12th Jul 2019, 15:58
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The main message from that article is that Boeing is too big to fail. And that Boeing failing would be a disaster for the US, so the lawmakers and the press should cut them some slack to prevent that. They also implied that Boeing doesn't "deserve" to fail, because Airbus became successful due to "illegal subsidies".
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Old 12th Jul 2019, 16:24
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An interesting if slightly biased overview of the issues.
‘… this is too important to be left to the engineering nerds?‘ I Disagree.

The technicalities identified so far cannot be overcome by political will, financial management, etc. They are real-world aviation safety problems which relate to agreed and published standards - Federal Register, ICAO.
In addition, they have to be considered globally, not just something in the US interest, but that US interest now depends on multinational consensus.

A further difficulty is that some technical issues hinge on judgement - the human contribution in detecting and managing abnormal conditions. This is not a national judgement, but that of a range of authorities and particularly cultures - safety culture.

Whereas historically Boeing was the dominant culture in aviation, this is no longer true.
Is the article a lament, attempting to restore what once was, or the realisation that the aviation industry has changed and requires national activity to restore confidence an profitability.
Maybe, but you cannot buy safety (or even tweet it), it’s an activity, that which is done; for that you require domain expertise, but if this is overlooked then … …

https://www.dropbox.com/s/7425e8yykg...20%2B.pdf?dl=0
Dominant Culture 2003
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Old 12th Jul 2019, 16:29
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'...........the penultimate flight crew did not log use of stab trim cutouts or the continuous stick shaker........."

Now THAT is something that I find completely incomprehensible.

"Hi darling. Careful with the car when you next go shopping. It pulls really hard to the left when you brake. Almost hit a semi on the highway. What's for supper?"

Mac

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Old 12th Jul 2019, 17:22
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Originally Posted by Mac the Knife
'...........the penultimate flight crew did not log use of stab trim cutouts or the continuous stick shaker........."

Now THAT is something that I find completely incomprehensible.

"Hi darling. Careful with the car when you next go shopping. It pulls really hard to the left when you brake. Almost hit a semi on the highway. What's for supper?"

Mac
In hindsight completely unacceptable but let me toss out something that might make it seem less crazy. Keep in mind this is the first time anyone has seen this malfunction, no one knows what MCAS is and certainly no one thinks this aircraft is going to crash the next day. I dont know what actual checklinsts these guys might have done, but neither the unreliable airspeed or runaway trim checklists have the phrase "Land at nearest suitable airport" like engine fire/failure. If Indonesian is one of those airlines where a pilot doesn't think he is allowed to sneeze unless he's got a written procedure to do so then the Captain may have felt pressured to continue to destination since nothing is telling him to land. So he lands but has second thoughts and doesn't want to confess on paper that he may have done something rather unwise so he maybe briefs the mechanic on the side but doesnt put anything incriminating in the logbook. I'd like to say this sort of thing doesn't happen but it does. Poor guy was probably just trying to get the passengers where they wanted to go and thought the maintenance folks would figure it out. Hindsight is always 20/20 and sometimes 20/10.
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Old 12th Jul 2019, 17:31
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Originally Posted by Mac the Knife
'...........the penultimate flight crew did not log use of stab trim cutouts or the continuous stick shaker........."

Now THAT is something that I find completely incomprehensible.

Mac
This has been bugging me for a while - how do we know that the shaker was on all flight?
Do we have a trace or could the CB have been pulled (3 Pilots - big book etc)?
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Old 12th Jul 2019, 17:39
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Originally Posted by bill fly


This has been bugging me for a while - how do we know that the shaker was on all flight?
Do we have a trace or could the CB have been pulled (3 Pilots - big book etc)?
Accident report says stick shaker was on for remainder of flight after trim was cutout. There is not actual procedure to pull the CB plus general policy not to pull CB unless part of a procedure, so unless pilot wanted to freelance he may have been more comfortable leaving it be than explaining to his superiors why he violated company policy.
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Old 12th Jul 2019, 17:43
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Originally Posted by Tomaski
Accident report says stick shaker was on for remainder of flight after trim was cutout. There is not actual procedure to pull the CB plus general policy not to pull CB unless part of a procedure, so unless pilot wanted to freelance he may have been more comfortable leaving it be than explaining to his superiors why he violated company policy.
Well since he didn’t report that either, he may as well have pulled the CB...
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Old 12th Jul 2019, 17:49
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Originally Posted by bill fly


Well since he didn’t report that either, he may as well have pulled the CB...
Good point. Hindsight is 20/20. Since this is the crew that lived to tell about it I suspect they've had there chance to explain there thinking so perhaps we will get to read about in the final report.
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Old 12th Jul 2019, 17:59
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Originally Posted by Tomaski
Good point. Hindsight is 20/20. Since this is the crew that lived to tell about it I suspect they've had there chance to explain there thinking so perhaps we will get to read about in the final report.
Yep Tom, more rumours than news at the moment...
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Old 12th Jul 2019, 18:10
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Originally Posted by bill fly
Well since he didn’t report that either, he may as well have pulled the CB...
The report doesn't support that theory.

P27: "The flight from Denpasar to Jakarta experienced stick shaker activation during the takeoff rotation and remained active throughout the flight."
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Old 12th Jul 2019, 18:42
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Originally Posted by LowObservable
Here's an interesting new line.

Is the message, then, that this is too important to be left to the engineering nerds?
it was this theory of commercial trumps engineering nerds that created the reliance on the single AoA, poor training, poor certification docs etc etc in the first place, and killed 300+ people. The re-learnt lesson at B should be "listen to the engineering nerds and if they say no it means no".

G
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Old 12th Jul 2019, 20:40
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Originally Posted by OldnGrounded
Multiple reports from reliable major international news outlets have reported that concerns about the effort required to trim using the manual wheels are on the EASA list.

Have you seen this video from Mentour Pilot?

https://www.youtube.com/watch?v=aoNOVlxJmow
As an attempt to better describe what the jackscrew looks like andhows it works ( on the NG - but MAX details are probably the same )





And this jpeg

should help

note that on the video showing jack screw in motion- the difference in speed as it reaches full nosedown position ( top of jackscrew )

Last edited by walkon19; 12th Jul 2019 at 20:53. Reason: fatfinger
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Old 12th Jul 2019, 21:01
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Originally Posted by DaveReidUK
The report doesn't support that theory.

P27: "The flight from Denpasar to Jakarta experienced stick shaker activation during the takeoff rotation and remained active throughout the flight."
Dave, I didn’t say the CB was pulled. I said that he may as well have pulled it as not to report continuous shaker.
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Old 12th Jul 2019, 21:40
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Originally Posted by bill fly


Dave, I didn’t say the CB was pulled. I said that he may as well have pulled it as not to report continuous shaker.
Bill, not try to fence here. The preliminary has a figure showind FDR tracks for this flight and you can see where left stick shaker was on until landing. I'd post the page but havent figured out how to do that yet. Maybe someone else could.
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Old 12th Jul 2019, 22:07
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Originally Posted by Tomaski
Bill, not try to fence here. The preliminary has a figure showind FDR tracks for this flight and you can see where left stick shaker was on until landing. I'd post the page but havent figured out how to do that yet. Maybe someone else could.
(From memory)
From discussion on older threads I don't believe we know for sure if the FDR trace reflects the stick tracer request/condition -or- the motor actually running, in other words not 100% clear what FDR would show if CB pulled.

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