Boeing 737 Max8 Aircraft Crashes and Investigations [Part 8] 24

[Sparweb]

This post is the continuation from this series of previous threads:

thread815-445840
thread815-450258
thread815-452000
thread815-454283
thread815-457125
thread815-461989
thread815-466401

This topic is broken into multiple threads due to the length to be scrolled, and images to load, creating long load times for some users and devices.
If you are NEW to this discussion, please read the above threads prior to posting, to avoid rehashing old discussions.

Thank you everyone for your interest! I have learned a lot from the discussion, too.

Some key references:
Ethiopian CAA preliminary report (Link from Ethiopia is now broken. See link from NTSB Investigations below)

Indonesian National Transportation Safety Committee preliminary report

NTSB Investigations

NTSB Safety Recommendation Report: Assumptions Used in the Safety Assessment Process and the
Effects of Multiple Alerts and Indications on Pilot Performance

A Boeing 737 Technical Site

Washington Post: When Will Boeing 737 Max Fly Again and More Questions

BBC: Boeing to temporarily halt 737 Max production in January

Pulitzer Prize, For groundbreaking stories that exposed design flaws in the Boeing 737 MAX that led to two deadly crashes and revealed failures in government oversight.

http://www.sparweb.ca

 

[moon161]

California's remodeling industry has some parallels; the California remodel pegs tax assessments against the ability to claim that a house has not been so substantially rebuilt that it should assessed as a new house. So, the law is written such that a "California remodel" is considered to be the original house, and tax base, if even a single wall of the original house remains;

I've seen a couple buildings in NY state that were either demolished to a framed door that was enclosed by new construction, or the old building was enclosed by a new one, then demolished, to get around a moratorium on new builds in the area.

 

[Lou Scannon]

...unintended consequences

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[dik]

Common in cottage country in Ontario... get the building inspector to agree that you can construct to the same footprint... then teardown and rebuild... there have been a few instances where the person has demolished the structure only to be prevented for new construction.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[IRstuff]

Didn't mean to completely derail the discussion. My point was that asking for a new type cert for every change would be prohibitive and result in much more expensive and rarer occurrences of new planes. That's not particularly desirable. Obviously, the California remodel isn't suitable either.

I'll pull an analogy from a file synchronization program that refuses to automatically synchronize if more that 30% of the files have changed; so we could require a new type cert if the plane changes by more than 20%. How to define the 20% would be the challenge, though; although one can imagine if there were more than 20% new or modified drawings, that would require a new type cert.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[LionelHutz]

It'd be a terrible idea, unless you wanted to very significantly reduce the number of planes in the sky.

 

[dik]

There has to be a mechanism to allow for 'minor' revisions and a complete 'rebuild'. What they have now is unworkable from a safety standard.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Eufalconimorph]

Yep. The current system can't distinguish when a thorough re-evaluation of the whole system is needed vs when a change doesn't cause substantial differences to the overall behavior. I don't want silicon valley style "move fast and break things" "innovation" applied to aircraft. I also don't want all progress to stop.

 

[waross]

I still can't believe the manual trim wheels.
As I understand it, you have to have manual trim but manual trim doesn't have to work.
That was my understanding of the answer given when last I asked about the manual trim issue.
In the event of a runaway trim, that cannot be corrected by electrical means, the manual wheels may not be able to be used.
Why not?
There is no regulation that says it has to work?
The organization that sets the rules cannot address the issue because they haven't written a rule?
The FAA may have more serious organizational problems than grandfathering.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Lou Scannon]

Beyond just satisfying a series of individual regulations, oughtn't there be a system level design assessment by the regulatory body? Along the lines of an engineering student competition where the entrants present their design to the judges, explain the design philosophy especially as it departs from current established practice or the grandfathered design, and provide a comprehensive theory of operation, including system DFMEA? And the regulator would of course have the opportunity to ask questions and probe into areas not clearly explained, or showing potential for serious failure modes not addressed in the DFMEA, or other possible lack of robustness. If such an oversight is already in place, why didn't it work? I guess that would be due to malfeasance and/or negligence on both sides.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[IRstuff]

That is all part and parcel to the political parties' desires to "trim the fat" from government agencies, which used to have scads of "subject matter experts" that could have done the job, but it was decided to forego that, and use industry SMEs instead, but the only available industry SMEs were those on the payroll of Boeing itself, particularly since we're also talking about opening the kimono and revealing ostensible proprietary information.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[davefitz]

as a follow up to the above comment on FAA SME's, it was reported that the FAA had 2 senior SME's leave the FAA during the evaluation of the 737 Max. It would be of interest to determine why they had left and where they went; if they were hired by a client of Boeing for a much higher salary then that would suggest Boeing complicity in preventing an FAA expert review of the max.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[LittleInch]

waross,

I agree and almost - my understanding was that there were no specified limits on the force required to move the manual trim lever / wheel. It might have been possible to move it if built like Arnie, but not a small pilot / female.

As I understand it the force required is quite variable and gets much higher as speed increases - a kind of squared velocity effect.

Hence why it might be feasible when going slowly, but not at the speed the Ethiopian pilots were going at.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[waross]

We are on the same page, LittleInch.
As well, the further out of trim, the greater the force required.
I'm open for correction here, but I understand that the further from the Center of Gravity the engines are, the more need there is for speed trim, and those Leap engines are a long way from the center of gravity.
The placement of the engines may also play a part in the amount of travel of the stabilizers and the forces due to out of trim conditions.


Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Alistair_Heaton]

On the scope of grandfathering.

The 737 MAx is a bit special due to the last version NG. It was certified just before the new grandfathering regulations came into force. If had been certified a year later then I suspect the max would be a completely different beast due to changes that would have been enforced on the NG.

But because the NG managed to get through then they had a window to grandfather through stuff which wouldn't be allowed if it had gone 500 directly to the MAX. But because it had been allowed in the NG and hadn't been changed NG to MAX then they didn't have to recertify it.

There is missing a big picture limitation on grandfathering from the initial full certification. Nobody wants to stop single step or dual step increments. But when it gets to 60 years worth of incremental reg's being avoided and your on the 7th iteration you need a big picture review how its all working together.

Something is happening though.

The 777x has been put back and the 737-10 is also put back. I believe they will be adding more AoA sensors to the 10 then retrofitting them to the 7,8,9

 

[Alistair_Heaton]

A lecture to the Royal Aeronautical Society on the 737 Max and history.

https://youtu.be/JApoVC6iIIE

 

[dik]

Long, but a good link...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Alistair_Heaton]

Just watched it twice and utterly excellent. Chris has no formal engineering training. Any of the acronyms used feel free to ask what they mean its even heavy going for me translating them while listening to it.

I have never flown with him but mates that have say he is an extremely knowledgably high IQ person.

So you know the this is the official controlling body for Aero engineers in the UK. I used to hold letters after my name off them. They are the ones that issue CEng status.

Edit to add I don't know how things can move forward from this. The regulator is defective which means the rest of it is nonsense.

 

[RedSnake]

I've only seen 15 minutes so far.
A reflection or more appropriate a memory came to mind.
My dear beloved CH always said that a machine is never better than its mechanical design or its tolerances.
Which is also my conviction and experience, that is...
It is not possible to program away "bad mechanics" or tolerances.
Now I do not say that the plane of origin was bad.
But the mechanical changes they made had a negative effect from a control perspective and then they tried to "program" it away.
Never a good idea.
A machine is never better than its mechanics.

Mixing manual and automatic control is as I see it from a "machine" perspective not possible.
I do not know how many times I have tried to explain to technicians and production people that I can not program away the problems they have when they operate the machines manually.
It is impossible to predict in the program when someone will do something to be able to program away the consequences.

Like I said, I've only seen 15 minutes so I hope this ends better than it started.

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[dik]

It explained a lot of things I only thought I understood... overall it was good.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[waross]

Thanks for the link, Alistair.
I enjoyed the history of the MAX.
The presentation was quietly pro Boeing.

All design flaws rectified.

But there were a few issues that were not mentioned.
Apparently Boeing did not consider re-positioning the engines.
Fix the problem, don't cover up the symptoms.

There is no question that the MAX is the most scrutinized aircraft in history.
It is probably the most compliant aircraft in history.
But;
Is it the safest aircraft?
I understand that the manual trim system is still unusable when it is most needed.
Apparently, there is no requirement for a manual trim system to be actually usable.
It appears that Boeing's and the regulator's mindset is more CYA and what can we get away with cheaper than it is on safety.
At this point, another crash due to design flaws may be the end of Boeing's presence in commercial aviation.
That's a lot to bet on a manual trim system that may be unusable when needed the most.

Unfortunately, serious questions remain as to whether Boeing and the FAA have fully and correctly learned the lessons from the MAX failures.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!