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United finds loose bolts on plug doors during 737 Max 9 inspections

theaircurrent.com

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Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#411

Post by paranoidrobot »

akira2501 wrote: post #404
AdrianB1 wrote: post #382

Earlier quoted context omitted.

They are not related. Probably different types of bolts, for sure different stress types. Rudder assembly is a moving part, these false door panels are not.

> these false door panels are not. It's not a control surface, but it is a "moving part." That's what's baffling to me, that they spent a lot of effort building this hinge and pin roller system, and designed the door to hinge open up to 15 degrees. It makes me wonder if there's maintenance procedures that at some point would require the operation of that door to successfully complete. Otherwise, the mechanism itself…

It's built to be an actual emergency exit.

It needs to be usable depending on how many passengers the interior is configured for.

So it has all of the door bits there. Maybe some parts like the emergency escape slide are not installed.

e: I should be clear that it's not usable as an emergency exit, as configured by Alaska. However the operator could choose to activate it later and install a usable exit.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#412

Post by actionfromafar »

ShadowBanThis01 wrote: post #386
ethbr1 wrote: post #371

Earlier quoted context omitted.

I expect even at its worst, software development could learn a lot from aircraft QA. Especially since most shops have pretty much tossed professional career QA out the window.

Except, of course, from Boeing's aircraft-software QA... which killed hundreds of people already.

The problem was not really the software in isolation, but that pilots expected the 737 NG to behave exactly like the old version - because Boeing decided it was too expensive to retrain pilots.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#413

Post by Eisenstein »

vegetablepotpie wrote: post #405
ethbr1 wrote: post #371

Earlier quoted context omitted.

I expect even at its worst, software development could learn a lot from aircraft QA. Especially since most shops have pretty much tossed professional career QA out the window.

I work in the defense industry, it’s very much like the aerospace industry in that we deal with human life as a consequence of our work. We have software QA departments that operate very much like manufacturing or aerospace QA. Software QA provides nothing of value to software development; having it as a dedicated function works against the overtly stated goals of the function and counterintuitively acts to degrade q…

It sounds like they are calling something QA but using it as a liability shield. It makes sense that you are upset about that, but naming something QA and having it do something else doesn't mean that QA as an effort is bad. It means that the people doing that are being deceptive.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#414

Post by mynameisnoone »

outside1234 wrote: post #260
avgDev wrote: post #238

Flying in this plane in a few days......a bit uneasy to be honest.

I think they are grounded - so it will be something else

You think. The bigger problem is the engineering and manufacturing processes that went into the 737 MAX is garbage. There will be no end to the problems because it's trying to nail mud to the wall. People who choose to continue flying on them are like people who don't wear seat belts: they know it's dangerous but refuse to act in their own interest of self-preservation.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#415

Post by serf »

echohack5 wrote: post #396
ethbr1 wrote: post #371

Earlier quoted context omitted.

I expect even at its worst, software development could learn a lot from aircraft QA. Especially since most shops have pretty much tossed professional career QA out the window.

QA was literally invented for the airline industry. Software QA when actually practiced is more advanced now than airline QA.

what does advanced mean when comparing things so unlike from each other?

also software is the least likely comparison I would have made; software quality is a shit-show on a general level, and the vast public is quite aware of this every time a subway timeboard blue-screens or gets frozen on an AMI screen, or the POS machine that they're forced to interact with at work does something equally as stupid.

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#416

Post by shawnz »

someguydave wrote: post #185
lokar wrote: post #87

Earlier quoted context omitted.

Or the lock wire was left off or done incorrectly

Aren’t there multiple signoffs & inspections to see if the lock wire was being done correctly?

No matter the real root cause, surely multiple layers of precautions must have failed to allow this to happen, right? So given that's a foregone conclusion, how can we discredit a hypothesis based on that?

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#417

Post by justinclift »

nolok wrote: post #356
jasode wrote: post #41

I found it interesting that Boeing did proactively tell airlines to inspect 737 MAXs for a possible loose bolt in a different part of the plane (rudder section) at least 8 days before the January 5th event. Example story: https://www.reuters.com/business/aerospace-defense/boeing-ur... Unfortunately, Boeing did not know they had other issues with the plug door bolts.

Imagine the quality of the manufacturing and QA / final inspection to have that kind of issue.

Maybe an inadequate torque specification for the bolt tightening?

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#418

Post by serf »

Scoundreller wrote: post #408
WheatMillington wrote: post #380

Earlier quoted context omitted.

Only grease fasteners if specified by the manufacturer, otherwise you're going to apply much higher than specified tension at the same torque value.

I need manufacturers to give "frame spent 3 decades in the salt belt, questionable metal compatibility and won't be taken apart until it breaks again" torque specs. It's like they think I'm going to take this thing apart and put it back together every year. j/k, finding torque specs for a decades old steel bike is a lost cause

a good machinists handbook will give you torque specs that take into account fastener size, material, and thread-locking style.[0]

mine is much older than linked version, but i doubt they'd revise that whole section out of it.

[0]: https://www.amazon.com/Machinerys-Handbook-Toolbox-Erik-Ober...

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#419

Post by mkl »

emchammer wrote: post #365
squirtle24 wrote: post #343

Earlier quoted context omitted.

Very interesting video that shows a clear picture of how the plug is held in place. Some interesting spots in the video, 8:44 shows how the upper two locking bolts lock the roller pins into the upper door tracks, and 10:00 show the lower two locking bolts onto the sliding hinge posts. 13:10 shows how the door blew cleanly off, with very little damage to the roller pins and lower hinge posts. Some comments say the sam…

Shear forces on four bolts, isn't that the same thing that caused the disaster in that hotel with the suspended walkway in the 1980s? With more than a hundred deaths. Is this not a basic case in engineering school, like THERAC-25? Not a licensed PE.

https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse

Longitudinal forces on the bolts there, not shear. A change during construction doubled the force on the nuts and the bolts went through weak weld joints in beams. (Also not a PE.)

Re: United finds loose bolts on plug doors during 737 Max 9 inspections

#420

Post by ethbr1 »

vegetablepotpie wrote: post #405
ethbr1 wrote: post #371

Earlier quoted context omitted.

I expect even at its worst, software development could learn a lot from aircraft QA. Especially since most shops have pretty much tossed professional career QA out the window.

I work in the defense industry, it’s very much like the aerospace industry in that we deal with human life as a consequence of our work. We have software QA departments that operate very much like manufacturing or aerospace QA. Software QA provides nothing of value to software development; having it as a dedicated function works against the overtly stated goals of the function and counterintuitively acts to degrade q…

> Good software teams build quality into projects by introducing continuous integration, unit testing, creating feedback, and tightening these feedback loops.

Agreed, for good software teams.

I would content that most software teams at most companies are not good.

Which is to ask, with an average to bad software team is it better to have integrated or separate QA?

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