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

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

#471

Post by ddoolin »

flamedoge wrote: post #170
Scoundreller wrote: post #34

Earlier quoted context omitted.

Or it means the torque specs were a little too low, or too high and stripped, or the bolt threading was defective/spec’d wrong. Or bad metallurgy. Or the spec didn’t specify which order to tighten the bolts, so which direction you go causes different outcomes. Lots of stuff is assembled consistently and carefully “wrong”, but as specified.

idk what aviation standards say but shouldnt loctite or spring washers at least be used

These bolts were fitted with a wire pin to prevent the nuts from spinning loose. The nuts were not locking nuts on their own.

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

#472

Post by dotancohen »

free2023 wrote: post #441
local_crmdgeon wrote: post #430

Earlier quoted context omitted.

Saves Boeing money by manufacturing 1 frame

Yes, certainly. But the carriers could configure it to make it non-functional, since it serves no purpose for them. Or they could spec it as a rivet-it-shut option from Boeing. Just seems crazy to have this big failure point in the fuselage, adding to their maintenance costs, for a thing they don't even use.

And mass.

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

#473

Post by ssivark »

throwup238 wrote: post #454
rectang wrote: post #425

Earlier quoted context omitted.

Is it plausible that Boeing has "learned" from software/startup/venture-capital culture with regards to tolerating higher risk to minimize costs? I suspect it's rather a case of parallel evolution between McDonnell Douglas brass and software startup culture, since cost-cutting culture goes back many decades (remember "Chainsaw" Al Dunlap[1] ?) — but I wonder if there's a more direct influence. [1] https://en.wikipedi…

"Better to ask for forgiveness than for permission" Ironically, I believe it was Grace Hopper who said it... Whoops.

That adage is okay, but for it to work not everything can be forgiven — there actually has to be an expectation to be held responsible towards acting on good faith.

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

#474

Post by Robotbeat »

ethbr1 wrote: post #371
nolok wrote: post #356

Earlier quoted context omitted.

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

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 agree.

I’m regularly critical of Boeing Defense (particularly space contracts where I’m a huge Boeing skeptic), but I think people are pretty off base if they think Boeing is just completely incompetent.

Airliner safety is insanely good. Just vast seas of competence, but when there’s a super rare failure, the incorrect impression people get is that Boeing (or Airbus) is just full of incompetency. Almost nothing that humans do is held to the same standard. Not spaceflight, not software, not healthcare, and certainly not automotive.

Flying a 737 Max with a bad door and without the fix to the angle of attack sensor is probably still better per mile than driving. In spite of going at 10 times the speed and miles above the Earth.

You can almost argue it’s held to a higher standard than it should, slowing development of cleaner aviation (and therefore killing more people in the future due to tertiary effects of climate change, etc).

It kind of annoys me when comment sections are filled with people talking about how incompetent Boeing is. It feels like out of shape slobs on their La-Z-boy chairs talking about how incompetent or slow some professional sports players are. Like, airliner safety is just a totally different league than almost anyone else plays in. On the worst day, their better than almost anyone else is on their best.

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

#475

Post by Robotbeat »

rectang wrote: post #425
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.

Is it plausible that Boeing has "learned" from software/startup/venture-capital culture with regards to tolerating higher risk to minimize costs? I suspect it's rather a case of parallel evolution between McDonnell Douglas brass and software startup culture, since cost-cutting culture goes back many decades (remember "Chainsaw" Al Dunlap[1] ?) — but I wonder if there's a more direct influence. [1] https://en.wikipedi…

Boeing Airliners are much safer now than before they merged with McDonnel-Douglas. (Because basically all airliners are.) And I say that as a regular Boeing critiquer.

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

#476

Post by selectodude »

AnthonyMouse wrote: post #434
selectodude wrote: post #403

Earlier quoted context omitted.

You realize how type ratings work yeah? An airline wants to fly a common model. They wanted a 737. They would buy a worse plane for twice as much (see: 737 max) over a brand new clean sheet model that’s incompatible with their pilots.

Type ratings work that way because there are so few types of planes, and because the incumbents like it that way. "Oh no, I guess it's impossible for anyone else to produce a new aircraft model because nobody's qualified to fly it, now we'll just have to rest on our laurels forever." If there were more competitors, they'd lobby to change how the regulations work so they didn't effectively destroy the market for new a…

The FAA doesn't work like that and I can assure you, the airlines find it to be an enormous pain in the ass.

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

#477

Post by free2023 »

arrakeenrevived wrote: post #463
free2023 wrote: post #421

Why are there bolts and machine screws in use in the first place? The seating configurations for United and Alaska, the 2 major customers for this aircraft, don't require this plug-door feature. Structurally, for these large carriers, the plug door serves only as a fuselage weakness and failure point. Why don't they just rivet it permanently to the fuselage and make it non-functional? Per the diagrams shown, it's a c…

Aircraft are often sold between airlines, or reconfigured even with the same airline. If United ever wants to reconfigure their 737s to be higher density (which is pretty common), they might need to start using that door as a real emergency exit.

Yes I see, that makes good sense. Given the course of events, it's still a fair question from a design standpoint: Can this be engineered with a reversible option to switch it from functional to non-functional, depending on the seat configuration?

It just seems like a lot of complexity and moving parts, for a feature that's not in use.

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

#478

Post by amluto »

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…

> We have software QA departments that operate very much like manufacturing or aerospace QA.

I don’t work in this industry, but this seems fairly ridiculous on its face: software is not at all like manufacturing.

In manufacturing, there’s a design and a manufacturing process, and a critical function of QA is ensuring that the manufactured produce is manufactured to spec.

With software, the software is written, compiled, and then repeatedly copied. And something should verify that it’s copied correctly, but this is straightforward and boring.

So software QA ought to be much more like the kind of validation that happens when designing hardware, not like the kind of testing and validation that happens as products are manufactured.

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

#479

Post by garyfirestorm »

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.

Bolts are most likely tightened with a torque wrench or a gun that is set to a torque spec. Over tightening a bolt is as bad as a loose bolt. I speculate these passed QA from Boeing because they might have been correctly torqued to the spec. What happens in field is hard to understand. One possibility is vicinity to the engine can cause extreme vibrations, these can make them loose. Other possibility is the maintenance side of things - maybe a badly calibrated torque wrench could be the reason. Mechanical systems are not inherently immutable.

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

#480

Post by Eisenstein »

vegetablepotpie wrote: post #446
Eisenstein wrote: post #413

Earlier quoted context omitted.

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.

Fair point, you are correct in your inference that there are some bad actors in my workplace. However, I’ll argue that the fundamental dynamics of bifurcating the responsibility of quality from software leads to a steady state where all QA departments end up as a liability shield given enough time. This is driven by Pournelle's iron law of bureaucracy [1], which says that people who promote the bureaucracy rather tha…

But what makes 'software QA' fundamentally different than 'non-software QA' to give it the problems you foresee?
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