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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

#371

Post by ethbr1 »

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.

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.

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

#372

Post by malfist »

nolok wrote: post #352
bobsomers wrote: post #329

Earlier quoted context omitted.

Correct, but I've seen a lot of confusion that its a systemic problem (ala MCAS) with the Max family. It doesn't look that way. It looks like a manufacturing problem on one particular variant.

The 8 had the great MCAS crashes (boeing solution ? tell the pilot to turn it off when it happens !), the 7 has anti icing that burnout the engine nacelle and make it fall (boeing solution ? being exempted from the certification requirement of your engines not falling off and we will fix it in a few years !), the 9 has doors that fall off (boeing doesn't even have a solution on that one, but they know others bolts ar…

To be fair to OP, cutting QA to save costs does lead to "their manufacturing is bad and their QA is not able to catch it"

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

#374

Post by robviren »

bigiain wrote: post #331
heads wrote: post #290

Earlier quoted context omitted.

Does wiring bolts actually help? I feel like if a bolt is going to come loose enough such that the wire is all that is holding it in then you have a big problem already. The wire is just delaying the inevitable. A bolt is either fastened or it isn’t. If the wire is all that’s left to hold it, then it isn’t fastened and your parts are being held together with a very weak piece of wire.

> Does wiring bolts actually help? There's different kinds of bolts that get wired, with different kinds of goals and results. My only experience is wiring bolts according to the rules for club racing motorcycles. Some things, like oil sump drain bolts for example, wiring them will stop them backing out so far as to fall our, and while it will probably weep oil if it loosened enough to take ups the writing slack, it…

We used it in nuclear power so I can say the procedures someone wrote at least believe they can prevent bolt rotation. We also used a lot of loctite.

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

#375

Post by tharkun__ »

tycho-newman wrote: post #354
Aqueous wrote: post #247

Literally just flew on a United Airlines 737 MAX 9 one week ago. It seems like the craft I flew on has probably been grounded in the week since. I noticed that we were flying on a MAX before boarding and nearly asked to switch flights, but consoled myself that I was being irrational and that the planes were almost certainly fine now. Guess my confidence was misplaced.

I mean, you're here now. Plane did its job. The safety margins on flying machines is really high, so while Boeing really should figure out what the hell is going on, the plane didn't fall out of the sky after a depressurization incident. It failed to a known state (ideally by design!)

What tells you that was by design vs. pure luck?

Given the MCAS thing and other shenanigans Boeing is trying with the MAX certification my bet is on luck.

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

#376

Post by inferiorhuman »

bobsomers wrote: post #329
alistairSH wrote: post #302

Earlier quoted context omitted.

7s and 10s aren’t out in the wild yet. Only 8s and 9s.

Correct, but I've seen a lot of confusion that its a systemic problem (ala MCAS) with the Max family. It doesn't look that way. It looks like a manufacturing problem on one particular variant.

  I've seen a lot of confusion that its a systemic problem
United found loose fasteners in a different locations on each of the five aircraft they found loose fasteners on. This is right on the heels of another emergency AD for the MAX about loose fasteners in a completely different location. That definitely hints at a systemic problem.

If you expand the scope a bit, Boeing's had nasty assembly and manufacturing problems across its whole model lineup. I highly doubt this is a one off problem.

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

#377

Post by NegativeLatency »

heads wrote: post #307

Bolts and machine screws are very interesting. One mistake I, an amateur bike mechanic, made for years was not greasing bolts properly before assembly. It sounds counterintuitive but without grease a bolt (or machine screw) will bind early with a high torque well before it is correctly tensioned lengthways. The torque is just a proxy for the tension and it is this tension which is needed to fasten your components tog…

I keep a toothbrush covered in grease for just this purpose.

It’s also a magnetic one so I can stick it to stuff and it stays put.

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

#378

Post by myself248 »

heads wrote: post #307

Bolts and machine screws are very interesting. One mistake I, an amateur bike mechanic, made for years was not greasing bolts properly before assembly. It sounds counterintuitive but without grease a bolt (or machine screw) will bind early with a high torque well before it is correctly tensioned lengthways. The torque is just a proxy for the tension and it is this tension which is needed to fasten your components tog…

There are different torque-to-tension equations for lubricated and unlubricated fasteners, of various materials and platings.

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

#379

Post by plagiarist »

consumer451 wrote: post #309
plagiarist wrote: post #297

Earlier quoted context omitted.

I think you're giving it too much credit for solving examples that are obviously wrong. Not only a non-expert but even most children know those pairings don't go together. Given that the discussion in this post is around torquing to the right specifications, I don't know if just fine tuning is enough. It might need more serious training on videos of assembly. Even then, can it distinguish between the right torque or…

Oh definitely, I was giving it some softballs. Maybe I am also giving too much credit to what fine tuning can achieve. But in a manufacturing environment, if one labelled wrench sizes with different colors, then things like noticing wrench size would be easier. Also, I imagined that the camera would of known (same) geometry during training and inference in a Boeing implementation. I also wonder if multimodal LLMs are…

They are a pretty huge leap! I just think for manufacturing and assembly where it is critical to get specific values right we cannot rely on neural nets in their current form.

I think there are digital wrenches that will record the torque they applied, you don't need to mess around with colors. But at that point, it's sort of like, why bother teaching the AI to notice if people are doing it right, stick a camera on the wrench and QR sticker on the bolt. Make a more formal verification process that can be guaranteed to match specifications.

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

#380

Post by WheatMillington »

heads wrote: post #307

Bolts and machine screws are very interesting. One mistake I, an amateur bike mechanic, made for years was not greasing bolts properly before assembly. It sounds counterintuitive but without grease a bolt (or machine screw) will bind early with a high torque well before it is correctly tensioned lengthways. The torque is just a proxy for the tension and it is this tension which is needed to fasten your components tog…

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