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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

#511

Post by nikau »

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

In the car world that torque is measured in ugga duggas from the impact wrench

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

#512

Post by Rapzid »

Syonyk wrote: post #306
Rapzid wrote: post #293

Earlier quoted context omitted.

That lock nut may not have lined up correctly for some reason and was backed off a bit to get the pin in? That could make it torqued under spec. But also, it doesn't look like that bolt clamps anything so it may not matter if it was a little "loose"..

Are you looking at the center nut in the photo that's cotter pinned in place, or the two over on the right side that appear to be "loosely threaded on at best, washer rattling along the shaft"? The center one doesn't concern me. The two that aren't even finger tight do.

I was and missed everyone was talking about those other bolts in this particular case.

Those are much more problematic as the remaining tight bolts could fail leading to a cascade. Though, would expect the flange to still be connected to the post in the aftermath images and the upper pins .. how did they get out of the track?

I wish we had close up pics of all the bits in the airframe opening.

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

#513

Post by bb88 »

ethbr1 wrote: post #502
Robotbeat wrote: post #474

Earlier quoted context omitted.

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 tha…

> Airliner safety is insanely good. Because I dug it up for another comment, commercial carriers operating under Part 121 (roughly: scheduled passenger and cargo operation) had 4 fatal incidents in the last 10 years. [0] Totalling 6 deaths. In 10 years of US commercial carrier aviation. One of those was literally 'the engine exploded and threw part of the turbine into the cabin (and also shredded some of the wing)'!!…

> Totalling 6 deaths. In 10 years of US commercial carrier aviation.

Okay, awesome. But how much of that was luck with the 737 Max that they didn't crash on US soil by US airlines?

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

#514

Post by johnnyworker »

bb88 wrote: post #488
vegetablepotpie wrote: post #405

Earlier quoted context omitted.

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. No. Good software teams are led by competent, technical management. Managers who aren't afraid to get down into the dirty details. Managers who aren't afraid to roll up their sleeves and write code if they need to. The process doesn't matter. The management of…

But that doesn't contradict the parent, does it? I'd say you both make good points.

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

#515

Post by nikau »

Eisenstein wrote: post #480
vegetablepotpie wrote: post #446

Earlier quoted context omitted.

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?

Because every QA is something new for development barring regression testing.

An equivalent software QA to building planes would be to verify a known process with existing tooling.

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

#516

Post by I_Am_Nous »

mkl wrote: post #419
emchammer wrote: post #365

Earlier quoted context omitted.

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.)

>A surgeon spent 20 minutes amputating one victim's pinned and unsalvageable leg with a chainsaw; that victim later died.

Wow

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

#517

Post by shermantanktop »

mikewarot wrote: post #447

At this point, I believe Boeing needs to suffer the corporate death penalty, because it no longer operates as a net benefit to the public. It needs to be dissolved, and its assets sold off. Criminal charges should be pursued to the maximum support of the law against all of the corporate officers. Those in the FAA and other oversight agencies who failed to properly oversee them should also be prosecuted. Failing the a…

How do you feel about car makers? They kill a lot of people. Food poisoning, bathtubs, lightning…

I don’t disagree that it appears that Boeing has acted badly here. And I’m frustrated with golden parachutes, out of court settlements, and other ways of evading corporate responsibility. But this is a moment in time, and I think Boeing could redeem itself.

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

#518

Post by irrational »

amluto wrote: post #478
vegetablepotpie wrote: post #405

Earlier quoted context omitted.

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, compil…

Ideally there should be a solid spec written and then qa can test against the spec. Maybe there is somewhere that does write solid specs, including accounting for corner cases, but in my 25 years working professionally in the industry, I’ve never seen it.

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

#519

Post by johnwalkr »

dylan604 wrote: post #70
Syonyk wrote: post #20

Earlier quoted context omitted.

No, it's as insane as it reads. It means people were careless and sloppy during assembly. Think of it like seeing "one cockroach in your kitchen." It's not one cockroach. You just haven't opened up the rest of the walls.

What's crazy to me is that these things do not roll of the factory line in large numbers. If it was a car plant or some other line where large numbers come off per shift, you could find that possibly one operator for one shift set their torque wrench to the wrong setting causing the finished items for that shift to be suspect. But seeing as not one plane rolls of the floor per shift, this is much more systemic like p…

It can be opposite of your interpretation too. If you make 100,000 cars in a year, each step is done at least 100,000 times and it's justified to have a single wrench, with single non-adjustable torque value, and automated datalogging of applied value for a particular step. Or even a robotic process. Maybe even computer vision to check fastener length.

If you make 10 or 500 planes in a year, you have to rely on multiple people to use multiple torque wrenches, with multiple attachments, to follow multiple procedures to assemble multiple planes using fasteners of multiple lengths, nearby multiple other processes and people. There is a big emphasis on procedures and traceability but there are still so many potential failure points that can go undiscovered for a long time.

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

#520

Post by bb88 »

acdha wrote: post #491
ethbr1 wrote: post #469

Earlier quoted context omitted.

Pilots are definitely trained how to disable the autopilot, if needed. Afaic, the fault apportionment was Boeing documentation > airlines >> pilots > Boeing technical design.

This wasn’t related to autopilot and they removed mention of the MCAS system from the documentation to support the main selling point of the 737 MAX, which was that existing 737 pilots would be able to switch easily without recertification. They knew that they’d lose most sales to Airbus if the aircraft were compared on their merits so they were banking hard on their huge pool of certified pilots as the competitive e…

You might enjoy this. I have a pin that blinks "AOA Disagree".

Back when I flew regularly before covid, I was tempted to create a bunch of these and hand them out to the flight crew for the flights I flew on.

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