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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

#461

Post by mc32 »

Groxx wrote: post #428
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…

In lots of ways, the "learning" there would just be "capitalism". It's inherently short-sighted unless forced to do otherwise by legislation. Cutting small corners pays off A LOT until the hammer falls, so there's a massive advantage to doing it / you need to do it if competition is doing it, or you eventually shut down as they take all your business. It's inherently a race to the bottom. Sometimes that's a net gain,…

All major economic systems of all major national economies over the last century have perverse incentives. It’s not a capitalist thing.

Other systems had incentives such as, get it running by such and such date or have yourself and relatives sent to inhospitable place. So people rushed flawed designs into production.

That said, upper management at Boeing needs a shake-up. People need to get fired. They need to do what Intel is trying and that is to get more engineers in charge, or at least grant them veto power on designs.

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

#462

Post by ethbr1 »

vegetablepotpie wrote: post #456
ethbr1 wrote: post #420

Earlier quoted context omitted.

> 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?

Does it make sense to degrade the performance of good software teams because bad software teams exist? Ideally we’d always have good software teams, but in the real world sometimes you have to build software with bad teams. Leaders have options, they can do things like reduce scope, increase budget, increase schedule, or full on abandon or cancel the project. These are all options available to leaders, but they requi…

It makes the most sense to me to match the org structure to the teams you have.

If I'm trying to build something with undertrained, demoralized, underpaid engineers... it's not optimal to use methods intended for self-motivated, high-performance teams.

And nothing says there must be company-wide mandates. Maybe this area gets a formal, independent QA team, but this other area doesn't.

My experience just doesn't bear out that collapsing the QA function into development always leads to better outcomes.

I've seen the opposite happen too often, and QA be the sole bulwark between idiocy and customers.

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

#463

Post by arrakeenrevived »

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.

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

#464

Post by 9659 »

WalterBright wrote: post #439
ethbr1 wrote: post #435

Earlier quoted context omitted.

Arguably, Boeing hit the uncanny safety valley -- similar enough so that pilots and airlines relaxed, but different enough so that relaxation ultimately killed people.

The emergency procedure for runaway trim was the same for both aircraft types, and was not followed. After the first crash, an Emergency Airworthiness Directive was issued to all MAX pilots reiterating the procedure, which was not followed in the second crash, as well as not reacting to an overspeed warning. Unreported by the media, there was another MAX incident before the first crash. The crew had no knowledge of M…

"Runaway stab trim". It is a memory item, every pilot should be able to perform it from memory.

Turn off the motor, and the trim is manual. There is a crank right there in the cockpit. If it is too hard to turn, change aircraft configuration to reduce the forces required to. Pilot know how to do this. This pilot stuff, they understand the forces on the flight controls and what impacts them.

Boeing made an engineering mistake. The pilots also made an operational mistake. Unfortunately, both mistakes at the same time were fatal.

I pray that pilot training has improved. And that Boeing has made systems level changes to the aircraft that will preclude it happening in the future.

And that is how aviation becomes safer every year; at a significant cost of customers lives.

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

#465

Post by deelowe »

paranoidrobot wrote: post #411
akira2501 wrote: post #404

Earlier quoted context omitted.

> 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.

Where did you see that? My understanding is that it's an optional plug door that's used to assist with interior installation. Once the interior is done, it's bolted shut and interior paneling is installed over top. From the inside, you can't tell it's there.

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

#466

Post by mc32 »

boringg wrote: post #460
Groxx wrote: post #428

Earlier quoted context omitted.

In lots of ways, the "learning" there would just be "capitalism". It's inherently short-sighted unless forced to do otherwise by legislation. Cutting small corners pays off A LOT until the hammer falls, so there's a massive advantage to doing it / you need to do it if competition is doing it, or you eventually shut down as they take all your business. It's inherently a race to the bottom. Sometimes that's a net gain,…

But all those communist airlines had no problems at all - exceptional build quality and operational efficiency! /S

Yep, Chernobyl being a prime example. Or Komarov's failed re-entry after complaining about the design faults of the vehicle long before launch. Then there was the more uhhm run of the mill backyard blast furnace campaign which contributed to misallocation of workforce which then led to mass starvation.

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

#467

Post by deelowe »

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…

A properly designed service manual will specific if the fastener should be lubed. If it doesn't say lube/thread locker should be used, then the fastener should be torqued dry.

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

#468

Post by disillusioned »

unyttigfjelltol wrote: post #453
actionfromafar wrote: post #412

Earlier quoted context omitted.

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.

The problem was software that prioritized input from a fauly external sensor, over pilot control, and literally crashed planes directly into the ground. At a certain step in the sequence it was not physically possible for a pilot to pull hard enough on the control element to counteract the software. Could they have disabled the system? Only if they could figure out the specific software trying to crash the plane. Is…

Even more ridiculous, Boeing offered a second source of truth option, but marked it as an upcharge, which the airlines in question rejected. "No thanks, no need for a second AoA sensor, one is none is probably fine!"

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

#469

Post by ethbr1 »

unyttigfjelltol wrote: post #453
actionfromafar wrote: post #412

Earlier quoted context omitted.

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.

The problem was software that prioritized input from a fauly external sensor, over pilot control, and literally crashed planes directly into the ground. At a certain step in the sequence it was not physically possible for a pilot to pull hard enough on the control element to counteract the software. Could they have disabled the system? Only if they could figure out the specific software trying to crash the plane. Is…

Pilots are definitely trained how to disable the autopilot, if needed.

Afaic, the fault apportionment was Boeing documentation > airlines >> pilots > Boeing technical design.

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

#470

Post by AdamJacobMuller »

rossjudson wrote: post #436
consumer451 wrote: post #400

This is the the best update I have seen so far on the incident Alaska Max 9. The presenter is a 777 pilot and A&P mechanic. Released 2hrs ago. https://www.youtube.com/watch?v=WhfK9jlZK1o [13:43]

blancolirio is really great at explaining...mishaps. He provides details and an explanation of those details that's accessible. It's the first place I go to "find out what happened" for any kind of air incident.

Not just aviation and not just mishaps, but, almoshaps too!

I first started watching his channel during the Oroville dam crisis in 2017 and he had some excellent coverage of that event. He seems to cover "things which interest him" the venn diagram of which which overlaps with mine quite a lot.

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