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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

#431

Post by WalterBright »

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…

Yes, that's the way aircraft fasteners are put on.

There's another reason to grease them - the grease keeps the water out which prevents corrosion.

In working on my cars, I always use a bit of grease when assembling fasteners. I've never had one come loose, nor have any rusted themselves on.

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

#432

Post by Scoundreller »

avidphantasm wrote: post #398
fshbbdssbbgdd wrote: post #174

Earlier quoted context omitted.

More rampant speculation! Some quotes from this article: https://www.reuters.com/business/aerospace-defense/spirit-ae... > As part of the production process, Spirit builds fuselages for 737s and sends them by train with the special door assembly “semi-rigged,” one of the people said. > “They are fitted but not completed," the person said. > At its Renton, Washington, plant, Boeing typically removes the pop-out, or no…

I’m no MBA or aerospace engineer, but why sub-contract the fuselage? I get subbing engines, since engine designs can be used on/adapted to other (possibly non-Boeing) airframes, hence opening up economies of scale, etc. But the fuselage is most of the plane by mass and integral to the design of everything else. If you don’t like making fuselages, maybe you should get out of the aircraft business. Was this just a unio…

Engines are weirder. My understanding is that the airline specs out what the engine requirements are, and any engine manufacturer is allowed to try to meet that requirement.

Customers get to decide which engine to fit and negotiate for them separately from the aircraft.

Sometimes there's only one choice, but other times gives you a chance to have the same (or similar) engine to maintain across your fleet (or avoid that to avoid a total grounding) and whatever other reasons to choose one over the other.

At least that's what the A380 tour in Toulouse said. Kinda makes sense to at least keep the big aircraft builders from throwing too much of their weight around.

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

#433

Post by sp332 »

nyokodo wrote: post #395
WheatMillington wrote: post #387

Earlier quoted context omitted.

Evidently not though....

> Evidently not though Bolts can be loosened by the physical and thermal stresses of use if there is a design flaw. So it’s not evidently an assembly QA problem.

The plane that lost a plug mid-flight was only two months old though. A design problem probably would have shown up in an older one.

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

#434

Post by AnthonyMouse »

selectodude wrote: post #403
AnthonyMouse wrote: post #318

Earlier quoted context omitted.

Make five of them that each have full rights to the existing company's designs and split their existing physical plant between them. Does one of the new companies have the only plant that makes a certain type of component? That's fine, customers can buy from them like they buy from the existing Boeing, but now the other sister companies have the incentive to build another plant to compete for that business, and the f…

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 aircraft types.

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

#435

Post by ethbr1 »

WalterBright wrote: post #427
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 expense for retraining pilots falls on the airline. Retraining has its own problems. No matter how well retraining is done, pilots still make mistakes from doing the right thing for the previous plane that is the wrong thing for the one they are currently flying. Adjusting airplanes to fly the same way is a major safety advantage.

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

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

#436

Post by rossjudson »

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.

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

#437

Post by adolph »

Shades of March 2019, below.

(CNN) In a blistering attack on Boeing, the Air Force's top acquisition official said the company has a "severe situation" with flawed inspections of its new KC-46 air refueling tanker aircraft, after trash and industrial tools were found in some planes after they were delivered to the Air Force.

Edit, remove: What is going on in Everett?

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

#439

Post by WalterBright »

ethbr1 wrote: post #435
WalterBright wrote: post #427

Earlier quoted context omitted.

The expense for retraining pilots falls on the airline. Retraining has its own problems. No matter how well retraining is done, pilots still make mistakes from doing the right thing for the previous plane that is the wrong thing for the one they are currently flying. Adjusting airplanes to fly the same way is a major safety advantage.

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 MCAS, but did follow the emergency runaway trim procedure, and continued the flight and landed safely.

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

#440

Post by mcbain »

applied_heat wrote: post #401
avidphantasm wrote: post #398

Earlier quoted context omitted.

I’m no MBA or aerospace engineer, but why sub-contract the fuselage? I get subbing engines, since engine designs can be used on/adapted to other (possibly non-Boeing) airframes, hence opening up economies of scale, etc. But the fuselage is most of the plane by mass and integral to the design of everything else. If you don’t like making fuselages, maybe you should get out of the aircraft business. Was this just a unio…

Spirit was spun out of Boeing

I don't always love the video format but Mentour talked about Spirit, Boeing, and the 737 MAX a few months ago: https://youtu.be/SmJgweFmoxs

The discussion about snowman hole issues and other problems is really alarming.

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