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

theaircurrent.com

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

#141

Post by [deleted] »

the_third_wave wrote: post #107
Scoundreller wrote: post #76

Earlier quoted context omitted.

My beef is that torque specs are for factory assembly. If you’re using new parts, sure, but once they’re old/re-used parts with some corrosion due to dissimilar metals, age or salt belt, you’re flying blind and probably undertorquing if going by the book. Given the amount of (soft) aluminum on aircraft, (737 is 80% aluminum), it would be insane to not precisely consider torque. Steel on steel is more forgiving.

> If you’re using new parts, sure, but once they’re old/re-used parts Most service manuals require new bolts, fasteners and washers for torque-critical parts.

[deleted]

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

#142

Post by the_third_wave »

leetrout wrote: post #85
thinkingtoilet wrote: post #69

Earlier quoted context omitted.

>People at large simply cannot be bothered to care about anything People care deeply about a lot of things, just not this. And why should they? When you have every business decision made either by private equity or public companies with a focus only on the next 90 days it turns out everything goes to shit. Wages are stagnant. Wealth inequality is massive. Our society is sick. Issues like this will only increase. Our…

Random aside: I looked up an Acela ticket this morning. $1000 for a first class ticket from DC to BOS. 6.5 hours. Same flight first class with Delta this week is $850. Also 6 hours with layover. Blows my mind first class rail travel is as much as first class air travel.

Those prices are extreme, I regularly travel 1st class by train from Göteborg/Sweden to Amsterdam/the Netherlands at about €85 for a single with ICE/EC/IC, a ~15 hour trip.

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

#143

Post by chippiewill »

queuebert wrote: post #58

I've seen on Toyotas and also at Universal Studios bolts on rides are marked with paint presumably to indicate that the nut hasn't backed out. Are airliners marked in this way? Is checking the bolts simply a visual inspection, or do the inspectors need to get out a torque wrench?

Unlike on a rollercoaster, these bolts are hidden within the fuselage behind the cabin panelling so a regular visual inspection to see if they've been loosening wouldn't be practical. During assembly the bolts should have been torqued and then checked and the bolts would only be reinspected when the panelling is removed after 3 years or so.

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

#144

Post by tw04 »

gruez wrote: post #121
intunderflow wrote: post #6

At what point do consumers en-masse refuse to fly on these aircraft, if ever? When there's a few more fatal crashes?

Statistically speaking it's not worth worrying about. In 2021 there were less than 0.001 deaths per 100M passenger miles. Assuming these aircraft are 10x more dangerous than the alternative, that works out to 0.01 deaths per 100M passenger miles, or 0.00000026 deaths NY to SF flight. For an average american aged 38.9 years[2] with 40 years of life left[3], that works out to a loss of life of 5.4 minutes. I don't thin…

>Statistically speaking it's not worth worrying about.

Those statistics don't really work out at all. They take number of miles and deaths, and nothing else. Let's say flown miles and driven miles are exactly the same for arguments sake. If the number of miles flown on planes were traveled by 4 million people, whereas the number of miles traveled by car were from 4 billion people, your likelihood of dying in a plane crash is FAR higher than by car if you're one of the 4 million who fly on a plane.

Miles and deaths alone are pretty poor metrics. There's also the part where I may only drive once or twice a week vs. the average which takes into account people who commute daily. So my odds of dying in a car crash are still lower. The frequency of travel seems just as pertinent as the miles traveled.

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

#145

Post by fshbbdssbbgdd »

Check out this video showing how the plug is supposed to be installed: https://youtu.be/maLBGFYl9_o?t=540

Some of the bolts that would be loosened when the plug is opened during maintenance have a pin to prevent them from turning. That pin is present in this photo: https://x.com/byerussell/status/1744460136855294106?s=46&t=s...

However, the same photo shows other critical bolts that hold the whole hinge on the door are loose, and there’s not meant to be a pin on those.

I’m curious how the decision is made whether to include that pin in the design. Did they idiot-proof the maintenance of the plug, but not the initial installation?

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

#146

Post by tavavex »

samstave wrote: post #35
bell-cot wrote: post #24

Earlier quoted context omitted.

How would compromise of the window encourage the plug to be ripped out?

My assumption is the decompression event would have put the velocity of that decompression on the door/bolts and they are going to be weaker - and the addition of a window into a plug/door like this adds structural mass to add to that which is being sucked out via the decompression putting them over spec load for that area - but since it was a plug, the surrounding structure was still sound - just that thing couldnt…

I don't think there were any modern cases of airliner windows just being removed like that. They're fairly strong and consist of multiple layers of acrylic that are sandwiched between other components, so the entire window assembly would need to get torn out. Even then, it doesn't seem realistic that the difference in pressure would be big enough to instantly rip a properly-attached door clean off. Of course, only the experts can tell for sure, but my money's on a failure of the whole structure.

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

#147

Post by 0xffff2 »

j-bos wrote: post #60
baq wrote: post #21

Earlier quoted context omitted.

It's a cliche thing to say, but if it was a known issue and management papered over it - as the alternative is incompetent engineering instead of just cost-center-managed engineering - someone should go jail?

Did anyone go to jail for the previous Boeing MAX crashes?

At this point there's a pretty clear implication that if some Boeing people had gone to jail that time maybe this wouldn't have happened at all.

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

#148

Post by Max-q »

psunavy03 wrote: post #104
fullshark wrote: post #30

Earlier quoted context omitted.

I think it would require a fatal air crash of an American flight with a major celebrity on board.

. . . and the US airline industry has still not had a fatal crash in just under 25 years.

* 15 years

Still impressive.

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

#150

Post by dan_quixote »

Night_Thastus wrote: post #19
hipadev23 wrote: post #2

[flagged]

Those claims that it was maintenance is a bit bizarre considering these were brand new craft, and that panel isn't exactly a wear item. (ofc, some wear with each pressurization cycle, but I digress) It'd be different if it was an engine issue on a 20+ year old plane. But still, this isn't anything like the prior MAX issue - and frankly could have just as easily happened to any manufacturer like Airbus. I don't think…

One major difference I recall back when working in the industry is that Airbus didn't rely on contract manufacturing like Boeing adopted after the McDonnell Douglas merger. Spirit was just Boeing Wichita until they divested the operation only to immediately contract work with the new owner at a discount.
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