Boeing 737 Max 9: United Airlines finds loose bolts during inspections

The US National Transportation Safety Board (NTSB), which is leading an investigation into the incident, said pilots had reported pressurisation warning lights on three previous flights made by the specific Alaska Airlines Max 9 involved in the incident.

As bad as it is if a manufacturing issue caused a piece to fall off an airplane, there's a huge amount of negligence in an airline continuing to fly an airplane that has triggered pressure warnings multiple times without investigating and resolving the issue.

And the next paragraph:
The jet had been prevented from making long-haul flights over water so that the plane "could return very quickly to an airport" in the event the warnings happened again, NTSB chief Jennifer Homendy said.
~~Which makes it sound like they couldn't find the source of that warning but weren't willing to completely write it off.~~
Nevermind:
"An additional maintenance look" was requested but "not completed" before the incident, Ms Homendy said.
Apparently it started immediately after Alaska installed their wifi equipment, which some sources have indicated requires opening that door plug. They apparently assumed it was due to the wifi install. Should have grounded it until the figured it out.
Alaska does have a history of poor maintenance causing crashes.
- Surely this bodes well for their acquisition of Hawaiian, which famously operates long trans-Pacific routes across thousands of miles of open water!
Ex-aircraft mechanic here. Nothing will have been done in this situation without paperwork backing the decision. There are often small niggles that could ground an aircraft, but there are manuals that can be consulted to see how many more flights can be taken before it must be grounded for rectification - the MEL (minimum equipment list) and CDL (configuration deviation list). So the airline will not have made the ultimate decision to keep flying, Boeing will.
The fact that this has now been found in two different airlines means that it’s a design flaw again, either the locking mechanism on the bolts is insufficient, or the reinstallation instructions in the maintenance manual is incorrect (the Alaska airlines aircraft door plug was recently removed to carry out maintenance on another part)
- As an airline customer, I would much rather have the airline tell me the plane was grounded due to parts being ready to fall off than the 3 hours I had to wait one time because of a busted tray table.
Agreed. This is a multi-layered fuckup. The manufacturer probably didn't tighten things down all the way, their QA didn't catch the critical defect, the plane inspectors didn't catch it during inspection, the airline didn't ground it after a pressurization warning, the pilot flew a plane with a known issue. There are several cultures of complacency at play. Hopefully the FAA can scare everyone into flying right.
- The reason I added the "if" is because I didn't see any information about age and don't know the specifics of the engineering/specs. Bolts needing the be checked annually and tightened every 5 on average could be perfectly reasonable with how much stress is on airplanes. There's a reason frequent inspection is enforced more heavily on airplanes, and it's not just because failures mean potentially falling out of the sky.
  But yeah, it's entirely possible they fucked up, but it's for sure ~~United~~ Alaska did.
- The Swiss Cheese Stack of failure modes
Failure is a chain.

MAX must stand for "MAX Profits" because they sure cut lots of corners on that aircraft.

More like unexpected new features, like the all new spontaneous exit row!
- Just think how much easier it will be to get extra leg room now.
I wonder how many cents they saved by not ensuring the bolts were properly tightened.
- Probably more than you think. This strikes me as an understaffing issue in the factory. Loose bolts happen when the person who is supposed to verify the work has been done correctly, is busy doing work elsewhere on the plane. Understaffing causes people to pitch-in to make deadlines, or to ease the burden on their co-workers. Seems trivial at first, but with airplanes, this behavior gets people killed.

After looking at that diagram I have to ask - why in the everliving fuck would a pressure bearing panel like that be hung by bolts and not inserted into the cabin and held in place by the ribs of the fuselage? I mean seriously?

I don’t get why they don’t just make it a bit bigger on the inside so that when pressurized, the pressure itself seals it. Seems like a fail safe solution instead of this shadiness.
- But mah profits!
  737 Max is still a developing example of what happens when you leave corporate to self-regulate themselves.
- I think it's to save space. See: DC-10 Cargo Door fiasco
- It does. It is still a plug-type door. It pushes against 12 stop pads. This design has been used for many years, including on the 737-900 that predated the Max9. You can see the exit plug in this photo form 2007, before the Max was even a thing. Also, cargo doors have worked the same way for many more years than that.
  They do it so that the door does not have to swing the whole way inside to fit out.
- It is, kind of. The plug is secured by 6 stops (or tabs) along each side. The positive pressure differential pushes the plug outwards into those stops.
  To remove the plug you uninstall 4 bolts which allow the plug to go up and over the stops, after which it can hinge outwards on a hinge found at the bottom of the plug.
  Source: https://youtu.be/WhfK9jlZK1o?si=dbUV1i2nNFcNixQh
It’s a door plug, which means it’s meant to be replaced with an actual door if required, so a lot of the hardware for an actual door are in place. Doors are designed to slide in, then raise up so the stop pins engage the stop fittings from the inside, so the door is in effect bigger than the hole it’s in. this video provides a detailed explanation of how it works.
The big issue here is that the airplane is only 2 months old, it was delivered from Boeing in late October. Which means it’s either a design flaw or a process flaw in the original manufacturing. This smacks of corporate cost cutting again. Boeing are totally on the hook for this and it’s only lucky there were no lives lost. You watch, they’ll blame it on the airline initially but the fault will come back round to them again.
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  this video provides a detailed explanation of how it works.
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That's how the normal doors work because they aren't permanently secured in place. The reason is weight as it pretty much always is in aviation design.

United Airlines make it sound like a mundane event finding those loose bolts.

“Oopsie-daisy!”
— Unities Airlines

This is the best summary I could come up with:

Bolts in need of "additional tightening" have been found during inspections of Boeing 737 Max 9s, United Airlines has said.

Inspections began after a section of the fuselage fell from an Alaska Airlines 737 Max 9 on Friday.

United Airlines said "installation issues" relating to door plugs would be "remedied" before the aircraft type would return to service.

In its statement, United said: "Since we began preliminary inspections on Saturday, we have found instances that appear to relate to installation issues in the door plug - for example, bolts that needed additional tightening."

The door plug is a piece of fuselage with a window that can be used as an emergency exit in certain configurations.

It was this part of the Alaska Airlines plane which dramatically fell off mid-flight over the US state of Oregon, eventually landing in a teacher's back garden.

The original article contains 204 words, the summary contains 142 words. Saved 30%. I'm a bot and I'm open source!

Lovely, I'm flying united to Ireland in two months. Fingers crossed I get an older version.

Better you're on the airline where they found the problems than the airline that didn't.
Ah, playin' it safe, are ya? Why not spice things up a bit? Flyin' United, might as well throw in a bit of turbulence for the craic!

So are they just going to tighten them up real well and call it a day? Also are these the same planes they were urging the FAA to let them flight without further inspection?

Picture of one of the aircraft’s bolts: https://x.com/byerussell/status/1744460136855294106?s=46

Not clear if this is the cause of the Alaska accident. Those bolts hold on the hinges at the bottom, and the photos appear to show those hinges still attached on the incident aircraft.

I hope the front doesn't fall off.

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front doesn't fall off
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Well, as long as it's not in the environment, at least.

I am glad to read all these reports, investigations and of course the emotional laden criticisms of actors associated with this. Because each time I check aviation incidents in Russia, they determine in the first 24 hours it must have been the pilots fault.