4 ms·

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

Check out this video showing how the plug is supposed to be installed: https://youtu.be/maLBGFYl9_o?t=540 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=soI_22ePcksISc752p6zkw 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?

fshbbdssbbgdd 3y ago
More rampant speculation! Some quotes from this article: https://www.reuters.com/business/aerospace-defense/spirit-aero-made-blowout-part-boeing-has-key-role-sources-2024-01-07/ 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 non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed. Finally, the hull is pressurized to 150% to make sure everything is working correctly, the person said. I can imagine a diffusion of responsibility as to whose job it is supposed to be to tighten those hinge bolts. Spirit is installing the plug in a “semi-rigged” state. Boeing is removing the plug to load the interior, then reinstalling it. I’d hazard a guess that Boeing is not removing the hinges, because the plug can be removed without doing so. What if, when reinstalling the plug, Boeing workers just redo the stuff they removed? They tighten the vertical movement arrestor bolt, put the pin through it, and believe they have done their job? If they never messed with those other hinge bolts, they don’t bother tightening them?
- thehappypm 3y ago
  There’s no way that this is what happened. They’re not building IKEA furniture, everything is tightly check-listed.
  - WheatMillington 3y ago
    Evidently not though....
    - nyokodo 3y ago
      > 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.
      - sp332 3y ago
        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.
        nyokodo 3y ago
        > A design problem probably would have shown up in an older one. Maybe, unless it required really specific conditions that have only occurred for this one or also required some maintenance snafu that also had nothing to do with Boeing assembly QA. We don’t have enough data to establish anything as the most probable explanation yet.
        guax 3y ago
        According to the linked article: at least five aircraft. So, not unique to this one. Or the one that blew the door out.
        jojobas 3y ago
        Surely you've heard of reliability bath-tub curve.
- avidphantasm 3y ago
  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 union-busting thing?
  - applied_heat 3y ago
    Spirit was spun out of Boeing
    - mcbain 3y ago
      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 https://youtu.be/SmJgweFmoxs The discussion about snowman hole issues and other problems is really alarming.
  - Scoundreller 3y ago
    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.
  - lotsofpulp 3y ago
    >Was this just a union-busting thing? Yes, and to lower compensation because Boeing’s benefits are probably better than Spirits, and so if Boeing wants to pay the people that make the fuselage less, then having them be employed by someone else helps them pass non discrimination testing for pre tax benefits offered to Boeing’s higher compensated employees. Also, lower unemployment insurance premiums if they want to reduce the amount of labor they buy, since Spirit would be the one laying people off.
1970-01-01 3y ago
The castle nut design requires the use of a cotter or other locking pin. https://en.wikipedia.org/wiki/Castellated_nut https://en.wikipedia.org/wiki/Castellated_nut https://en.wikipedia.org/wiki/Positive_locking_device https://en.wikipedia.org/wiki/Positive_locking_device
Rapzid 3y ago
"Loose bolts" is not a ton of detail. It could have nothing to do with any of the bolts discussed in that video. I'm having a hard time imagining how this failure could occur from just those bolts "needing tightening". They are lock bolts with pins and appear to take shear forces and provide no clamping functionality. Even if the bolts were "loose", or not torqued to spec, how would they come all the way undone? Then the bolts, under shear, work their way out completely? And isn't the lift spring forcing the top pins into the upper part of the track? On top of that the curve of the track appears to be such that outward force on the door would actually cause the pins to go into the upper part of the track. IDK, seems like there is something else going on. Different bolts maybe.
- deleted 3y ago
  [deleted]
- pests 3y ago
  The bolts themselves don't take the entirety of the shear forces. They provide tension and therefore friction between the mounting surfaces which is where the shear is handled. By being loose, there is no friction to handle shear and also the item can gain additional momentum (more distance to travel) during shakes and impacts which might increase the impact force above the rated strengths strength.
userbinator 3y ago
I'm not an aerospace engineer, but it seems those hinge bolts might be better replaced with rivets --- if the hinge isn't frequently removed from the door.

fshbbdssbbgdd 3y ago

More rampant speculation! Some quotes from this article: https://www.reuters.com/business/aerospace-defense/spirit-aero-made-blowout-part-boeing-has-key-role-sources-2024-01-07/ 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 non-functioning, door and uses the gap to load interiors. Then, the part is put back and the installation in completed. Finally, the hull is pressurized to 150% to make sure everything is working correctly, the person said. I can imagine a diffusion of responsibility as to whose job it is supposed to be to tighten those hinge bolts. Spirit is installing the plug in a “semi-rigged” state. Boeing is removing the plug to load the interior, then reinstalling it. I’d hazard a guess that Boeing is not removing the hinges, because the plug can be removed without doing so. What if, when reinstalling the plug, Boeing workers just redo the stuff they removed? They tighten the vertical movement arrestor bolt, put the pin through it, and believe they have done their job? If they never messed with those other hinge bolts, they don’t bother tightening them?

thehappypm 3y ago
There’s no way that this is what happened. They’re not building IKEA furniture, everything is tightly check-listed.
- WheatMillington 3y ago
  Evidently not though....
  - nyokodo 3y ago
    > 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.
    - sp332 3y ago
      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.
      - nyokodo 3y ago
        > A design problem probably would have shown up in an older one. Maybe, unless it required really specific conditions that have only occurred for this one or also required some maintenance snafu that also had nothing to do with Boeing assembly QA. We don’t have enough data to establish anything as the most probable explanation yet.
        guax 3y ago
        According to the linked article: at least five aircraft. So, not unique to this one. Or the one that blew the door out.
      - jojobas 3y ago
        Surely you've heard of reliability bath-tub curve.
avidphantasm 3y ago
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 union-busting thing?
- applied_heat 3y ago
  Spirit was spun out of Boeing
  - mcbain 3y ago
    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 https://youtu.be/SmJgweFmoxs The discussion about snowman hole issues and other problems is really alarming.
- Scoundreller 3y ago
  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.
- lotsofpulp 3y ago
  >Was this just a union-busting thing? Yes, and to lower compensation because Boeing’s benefits are probably better than Spirits, and so if Boeing wants to pay the people that make the fuselage less, then having them be employed by someone else helps them pass non discrimination testing for pre tax benefits offered to Boeing’s higher compensated employees. Also, lower unemployment insurance premiums if they want to reduce the amount of labor they buy, since Spirit would be the one laying people off.

1970-01-01 3y ago

The castle nut design requires the use of a cotter or other locking pin. https://en.wikipedia.org/wiki/Castellated_nut https://en.wikipedia.org/wiki/Castellated_nut https://en.wikipedia.org/wiki/Positive_locking_device https://en.wikipedia.org/wiki/Positive_locking_device

Rapzid 3y ago

"Loose bolts" is not a ton of detail. It could have nothing to do with any of the bolts discussed in that video. I'm having a hard time imagining how this failure could occur from just those bolts "needing tightening". They are lock bolts with pins and appear to take shear forces and provide no clamping functionality. Even if the bolts were "loose", or not torqued to spec, how would they come all the way undone? Then the bolts, under shear, work their way out completely? And isn't the lift spring forcing the top pins into the upper part of the track? On top of that the curve of the track appears to be such that outward force on the door would actually cause the pins to go into the upper part of the track. IDK, seems like there is something else going on. Different bolts maybe.

deleted 3y ago
[deleted]
pests 3y ago
The bolts themselves don't take the entirety of the shear forces. They provide tension and therefore friction between the mounting surfaces which is where the shear is handled. By being loose, there is no friction to handle shear and also the item can gain additional momentum (more distance to travel) during shakes and impacts which might increase the impact force above the rated strengths strength.

userbinator 3y ago

I'm not an aerospace engineer, but it seems those hinge bolts might be better replaced with rivets --- if the hinge isn't frequently removed from the door.