4 ms·

I'd be really surprised if it was just one loose bolt that would allow this to happen, but I don't know. It would be hard to believe they were that stupid, so I

I'd be really surprised if it was just one loose bolt that would allow this to happen, but I don't know. It would be hard to believe they were that stupid, so I'd rather not assume.

beej71 3y ago
I'm not a structural engineer or anything, but I don't see how a single missing bolt would allow this to happen. It would have to be at least the two upper retaining bolts, neither of which were particularly picky about torque and both of which had cotter pins on castle nuts, ideally. In my humble, ignorant opinion, this. You heard it here on the Internet. :) Last I heard, though, none of the 4 main bolts were recovered, and they were going to do lab tests to try to determine if they were present to begin with.
- bcrl 3y ago
  Watch Mayday. There are a number of accidents that were caused by a single bolt, but it is usually a systemic series of faults that allowed that to happen as was the case for Flight 17: https://www.avm-mag.com/a-loose-bolt-and-lives-lost-the-crash-of-emery-flight-17 https://www.avm-mag.com/a-loose-bolt-and-lives-lost-the-cras...
- WalterBright 3y ago
  Speculation: if none of the 4 bolts were tightened, the bolts may have vibrated loose one by one. The door blew out when the last bolt fell out. Or the wrong bolts were used - bolts that were not strong enough. Or the particular batch of bolts used were not heat treated, making them not strong enough. (You can't tell if a bolt is heat treated by looking at it.)
  - _a_a_a_ 3y ago
    Unlike you I have less than no background in this, most especially in aero, but if the faults were as basic as you've described, that would be not failure but outright engineering negligence.
    - WalterBright 3y ago
      It's not engineering negligence. It's the process that is supposed to implement the design. That said, it's also a goal of engineering to make the process easier. One such technique is to design things in patterns. Then, if something doesn't fit the pattern, attention is easily drawn to it to investigate the problem. Design things so that when they look right, they are right. For example, look at the line of rivets holding an assembly together. They should form a nice neat pattern. I try to write software the same way. I lay out the code in patterns. Anything that looks out of place in the pattern draws attention as being a mistake.
      - _a_a_a_ 3y ago
        > It's the process that is supposed to implement the design Not sure I understand, are you saying that this is a failure not of engineering but of processes? In that, the original engineering was sound but somebody took shortcuts in the implementation? Or do you mean something else?
- noduerme 3y ago
  When I test-drove my 1980 Datsun, the owner had just been working on the brakes. As I drove with him through the neighborhood, I kept hearing a clunk. I thought it was the transmission. Then at about 40mph, the rear driver's side wheel detached and went flying past my door. The rear of the car skidded on the axle until I managed to get it to a stop. Turns out the guy's family had come over right as he was tightening the lugnuts and he forgot to finish them. Maybe only one was properly tightened. He'd wanted $5k for it, but I offered him $2800 as we retrieved the wheel and he accepted.
  - inferiorhuman 3y ago
    Right but that's not a single fastener. A single missing wheel bolt or lug nut is not a catastrophic problem. If all of them are loose or missing that can be a problem.
    - noduerme 3y ago
      I mean, there's a reason there aren't just two. The other ones aren't just for backup but to reduce the stress on each other. So if you have a situation where you think you only needed two, but only one is tight, the other one shears off. In that case, it's one bolt that broke because one other one wasn't tight.

I'd be really surprised if it was just one loose bolt that would allow this to happen, but I don't know. It would be hard to believe they were that stupid, so I'd rather not assume.

beej71 3y ago

I'm not a structural engineer or anything, but I don't see how a single missing bolt would allow this to happen. It would have to be at least the two upper retaining bolts, neither of which were particularly picky about torque and both of which had cotter pins on castle nuts, ideally. In my humble, ignorant opinion, this. You heard it here on the Internet. :) Last I heard, though, none of the 4 main bolts were recovered, and they were going to do lab tests to try to determine if they were present to begin with.

bcrl 3y ago
Watch Mayday. There are a number of accidents that were caused by a single bolt, but it is usually a systemic series of faults that allowed that to happen as was the case for Flight 17: https://www.avm-mag.com/a-loose-bolt-and-lives-lost-the-crash-of-emery-flight-17 https://www.avm-mag.com/a-loose-bolt-and-lives-lost-the-cras...
WalterBright 3y ago
Speculation: if none of the 4 bolts were tightened, the bolts may have vibrated loose one by one. The door blew out when the last bolt fell out. Or the wrong bolts were used - bolts that were not strong enough. Or the particular batch of bolts used were not heat treated, making them not strong enough. (You can't tell if a bolt is heat treated by looking at it.)
- _a_a_a_ 3y ago
  Unlike you I have less than no background in this, most especially in aero, but if the faults were as basic as you've described, that would be not failure but outright engineering negligence.
  - WalterBright 3y ago
    It's not engineering negligence. It's the process that is supposed to implement the design. That said, it's also a goal of engineering to make the process easier. One such technique is to design things in patterns. Then, if something doesn't fit the pattern, attention is easily drawn to it to investigate the problem. Design things so that when they look right, they are right. For example, look at the line of rivets holding an assembly together. They should form a nice neat pattern. I try to write software the same way. I lay out the code in patterns. Anything that looks out of place in the pattern draws attention as being a mistake.
    - _a_a_a_ 3y ago
      > It's the process that is supposed to implement the design Not sure I understand, are you saying that this is a failure not of engineering but of processes? In that, the original engineering was sound but somebody took shortcuts in the implementation? Or do you mean something else?
noduerme 3y ago
When I test-drove my 1980 Datsun, the owner had just been working on the brakes. As I drove with him through the neighborhood, I kept hearing a clunk. I thought it was the transmission. Then at about 40mph, the rear driver's side wheel detached and went flying past my door. The rear of the car skidded on the axle until I managed to get it to a stop. Turns out the guy's family had come over right as he was tightening the lugnuts and he forgot to finish them. Maybe only one was properly tightened. He'd wanted $5k for it, but I offered him $2800 as we retrieved the wheel and he accepted.
- inferiorhuman 3y ago
  Right but that's not a single fastener. A single missing wheel bolt or lug nut is not a catastrophic problem. If all of them are loose or missing that can be a problem.
  - noduerme 3y ago
    I mean, there's a reason there aren't just two. The other ones aren't just for backup but to reduce the stress on each other. So if you have a situation where you think you only needed two, but only one is tight, the other one shears off. In that case, it's one bolt that broke because one other one wasn't tight.