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Comment by Scoundreller | Hacker News Reader

Or it means the torque specs were a little too low, or too high and stripped, or the bolt threading was defective/spec’d wrong. Or bad metallurgy. Or the spec didn’t specify which order to tighten the bolts, so which direction you go causes different outcomes.

Lots of stuff is assembled consistently and carefully “wrong”, but as specified.

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It could also mean their torque wrenches are not being properly calibrated and traced, and have become out of spec. Out of college I worked as a mechanical engineer at a torque testing firm. We made devices with high quality torque sensors which are calibrated against NIST certified weights every 3-6 months, and those sensors are supposed to be used to check every single torque wrench both before and after each work shift to ensure they are accurate. Someone could choose to ignore that process, if they were sloppily cutting costs.

A recent example of your points: Toyota recently had wheels literally falling off cars due to mistakes like those.

Just because I'm a pedant and had to check, I can't find anything saying that wheels had actually fallen off, the recall was just that they could :D

To be fair it seems there is an image of some of the loose bolts:

https://nitter.net/ByERussell/status/1744460136855294106

I think this should stick out to an assembly person as not quite right.

Note that, as a comment there states, there are tool marks indicating the bolts were both tightened and loosened at various points.

Complicates the issue of who is at fault; where/when were they loosened?

Maybe it was opened for maintenance reasons after it was initially installed. Maybe it was torqued twice to get the lock pin through.

That lock nut may not have lined up correctly for some reason and was backed off a bit to get the pin in? That could make it torqued under spec. But also, it doesn't look like that bolt clamps anything so it may not matter if it was a little "loose"..

Are you looking at the center nut in the photo that's cotter pinned in place, or the two over on the right side that appear to be "loosely threaded on at best, washer rattling along the shaft"?

The center one doesn't concern me. The two that aren't even finger tight do.

I was and missed everyone was talking about those other bolts in this particular case.

Those are much more problematic as the remaining tight bolts could fail leading to a cascade. Though, would expect the flange to still be connected to the post in the aftermath images and the upper pins .. how did they get out of the track?

I wish we had close up pics of all the bits in the airframe opening.

idk what aviation standards say but shouldnt loctite or spring washers at least be used

Bolts are torqued down to spec and if specified will have a retention mechanism, usually a pin, a foldover or a wire.

These bolts were fitted with a wire pin to prevent the nuts from spinning loose. The nuts were not locking nuts on their own.

So it's not the worker who ducked up, but there are loose bolts either way because the Walsh gang took over.

Some part of the process -- anywhere from specs to assembly-- had some cost cutting that led to the outcome. The root cause of this problem is something financially motivated.

While I don’t disagree with you that it is possible, it isn’t a very “engineering” approach to declare that is the case without doing a root cause analysis. Stating it as fact is as bad as the MBAs…

You don't know that.

Cost cutting could have been a factor. Or the root cause might have been something entirely different.

It's quite possible to choose to spend more money on a process or method you believe is higher quality, but still discover it has some specific problem that the previous cheaper version didn't.

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