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.
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.
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.
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…
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.
Well they left a ladder in the tail of a plane during assembly in the not distant past. It's not like just a couple screws or washers were left behind to rattle around.
An ex worked on a QA-type project related to production for them. It makes me wonder if some of the issues were more fundamental than that project could ever have addressed.
What's crazy to me is that these things do not roll of the factory line in large numbers. If it was a car plant or some other line where large numbers come off per shift, you could find that possibly one operator for one shift set their torque wrench to the wrong setting causing the finished items for that shift to be suspect. But seeing as not one plane rolls of the floor per shift, this is much more systemic like possibly the documentation was wrong or similar where it is persistently done incorrectly. Or maybe just the one plane for that one day that the worker incorrectly set their torque wrench that day.
It can be opposite of your interpretation too. If you make 100,000 cars in a year, each step is done at least 100,000 times and it's justified to have a single wrench, with single non-adjustable torque value, and automated datalogging of applied value for a particular step. Or even a robotic process. Maybe even computer vision to check fastener length.
If you make 10 or 500 planes in a year, you have to rely on multiple people to use multiple torque wrenches, with multiple attachments, to follow multiple procedures to assemble multiple planes using fasteners of multiple lengths, nearby multiple other processes and people. There is a big emphasis on procedures and traceability but there are still so many potential failure points that can go undiscovered for a long time.
When a junior software engineer drops a table in production, we don’t say the junior engineer was sloppy. We say the protections and process in place were bad.
I don’t like how the sentence in this parent comment blames individuals for process problems.
Those don’t sound very reassuring either. What’s to say that this is the only bolt with incorrect torque spec, or if this part is bad why not others, and if bad parts are not being caught during quality control then what other parts will be next to fail prematurely? And if there are unexpected vibrations in that area, why wasn’t it discovered during test flights? What other vibration issues would they not have accounted for if they weren’t capable of detecting this one?
To be fair, I read recently that another issue with MAX 7 was discovered through flight testing. The issue is that now Boeing wants to exempt plane from safety rules…
Lots of stuff is assembled consistently and carefully “wrong”, but as specified.