by potato3732842 | 2026-01-16 12:49:50+00:00
>The forces on that mount are pretty extreme. Once the bearing seized it was really a matter of time before something gave and given the strength of the casing as well as the strength of the material and mount points it was a toss-up between the bolts and the casing. The previous evidence showed a clear order to the bolts breaking suggesting one bolt was heavier loaded than the remaining ones. The new evidence points to a much more extreme failure.
As for your 'limit to rotational torque': seized bearings do not 'rotate if given enough torque' they will break right out of their casings and whatever those casings are surrounded by. The reason is that unlike your cartilage the bearings are orders of magnitude harder than the materials around them. For a bearing to seize indicates that the material has already deformed, you either catch it before the race goes or it will crack and after that all bets are quite literally off. I'm not aware of any design that would spec a bearing in a situation with such forces that would still happily work with that bearing replaced by a bushing welded to the shaft and the surrounding material even if it is statically in exactly the same position.

>What you describe is a worn bearing with an excess of play, not a seized one, which tends to exhibit roughly the same characteristics as a welded joint with dissimilar materials.

>Bearings are wear items, bearings that are worn or seized are something that should never ever happen in an aircraft, there is no way that this particular design would continue to function with sufficient margin if that bearing would fail. If not caught before it breaks the next flight is going to be a disaster. Take off in a fully loaded aircraft of this size puts extreme stress on the engine mounts. They are designed with all of their parts in working order, this is not a case of 'oh, we'll fix that the next time this craft is in for maintenance'. All parts of a plane that is certified as airworthy are supposed to be operating as originally specified.

Have you ever dicked around with servicing stuff in an application that has a lot of bearing, plain or roller element? Because it sure doesn't sound like you have with the way you're talking. Words like "sized" and "deformed" are far less binary that your spherical cow assessment implies they are. A bearing that fails for whatever reason, welds it self, and then gets spun around in the bore by its shaft is nowhere near unheard of. For bearings that are there to allow for misalignment/flex and only move a few degrees often times they simply flex the parent assembly if seized. I can't say what would be a reasonable failure mode for this assembly though because I didn't design it nor similar ones.

Unless you personally designed the mount of have insider knowledge of you are speaking with degrees of certainty that are indicative of ignorance so massive it is functionally malice. The lying bullshit about how aircraft don't fly with worn bearings is just that, bullshit. Everything has service limits that allow degrees of wear. Now on some parts it might be zero or specific preload, but all that stuff is well defined.

This is a highly nuanced technical topic. None of us have the full facts at our disposal. I think the degree to which you are up and down these comments peddling a very specific chain of causality and putting down anyone who even has the most narrow or nuanced suggestion that it might not be exactly as you suggest is indicative of a moral failing.