[Chad C. Mulligan]

A balance issue cropping up with the engine or the fan itself would be almost impossible, unless one or the other threw a blade.

I’m thinking some sort of acoustic resonance. There’s a lot of very high energy airflows going on in and around around that fan. And there’s could be interesting stuff with that high-bypass engine. An acoustic resonance could drive mechanical vibration in turn.

[Cold Heart]

My Dad finished up his career investigating engineering failures/disasters. Some were simple some were complicated, but there were occasionally the surprises.