FredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26 Reply 1, posted (11 years 8 months 2 weeks 6 days 6 hours ago) and read 4060 times:
Lots of things. We can start making a list, see how many things we can think of? I'll start with
1) Unbalanced rotors
2) Bent shafts
3) Bearings with defects
I assume you mean jet engines/gas generator related vibrations? If you add turboprops, engine accessories and so on, there's a sh*tload of other potential sources. If you throw recips into the mix.... well, they're vibrating rather severely to begin with but you can still detect lots of things about to go wrong by monitoring vibrations in the right part of the spectrum.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
ThirtyEcho From United States of America, joined Dec 2001, 1638 posts, RR: 1 Reply 3, posted (11 years 8 months 2 weeks 5 days 16 hours ago) and read 4002 times:
Vibration in a turbine engine is caused by loose or bent things; bad vibration is caused by big loose or bent things. Vibration in a piston engine is caused by normal operation; lack of vibration in a piston engine is usually caused by fuel starvation.