Bowed rotor is the convective temp gradient after shutdown. It can happen with any engine, and it's usually at its worst 30-60 minutes after shutdown (i.e. normal turnaround time
). If the engine is restarted at this point, vibs will be abnormally high for a few minutes. I suppose the bowing could be bad enough to cause a rotor/stator bind, although I'm not familiar with this occurring in real life.
In any case, while bowed rotor and core lock are related (differential cooling after shutdown), they are really separate phenomena.
milt said -
The Avon engine, and I guess most others, have what is called a balance piston as part of the rotating spool. Using compressor bleed air pressure on one side and atmospheric pressure on the other side the resulting imbalance is supposed to take out most of the end thrust on the spool bearings.
I suspect many different engine types have had this problem at one time or another. The fact that the Avon bearing thrust fell to zero is really a matter of bad luck on the designer\'s part. Designing just the right amount of preload into the bearing is a real crapshoot; there are so many variables in the game. Fortunately the fix action is usually fairly simple.
But bearing thrust load is a different problem from either core lock or bowed rotor.