Marv, (sorry)
It is a condition indicator looking at a spectrum of vibration at discrete frequencies or over a specific broad frequency range. As bearings fail or are loaded abnormally the discrete or broadband magnitude/energy increases. Unless the HUMS accelerometer is actually at the bearing these signs are not present and the fault is not detectable.
The Sultan
Last edited by The Sultan; 4th Jan 2017 at 03:29.
Reason: Typo in name