It might be of interest to some to have a look at the Norwegian AAIBs report on the fatal AS332L1 (LN-OPG) accident in 1997. Not that I have any reason to think there is any similarity whatsoever in what happened, but since HUMS has come up, this is a sobering reminder to all that think new equipment automatically makes a huge difference to the level of safety.
Appendix 2 to the report on page 27 shows the HUMS recordings for the relevant area. They indicate an increase in vibration levels for almost the last 100 hours before the accident. HUMS data is analysed in chapter 2.3.6 on page 105 of the main report and HUMS use in chapter 2.10 on page 151.
The english version of the report and appendices may be found here:
Havarikommisjonen