To try and avoid a raft of posts along the lines of "I heard that...", the AAIB report on the 2012 225 ditchings details generally how the operators used their HUMS at the time, and then specifically how the HUMS was used on each of the affected aircraft.
https://assets.digital.cabinet-offic...and_G-CHCN.pdf
The relevant sections start on page 45 at 1.11.4.4 G-REDW operator’s internal HUMS procedures.