riff_raff -
From the same report, however:
1.12.5 “…Testing of the occurrence and exemplar studs and nuts showed that after 13 to 17 assembly cycles, the nut self-locking feature was significantly damaged… “
Curiously, although Cougar CH191 and worldwide fleet maintenance records were averaging around 200 – 220 hours between filter replacements, the CHC VH-LOH had averaged only 72.6 hours over 17 replacements, so the self locking effectiveness may have been lost anyway.
Sikorsky did not recommend renewing the nuts at every filter removal/replacement until September or November 2008, several months after the CHC failure.
So, at least as far as nut (and preload) retention is concerned, it may have been little worse than refitting a worn self locking nut. Neither is desirable but only the improvised repair looks obviously suspect. The studs of both failed, at much the same time, the fatigue damage possibly having been largely done under the original attachment conditions, as later with CH191.