What was found
(CAN) DURING HELI-SKI OPRATIONS UNUSUAL, INTERMITTENT VIBRATION FELT BY PILOT & NOTICED TO BE INCREASING WITH TIME. ON-SITE ENGINEER BEGAN TROUBLESHOOTING PROCESS BY REMOVING & INSPECTING ENGINE OIL COOLER BLOWER FANS. ON INSTATI ON NR 2 POWER SECTION COULD NOT BE ROTATED BY HAND TO ALIGN BLOWER. AS IS NOT NORMAL FOR PT6 TWIN PAC A/C GROUNDED & POWER SECTION REPL COMPLETE WITH AFCU, MFCU, FUEL PUMP&BLEED VALVE. GROUND RUN AND TEST FLT INDICATED NORMAL VIBRATION LEVEL&A/C FLOWN TO HOME BASE IN KELOWNA. SHORTLY BEFORE LDG WITH INCREASED POWER SETTINGS VIBRATION RETURNED TO IT'S PREVIOUS LEVEL.