What was found
(CAN) DURING A ROUTINE PHASE 4 INSPECTION, METALLIC POWDER WAS DISCOVERED TRAPPED IN THE ENGINE MAIN OIL FILTER. SOURCE OF CONTAMINATION WAS CONFIRMED TO BE THE PROPELLER GOVERNOR AS SOME NON-METALLIC DEBRIS WAS FOUND IN THE OVERSPEED GOVERNOR GASKET SCREEN. ONCE REMOVED, THE CSU SPLINED SHAFT CAN ONLY BE ROTATED IN ONE DIRECTION AND FEELS (ROUGH). CSU REPLACED. O/S GOVERNOR INSPECTED BY APPROVED SHOP, REINSTALLED. MFG AND PC12 MANUALS CONSULTED FOR PROPER FLUSHING ETC.