What was found
(CAN) IMMEDIATELY AFTER STARING DESCENT, CREW NOTED OIL PRESSURE DROPPING FOLLOWED BY WARNING ANNUCIATORS ON LT POSITION. ENGINE CONTINUED TO LOSE OIL PRESSURE AND ENGINE WAS SHUTDOWN AND FEATHERED. MAINT FOUND OIL BOSS (ELBOW) FOR REDUCTION GEAR CASE RETURN OIL LINE HAD FRACTURED THROUGH 1 OF 2 ATTACHING BOLT HOLES AND HEAD OF 1 BOLT WAS DETACHED FROM STUD PORTION. HEAD WAS RETAINED BY SAFETY WIRE. IT WAS UNCERTAIN AS TO WHY THE BOSS HAD FRACTURED SO ENGINE WAS REPLACED FOR PRECAUTIONARY REASONS. ENGINE HAS SINCE BEEN CHECKED AND IS IN NORMAL OPERATING CONDITION LEADING TO DETERMINATION THAT BOSS AND/OR ATTACHING BOLTS SIMPLY FAILED AND WAS NOT CAUSED BY OIL PRESSURE SPIKES OR.