What was found
DURING PRE-FLIGHT INSPECTION, PILOT NOTICED A PUDDLE OF OIL (BLUE IN COLOR) ON THE GROUND BENEATH THE HELICOPTER. INSPECTION OF THE HELICOPTER BY A MAINTENANCE TECHNICIAN REVEALED TRANSMISSION OIL WAS LEAKING FROM THE LOWER TRANSMISSION HOUSING COVER PARTING SURFACE. INSPECTION OF TRANSMISSION COVER AFTER DISASSEMBLY REVEALED POROSITY IN AREA OF O-RING SEALING SURFACE OF THE COVER. THE O-RING SHOWS INDICATION OF POROSITY TRANSFER MARKS IN O-RING.