What was found
DURING GROUND OPERATION BETWEEN FLIGHTS, MAINTENANCE CREW DISCOVERED OIL ON THE COWL FLAPS. UPON INVESTIGATION IT WAS DISCOVERED THAT THE UPPER OUTBOARD OIL TRANSFER TUBE PLUG WAS LOOSE. THE O-RING HAD BECOME DISPLACED. THE PLUG WAS REMOVED AND THE THREADS WERE INSPECTED AND FOUND SERVICEABLE. THE O-RING WAS REPLACED. THE PLUG WAS RE-INSTALLED AND TORQUED IAW MM. THE ENGINE WAS GROUND RUN, A PROP FEATHER FUNCTION CHECK AND LEAK CHECK WERE ACCOMPLISHED. ENGINE WAS SERVICEABLE. THE AIRCRAFT COMPLETED A FLIGHT AND A LEAK CHECK WAS ACCOMPLISHED WITH NO SIGNS OF FURTHER LEAKAGE NOTED.