What was found
APPROXIMATELY 50 MINUTES AFTER DEPARTURE THE CREW HAD DECLARED AN EMERGENCY DUE TO NR 1 ENGINE OIL LOSS, HAD DONE AN IFSD, AND WAS RETURNING TO THE DEPARTURE AIRPORT. THE AIRCRAFT MADE AN UNEVENTFUL LANDING WITH NO ADDITIONAL ISSUES. THE INITIAL INVESTIGATION SHOWED THE OIL LEAK WAS FROM THE FUEL SERVO HEATER BUT, AFTER THAT COMPONENT WAS CHANGED AND AN OFF IDLE RUN WAS PERFORMED, ANOTHER LEAK WAS FOUND FROM A SCAVENGE LINE GEARBOX FITTING. THE RING-LOCK INSERT WAS FOUND LOOSE IN THE GEARBOX BORE. THE RING-LOCK INSERT WAS REPLACED AND ALL ENGINE LEAK CHECKS AND GROUND RUNS WERE PERFORMED WITH NO FURTHER FAULTS. THE AIRCRAFT WAS RELEASED FOR SERVICE.