What was found
AFTER LEVELING OFF AT 5,500 MSL THE CREW BEGAN LEANING MIXTURES AND THE RT ENGINE RPM BEGAN TO DROP AT A STEADY RATE. NO ENGINE ANNUNCIATORS APPEARED AND ALL ENGINE INSTRUMENTS READ NORMAL AFTER 15 SECONDS THE RT PROP WENT FULL FEATHER AND THE ENGINE WAS SHUTDOWN BY THE CREW. THEY RETURNED TO THE AIRPORT AND LANDED WITHOUT INCIDENT, ON ONE ENGINE. MX INSPECTED ACFT AND FOUND THE RT GOVERNOR WAS LEAKING AT THE TOP OF THE GOVERNOR BODY. GOVERNOR WAS REPLACED AND ALL SYS CHECKED GOOD. GOVERNOR WAS SENT TO OVERHAUL FACILITY FOR TEAR DOWN AND REPORT OF INTERNAL CONDITION. UPON TEARDOWN A ROTATION OIL PLUG IN THE BODY HAD CAME LOOSE AND OUT OF BODY CAUSING GOVERNOR TO LOOSE OIL PRESSURE. DURING DISCUSSION WITH OVERHAULER HE STATED THAT HE HAD NEVER SEEN THIS HAPPEN BEFORE.