Incident Overview
A pilot reported an in-flight emergency after noting oil trailing from the left engine access door and subsequently observing a fire from the right engine compartment. The aircraft had just completed an annual inspection, with each engine accumulating about one hour of flight time since.
Flight Events
After takeoff, the pilot climbed to a cruise altitude of 9,000 feet, closed the cowl flaps, and set the fuel settings for 75% power. While en route, the pilot observed oil trailing from the left engine oil access door, but the left oil pressure remained within the normal range. The pilot reduced power on the left engine and requested vectors to the nearest airport. During the diversion, the pilot saw fire emanating from the aft end of the right engine compartment. The pilot shut down the right engine, declared an emergency, and subsequently executed a gear-up landing in a wet field. The approach was made over trees, and the pilot had to maneuver to avoid power lines.
Findings
Tear-down inspections of both engines revealed melting on the edges and tops of several pistons. In one engine, there was melting in the head of one cylinder and the exhaust valve seat was damaged. However, no maintenance or pre-accident discrepancies were found that would have resulted in pre-ignition or detonation. Evidence indicated that the reported fire was actually oil being consumed and ignited by the turbochargers.