Incident Description
The pilot reported that during the preflight inspection, the oil level dipstick indicated 8 quarts and he did not remove the oil filler cap to add oil. After departure, approximately 15 minutes into the flight, the pilot heard a "loud bang." A film of oil then covered the windshield, and the engine lost total power. The pilot executed a forced landing to a muddy field, and the airplane came to rest upright.
Post-Accident Examination
An FAA inspector noted an oil film covering the windshield and extending aft along the fuselage. The engine, a Lycoming O-540-L3C5D, was examined. Boroscoping through two holes on the top side of the engine crankcase revealed that the #4 and #5 connecting rods were partially separated, and the #6 connecting rod was completely separated from the crankshaft. All connecting rods displayed signatures consistent with heat distress. The engine was removed from the airframe firewall, and no loose fittings or compromised oil lines were noted during removal. The inlet and outlet lines for the oil cooler and turbocharger were pressurized with 80 psi of air, and no leaks were found. The oil filter was removed and examined; metal shavings were present but did not completely obstruct the filter. The oil pump was removed and all internal components were intact; however, galling was observed on the pump's internal housing and on the gear teeth. The oil suction screen was removed and metal shavings were present but did not completely obstruct the screen. The oil sump contained approximately 1 quart of oil and metal fragments. The oil filler cap was not located during the examination.