Incident Overview
Approximately ten minutes after departure, the engine oil pressure dropped to zero. The pilot attempted to return to the departure airport. As the engine began to seize, the pilot pulled the mixture to idle-cutoff and executed a forced landing in a field.
Events During Flight
During the landing roll, the nose wheel contacted soft ground and dug in, causing the airplane to nose over.
Post-Accident Findings
Post-accident inspection revealed the oil drain valve was in the open position, with fresh oil present on the airplane. The mechanic responsible for the aircraft's maintenance stated that he had placed a paper plug in the drain to prevent drips but failed to close the valve.