Accident Details
During an instructional cross-country flight, after reaching the intended cruise altitude, the flight instructor noticed the airplane was not accelerating to the desired cruise speed. Within one to two minutes, after adjusting the mixture and applying carburetor heat, the engine began to operate roughly. The student pilot turned the airplane back toward the departure airport. As the flight proceeded, the engine roughness and power loss amplified. Approximately 9 miles southeast of the airport, the flight instructor elected to execute a precautionary landing on a dirt road.
During the precautionary landing, the airplane touched down on the nose landing gear. After impacting a ditch, the nose gear separated. The airplane then nosed over and came to rest inverted.
Examination Findings
During an examination of the engine, the single-drive dual magneto's lower timing inspection port was removed, and approximately 2 cups of engine oil drained from the magneto. It was determined that the magneto driveshaft oil seal had failed, allowing engine oil to enter the magneto. At the time of the accident, the engine had accumulated 2,030 hours since major overhaul.