Incident Overview
During flight, the engine's rotational speed (RPM) exceeded its maximum limit. The pilot attempted to reduce RPM using the propeller control, but the control had no effect. While in the process of shutting down the engine, engine oil sprayed out from the cowling and onto the windshield. Unable to glide to an airport, the pilot elected to land in a corn field. As the aircraft approached the field, the pilot observed powerlines in the glide path and maneuvered to avoid them. The aircraft then landed hard with the landing gear retracted.
Mechanical Findings
A teardown inspection of the engine revealed that the No. 3 cylinder exhaust valve guide was worn well beyond its service limit. This wear allowed excessive blowby from the crankcase. Consequently, the oil supply had been depleted, and there was deterioration of metal-to-metal parts due to loss of lubrication. The valve guide, part number 631496, had been out of production for approximately 8 to 9 years.