What happened
Prior to departure, the pilot reported that maintenance was performed on the engine, including cleaning and inspecting the spark plugs and adding eleven quarts of oil. Approximately three hours into the flight, the aircraft encountered instrument meteorological conditions accompanied by rain. Shortly after entering these conditions, the oil pressure dropped to zero and the engine began running roughly.
The pilot secured the engine, declared an emergency, and initiated a descent under instrument meteorological conditions with guidance from Kansas City Air Route Traffic Control Center. After breaking out of the clouds, the pilot identified a rolling pasture as the only available landing site. The approach path included a drainage ditch across the landing area.
The investigation
A post-accident examination of the engine revealed evidence of oil starvation. The mechanical failure was attributed to the failure of the number six pushrod and subsequent damage to the crankcase.