Pilot Report
The pilot stated that prior to departure for a cross-country flight, one quart of oil was added to the engine, bringing the total to seven quarts. Approximately one hour and 30 minutes into the flight, the pilot observed an increase in oil temperature. Cowl flaps were opened and the mixture was enriched, resulting in a drop in exhaust gas temperature (EGT). Despite these actions, the oil temperature continued to rise and oil pressure indicated a low reading. The pilot declared an emergency and prepared to land on a dirt road. The engine began backfiring before suddenly stopping (froze). After the engine quit, the airplane rolled sharply to the right; the pilot corrected back to level flight and landed in a sagebrush field near a road. The landing resulted in substantial damage to the wings.
Engine Examination
Post-accident examination of the wreckage revealed a hole in the crankcase above and below the number 4 cylinder. Manual rotation of the crankshaft was attempted but only partial rotation was possible—about 8 inches in either direction. No oil was observed on the outside of the airplane or on the cowl. The oil sump was drained, yielding between 0.75 and 1.25 quarts of oil. Along with the oil, portions of crankcase, lifter, piston, and connecting rod material were found in the sump. The oil filter contained metallic debris throughout the filament and in the can. All cylinders exhibited internal mechanical damage, and thermal damage was noted on the number 4 connecting rod journal. The number 2 piston compression ring remained in its ring land but had broken into several pieces. Extensive oil coking signatures were observed around the circumference of the number 2 piston at the ring land, consistent with oil burn.