Cessna 182 N378ES accident near West Chester, Pennsylvania

Probable cause

An engine crankcase overpressurization and the subsequent loss of engine oil for reasons that could not be determined, which resulted in the failure of the No. 6 cylinder connecting rod due to a lack of lubrication.

NTSB analysis

The private pilot reported that, about 20 minutes into a cross-country, personal flight, he noticed a loss of oil pressure, Subsequently, he attempted to divert to a nearby airport. The pilot stated that, a few minutes later, the engine began to "shudder," making it difficult to control the airplane, and the oil temperature had increased, so he decided to shut down the engine. The pilot was unable to glide the airplane to the diversionary airport, so he conducted an off-airport landing at a nearby field, during which the airplane struck a utility pole, which resulted in the left wing separating from the airplane.

Examination of the airframe revealed oil streaks along the fuselage belly aft of the engine breather tube. Metal fragments were found trapped in the oil suction screen. About 1/4 quart of oil was present in the sump. Examination of the engine revealed that the crankcase and oil sump were intact, and no indications of oil leaks from the crankcase were found. Thumb compression and suction were established on all cylinders except for the No. 6 cylinder. The No. 6 connecting rod was separated from the crankshaft, and the connecting rod journal and rod end were discolored, smeared, and had gouges, consistent with thermal damage. Remnants of connecting rod bearing material were found loose inside the crankcase. A borescope examination of the remaining cylinders did not reveal any damage or unusual marks. Based on this evidence, it is likely that an engine crankcase overpressurization occurred, which resulted in the ejection of nearly all the engine oil through the breather tube; the reason for the overpressurization could not be determined. The engine likely began to shudder after the overpressurizaton as a result of the No. 6 cylinder connecting rod failing due to a lack of lubrication.

Text from the NTSB. Open the NTSB docket for ERA17LA185 for the full record.