Cirrus SR22 N6JA accident near Red Oak, Iowa

Probable cause

The fatigue failure of the exhaust valve due to excessive combustion deposits, which resulted in a partial loss of engine power. Contributing to the accident was the pilot’s failure to ensure that the required scheduled maintenance was completed.

NTSB analysis

The pilot reported that the engine began to run rough during the cross-country flight, and the pilot diverted to a nearby non-tower-controlled airport, where he flew the RNAV (GPS) approach to runway 5, the airport’s longest runway. During the descent and approach, the air traffic controller informed the pilot that runway 5 was closed; however, the pilot proceeded to land, and the airplane impacted a barricade and ground equipment, which resulted in substantial damage to the left wing.

Examination of the engine found excessive combustion products on the No. 4 cylinder exhaust valve. The deposits wore the valve guide, which resulted in the improper seat of the valve, abnormal valve operation, and fatigue failure of the valve face.

The excessive combustion product deposits were most likely due to a rich fuel/air mixture, which prevented the cylinder from reaching the temperature required to ensure that lead combustion products were expelled from the cylinder with the exhaust gas. Review of the airplane’s maintenance records revealed that the engine was 15 days overdue for an annual inspection. Had the required inspection had been performed on time, the exhaust valve issues likely would have been discovered before the accident occurred.

Text from the NTSB. Open the NTSB docket for CEN24LA011 for the full record.