Amateur-built XS N120EJ accident near Winters, California

Probable cause

The pilot's failure to properly install a wrist pin circlip, which resulted in internal damage to the No. 5 cylinder and a subsequent total loss of engine power.

NTSB analysis

During a local flight, the pilot, who was also the builder of the airplane, heard a noise accompanied by a sudden vibration and partial loss of engine power. He noted that the No. 5 cylinder exhaust gas temperature was abnormally low. He recycled the throttle, but the vibration persisted, and the engine lost total power. The pilot performed a forced landing into a field, during which the airplane nosed over and was substantially damaged.

The pilot had removed cylinder Nos. 3 and 5 from the airplane to install new piston rings several months (4 flight hours) before the accident. Postaccident examination revealed internal catastrophic damage to the No. 5 cylinder and engine case, consistent with a No. 5 cylinder wrist pin circlip being improperly installed.

Text from the NTSB. Open the NTSB docket for WPR19LA108 for the full record.