Amateur-built SPORTSTAR N503RK accident near Lancaster, Ohio

Probable cause

The improper installation and subsequent failure of the pushrod O-rings, which resulted in failure of the No. 4 connecting rod due to oil starvation.

NTSB analysis

The pilot observed a reduction in engine power shortly after takeoff. While attempting to return to the airport, the engine lost power completely while on the downwind leg of the airport traffic pattern, after which the pilot performed an off-airport landing. The airplane’s fuselage and horizontal stabilizer were substantially damaged during the landing.

Postaccident examination of the engine revealed that the pushrod O-rings had been incorrectly installed. This improper installation led to the disintegration of the O-rings, and the resulting debris to blocked the oil ports to the No. 4 connecting rod bearing. The lack of oil to the bearing resulted in the failure of the connecting rod, and the subsequent total loss of engine power.

The airplane’s maintenance logbooks did not document any recent engine maintenance that would have required removing the engine’s cylinder heads. The cylinders were removed and reinstalled following repair nearly 9 years, and about 58 tachometer hours, before the accident. Based on available information, it is likely that the O-rings were improperly installed during this maintenance.

Text from the NTSB. Open the NTSB docket for ERA22LA241 for the full record.