Amateur-built Velocity STD RG N133SV accident near Rosamond, California

Probable cause

A partial loss of engine power due to failure of the No. 1 connecting rod as a result of multiple fatigue cracks for reasons that could not be determined during on postaccident examination.

NTSB analysis

Shortly after departure on the local flight, the private pilot observed that the engine temperature was higher than it had been on the previous day's flight. After reducing power, the engine began to surge, which prompted the pilot to return to the airport. Unable to maintain altitude, the pilot elected to land in a vacant field. The left wing sustained substantial damage during the landing. A postaccident examination of the engine revealed that the No. 1 connecting rod assembly had failed. Although the reason for the failure could not be determined, the fracture surfaces exhibited signatures of fatigue consistent with a malfunction of the connecting rod bearing, such as improper bearing size, rotation of the bearing during service, or operation of a severely worn bearing. Such conditions would result in higher-than-normal operating stress, and likely contributed to the propogation of the fatigue cracking.

Text from the NTSB. Open the NTSB docket for WPR16LA047 for the full record.