Amateur-built Glastar N4579J accident near Concord, California

Probable cause

A total loss of engine power for reasons that could not be determined based on the available evidence.

NTSB analysis

The student pilot reported that the purpose of the flight was to practice landings. The takeoff was uneventful, but when the airplane was on the base leg, the engine suddenly quit without warning or making any abnormal noises. The pilot attempted to restart the engine several times without success. He initiated a forced landing onto a roadway, during which the left wing impacted a light pole. The nosewheel collapsed, and the airplane then crossed an intersection and slid to a rest.

Postaccident engine examination revealed that the carburetor was fracture-separated at the attachment flange, and the air box exhibited heavy impact damage. The carburetor was disassembled, and the needle valve and floats were observed stuck in the "up" position. Slight force was applied to the float assembly, and it moved freely. No contaminants or obvious bends in the float system were found. Although a stuck needle valve can restrict fuel from entering the carburetor bowl and lead to a loss of engine failure, impact damage precluded a determination of whether the needle was stuck before the accident or during the impact sequence. No other mechanical anomalies were found with the engine that would have precluded normal operation; therefore, the reason for the loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for WPR17LA110 for the full record.