Incident Overview
A pilot experienced severe engine vibration approximately 500 feet above ground level during initial climb. Attempts to reduce the vibration by lowering power were unsuccessful. Unable to return to the airport due to insufficient altitude, the pilot performed a forced landing to a vacant field.
Pilot Account
According to the pilot, the engine began losing power after takeoff. He initially aimed for a field south of the crash site but reported being too high and fast to land there. He then turned to land downwind. At about 30 feet above ground level, the airplane stalled, fell to the ground, and nosed over.
Witness Observations
Witnesses reported hearing an aircraft overhead making strange noises. They observed the aircraft make an abrupt turn for landing, after which the landing gear struck the ground. The gear collapsed, and the aircraft nosed over onto its back.
Subsequent Investigation
A flight crew from the Los Angeles County Sheriff's Department responded, interviewing the pilot at the scene. The pilot, who was also the owner and builder of the aircraft, stated that the drive belt had rolled forward out of the pulley in the belt reduction drive unit. This failure induced the vibration and caused a loss of drive power to the propeller.
Probable Cause Determination
The pilot-reported failure of the drive belt to remain in its pulley within the reduction drive unit was identified as the direct cause of the engine vibration and subsequent loss of propeller power.