Accident Synopsis
A commercial pilot with 5,475 hours of experience was conducting aerial application operations. While reversing direction after a pass, he initiated a turn. At the top of the turn, a loud bang emanated from the radial engine, followed by the sound of the engine winding down. White smoke appeared from the exhaust, and the pilot noted a loss of power and a drop in manifold pressure. He executed a forced landing to a field. After touchdown, the airplane rolled approximately 250 yards before flipping over.
Post-Accident Events
The aircraft was released to the owner after the accident and later sold to another operator. Due to the damage sustained in the accident, the engine was disassembled and examined before the new owner could return the airplane to service. The new owner provided an engine disassembly report summarizing the findings.
Findings from Engine Examination
According to the engine disassembly report, undetermined causes resulted in distress to the phenolic separator bracket of the rear impeller support bearing, causing it to separate and fragment. This initiated a chain reaction of events throughout the engine, involving clearance issues, lack of lubrication, and subsequent wearing of components. The damage ultimately led to the destruction of the blower labyrinth seal and the impeller gear train, which reduced power output. The report concluded that the destroyed impeller drive gear train, coupled with the distress caused by the displaced blower spring drive mechanism and reduced power output, resulted in seizure of the propeller shaft and crankshaft, leading to a complete loss of power.