Incident Overview
During the initial approach descent from cruise altitude, the engine experienced a loss of power. The pilot responded by richening the fuel mixture, which resulted in increased engine vibrations. Shortly thereafter, the pilot observed a drop in manifold pressure and reduced the throttle setting. When power was reapplied, vibrations of a greater magnitude occurred.
Emergency Response
The pilot notified Los Angeles Air Route Traffic Control Center (ARTCC) of the emergency. Controllers directed the pilot toward the nearest airport for landing. However, after evaluating the distance to the closest airport, the pilot decided to execute an off-airport landing in a vacant dirt lot.
Postcrash Examination
The engine that failed was a factory remanufactured Continental IO-550, which had been installed the previous May. This engine replaced the original Continental IO-520, and the installation was authorized under a supplemental type certificate (STC). During the postcrash inspection, a broken cam gear was discovered.
Investigation Findings
The official investigation did not assign a probable cause for the accident. The broken cam gear was documented, but no causal relationship was explicitly stated between the gear failure and the engine power loss.