Accident Summary
The accident flight was the first flight following the completion of the aircraft's annual inspection. During the flight, the pilot reported that he had no throttle control and that the engine was operating at 1,400 rpm. The airplane was losing altitude, and the pilot attempted a forced landing to an access road. However, the airplane struck trees, and a postcrash fire ensued.
Investigation Findings
Examination of the wreckage revealed that the throttle body portion of the carburetor remained attached to the engine. The cotter pin was missing from the throttle lever locknut, and the locknut was partially backed off from its stop. The throttle lever was loose, and the serrations on the throttle shaft stop were disengaged from the serrations on the throttle lever. No other preimpact mechanical malfunctions were observed.
Maintenance History
Review of maintenance records indicated that during the annual inspection, the throttle shaft bushings and shaft assembly were noted as worn and were subsequently removed and replaced. The mechanic who performed the work stated that he recalled installing a throttle shaft bushing and a throttle shaft but did not recall a missing cotter pin. Review of a Cessna service manual revealed instructions and diagrams specifying the locknut be secured with a cotter pin.