Incident Overview
The pilot reported that while in cruise flight, the engine RPM decreased to 2,100. After pulling the throttle out, the RPM dropped further to 1,900. Applying full throttle only increased the RPM to 2,000. The pilot subsequently performed a forced landing to a young pecan orchard.
Fuel System Examination
Post-incident inspection of the aircraft's fuel system showed that the right fuel tank contained approximately 20 gallons of fuel, while the left fuel tank was empty.
Throttle Assembly Examination
Further examination of the throttle assembly revealed that the throttle arm castellated nut was loose, and the cotter pin was missing. This condition allowed the throttle arm to move without actuating the throttle shaft.
Maintenance History
A review of the maintenance records indicated that the throttle shaft had been replaced 6.2 hours earlier during an annual inspection. The person who performed the throttle shaft replacement reported that the airplane left his facility with the cotter pin installed.