What was found
THROTTLE CABLE FAILED WHILE IN-FLIGHT. DEFECT DISCOVERED AT FIRST ATTEMPT TO REDUCE POWER FOR DESCENT. INNER CONTROL CABLE FAILED (SEPARATED) AT SWAGED TERMINAL END AT ENGINE. UNABLE TO CONTROL POWER OUTPUT OF ENGINE. THIS ASSEMBLY CANNOT BE VISUALLY INSPECTED DUE TO CONSTRUCTION OF THE CABLE. DEFECT AREA IS INSIDE PROTECTIVE TUBE. THIS IS NOT A LIFE LIMITED PART NOR IS THERE ANY MANUFACTURER RECOMMENDATION FOR TIME IN SERVICE BEFORE RETIREMENT. RECOMMEND REPLACEMENT AT 3,500 HOURS TIME IN SERVICE FOR ANY MIXTURE, THROTTLE, OR PROPELLER CONTROL INSTALLED IN 310 AIRPLANES DUE TO INABILITY TO INSPECT PERIODICALLY.