What was found
WHILE ATTEMPTING TO TRIM THE AIRCRAFT FOR STRAIGHT AND LEVEL FLIGHT, THE PILOT RAN OUT OF NOSE DOWN TRIM. AFTER A SUCCESSFUL LANDING AND MAINTENANCE INVESTIGATION IT WAS FOUND THAT THE ELEVATOR TRIM TAB WAS NOT MAKING IT ALL THE WAY TO THE NOSEDOWN/ TABUP LIMIT. FURTHER INVESTIGATION REVEALED THAT THE ELEVATOR TAB ACTUATOR SPROCKET WAS SPINNING ON THE SHAFT DUE TO ONE OF THE GROOVE PINS THAT TIE THE TWO PIECES TOGETHER WAS MISSING AND THE OTHER WAS SHEARED IN HALF. THE TWO PINS WERE REPLACED WITH NEW, USING LOCTITE TO INSTALL, AND THE SYSTEM WAS RERIGGED AND OPERATIONALLY CHECKED OK. RECOMMEND CAREFUL INSPECTION OF THESE PINS EVERY 100 HOURS OF OPERATION.