What was found
WHEN PILOT SELECTED GEAR DOWN INCOMPLETE EXTENSION OCCURRED. ATTEMPTS TO EXTEND THE GEAR MANUALLY ALSO FAILED. AFTER THE AIRCRAFT WAS RETREIVED, PLACED ON JACKS AND BELLY PANELS REMOVED, IT WAS DISCOVERED THE MAIN LANDING GEAR ACTUATOR (DUKES) COUPLING BETWEEN THE MOTOR AND TRANSMISSION WAS SEPARATED, ALSO, THE MOTOR WAS FOUND NOT TO RUN ELECTRICALLY. PROBABLE CAUSE: MOTOR/ TRANSMISSION COUPLING SEPARATED, CAUSING MOTOR TO SEIED. COUPLING IS 30+YEARS OLD.