What was found
IN CRUISE FLIGHT, WITH AUTOPILOT ON, EXPERIENCED A SUDDEN YAW MOVEMENT AND BALL WENT OUT OF CENTER. RETRIMMED WITH NO PROBLEMS. THEN IN DESCENT, WITH AUTOPILOT OFF, NOTICED TRIM WOULD NOT CENTER BALL. THEN 2 OR 3 MINUTES LATER THERE WAS ANOTHER SUDDEN YAW. AP WAS OFF ON DESCENT, BUT YAW DAMPER WAS ON THROUGHOUT FLIGHT. FERRIED TO SLC FOR MAINTENANCE. REPLACED RUDDER TRIM SERVO IAW MM 32-10-05. OPS CHECKS GOOD. P/N, S/N ON 8092, OFF 5875.