What was found
RUDDER TRIM WOULD NOT OPERATE, NOTICED DURING CRUISE FLIGHT, INOP WITH A/P ON AND OFF. DEBRIEFED FLIGHT CREW IN DETAIL. IN CRUISE FLIGHT, WITH AUTO PILOT IN COMMAND THEY NOTICED THEY COULD NOT GET THE RUDDER TRIM TO OPERATE, NO FAULTS ON PANEL OR ECAM, INDICATIONS NORMAL. PERFORMED GROUND SCANS, AUTOPILOT FUNCTION TESTS WITH HYDRO POWER RUNNING RUDDER TRIM FULL SCALE 22DEG /- WITH AUTO RECENTERING. PERFORMED FULL SCALE AIL TRIM WITH NORMAL INDICATIONS NO FAULTS NOTED ON CONTROL PANEL. ALL TESTS AND CHECKS ON GROUND NORMAL A/P SYSTEM NORMAL CHECKS. SUSPECT CREW ERROR IN TRIM OPERATIONS WITH A/P'S IN COMMAND MODE. SYSTEM OK TO RETURN TO SERVICE, NO CHANGE TO CAT STATUS OR RVSM.