What was found
(CAN) DURING LEVEL FLIGHT, THE CREW ATTEMPTED TO INITIATE A SLOW DESCENT USING HORIZONTAL STAB PITCH TRIM AND NOTICED IT WAS INOPERATIVE. THEY TRIED TO USE THE SECONDARY (ALTERNATE) TRIM FUNCTION AND NOTICED IT WAS ALSO INOPERATIVE. THEY PERFORMED APPROPRIATE CHECK LIST FUNCTIONS AND FINISHED FLIGHT WITHOUT USE OF PITCH TRIM WITHOUT INCIDENT. WHEN TROUBLESHOOTING THE SYSTEM WE COULD HEAR THE MOTORS ON BOTH PRIMARY AND ALTERNATE SYSTEMS WHEN ACTIVATED BUT NO MOVEMENT WAS NOTICED. THE REST OF THE SYS WAS OK SO WE CONCLUDED THAT PITCH TRIM ACTUATOR WAS FAULTY AND HAD FAILED INTERNALLY. THE ACTUATOR WAS REPLACED AND THE SYSTEM RESUMED BEING AIRWORTHY.