What was found
UNABLE TO HOLD ALTITUDE AT 10,000 FEET ON AUTO-PILOT. DISCONNECTED AUTO-PILOT AND ELEVATOR WAS STIFF. FLEW FOR 5 TO 10 MINUTES USING STABILIZER FOR PITCH CONTROL. WHILE PUSHING UP AND DOWN SOMETHING LET GO AT 4,000 FEET. AIRCRAFT FLEW NORMAL FOR THE REST OF THE FLIGHT. *S/D* PERFORMED VISUAL INSPECTION OF CONTROL CABLE SYSTEM PER MM 27-31-00. NO FAULTS WERE FOUND IN MAINTENANCE CONTROL DISPLAY UNIT. CHECKED ELEVATOR WITH EACH HYDRAULIC SYSTEM INDIVIDUALLY AND FOUND NO FAULTS. NO SPECIFIC PARTS FOUND DAMAGED OR FAULTED.