What was found
ELEVATOR LOCKED UP DURING CRUISE FLIGHT AT 31,000 FEET WITH AUTO-PILOT INOPERATIVE. CREW DECLARED AN EMERGENCY AND FLIGHT DIVERTED TO STL. AIRCRAFT LANDED WITHOUT INCIDENT. NOTE: FREE MOVEMENT OF ELEVATOR WAS ACCOMPLISHED AT 3,000 FEET AND 140 KNOTS AIRSPEED. MAINTENANCE INSPECTED ELEVATOR SYSTEM AND CABLE RUNS, ALL CHECKED NORMAL. NO BINDING WAS NOTED. REPLACED AUTO-PILOT SERVO AS A PRECAUTION, OPERATIONAL CHECK NORMAL.