What was found
DURING A FLIGHT, THE PILOT EXPERIENCED SLUGGISH ELEVATOR CONTROL WHEEL MOVEMENT. ELEVATOR CONTROL WOULD MOVE FREELY IN NOSE UP DIRECTION BUT THE MOVEMENT IN THE NOSE DOWN DIRECTION WOULD SOMETIMES BE HARD TO MOVE AND THEN EASY TO MOVE. THIS CAUSED SEVERE PITCH OSCILLATION. PILOT FOUND THAT IF HE MOVED THE CONTROL SLOWLY, ALL WAS OK. AIRCRAFT LANDED WITHOUT INCIDENT. INVESTIGATION FOUND THE ELEVATOR AUTOPILOT SERVO INTERMITENTLY LOCKING UP IN THE THE NOSE DOWN DIRECTION CAUSING THE PILOT TO HAVE TO FIGHT THE SERVO CLUTCH. REPLACED SERVO MOTOR. ALTHOUGH THIS IS A MILITARY AIRCRAFT, THE SAME SERVO IS INSTALLED IN OTHER RAYTHEON A200 AIRCRAFT.