What was found
DISCONNECTED AUTOPILOT AND HAND FLEW ACFT FOR SEVERAL MINUTES. SHORTLY AFTER INITIATING DESCENT TO LAND, AILERONS BEGAN TO "SEIZE." ELEVATOR STILL HAD FULL MOVEMENT, THEN IT ALSO BEGAN TO SEIZE. IT TOOK ABOUT FIVE TO TEN SECONDS TO LOSE AILERON AUTHORITY, THEN ELEVATOR AUTHORITY. STILL HAD FULL RUDDER AUTHORITY. HAD TO MAKE EMERGENCY LANDING WITH ONLY A FEW DEGREES OF OPERABLE AILERON AND ELEVATOR. CONTROLLED AIRPLANE WITH RUDDER AND THROTTLE. LANDED WITHOUT DAMAGE OR INJURY. DISCOVERED ON THE GROUND THAT A/P HAD RE-ENGAGED AND THAT SERVO CLUTCHES HAD "FROZEN." DID NOT ATTEMPT TO DISCONNECT A/P IN FLIGHT BECAUSE DIDN'T KNOW IT WAS ON.