At 14:45 EDT, an American Airlines A300 landed successfully after the flightcrew experienced multiple rudder deflections that caused the airplane to yaw excessively from side to side while on final approach to runway 9R. There were no reported injuries. During the initial approach to runway 9R, as the crew configured the airplane for landing with flaps 40 degrees and the landing gear down, the airplane began to yaw left and right. The flightcrew said the rudder pedals did not move, but the yaw was enough that the captain abandoned the approach. During the go around the yaw deviations increased and became extreme. Initial examination of the flight data recorded shows that that rudder deviated continuously but not rhythmically between 5 and 11 degrees each side of center during both approaches.