A300 CREW HAD UNCOMMANDED RUDDER INPUT IN ZNY OCEANIC.

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ACFT EXPERIENCED A LARGE UNCOMMANDED RUDDER TRANSIENT. THE EVENT OCCURRED 1 HOUR AND 50 MINUTES; (APPROX) INTO THE FLIGHT. DURATION OF THE EVENT WAS 1 SECOND OR LESS. FLIGHT CONDITIONS AT TIME OF EVENT WERE: FL350; MACH .78; NUMBER 2 AUTOPLT ENGAGED IN ALT HOLD AND NAV; AUTOTHROTTLES ENGAGED IN MACH MODE. RIDE CONDITIONS: VERY SMOOTH; NO WX PHENOMENA IN PROXIMITY; NO ACFT IN PROXIMITY. NO FLIGHT CTL INPUT. NO CAUTIONS; WARNINGS OR ALERTS. NO ABNORMAL INDICATIONS OBSERVED ON ECAM HYD OR FLIGHT CTL PAGES. NO ABNORMAL INDICATIONS OBSERVED PRIOR TO OR AFTER EVENT. SUPPLEMENTAL INFO FROM ACN 484142: APPROX ONE HOUR AND FIFTY MINUTES INTO FLIGHT FROM POP TO JFK; ACFT EXPERIENCED AN UNCOMMANDED RUDDER TRANSIENT. THE FLIGHT HAD BEEN NORMAL UP TO THE EVENT AND WAS NORMAL AFTER THE EVENT. I ESTIMATE THE DURATION OF THE TRANSIENT AS ONE SECOND OR LESS. IT CONSISTED OF ONE RUDDER DISPLACEMENT WITH A RETURN TO NORMAL. WE WERE IN CLEAR (NEARLY CLOUDLESS) AND SMOOTH AIR AT FL350. THE AFS PANEL WAS SET TO .78M; ALT HLD; NAV; AND AUTOPLT NUMBER 2 ENGAGED AS IT WAS THE FO LEG. THE EVENT WAS SO QUICK THAT I CANNOT SWEAR AS TO WHICH WAY THE ACFT YAWED; BUT IT IS MY RECOLLECTION THAT IT YAWED TO THE RIGHT. I CONSIDERED THE AMOUNT OF YAW TO BE LARGE. FLIGHT ATTENDANTS DESCRIBED IT AS 'WAY MORE THAN NORMAL' (PURSER) TO 'SEVERE' (NUMBER 6); WHO WAS IN THE AFT GALLEY AND WOULD HAVE BEEN THROWN TO THE FLOOR HAD SHE NOT BEEN THROWN INTO ANOTHER FLIGHT ATTENDANT WHO CAUGHT HER. I BELIEVE THE CAPT DESCRIBED IT AS VERY LARGE IN THE LOG BOOK. THE AMOUNT OF YAW IS PROBABLY IRRELEVANT. THE ONLY REASON FOR DESCRIBING THE AMOUNT OF YAW IS TO INDICATE THAT IT WAS OF SUCH AN AMOUNT THAT NEITHER THE CAPT NOR MYSELF COULD HAVE MADE A RUDDER INPUT CAUSING THAT AMOUNT OF YAW WITHOUT KNOWING WE WERE MAKING THE INPUT. ALSO BOTH OF US JUMPED FOR THE CONTROLS INDICATING COMPLETE SURPRISE; AGAIN AN INDICATION THAT THE INPUT WAS NOT COMMANDED BY EITHER OF US. WE MONITORED THE FLIGHT CTL PAGE OF THE ECAM FOR MOST OF THE REMAINDER OF THE FLIGHT; EXCEPT FOR GLANCES AT CONDITIONING AND FUEL; AND THERE WERE NO ANOMALIES. DURING AUTOPLT DISCONNECT AT CAMRN AND DURING CONFIGN FOR LNDG; THERE WERE NO ANOMALIES NOTED ON THE ECAM NOR IN THE YOKE OR RUDDER PEDALS. THE FLIGHT WAS COMPLETELY NORMAL EXCEPT FOR THE ONE SPLIT SECOND RUDDER TRANSIENT. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING INFO: THE ACR REMOVED THE FLT RECORDER AND HAD A READOUT PRINTED. IT SHOWED THAT THERE WAS A LARGE RUDDER EXCURSION. SIMULTANEOUSLY IT SHOWED RUDDER PEDAL MOVEMENT. THIS WOULD RULE OUT THE YAW DAMPER SYSTEM; AS IT DOES NOT CAUSE MOVEMENT IN THE RUDDER PEDALS. THE ACR REPLACED NUMEROUS ITEMS IN THE ACFT AND HAD A FLIGHT TEST CREW FLY THE ACFT. THEY RETURNED THE ACFT TO SERVICE. THE ACFT HAS FLOWN SINCE THEN WITH NO FURTHER PROBLEMS. THE REPORTER DOES NOT KNOW WHAT WAS FOUND IN THE ACR SHOP ON THE REMOVED ITEMS.