B767 CREW HAD UNCOMMANDED R ROLL.

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ON CLBOUT AFTER DEPARTING JFK ON AN ASSIGNED HDG OF 155 DEGS; GIVEN CLRNC FOR L TURN TO BETTE INTXN. I WAS MANUALLY FLYING THE ACFT AND INITIATED A SHALLOW L TURN. THE ACFT STARTED A HARD R TURN; IT TOOK FULL L AILERON TO STOP THE ACFT AT APPROX 60 DEGS R BANK. THE ACFT DID NOT RECOVER UNTIL L RUDDER WAS APPLIED. AFTER REGAINING WINGS LEVEL ATTITUDE THE ACFT FLEW NORMALLY. AN EMER WAS DECLARED AND WE RETURNED TO JFK FOR AN UNEVENTFUL LNDG. I DO NOT KNOW WHAT CAUSED THE PROB. THE PRESENCE OF THE THIRD PLT PROVED INVALUABLE FOR SITUATIONAL AWARENESS AND HANDLING THE EMER. THIS STATEMENT IS GIVEN AT THE REQUEST OF ACR CONCERNING THE OP OF FLT ABC ON MAR/XA/00. I SERVED AS FO AND PF OF THIS FLT. THE CAPT WAS PNF. THE RELIEF FO WAS OBSERVING FROM THE JUMP SEAT. THE ACFT WAS A B767-300-ER. FLT ABC WAS THE FIRST DAY OF OUR ROTATION. FLT ABC WAS SCHEDULED TO OP FROM JFK TO FRA. THE PREFLT PHASE; TAXI AND TKOF OF FLT ABC WERE UNEVENTFUL AND NORMAL AND ALL SYS WERE OBSERVED AS FUNCTIONING NORMALLY. I WAS HAND FLYING THE ACFT ON DEP FROM JFK. WE WERE CLBING THROUGH 8000 FT TO 9000 FT; ON AN ASSIGNED HDG OF 155 DEGS; CLB 1 PWR; 250 KTS AND A CLEAN CONFIGN. BOS CTR CLRED US DIRECT TO BETTE INTXN. CAPT ENTERED DIRECT BETTE IN THE FMS AND SELECTED LNAV. I STARTED AN EASY L TURN; FOLLOWING THE FLT DIRECTOR AND THEN MOMENTARILY SCANNED OUTSIDE FOR OTHER ACFT. I RETURNED MY CROSSCHECK TO THE INSTRUMENTS AND RECOGNIZED THE ACFT WAS IN AN UNCOMMANDED R ROLL APPROACHING 60 DEGS OF BANK. I APPLIED FULL L AILERON TO STOP THE ROLL AT 60 DEGS OF BANK. AS I APPLIED FULL L AILERON INPUT I FELT RESISTANCE IN THE YOKE; AS IF THE YOKE WAS APPLYING A R TURN CTL INPUT. I CROSSCHECKED THE CAPT'S INSTRUMENTS TO CONFIRM THE ACFT WAS IN A 60 DEG R BANK. THE CAPT'S INSTRUMENTS AND MY INSTRUMENTS INDICATED THE ACFT IN A 60 DEG R BANK. BOTH YOKES WERE FULL L AILERON WITH THE RUDDER NEUTRAL. RELIEF FO CALLED OUT; 'TRY RUDDER.' I APPLIED L RUDDER AND THE ACFT BEGAN TO RECOVER. WE RECOVERED WINGS LEVEL; APPROX 7 DEGS NOSE DOWN; 300 KTS AND SEVERAL HUNDRED FT LOWER. CAPT CALLED BOS CTR FOR A HDG AND REQUESTED 250 KTS AND 10000 FT. THE ACFT FLEW NORMALLY AFTER RECOVERY. WE ANALYZED THE SIT AND OBSERVED NO EICAS MESSAGES AND THE FLT CTLS SHOWED NORMAL INDICATIONS ON THE STATUS PAGE. BOS CTR RPTED THAT THERE WAS NO ACFT IN THE AREA TO CAUSE WAKE TURB FOR THIS FLT. WE DECLARED AN EMER; DUMPED 20000 LBS AND RETURNED FOR A NORMAL (OVERWEIGHT) LNDG AT JFK. UNTIL THE INCIDENT OCCURRED THE FLT WAS NORMAL; I OBSERVED NO UNUSUAL WX OR ACFT ABNORMALITIES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CREW WAS ON A JFK TO EDFF LEG. THE R ROLL WAS VERY RAPID AND TOOK FULL L WING DOWN LATERAL CTL INPUT AND L RUDDER TO COUNTERACT. THIS LASTED FOR ABOUT 5 SECONDS AND THEN CTL BECAME NORMAL. THE RPTR DOES NOT KNOW WHAT WAS FOUND. STATEMENTS HAVE BEEN GIVEN TO THE COMPANY; UNION AIR SAFETY; THE NTSB AND THE ACFT MANUFACTURER. NUMEROUS COMPONENTS HAVE BEEN REPLACED AND THE ACFT HAS BEEN TEST FLOWN.