B767 FLC INITIATE EVASIVE MANEUVER FOLLOWING A B747 TIGHTLY SEQUENCED IN FRONT ON APCH THE JFK. N90 PASSES THE PROB ON TO JFK TWR.

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WE WERE ON VECTORS FOR THE VOR RWY 13L APCH AT JFK; FOLLOWING A DC10. NY APCH SQUEEZED A B747 BTWN OUR ACFT AND THE DC10. AT THE TIME WE WERE APPROX 8 MI IN TRIAL OF THE DC10. WE WERE TOLD BY ATC TO MAINTAIN 180 KIAS UNTIL CRI VOR. THE B747 WAS ALSO TOLD TO MAINTAIN 180 KIAS TO THE VOR. AT THE TIME THE SPD CLRNC WAS ISSUED WE WERE APPROX 3 1/2 MI IN TRAIL OF THE B747. WE REQUESTED THE PARALLEL RWY (13R) AS SOON AS WE REALIZED THE SPACING WAS GOING TO BE INADEQUATE; AND WE ADVISED ATC THAT THE REASON WAS FOR WAKE TURB AVOIDANCE. WHILE HOLDING 180 KTS AND WAITING FOR CLRNC TO RWY 13R WE NOTICED THAT THE SPACING WITH THE B747 WAS DETERIORATING. ATC CAME BACK WITH A CLRNC TO CONTACT TWR WITH OUR REQUEST. AS JFK APPROVED OUR REQUEST FOR RWY 13R WE ENCOUNTERED THE B747'S WAKE. OUR ACFT BANKED STEEPLY TO THE R AND BEGAN TO DSND. THE CAPT APPLIED A LARGE AMOUNT OF L AILERON; BUT THE ACFT DIDN'T RESPOND UNTIL HE APPLIED L RUDDER. THE ACFT RECOVERED AFTER APPROX LOSING 200 FT AND 10 TO 15 KIAS. WE LANDED WITHOUT FURTHER INCIDENT. SUPPLEMENTAL INFO FROM ACN 523855: BOTH THE FO AND I THEN NOTICED THE B747 HAD EXTENDED HIS GEAR AND LNDG FLAPS. WE STARTED TO SLOW; WITH A DRIFT OUT TO HIS RIGHT SIDE. OUR ACFT ROLLED 45 DEGS TO 60 DEGS R WING DOWN AND APPROX 15 DEGS NOSE LOW. AILERONS HAD NO EFFECT TO STABILIZE ACFT; BUT STEADY L RUDDER BROUGHT THE WINGS TO LEVEL. AIRSPEED WAS ABOUT 150 KIAS AT THE CONCLUSION OF EVENT.