AT 11000 FT; A BEECH JET 400 FLC RECOVERS FROM A WAKE ENCOUNTER BEHIND A B747; 2 NM S OF CAMRN; NJ.

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FLT ENCOUNTERED JET UPSET CAUSED BY WAKE TURB FOLLOWING A HVY B747 ON ARR INTO JFK ARPT. ON HDOF FROM ZDC TO ZNY AT FL290; APPROX 30 NM W OF SIE; ZNY ASKED WHAT OUR SPD WAS IN KTS. WE RESPONDED WITH 290 KTS AND INSTRUCTED TO REDUCE TO 280 KTS OR LESS AND DSND TO FL230. LISTENING TO THE OTHER XMISSIONS WE SAW WHAT ZNY WAS DOING; DSNDING A B747 FROM FL340 ON A PARALLEL 10 MI COURSE TO PUT IN FRONT OF US GOING INTO JFK. WE WERE NEVER ADVISED THAT WE WERE FOLLOWING A HVY B747; BUT PNF AND I KNEW IT. WE WERE MONITORING OUR DISTANCE AND ALT FROM THE B747. WE WERE AVERAGING BTWN 10-15 MI HORIZ SEPARATION AND BECAME STEADY AT 10 MI SEPARATION APCHING THE CAMRN INTXN. PF WAS PIC; ACFT WAS ON AUTOPLT AND BEGAN TO ENCOUNTER SIGNS OF IMPENDING WAKE TURB. TO PREPARE TO REACT QUICKLY SHOULD THE TURB INCREASE IN INTENSITY; THE AUTOPLT WAS DISENGAGED. AT THAT POINT OF DISENGAGEMENT; THE AIRPLANE ROLLED TO THE R 100 DEGS AND PITCHED DOWN. IMMEDIATE OPPOSITE SPOILERON WAS USED TO STOP THE ROLL AND WINGS WERE RETURNED TO LEVEL AND PITCH DOWN TOPPED AT 400 FT BELOW OUR ASSIGNED ALT. THE AIRPLANE WAS AT 250 KTS AND 11000 FT WHEN THE UPSET OCCURRED. THE AIRPLANE LOST 400 FT IN ALT AND OFF HDG 30 DEGS. RECOVERY WAS BACK TO ALT AND OFF HDG UNTIL ATC WAS ADVISED OF OUR DEVS DUE TO SEVERE WAKE TURB FOLLOWING THE B747. WE DID NOT EXCEED ANY LIMITATIONS ON THE AIRPLANE AT ANY TIME DURING THIS EVENT. WE CONTINUED ON TO AN ILS RWY 22L APCH TO JFK UNDER NORMAL FLT CONDITIONS. ON LNDG AT JFK; CREW CALLED ZNY; SPEAKING TO SUPVR; TO VERIFY OUR ALTDEV UNTIL WE WERE UNDER CTL. HE THANKED US FOR CALLING TO CONFIRM THAT DEV AND HE CONFIRMED THAT IT WAS NOT A PROB WITH THE ALT LOSS.