LNDG MD11 EXPERIENCED BLAST TURB FROM DEPARTING B747 ON RWY 31L AT JFK.

Narrative

LNDG AND DEPARTING RWY 31L (ALL OTHER RWYS CLOSED). NUMEROUS INBOUNDS; WITH DEPS WAITING. ACFT #1 CALLED ON FINAL. I ADVISED THE ACFT TO REDUCE TO FINAL APCH SPD; THAT THERE WOULD BE A HVY B747 DEP (ACFT #2) PRIOR TO HIS ARR; WHICH HE ACKNOWLEDGED. PREVIOUS ARR LANDED AND I INSTRUCTED ACFT #2 TO TAXI INTO POS AND HOLD; AND ADVISED THAT TFC WAS ON A 5 MI FINAL. WHEN THE ARR CLRED; I CLRED ACFT #2 FOR TKOF; 'WITHOUT DELAY.' HE ACKNOWLEDGED THAT HE WAS ROLLING; AND I THEN CLRED ACFT #1 TO LAND; WITH A CAUTIONARY WAKE TURB ADVISORY. ACFT #2 WAS 6000 FT FROM THE LNDG THRESHOLD AND AIRBORNE; WHEN ACFT #1 CROSSED THE THRESHOLD; LEGAL PER FAA 7110.65. WHILE ROLLING OUT; I ADVISED ACFT #1 TO TURN R; WHICH THE PLT ACKNOWLEDGED; ADDING ('...FOR YOUR INFO; THAT SEPARATION SUCKED.') I REPLIED THAT I HAD ASKED HIM TO REDUCE ON FINAL; THAT IT WAS LEGAL; AND IF IT WAS A PROB I WOULD HAVE ISSUED A GAR; OR THAT HE COULD HAVE INITIATED A GAR ON HIS OWN. HE THEN ADVISED THAT HE WAS AT FINAL SPD 164 KTS OUT OF 2500 FT; WHICH WAS BEFORE HE WAS ON MY FREQ. I ADVISED THAT; IN THE FUTURE; IF HE IS AT FINAL APCH SPD WHEN I ASK HIM TO REDUCE; TO ADVISE AT THAT TIME. I HAD THE OPTION OF ISSUING A GAR TO ACFT #1; BUT ANTICIPATED AND ULTIMATELY HAD; THE LEGAL RWY SEPARATION. I ISSUED TA'S TO BOTH ACFT; ISSUED A CAUTIONARY WAKE TURB ADVISORY AND FEEL THAT; AS THE PIC IS THE FINAL AUTH AS TO THE OP OF THE ACFT; HE HAD THE OPTION OF EXECUTING A GAR ON HIS OWN IF HE WAS UNCOMFORTABLE. AS THE SEPARATION WAS LEGAL; I SAW NO NEED TO ISSUE A GAR; AS THAT WOULD HAVE PLACED ACFT #1 IN THE AIR BEHIND ACFT #2 AND; DUE TO AIRSPACE CONSTRAINTS; BOTH ACFT WOULD HAVE BEEN REQUIRED TO TURN L; WHICH WOULD HAVE MADE CONTINUED SEPARATION DIFFICULT.