ATX X DSCNT THROUGH OCCUPIED ALT HAD LTSS FROM SMA Y. SYS ERROR.

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THIS WAS A CLASSIC CASE OF R/A SIDE PASSING AN INSTRUCTION FROM APCH (DSND TO 6000 FT AND DIRECT IGN) AND THE R SIDE (ME) ISSUING THE INSTRUCTION WITHOUT BEING POSITIVE IT WAS CLR OF ANY CONFLICT. ATX X ENTERED AIRSPACE APPROX 2000 FT HIGHER THAN NORMAL FOR NEWBURGH (SWF) ARRS ACCORDING TO AGREEMENT WITH ZNY. ACFT WAS DELAYED SWITCHING TO FREQ AS ZNY WAS ISSUING VFR TFC. FLT PLAN HAD INCORRECT (RED XXX) ROUTING WHICH REQUIRED MANUAL HDOF TO N90. DSNDING OUT OF 13000 FT FOR 9000 FT. SMA Y ESTABLISHED DIRECT DNY AFTER BEING VECTORED AROUND N90 DEP TFC. LEVEL AT 8000 FT. COORD BY R/A CTLR FOR HDOF DONE IN TIMELY FASHION. N90 REQUESTED ATX X DSNDING TO 6000 FT AND DIRECT IGN. R/A CTLR PASSED COORD INFO TO ME IN APPROPRIATE MANNER. DSNDED ATX X TO 6000 FT AND ISSUED TURN TO 120 DEG HDG DIRECT IGN DIRECT SWF. AT X; X RPTED LEAVING 9000 FT AND IN TURN WITH REMAINDER OF READBACK. AT THIS POINT; I OBSERVED POTENTIAL CONFLICT WITH SMA Y AS DATA BLOCK HAD BEEN PARTIALLY COVERED BY VFR TFC. SINCE ATX X WAS ESTABLISHED IN THE TURN I BELIEVED ANY ADDITIONAL TURN BY THIS ACFT WOULD NOT TAKE EFFECT WITH SUFFICIENT TIME TO ENSURE SEPARATION. I INSTRUCTED ATX X TO INCREASE DSCNT RATE DOWN TO 6000 FT TO AVOID TFC AT 8000 FT. SMA Y WAS TURNED TO A HDG OF 360 DEGS; APPROX 40 DEGS TO THE R OF COURSE. I BELIEVED THAT GIVEN THE PERFORMANCE CHARACTERISTICS OF SMA Y ANY ADDITIONAL ACTION (I.E.; FURTHER TURN; CLB; ETC) WOULD NOT BE ACCOMPLISHED IN SUFFICIENT TIME. SMA Y HAD CLBED AT A NORMAL RATE FOR A SINGLE ENG (PROP) ACFT ON DEP. I REQUESTED A RPT FROM ATX X REACHING 7000 FT AND ISSUED TFC. ATX X RPTED TFC IN SIGHT AND LEAVING 7600 FT. DATA BLOCK INDICATED 7900 FT. WHEN ATX X RPTED REACHING 7000 FT DATA BLOCK INDICATED 7300 FT. ATX X COM TRANSFERRED TO N90. SMA Y RETURNED TO DNY ON COURSE. I BELIEVE THE REASON FOR THIS INCIDENT WAS DUE TO MY FAILURE TO INITIALLY OBSERVE SMA Y AS TFC DUE TO PARTIALLY OVERLAPPING DATA BLOCK. ADDITIONAL FACTORS WOULD INCLUDE SMA Y BEING HIGHER THAN NORMAL AT BOUNDARY; LATE INITIAL CONTACT WITH ATX X; MANUAL HDOF REQUIREMENT AND PREVAILING WIND WHICH ACCELERATED CLOSURE. I DID NOT LEARN UNTIL FURTHER DISCUSSION THAT R/A HAD APPROVED ATX X AT HIGHER/LATER HDOF FOR TFC. (NOTE: TFC WAS VFR IN SECTOR 05.)