TRACON INTRAFAC COORD ACR Y CLB TO OCCUPIED ALT HAD LTSS FROM ACR X. SYS ERROR.

Narrative

ACR X WAS ON A VECTOR FOR AN ILS APCH AT BWI. ACR Y WAS DEPARTING BWI TO MIA. ACR X WAS APPROX 18 MI SSW OF BWI WHEN I NOTICED THAT HE WAS HDG STRAIGHT AT ACR Y AT THE SAME ALT. I IMMEDIATELY ISSUED A TURN TO ACR X TO A HDG OF 270 DEGS AND DSNDED HIM TO 4000. I THEN POINTED THE TFC OUT TO THE GRACO CTLR WORKING ACR Y AND TOLD HER TO TURN ACR Y AND CLB. AT THIS POINT; THE ACFT WERE APPROX 7-8 MI APART. ACR X MODE C INDICATED HE CLBED 100 FT AND HIS RADAR TRACK DID NOT SHOW HIM TURNING. I THEN WENT BACK TO ACR X AND TOLD HIM TO EXPEDITE HIS DSCNT AND CALLED THE TFC. THE ACFT MISSED BY APPROX 200 FT VERT AND 1/8 OF A MI LATERALLY. THIS TOOK PLACE ABOUT 30 SECONDS AFTER I ASSUMED THE POS. THE CTLR I RELIEVED DID NOT RELAY THE INFO THAT ACR X WAS ON A HDG AND NOT ON THE STAR TO BWI. THE CTLR THAT WAS ACR X LEFT THE OPERATING QUARTERS RIGHT AWAY. HAD HE STAYED FOR 1-2 MINS; HE MIGHT HAVE SEEN THE SIT EARLIER. HOWEVER; ACR X WAS TURNED AND DSNDED ABOUT 8 MI FROM ACR Y AND DID NOT LEAVE 5000 FT UNTIL HE FLEW ABOUT 4 MI. A MORE EXPEDITIOUS COMPLIANCE WITH ATC INSTRUCTIONS WOULD HAVE AVOIDED THE ACFT FROM COMING SO CLOSE. SUPPLEMENTAL INFO FROM ACN 224888: AFTER DEP; ACR Y WAS ISSUED CLB TO 5000 FT. A FEW MINS LATER ACR Y WAS ISSUED A TURN AND CLB TO AVOID ACR X AT SAME ALT.