Narrative:

I was working north scope with arrs to dayton airport. Aircraft X was established on the localizer at 3000 ft cleared for the ILS runway 24R approach. I had aircraft Y on a tight base behind aircraft X. When I turned aircraft Y to a 150 degree heading this was pointed at about a 10 mi final, 10 mi north of dayton airport, aircraft X at the time was on a 11 mi final. When aircraft Y was 8 mi north, I observed aircraft Y was too tight so I turned aircraft Y to a 080 degree heading, with pilot acknowledgement. I then had a departure come off dayton airport, idented him with instructions. I then observed aircraft Y still on a 150 degree heading. I initiated a turn to a heading of 080 degrees with a traffic call on the aircraft X on final at 12 O'clock position, 3 mi. The aircraft Y was then taking the turn descending out of 4000 ft. With the tailwind push on aircraft Y I estimate that aircraft Y came within 2-2 1/2 mi of aircraft X laterally and about 500-600 ft vertically. Aircraft Y was pointed about 3/4-1 mi behind aircraft X on the approach. My first instinct was to turn aircraft Y out first, for safety concerns, rather than attempt to climb back up to 4000 ft as lateral separation would have decreased with that option. To rectify the whole scenario, I realize I should have aircraft Y at 4000 ft, ensured vertical separation at all times, left until lateral separation was established.

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Original NASA ASRS Text

Title: DAY CTLR LOST SEPARATION WHILE VECTORING 2 ACFT TO ILS FINAL BTWN 3000 FT AND 4000 FT.

Narrative: I WAS WORKING N SCOPE WITH ARRS TO DAYTON ARPT. ACFT X WAS ESTABLISHED ON THE LOC AT 3000 FT CLRED FOR THE ILS RWY 24R APCH. I HAD ACFT Y ON A TIGHT BASE BEHIND ACFT X. WHEN I TURNED ACFT Y TO A 150 DEG HDG THIS WAS POINTED AT ABOUT A 10 MI FINAL, 10 MI N OF DAYTON ARPT, ACFT X AT THE TIME WAS ON A 11 MI FINAL. WHEN ACFT Y WAS 8 MI N, I OBSERVED ACFT Y WAS TOO TIGHT SO I TURNED ACFT Y TO A 080 DEG HDG, WITH PLT ACKNOWLEDGEMENT. I THEN HAD A DEP COME OFF DAYTON ARPT, IDENTED HIM WITH INSTRUCTIONS. I THEN OBSERVED ACFT Y STILL ON A 150 DEG HDG. I INITIATED A TURN TO A HEADING OF 080 DEGS WITH A TFC CALL ON THE ACFT X ON FINAL AT 12 O'CLOCK POS, 3 MI. THE ACFT Y WAS THEN TAKING THE TURN DSNDING OUT OF 4000 FT. WITH THE TAILWIND PUSH ON ACFT Y I ESTIMATE THAT ACFT Y CAME WITHIN 2-2 1/2 MI OF ACFT X LATERALLY AND ABOUT 500-600 FT VERTLY. ACFT Y WAS POINTED ABOUT 3/4-1 MI BEHIND ACFT X ON THE APCH. MY FIRST INSTINCT WAS TO TURN ACFT Y OUT FIRST, FOR SAFETY CONCERNS, RATHER THAN ATTEMPT TO CLB BACK UP TO 4000 FT AS LATERAL SEPARATION WOULD HAVE DECREASED WITH THAT OPTION. TO RECTIFY THE WHOLE SCENARIO, I REALIZE I SHOULD HAVE ACFT Y AT 4000 FT, ENSURED VERT SEPARATION AT ALL TIMES, LEFT UNTIL LATERAL SEPARATION WAS ESTABLISHED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.