Narrative:

I was working final vector position at ny TRACON (lga area). The approach in use was expressway visual runway 31. Aircraft are vectored to the lga 225 degree radial to a point 5 DME southwest of lga for a right turn to downwind and base and land runway 31. Aircraft a (B727) is level at 3000 ft 8-10 DME southwest of lga, on lga 225 degree. Aircraft B (gulf) level at 4000 ft swbound 2-3 DME from lga. I plan to vector aircraft B to the downwind in front of aircraft a. I reduce aircraft a's airspeed. Aircraft B is first turned left heading 250 degrees and descent to 3000 ft, then 100 degrees turn to left and issued traffic at 1 O'clock position and 4 mi. Aircraft a is issued left turn 350 degrees and issued traffic. Aircraft B is turned again, left 080 degrees. Aircraft a turned further left to 320 degrees, issued traffic again. At this time aircraft a is approximately 2 NM from aircraft B on diverging headings. Aircraft a (B727) advises he sees aircraft B. I ask aircraft a to maintain visual separation. Aircraft B (gulf) airspeed is too fast for the turn and a strong northwest wind did not help in this situation. Pilots that fly this approach, most times make this turn within 3-4 mi radius of lga VOR. This aircraft's turn was 6-7 mi radius, much wider than normal. The other factor in this is, normally I do not have aircraft at same altitude, head on. I saw a hole and thought I could fit the gulf into this so called gap.

Google
 

Original NASA ASRS Text

Title: CTLR AT LGA ATTEMPTS TO ESTABLISH 2 ACFT IN-TRAIL FOR RWY 31. SEPARATION WAS LOST WHEN THE CTLR MISJUDGED SPD AND RATE OF TURN OF THE LEAD ACFT.

Narrative: I WAS WORKING FINAL VECTOR POS AT NY TRACON (LGA AREA). THE APCH IN USE WAS EXPRESSWAY VISUAL RWY 31. ACFT ARE VECTORED TO THE LGA 225 DEG RADIAL TO A POINT 5 DME SW OF LGA FOR A R TURN TO DOWNWIND AND BASE AND LAND RWY 31. ACFT A (B727) IS LEVEL AT 3000 FT 8-10 DME SW OF LGA, ON LGA 225 DEG. ACFT B (GULF) LEVEL AT 4000 FT SWBOUND 2-3 DME FROM LGA. I PLAN TO VECTOR ACFT B TO THE DOWNWIND IN FRONT OF ACFT A. I REDUCE ACFT A'S AIRSPD. ACFT B IS FIRST TURNED L HDG 250 DEGS AND DSCNT TO 3000 FT, THEN 100 DEGS TURN TO L AND ISSUED TFC AT 1 O'CLOCK POS AND 4 MI. ACFT A IS ISSUED L TURN 350 DEGS AND ISSUED TFC. ACFT B IS TURNED AGAIN, L 080 DEGS. ACFT A TURNED FURTHER L TO 320 DEGS, ISSUED TFC AGAIN. AT THIS TIME ACFT A IS APPROX 2 NM FROM ACFT B ON DIVERGING HEADINGS. ACFT A (B727) ADVISES HE SEES ACFT B. I ASK ACFT A TO MAINTAIN VISUAL SEPARATION. ACFT B (GULF) AIRSPD IS TOO FAST FOR THE TURN AND A STRONG NW WIND DID NOT HELP IN THIS SIT. PLTS THAT FLY THIS APCH, MOST TIMES MAKE THIS TURN WITHIN 3-4 MI RADIUS OF LGA VOR. THIS ACFT'S TURN WAS 6-7 MI RADIUS, MUCH WIDER THAN NORMAL. THE OTHER FACTOR IN THIS IS, NORMALLY I DO NOT HAVE ACFT AT SAME ALT, HEAD ON. I SAW A HOLE AND THOUGHT I COULD FIT THE GULF INTO THIS SO CALLED GAP.

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.