Narrative:

Working approach, departure and handoff at the sioux falls airport, I experienced an operational error in which 2 small transport aircraft lost sep. Small transport X was handed off from ZMP at 11000', my control approximately 40 mi west. On initial contact with X I told him to descend at pilot's discretion and maintain 4000', turn right heading 120 degrees for vectors to the VOR DME runway 33 final approach course. Approximately 4 mins later X requested a contact approach, when he was approximately 20 mi west. I told him it would be less delay to be vectored for the approach. Approximately 5 mins later X reported the airport in sight. I cleared X for a visual approach to runway 33. Immediately following that aircraft Y reported the airport in sight. I told him to 'continue present heading, you're following an small transport at 12 O'clock and 6 mi, eastbound at 3400.' approximately 2 mins later I observed X track to be northbound toward aircraft Y and not toward the airport. I issued a turn to Y to the southwest and issued traffic as small transport X, 12 O'clock, 4 mi descending out of 3100', then issued a turn farther to the southwest to Y. Because of X's turn to the north, sep decreased to approximately 2 mi latitude and 700' vertical. I believe that X did not actually have the airport in sight and turned to follow the interstate to the airport causing this error. The aircraft did not make a normal track to the airport/runway. During this entire period, our radar map was fading in and out, causing some confusion and problems vectoring for the approach.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN 2 GA-TWIN ENGINE ACFT. PLT DEVIATION.

Narrative: WORKING APCH, DEP AND HDOF AT THE SIOUX FALLS ARPT, I EXPERIENCED AN OPERROR IN WHICH 2 SMT ACFT LOST SEP. SMT X WAS HANDED OFF FROM ZMP AT 11000', MY CTL APPROX 40 MI W. ON INITIAL CONTACT WITH X I TOLD HIM TO DSND AT PLT'S DISCRETION AND MAINTAIN 4000', TURN RIGHT HDG 120 DEGS FOR VECTORS TO THE VOR DME RWY 33 FINAL APCH COURSE. APPROX 4 MINS LATER X REQUESTED A CONTACT APCH, WHEN HE WAS APPROX 20 MI W. I TOLD HIM IT WOULD BE LESS DELAY TO BE VECTORED FOR THE APCH. APPROX 5 MINS LATER X RPTED THE ARPT IN SIGHT. I CLRED X FOR A VISUAL APCH TO RWY 33. IMMEDIATELY FOLLOWING THAT ACFT Y RPTED THE ARPT IN SIGHT. I TOLD HIM TO 'CONTINUE PRESENT HDG, YOU'RE FOLLOWING AN SMT AT 12 O'CLOCK AND 6 MI, EBND AT 3400.' APPROX 2 MINS LATER I OBSERVED X TRACK TO BE NBOUND TOWARD ACFT Y AND NOT TOWARD THE ARPT. I ISSUED A TURN TO Y TO THE SW AND ISSUED TFC AS SMT X, 12 O'CLOCK, 4 MI DSNDING OUT OF 3100', THEN ISSUED A TURN FARTHER TO THE SW TO Y. BECAUSE OF X'S TURN TO THE N, SEP DECREASED TO APPROX 2 MI LAT AND 700' VERT. I BELIEVE THAT X DID NOT ACTUALLY HAVE THE ARPT IN SIGHT AND TURNED TO FOLLOW THE INTERSTATE TO THE ARPT CAUSING THIS ERROR. THE ACFT DID NOT MAKE A NORMAL TRACK TO THE ARPT/RWY. DURING THIS ENTIRE PERIOD, OUR RADAR MAP WAS FADING IN AND OUT, CAUSING SOME CONFUSION AND PROBS VECTORING FOR THE APCH.

Data retrieved from NASA's ASRS site as of August 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.