Narrative:

Small transport IFR inbound from the northwest to enter a right downwind for runway 31R. I issued a landing clearance. The small transport entered an apparently normal right downwind just north of dal airport. Light transport, IFR appeared on the edge of radar coverage area approximately 10 southeast on a straight-in approach to runway 31R. I advised light transport to continue and that he was number two to follow the small transport on a right downwind midfield. The light transport pilot did not have the small transport in sight. Small transport continued sebnd on downwind until approximately 3 mi northeast. They then appeared to turn due eastbound instead of turning base leg. The light transport was approximately 7 mi on final. The small transport finally began a base turn. This was going to be a tie. I issued instructions to the small transport to turn eastbound immediately, that he would require to follow a light transport on a 5 mi final. The light transport had an indicated 50 KT overtake. I issued traffic again to the light transport. The small transport had begun the turn to the east. The light transport was made #1 for landing. Both aircraft got each other in sight. Small transport approximately heading 090 +/- to 110 +/- although still in the slow turn eastbound. The final heading of the light transport was about 310. The small transport pilot repeatedly asked what the 'deal' was. I advised that they had extended their downwind too far before turning base and that I felt it had become an unsafe situation. (Both aircraft were converging on the same point on final). (Same altitude). Dfw runs our approach control but apparently failed to advise the light transport of the inbound small transport to follow.

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Original NASA ASRS Text

Title: TWO ACFT CAME CLOSE IN THE TRAFFIC PATTERN.

Narrative: SMT IFR INBND FROM THE NW TO ENTER A R DOWNWIND FOR RWY 31R. I ISSUED A LNDG CLRNC. THE SMT ENTERED AN APPARENTLY NORMAL R DOWNWIND JUST N OF DAL ARPT. LTT, IFR APPEARED ON THE EDGE OF RADAR COVERAGE AREA APPROX 10 SE ON A STRAIGHT-IN APCH TO RWY 31R. I ADVISED LTT TO CONTINUE AND THAT HE WAS NUMBER TWO TO FOLLOW THE SMT ON A R DOWNWIND MIDFIELD. THE LTT PLT DID NOT HAVE THE SMT IN SIGHT. SMT CONTINUED SEBND ON DOWNWIND UNTIL APPROX 3 MI NE. THEY THEN APPEARED TO TURN DUE EBND INSTEAD OF TURNING BASE LEG. THE LTT WAS APPROX 7 MI ON FINAL. THE SMT FINALLY BEGAN A BASE TURN. THIS WAS GOING TO BE A TIE. I ISSUED INSTRUCTIONS TO THE SMT TO TURN EBND IMMEDIATELY, THAT HE WOULD REQUIRE TO FOLLOW A LTT ON A 5 MI FINAL. THE LTT HAD AN INDICATED 50 KT OVERTAKE. I ISSUED TFC AGAIN TO THE LTT. THE SMT HAD BEGUN THE TURN TO THE E. THE LTT WAS MADE #1 FOR LNDG. BOTH ACFT GOT EACH OTHER IN SIGHT. SMT APPROX HDG 090 +/- TO 110 +/- ALTHOUGH STILL IN THE SLOW TURN EBND. THE FINAL HDG OF THE LTT WAS ABOUT 310. THE SMT PLT REPEATEDLY ASKED WHAT THE 'DEAL' WAS. I ADVISED THAT THEY HAD EXTENDED THEIR DOWNWIND TOO FAR BEFORE TURNING BASE AND THAT I FELT IT HAD BECOME AN UNSAFE SITUATION. (BOTH ACFT WERE CONVERGING ON THE SAME POINT ON FINAL). (SAME ALT). DFW RUNS OUR APCH CTL BUT APPARENTLY FAILED TO ADVISE THE LTT OF THE INBND SMT TO FOLLOW.

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.