Narrative:

I was working the feeder east position during a busy arrival push. I assigned air carrier X a heading to get him up in the arrival sequence, which he read back. He failed to make the turn, resulting in an near midair collision with an E145. Air carrier X had several mi to make the turn. If he would have, the near midair collision would not have occurred. Supplemental information from acn 461905: we (aircraft Y) were given a vector to intercept ILS localizer runway 35C and slow to 180 KIAS. First officer (PF) began to slow aircraft from 245 KIAS. Flight X ahead of us was told to maintain 210 KIAS or greater, as he was #1 for the runway. We were then told to slow to 170 KIAS. As we intercepted ILS localizer runway 35C, flight X ahead overshot the localizer as it attempted to join it. We reported this traffic in sight. The controller, concerned over separation, queried the flight X that it was at 210 KIAS. Flight X stated it was at 210 KIAS. From our perspective, it appeared to be slower than that. ATC then asked if we were at 170 KIAS yet. The captain stated that we were not at 170 KIAS, but were slowing through 180 KIAS. At this time, flight X was about 2 mi ahead and appeared to be increasing its speed. ATC then asked if we were in our left turn to 270 degrees yet. Captain stated we had not received that vector. ATC then issued an immediate turn to 270 degrees, which we complied with. From this point we received numerous vectors but never a climb instruction. This subsequently placed us in front of another flight Z, which we had in sight. We received a TCASII RA to descend, at the same time ATC issued a climb to 6000 ft. The other flight Z also had us in sight, and did not change altitude as it was intercepting its assigned ILS localizer and was turning away from us. First officer lowered the nose into the green until our RA ended, then began an immediate climb to 6000 ft. We maintained 170 KIAS through this entire time, vectors to ILS runway 35C localizer after this were uneventful. In our judgement, the controller was doing a very good job. I think he misjudged our ability to slow the EMB145 from 245 KIAS to 180 KIAS then 170 KIAS. The flight X ahead of us may have been slower than 210 KIAS or greater ATC had assigned. We think it would be helpful if aircraft were given assigned airspds by approach as we make our initial contact. From our picture, the controller overreacted by vectoring us off the approach. This made separation that much more difficult and subsequently placed us in jeopardy with another aircraft.

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Original NASA ASRS Text

Title: D10 CTLR ALLEGES NMAC WHEN SEQUENCING 3 ACR JETS ONTO FINAL APCH AT DFW.

Narrative: I WAS WORKING THE FEEDER E POS DURING A BUSY ARR PUSH. I ASSIGNED ACR X A HDG TO GET HIM UP IN THE ARR SEQUENCE, WHICH HE READ BACK. HE FAILED TO MAKE THE TURN, RESULTING IN AN NMAC WITH AN E145. ACR X HAD SEVERAL MI TO MAKE THE TURN. IF HE WOULD HAVE, THE NMAC WOULD NOT HAVE OCCURRED. SUPPLEMENTAL INFO FROM ACN 461905: WE (ACFT Y) WERE GIVEN A VECTOR TO INTERCEPT ILS LOC RWY 35C AND SLOW TO 180 KIAS. FO (PF) BEGAN TO SLOW ACFT FROM 245 KIAS. FLT X AHEAD OF US WAS TOLD TO MAINTAIN 210 KIAS OR GREATER, AS HE WAS #1 FOR THE RWY. WE WERE THEN TOLD TO SLOW TO 170 KIAS. AS WE INTERCEPTED ILS LOC RWY 35C, FLT X AHEAD OVERSHOT THE LOC AS IT ATTEMPTED TO JOIN IT. WE RPTED THIS TFC IN SIGHT. THE CTLR, CONCERNED OVER SEPARATION, QUERIED THE FLT X THAT IT WAS AT 210 KIAS. FLT X STATED IT WAS AT 210 KIAS. FROM OUR PERSPECTIVE, IT APPEARED TO BE SLOWER THAN THAT. ATC THEN ASKED IF WE WERE AT 170 KIAS YET. THE CAPT STATED THAT WE WERE NOT AT 170 KIAS, BUT WERE SLOWING THROUGH 180 KIAS. AT THIS TIME, FLT X WAS ABOUT 2 MI AHEAD AND APPEARED TO BE INCREASING ITS SPD. ATC THEN ASKED IF WE WERE IN OUR L TURN TO 270 DEGS YET. CAPT STATED WE HAD NOT RECEIVED THAT VECTOR. ATC THEN ISSUED AN IMMEDIATE TURN TO 270 DEGS, WHICH WE COMPLIED WITH. FROM THIS POINT WE RECEIVED NUMEROUS VECTORS BUT NEVER A CLB INSTRUCTION. THIS SUBSEQUENTLY PLACED US IN FRONT OF ANOTHER FLT Z, WHICH WE HAD IN SIGHT. WE RECEIVED A TCASII RA TO DSND, AT THE SAME TIME ATC ISSUED A CLB TO 6000 FT. THE OTHER FLT Z ALSO HAD US IN SIGHT, AND DID NOT CHANGE ALT AS IT WAS INTERCEPTING ITS ASSIGNED ILS LOC AND WAS TURNING AWAY FROM US. FO LOWERED THE NOSE INTO THE GREEN UNTIL OUR RA ENDED, THEN BEGAN AN IMMEDIATE CLB TO 6000 FT. WE MAINTAINED 170 KIAS THROUGH THIS ENTIRE TIME, VECTORS TO ILS RWY 35C LOC AFTER THIS WERE UNEVENTFUL. IN OUR JUDGEMENT, THE CTLR WAS DOING A VERY GOOD JOB. I THINK HE MISJUDGED OUR ABILITY TO SLOW THE EMB145 FROM 245 KIAS TO 180 KIAS THEN 170 KIAS. THE FLT X AHEAD OF US MAY HAVE BEEN SLOWER THAN 210 KIAS OR GREATER ATC HAD ASSIGNED. WE THINK IT WOULD BE HELPFUL IF ACFT WERE GIVEN ASSIGNED AIRSPDS BY APCH AS WE MAKE OUR INITIAL CONTACT. FROM OUR PICTURE, THE CTLR OVERREACTED BY VECTORING US OFF THE APCH. THIS MADE SEPARATION THAT MUCH MORE DIFFICULT AND SUBSEQUENTLY PLACED US IN JEOPARDY WITH ANOTHER ACFT.

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.