Narrative:

Departed fsm, joined BYP5 arrival to dfw. After a heading vector, ATC assigned the WILBR3 arrival. ATC assigned a 10-15 min hold at birle intersection. After holding, ATC cleared us to dfw via BYP5 arrival. South of byp ATC advised us dfw flow was changing from south to north and assigned runway 35C. We advised of our west side parking, and told to expect runway 36L. On downwind, cleared from 11000 ft to 4000 ft. Base leg was a heading of 270 degrees and airspeed of 180 KTS. Frequency was busy and prompted first officer on confirmation of runway assignment. Could not get a word in. At 1 DOT to 1/2 DOT localizer deflection of runway 35C, ATC assigned heading of 350 degrees to join. We queried him to which runway and he asked if we had the traffic or airport in sight. We told him we were IMC. At a point, I don't recall when, a clearance for ILS runway 35C was given. As we turned through approximately 330 degrees, ATC said to tighten turn to 010 degrees. Simultaneously, TCASII gave us a TA to the left of our aircraft and looked to try to see the TA traffic, but we were IMC. I turned the autoplt off to hand-fly a steep turn. ATC gave us a 040 degree heading to join, at approximately 030 degree heading we were visual with the airport and I realized I inadvertently had descended to 3600 ft during the maneuver. When initiating altitude correction, ATC cleared us for a visual to runway 35C. First officer inquired after landing if everything was ok and the controller responded, 'no problem.' we had no reason to think a loss of separation had occurred. We complied with ATC instructions as best as we could, while there seemed to be some clarity in phraseology and a late or bad turn onto the localizer in the dfw terminal. Supplemental information from acn 622495: I was working the AR3 position at D10. Air carrier Y was inbound from the northwest. I was vectoring them for a visual approach to runway 36L. Air carrier X was inbound from the southeast, being vectored to a visual approach to runway 35C by another controller. I told air carrier Y to turn to a 010 degree heading to join the runway 36L localizer about 10 mi ssw of dfw. They were descending through about 4500 ft. I then noticed air carrier X flying through the runway 35C final approach course. They were about 4 mi southeast of air carrier Y and also at 4000 ft. I heard the other controller telling air carrier X to turn right and join the runway 35C final approach course. I issued traffic to air carrier Y about air carrier X. The pilot replied with 'roger.' air carrier Y was at 4000 ft and air carrier X was at 3800 ft about 2 1/2 mi southeast of air carrier Y when air carrier X called the airport in sight. Visual separation was accomplished, but I don't know if it was before separation was lost. According to the other controller air carrier X was instructed 2 times before they went through the localizer, to turn right to join the runway 35C localizer. Air carrier X didn't begin their turn in time to join without flying through.

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Original NASA ASRS Text

Title: WHILE DSNDING ON RADAR VECTOR INTO DFW RWY 35C, AN EMJ CREW WAS CLRED TO 4000 FT BUT OVERSHOT TO 3600 FT.

Narrative: DEPARTED FSM, JOINED BYP5 ARR TO DFW. AFTER A HDG VECTOR, ATC ASSIGNED THE WILBR3 ARR. ATC ASSIGNED A 10-15 MIN HOLD AT BIRLE INTXN. AFTER HOLDING, ATC CLRED US TO DFW VIA BYP5 ARR. S OF BYP ATC ADVISED US DFW FLOW WAS CHANGING FROM S TO N AND ASSIGNED RWY 35C. WE ADVISED OF OUR W SIDE PARKING, AND TOLD TO EXPECT RWY 36L. ON DOWNWIND, CLRED FROM 11000 FT TO 4000 FT. BASE LEG WAS A HDG OF 270 DEGS AND AIRSPD OF 180 KTS. FREQ WAS BUSY AND PROMPTED FO ON CONFIRMATION OF RWY ASSIGNMENT. COULD NOT GET A WORD IN. AT 1 DOT TO 1/2 DOT LOC DEFLECTION OF RWY 35C, ATC ASSIGNED HDG OF 350 DEGS TO JOIN. WE QUERIED HIM TO WHICH RWY AND HE ASKED IF WE HAD THE TFC OR ARPT IN SIGHT. WE TOLD HIM WE WERE IMC. AT A POINT, I DON'T RECALL WHEN, A CLRNC FOR ILS RWY 35C WAS GIVEN. AS WE TURNED THROUGH APPROX 330 DEGS, ATC SAID TO TIGHTEN TURN TO 010 DEGS. SIMULTANEOUSLY, TCASII GAVE US A TA TO THE L OF OUR ACFT AND LOOKED TO TRY TO SEE THE TA TFC, BUT WE WERE IMC. I TURNED THE AUTOPLT OFF TO HAND-FLY A STEEP TURN. ATC GAVE US A 040 DEG HDG TO JOIN, AT APPROX 030 DEG HDG WE WERE VISUAL WITH THE ARPT AND I REALIZED I INADVERTENTLY HAD DSNDED TO 3600 FT DURING THE MANEUVER. WHEN INITIATING ALT CORRECTION, ATC CLRED US FOR A VISUAL TO RWY 35C. FO INQUIRED AFTER LNDG IF EVERYTHING WAS OK AND THE CTLR RESPONDED, 'NO PROB.' WE HAD NO REASON TO THINK A LOSS OF SEPARATION HAD OCCURRED. WE COMPLIED WITH ATC INSTRUCTIONS AS BEST AS WE COULD, WHILE THERE SEEMED TO BE SOME CLARITY IN PHRASEOLOGY AND A LATE OR BAD TURN ONTO THE LOC IN THE DFW TERMINAL. SUPPLEMENTAL INFO FROM ACN 622495: I WAS WORKING THE AR3 POS AT D10. ACR Y WAS INBOUND FROM THE NW. I WAS VECTORING THEM FOR A VISUAL APCH TO RWY 36L. ACR X WAS INBOUND FROM THE SE, BEING VECTORED TO A VISUAL APCH TO RWY 35C BY ANOTHER CTLR. I TOLD ACR Y TO TURN TO A 010 DEG HDG TO JOIN THE RWY 36L LOC ABOUT 10 MI SSW OF DFW. THEY WERE DSNDING THROUGH ABOUT 4500 FT. I THEN NOTICED ACR X FLYING THROUGH THE RWY 35C FINAL APCH COURSE. THEY WERE ABOUT 4 MI SE OF ACR Y AND ALSO AT 4000 FT. I HEARD THE OTHER CTLR TELLING ACR X TO TURN R AND JOIN THE RWY 35C FINAL APCH COURSE. I ISSUED TFC TO ACR Y ABOUT ACR X. THE PLT REPLIED WITH 'ROGER.' ACR Y WAS AT 4000 FT AND ACR X WAS AT 3800 FT ABOUT 2 1/2 MI SE OF ACR Y WHEN ACR X CALLED THE ARPT IN SIGHT. VISUAL SEPARATION WAS ACCOMPLISHED, BUT I DON'T KNOW IF IT WAS BEFORE SEPARATION WAS LOST. ACCORDING TO THE OTHER CTLR ACR X WAS INSTRUCTED 2 TIMES BEFORE THEY WENT THROUGH THE LOC, TO TURN R TO JOIN THE RWY 35C LOC. ACR X DIDN'T BEGIN THEIR TURN IN TIME TO JOIN WITHOUT FLYING THROUGH.

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.