Narrative:

Lax operation of vectoring aircraft on the downwind for the north complex. Not so normal operation of clearing aircraft for approach to ILS runway 24L with sidestep to runway 24R. Moderate or greater traffic level with no handoff assisting me the radar controller. Supervisor monitoring frequency intermittently. Air carrier X's last instructions were to 'fly heading 090 degrees' (to stay on downwind leg and stay within the airspace for the position). Air carrier X read back correctly but I noticed while clearing preceding aircraft for the approach aircraft X was in a turn to the south towards it. I instructed air carrier X to turn to a heading of 070 degrees and they replied with a readback that was part readback and part verifying. I acknowledge the heading and issued traffic to aircraft 12 O'clock position and 3 mi. Aircraft said they were looking. Their turn seemed very slow. I finally had to ask for an immediate turn to a heading of 060 degrees and tried to get some sort of separation standard going by asking the pilots if they had the traffic in sight. They finally did see their traffic but by then separation standard was lost (3 mi or a thousand ft). Initially; I thought that I may have missed a readback by the air carrier X pilot because of the preoccupation that can sometimes occur with an unusual operation as well as a busy radar session with no assistance. After reviewing the tapes; it appears the pilot read back 090 degree heading and somehow turned to a 190 degree heading (or a heading close to). It should be noted that the downwind was extended at the time due to sector saturation and; coincidentally; aircraft had turned at the 'target point' that we strive for. At the time there was a slight wind from the north and I think that slowed up the aircraft's turn rate back to the downwind. Finally; I can only speculate but it seemed his turn to the downwind was slower (even with a tailwind) because it was doing what all landing airplanes hate to do (turn away from the airport). Supplemental information from acn 795601: at 2500 ft on extended downwind into lax runway 24L on a heading of 065 degrees; we were given a turn to 180 degrees. While in the turn to 180 degrees; ATC called traffic at 12 O'clock position and gave us a turn back to 070 degrees. On taxi in; we were given a phone number to call regarding a possible loss of separation. I called the facility and was told that we turned to the wrong assigned heading. Both the PF and I were certain that we followed ATC instructions as given.

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Original NASA ASRS Text

Title: SCT CTLR DESCRIBED PLTDEV WHEN ACR ON DOWNWIND FOR LAX RWY 24R APPARENTLY TURNED TO HEADING 190 WHEN 090 WAS ISSUED.

Narrative: LAX OP OF VECTORING ACFT ON THE DOWNWIND FOR THE N COMPLEX. NOT SO NORMAL OP OF CLRING ACFT FOR APCH TO ILS RWY 24L WITH SIDESTEP TO RWY 24R. MODERATE OR GREATER TFC LEVEL WITH NO HDOF ASSISTING ME THE RADAR CTLR. SUPVR MONITORING FREQ INTERMITTENTLY. ACR X'S LAST INSTRUCTIONS WERE TO 'FLY HDG 090 DEGS' (TO STAY ON DOWNWIND LEG AND STAY WITHIN THE AIRSPACE FOR THE POS). ACR X READ BACK CORRECTLY BUT I NOTICED WHILE CLRING PRECEDING ACFT FOR THE APCH ACFT X WAS IN A TURN TO THE S TOWARDS IT. I INSTRUCTED ACR X TO TURN TO A HDG OF 070 DEGS AND THEY REPLIED WITH A READBACK THAT WAS PART READBACK AND PART VERIFYING. I ACKNOWLEDGE THE HDG AND ISSUED TFC TO ACFT 12 O'CLOCK POS AND 3 MI. ACFT SAID THEY WERE LOOKING. THEIR TURN SEEMED VERY SLOW. I FINALLY HAD TO ASK FOR AN IMMEDIATE TURN TO A HDG OF 060 DEGS AND TRIED TO GET SOME SORT OF SEPARATION STANDARD GOING BY ASKING THE PLTS IF THEY HAD THE TFC IN SIGHT. THEY FINALLY DID SEE THEIR TFC BUT BY THEN SEPARATION STANDARD WAS LOST (3 MI OR A THOUSAND FT). INITIALLY; I THOUGHT THAT I MAY HAVE MISSED A READBACK BY THE ACR X PLT BECAUSE OF THE PREOCCUPATION THAT CAN SOMETIMES OCCUR WITH AN UNUSUAL OP AS WELL AS A BUSY RADAR SESSION WITH NO ASSISTANCE. AFTER REVIEWING THE TAPES; IT APPEARS THE PLT READ BACK 090 DEG HDG AND SOMEHOW TURNED TO A 190 DEG HDG (OR A HDG CLOSE TO). IT SHOULD BE NOTED THAT THE DOWNWIND WAS EXTENDED AT THE TIME DUE TO SECTOR SATURATION AND; COINCIDENTALLY; ACFT HAD TURNED AT THE 'TARGET POINT' THAT WE STRIVE FOR. AT THE TIME THERE WAS A SLIGHT WIND FROM THE N AND I THINK THAT SLOWED UP THE ACFT'S TURN RATE BACK TO THE DOWNWIND. FINALLY; I CAN ONLY SPECULATE BUT IT SEEMED HIS TURN TO THE DOWNWIND WAS SLOWER (EVEN WITH A TAILWIND) BECAUSE IT WAS DOING WHAT ALL LNDG AIRPLANES HATE TO DO (TURN AWAY FROM THE ARPT). SUPPLEMENTAL INFO FROM ACN 795601: AT 2500 FT ON EXTENDED DOWNWIND INTO LAX RWY 24L ON A HDG OF 065 DEGS; WE WERE GIVEN A TURN TO 180 DEGS. WHILE IN THE TURN TO 180 DEGS; ATC CALLED TFC AT 12 O'CLOCK POS AND GAVE US A TURN BACK TO 070 DEGS. ON TAXI IN; WE WERE GIVEN A PHONE NUMBER TO CALL REGARDING A POSSIBLE LOSS OF SEPARATION. I CALLED THE FACILITY AND WAS TOLD THAT WE TURNED TO THE WRONG ASSIGNED HDG. BOTH THE PF AND I WERE CERTAIN THAT WE FOLLOWED ATC INSTRUCTIONS AS GIVEN.

Data retrieved from NASA's ASRS site as of May 2009 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.