Narrative:

Widebody transport X captain, I was cleared for ILS runway 25L approach out of 5000'. Approximately 15 mi out I noticed a widebody transport Y below and to the right on a 90 degree course relative to our heading in a right turn (see diagram reverse side). Widebody transport Y's turn carried him across our flight path and approximately 800' below us. Momentarily I lost sight of widebody transport Y under our nose applied thrust and leveled aircraft . Widebody transport Y reappeared to the left in a right turn that now was taking him back across our flight path. I asked lax approach about traffic. We were told to maintain 3500'. Widebody transport Y then turned back left again across our flight path heading. I was now clrd to land and given a 140 KT restriction. I was very high and asked to side step to runway 25R. A very steep descent resulted in a normal landing. No further incident. After landing, I called the ATC supervisor who told me that 'widebody transport Y' was given a clearance to turn right heading 240 degree to intercept the runway 24 localizer, cleared for approach. Just then, a second widebody transport Y acknowledged the transmission meant for widebody transport Y. In the resultant confusion widebody transport Y held his heading and xed both locs. Before being turned back to correct and then back south again for another approach. Visibility approximately 5 mi. Recommendations. Better 'hearback' by widebody transport Y's flight crew. Widebody transport Y and Y possible unfamiliar with area. Should know that nontransgression area between runway exists. Possible 'backside of the clock' or widebody transport Y and Y crew's crew rest? ATC more timely 'catch' of widebody transport Y's ATC deviation.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION OCCURRED BETWEEN WDB X AND WDB Y WHEN WDB Y DID TAKE A NEW ASSIGNED HEADING.

Narrative: WDB X CAPT, I WAS CLRED FOR ILS RWY 25L APCH OUT OF 5000'. APPROX 15 MI OUT I NOTICED A WDB Y BELOW AND TO THE R ON A 90 DEG COURSE RELATIVE TO OUR HDG IN A R TURN (SEE DIAGRAM REVERSE SIDE). WDB Y'S TURN CARRIED HIM ACROSS OUR FLT PATH AND APPROX 800' BELOW US. MOMENTARILY I LOST SIGHT OF WDB Y UNDER OUR NOSE APPLIED THRUST AND LEVELED ACFT . WDB Y REAPPEARED TO THE L IN A R TURN THAT NOW WAS TAKING HIM BACK ACROSS OUR FLT PATH. I ASKED LAX APCH ABOUT TFC. WE WERE TOLD TO MAINTAIN 3500'. WDB Y THEN TURNED BACK L AGAIN ACROSS OUR FLT PATH HDG. I WAS NOW CLRD TO LAND AND GIVEN A 140 KT RESTRICTION. I WAS VERY HIGH AND ASKED TO SIDE STEP TO RWY 25R. A VERY STEEP DSNT RESULTED IN A NORMAL LNDG. NO FURTHER INCIDENT. AFTER LNDG, I CALLED THE ATC SUPVR WHO TOLD ME THAT 'WDB Y' WAS GIVEN A CLRNC TO TURN R HDG 240 DEG TO INTERCEPT THE RWY 24 LOC, CLRED FOR APCH. JUST THEN, A SEC WDB Y ACKNOWLEDGED THE XMISSION MEANT FOR WDB Y. IN THE RESULTANT CONFUSION WDB Y HELD HIS HDG AND XED BOTH LOCS. BEFORE BEING TURNED BACK TO CORRECT AND THEN BACK S AGAIN FOR ANOTHER APCH. VISIBILITY APPROX 5 MI. RECOMMENDATIONS. BETTER 'HEARBACK' BY WDB Y'S FLC. WDB Y AND Y POSSIBLE UNFAMILIAR WITH AREA. SHOULD KNOW THAT NONTRANSGRESSION AREA BTWN RWY EXISTS. POSSIBLE 'BACKSIDE OF THE CLOCK' OR WDB Y AND Y CREW'S CREW REST? ATC MORE TIMELY 'CATCH' OF WDB Y'S ATC DEV.

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.