ACR HAS TCASII TA THEN RA; THEN SIGHTS TFC. DSNDS AS INDICATED.

Narrative

APCHING LAX ON THE JULIAN 3 ARR JUST PRIOR TO PARADISE VOR; WERE GIVEN HDG OF 340 DEGS TO INTERCEPT RWY 25L LOC. JUST PRIOR TO INTERCEPT; TCASII TA SOUNDED. TARGET ACFT WAS APCHING FROM ABOVE AND R OF OUR POS. CREW DID NOT VISUALLY ACQUIRE OTHER ACFT BUT COULD SEE IT ON TCASII DISPLAY AS IT WAS STEPPED FROM 25 TO 10 MI RANGE. AT APPROX 5 MI RANGE THE FO; WHO WAS THE PF; VISUALLY ACQUIRED THE TARGET ACFT; AN LTT. SIMULTANEOUSLY THE DSND WARNING WAS DIRECTING A DSCNT; THE FO DISENGAGED THE AUTOPLT AND INITIATED DSCNT TO APPROX 15300 FT MSL. DURING ENTIRE DSCNT THE LTT WAS KEPT IN SIGHT AND HE PASSED OVERHEAD OUR ACFT AT 16500 FT MSL. DSCNT WAS INITIATED DUE TO TCASII DIRECTION AND VISUAL ASSESSMENT OF ANOTHER ACFT DSNDING DIRECTLY INTO OUR PROPOSED POS. WE DID NOT KNOW HE WAS STOPPING HIS DSCNT AT 16500 FT. OUR CREW WAS NEVER INFORMED OF THE OTHER ACFT'S POS OR INTENTION UNTIL WE INITIATED THE INQUIRY WELL INTO OUR DSCNT. CTLR'S RESPONSE WAS TO THE EFFECT OF RPTING 'ANOTHER ACFT VFR AT 16500 FT.' LOS ANGELES HAS BUSY AIRSPACE. SEE AND AVOID IF POSSIBLE. HEADS UP FROM THE CTLR WOULD HAVE HELPED. THE TCASII SYS WORKED PERFECTLY THROUGHOUT.