Narrative:

We were on approach to lax runway 25L. At about 25-30 mi out, we were given a traffic call for a commuter flight 11 O'clock position and at 10 mi. We searched but did not see the traffic. The commuter flight called 'traffic in sight.' what I now realize must have happened, the commuter aircraft saw the B757 who was at 3 1/2 mi in front of us. About 1 min after this exchange, our B757 encountered the wake turbulence of the B757 in front of us. Our autoplt disengaged and I proceeded to hand fly the approach. I elevated 1/2 DOT above glide path to get out of wake turbulence. Since I was hand-flying, my outside scan was degraded. A min or two later we got a TCASII warning. The display showed an aircraft slightly ahead to the left at 500 ft separation. We searched but did not see the traffic. We called tower and asked if there was traffic in our vicinity. He responded 'yes the commuter.' at this point, commuter was directly above us with TCASII showing 200-300 ft separation. TCASII called out, 'descend, descend,' so we descended. We then started opening from traffic. Captain thought the commuter captain was showing off for a new first officer. I now realize, he never saw us to begin with. Solution: 1 aircraft calling traffic in sight in a situation such as this should not relieve ATC of their traffic separation responsibilities. Also, if a pilot calls traffic in sight in the approach environment he is way too busy to stare at that traffic indefinitely.

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Original NASA ASRS Text

Title: A B757 FLC IS CONFUSED REGARDING TA'S AND DURING A DISTR WITH WAKE TURB ENCOUNTER THEY EXPERIENCE AN NMAC WITH A COMMUTER FLT WHILE ON APCH TO RWY 25L, E OF LAX, CA.

Narrative: WE WERE ON APCH TO LAX RWY 25L. AT ABOUT 25-30 MI OUT, WE WERE GIVEN A TFC CALL FOR A COMMUTER FLT 11 O'CLOCK POS AND AT 10 MI. WE SEARCHED BUT DID NOT SEE THE TFC. THE COMMUTER FLT CALLED 'TFC IN SIGHT.' WHAT I NOW REALIZE MUST HAVE HAPPENED, THE COMMUTER ACFT SAW THE B757 WHO WAS AT 3 1/2 MI IN FRONT OF US. ABOUT 1 MIN AFTER THIS EXCHANGE, OUR B757 ENCOUNTERED THE WAKE TURB OF THE B757 IN FRONT OF US. OUR AUTOPLT DISENGAGED AND I PROCEEDED TO HAND FLY THE APCH. I ELEVATED 1/2 DOT ABOVE GLIDE PATH TO GET OUT OF WAKE TURB. SINCE I WAS HAND-FLYING, MY OUTSIDE SCAN WAS DEGRADED. A MIN OR TWO LATER WE GOT A TCASII WARNING. THE DISPLAY SHOWED AN ACFT SLIGHTLY AHEAD TO THE L AT 500 FT SEPARATION. WE SEARCHED BUT DID NOT SEE THE TFC. WE CALLED TWR AND ASKED IF THERE WAS TFC IN OUR VICINITY. HE RESPONDED 'YES THE COMMUTER.' AT THIS POINT, COMMUTER WAS DIRECTLY ABOVE US WITH TCASII SHOWING 200-300 FT SEPARATION. TCASII CALLED OUT, 'DSND, DSND,' SO WE DSNDED. WE THEN STARTED OPENING FROM TFC. CAPT THOUGHT THE COMMUTER CAPT WAS SHOWING OFF FOR A NEW FO. I NOW REALIZE, HE NEVER SAW US TO BEGIN WITH. SOLUTION: 1 ACFT CALLING TFC IN SIGHT IN A SIT SUCH AS THIS SHOULD NOT RELIEVE ATC OF THEIR TFC SEPARATION RESPONSIBILITIES. ALSO, IF A PLT CALLS TFC IN SIGHT IN THE APCH ENVIRONMENT HE IS WAY TOO BUSY TO STARE AT THAT TFC INDEFINITELY.

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.