Narrative:

Copilot was flying. We experienced several delay vectors and were kept high, apparently due to traffic. From an east downwind at 5000 ft to runway's 16, we were turned base heading 250 degrees assigned speed was 210 KTS. Approach asked if we had airport and md-80 at 1 O'clock. We replied that we had the airport and were looking for the traffic. We located the md-80 traffic which was apparently on extended final for runway 16R, but we were unable to report it due to radio congestion. We were given clearance for the visual to runway 16L based on the md-80's sighting of us. I considered that our traffic was close at 1 O'clock low, that a sharp 90 degrees descending left turn would put our belly toward the md-80, and that we might well overshoot his flight path. My reply to approach was that we had the traffic in sight, acknowledged the visual to runway 16L, but would continue our heading long enough to pass above and behind the md-80. When md-80 passed from right to left, we began our turn from base to final. Our flight path crossed both finals in this turn and put us considerably west of the runway 16R final during the turn. While turning, we noted that a third aircraft was cleared for a visual after reporting 'the B757 and MD80 in sight.' this clearance was to runway 16R behind MD80. Since we would be crossing this final, I attempted to locate this aircraft behind us to the left, but was unsuccessful. As we aligned with runway 16L and slowed at boeing, we got a TCASII alert. I noted several targets, one of which was collocated with our aircraft symbol reading plus 3. Immediately a conflict warning 'descend now' was announced. Copilot moved forward with the yoke and descent rate was increased. TCASII separation decreased to plus 1. Copilot saw a B737 aircraft passing overhead. His heading was slightly greater than ours, and his speed somewhat higher. Copilot noted his gear extending. The B737 landed on runway 16R. We were between a half a mi and a mi out when he landed. We landed on runway 16L. There were no communications with us from ATC about this aircraft.

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Original NASA ASRS Text

Title: OPERROR NMAC INVOLVING ACR X ON VISUAL APCH TO PARALLEL RWY OF ACR Y AND ACFT Z ON VISUAL APCH BEHIND ACR Y.

Narrative: COPLT WAS FLYING. WE EXPERIENCED SEVERAL DELAY VECTORS AND WERE KEPT HIGH, APPARENTLY DUE TO TFC. FROM AN E DOWNWIND AT 5000 FT TO RWY'S 16, WE WERE TURNED BASE HDG 250 DEGS ASSIGNED SPD WAS 210 KTS. APCH ASKED IF WE HAD ARPT AND MD-80 AT 1 O'CLOCK. WE REPLIED THAT WE HAD THE ARPT AND WERE LOOKING FOR THE TFC. WE LOCATED THE MD-80 TFC WHICH WAS APPARENTLY ON EXTENDED FINAL FOR RWY 16R, BUT WE WERE UNABLE TO RPT IT DUE TO RADIO CONGESTION. WE WERE GIVEN CLRNC FOR THE VISUAL TO RWY 16L BASED ON THE MD-80'S SIGHTING OF US. I CONSIDERED THAT OUR TFC WAS CLOSE AT 1 O'CLOCK LOW, THAT A SHARP 90 DEGS DSNDING L TURN WOULD PUT OUR BELLY TOWARD THE MD-80, AND THAT WE MIGHT WELL OVERSHOOT HIS FLT PATH. MY REPLY TO APCH WAS THAT WE HAD THE TFC IN SIGHT, ACKNOWLEDGED THE VISUAL TO RWY 16L, BUT WOULD CONTINUE OUR HDG LONG ENOUGH TO PASS ABOVE AND BEHIND THE MD-80. WHEN MD-80 PASSED FROM R TO L, WE BEGAN OUR TURN FROM BASE TO FINAL. OUR FLT PATH CROSSED BOTH FINALS IN THIS TURN AND PUT US CONSIDERABLY W OF THE RWY 16R FINAL DURING THE TURN. WHILE TURNING, WE NOTED THAT A THIRD ACFT WAS CLRED FOR A VISUAL AFTER RPTING 'THE B757 AND MD80 IN SIGHT.' THIS CLRNC WAS TO RWY 16R BEHIND MD80. SINCE WE WOULD BE XING THIS FINAL, I ATTEMPTED TO LOCATE THIS ACFT BEHIND US TO THE L, BUT WAS UNSUCCESSFUL. AS WE ALIGNED WITH RWY 16L AND SLOWED AT BOEING, WE GOT A TCASII ALERT. I NOTED SEVERAL TARGETS, ONE OF WHICH WAS COLLOCATED WITH OUR ACFT SYMBOL READING PLUS 3. IMMEDIATELY A CONFLICT WARNING 'DSND NOW' WAS ANNOUNCED. COPLT MOVED FORWARD WITH THE YOKE AND DSCNT RATE WAS INCREASED. TCASII SEPARATION DECREASED TO PLUS 1. COPLT SAW A B737 ACFT PASSING OVERHEAD. HIS HDG WAS SLIGHTLY GREATER THAN OURS, AND HIS SPD SOMEWHAT HIGHER. COPLT NOTED HIS GEAR EXTENDING. THE B737 LANDED ON RWY 16R. WE WERE BTWN A HALF A MI AND A MI OUT WHEN HE LANDED. WE LANDED ON RWY 16L. THERE WERE NO COMS WITH US FROM ATC ABOUT THIS ACFT.

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.