Narrative:

Our aircraft was medium large transport on visual approach to runway 25L on localizer and GS. Traffic was issued going to runway 25R. Acknowledged, but not in sight. Aircraft came from above and behind our aircraft. It was an light transport. It apparently had overshot the 25R centerline. I immediately told the captain, 'turn left, now.' he hesitated for a second and I initiated a left turn myself, stating again, 'turn left.' the conflict aircraft came within approximately 200 ft of our aircraft. The conflict aircraft gradually returned to the 25R centerline, which further reinforced my notion that he never saw us during the occurrence. We returned to the 25L localizer and flew to normal approach and landing. Please note that these estimates of distance are my best guesses at the horizontal and vertical separation. I might be off by 100 ft, which would put it at approximately 300 ft, but certainly no more. No comments were made by either aircraft or the tower. According to scale on the airport diagram, the ctrlines for 25L and 25R are displaced by approximately 800 ft. My suggestion to alleviate this problem would of course be to stagger inbound aircraft when both runways are active.

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Original NASA ASRS Text

Title: ACR ON VISUAL APCH WAS NMAC WITH ACFT ON APCH TO PARALLEL RWY.

Narrative: OUR ACFT WAS MLG ON VISUAL APCH TO RWY 25L ON LOC AND GS. TFC WAS ISSUED GOING TO RWY 25R. ACKNOWLEDGED, BUT NOT IN SIGHT. ACFT CAME FROM ABOVE AND BEHIND OUR ACFT. IT WAS AN LTT. IT APPARENTLY HAD OVERSHOT THE 25R CTRLINE. I IMMEDIATELY TOLD THE CAPT, 'TURN L, NOW.' HE HESITATED FOR A SECOND AND I INITIATED A L TURN MYSELF, STATING AGAIN, 'TURN L.' THE CONFLICT ACFT CAME WITHIN APPROX 200 FT OF OUR ACFT. THE CONFLICT ACFT GRADUALLY RETURNED TO THE 25R CTRLINE, WHICH FURTHER REINFORCED MY NOTION THAT HE NEVER SAW US DURING THE OCCURRENCE. WE RETURNED TO THE 25L LOC AND FLEW TO NORMAL APCH AND LNDG. PLEASE NOTE THAT THESE ESTIMATES OF DISTANCE ARE MY BEST GUESSES AT THE HORIZ AND VERT SEPARATION. I MIGHT BE OFF BY 100 FT, WHICH WOULD PUT IT AT APPROX 300 FT, BUT CERTAINLY NO MORE. NO COMMENTS WERE MADE BY EITHER ACFT OR THE TWR. ACCORDING TO SCALE ON THE ARPT DIAGRAM, THE CTRLINES FOR 25L AND 25R ARE DISPLACED BY APPROX 800 FT. MY SUGGESTION TO ALLEVIATE THIS PROB WOULD OF COURSE BE TO STAGGER INBND ACFT WHEN BOTH RWYS ARE ACTIVE.

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.