Narrative:

Cleared the visual for runway 28L, sfo told us to maintain 180 KTS to the bridge, also told us to maintain visual separation on a commander aircraft which was on a right base, just inside the bridge for runway 28R. The commander rolled out on final 100 ft above us and slightly behind us, about 200 ft to our right. I believe he was also told to maintain visual separation. Our TCASII gave us an RA to descend as the commander rolled out over us. First of all, 2 aircraft cannot maintain visual separation on each other unless they fly abreast (side-by-side) from each other. This is impracticable since no one is leading and who will react to who? In other words, only 1 aircraft can lead and one can follow. Also, it is impossible to maintain visual separation when you are assigned an airspeed to maintain. You can't have both. Sfo needs to be told this. Again, it is very poor planning to ever have 2 aircraft side by side on any approachs to runway 28L/right at sfo, regardless of WX. This my friends, is an accident waiting to happen. If you continue to operate in this fashion, you will have a midair. Just like the one we narrowly averted on this incident.

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Original NASA ASRS Text

Title: A319 FLT CREW QUESTIONS APPLICATION OF VISUAL SIDE-BY-SIDE APCH PROC WHEN UNABLE TO MAINTAIN VISUAL SEPARATION FROM A COMMANDER ACFT OVERSHOOTING BASE TO FINAL ON APCH TO SFO RWYS 28.

Narrative: CLRED THE VISUAL FOR RWY 28L, SFO TOLD US TO MAINTAIN 180 KTS TO THE BRIDGE, ALSO TOLD US TO MAINTAIN VISUAL SEPARATION ON A COMMANDER ACFT WHICH WAS ON A R BASE, JUST INSIDE THE BRIDGE FOR RWY 28R. THE COMMANDER ROLLED OUT ON FINAL 100 FT ABOVE US AND SLIGHTLY BEHIND US, ABOUT 200 FT TO OUR R. I BELIEVE HE WAS ALSO TOLD TO MAINTAIN VISUAL SEPARATION. OUR TCASII GAVE US AN RA TO DSND AS THE COMMANDER ROLLED OUT OVER US. FIRST OF ALL, 2 ACFT CANNOT MAINTAIN VISUAL SEPARATION ON EACH OTHER UNLESS THEY FLY ABREAST (SIDE-BY-SIDE) FROM EACH OTHER. THIS IS IMPRACTICABLE SINCE NO ONE IS LEADING AND WHO WILL REACT TO WHO? IN OTHER WORDS, ONLY 1 ACFT CAN LEAD AND ONE CAN FOLLOW. ALSO, IT IS IMPOSSIBLE TO MAINTAIN VISUAL SEPARATION WHEN YOU ARE ASSIGNED AN AIRSPD TO MAINTAIN. YOU CAN'T HAVE BOTH. SFO NEEDS TO BE TOLD THIS. AGAIN, IT IS VERY POOR PLANNING TO EVER HAVE 2 ACFT SIDE BY SIDE ON ANY APCHS TO RWY 28L/R AT SFO, REGARDLESS OF WX. THIS MY FRIENDS, IS AN ACCIDENT WAITING TO HAPPEN. IF YOU CONTINUE TO OPERATE IN THIS FASHION, YOU WILL HAVE A MIDAIR. JUST LIKE THE ONE WE NARROWLY AVERTED ON THIS INCIDENT.

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.