Narrative:

On the quiet bridge visual to sfo runway 28R approach control called out an aircraft ahead. Below and to our left also on approach. We did not sight the aircraft and responded to the controller negative contact. Controller then cleared our aircraft to maintain 2500 ft and 250 KTS. Our aircraft was now approximately 7 DME from runway 28R. We queried the controller about the airspeed he wanted us to maintain and he replied his intentions were to have us overtake the aircraft that was ahead, below and to our left and then have us visually land on runway 21R. At approximately 6.5 DME we told the controller that unless we could reduce our airspeed we could not land. Controller replied by having us discontinue the approach. We were vectored to the south then east in abcx pattern to align our aircraft with runway 28L. We then were allowed to reduce our airspeed. While heading east controller called out traffic, a commuter aircraft approaching from the east. We did not sight the commuter aircraft and informed the controller. The controller then vectored us to the north and then to the west for runway 28L. While in the turn to align aircraft with the runway the commuter aircraft was spotted at our 2 O'clock position and above our altitude in the turn for runway 28R. We informed the controller that we now had the commuter aircraft in sight and that it was above us and behind us. Controller responded roger, maintain visual with the commuter aircraft and switch to tower frequency. We switched over to sfo tower control and informed the controller that we could not maintain visual with an aircraft that was above and behind us. The tower controller replied that it was not a problem and that we were cleared to land. We landed on runway 28L. I feel that approach controls actions in this particular event were potentially dangerous. We were not vectored to a position from which a safe landing could be made during approach to runway 28R. Approach controls direction to have a flight crew maintain visual with an aircraft that is above and behind them while on final approach is not only impractical, but impossible and dangerous if attempted. Furthermore, approach control's clrncs set the stage for the development of a serious conflict.

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Original NASA ASRS Text

Title: PARALLEL VISUAL APCH SIT IN WHICH LEAD ACFT (ACR X IS TO MAINTAIN VISUAL SEPARATION WITH ACR Z).

Narrative: ON THE QUIET BRIDGE VISUAL TO SFO RWY 28R APCH CTL CALLED OUT AN ACFT AHEAD. BELOW AND TO OUR L ALSO ON APCH. WE DID NOT SIGHT THE ACFT AND RESPONDED TO THE CTLR NEGATIVE CONTACT. CTLR THEN CLRED OUR ACFT TO MAINTAIN 2500 FT AND 250 KTS. OUR ACFT WAS NOW APPROX 7 DME FROM RWY 28R. WE QUERIED THE CTLR ABOUT THE AIRSPD HE WANTED US TO MAINTAIN AND HE REPLIED HIS INTENTIONS WERE TO HAVE US OVERTAKE THE ACFT THAT WAS AHEAD, BELOW AND TO OUR L AND THEN HAVE US VISUALLY LAND ON RWY 21R. AT APPROX 6.5 DME WE TOLD THE CTLR THAT UNLESS WE COULD REDUCE OUR AIRSPD WE COULD NOT LAND. CTLR REPLIED BY HAVING US DISCONTINUE THE APCH. WE WERE VECTORED TO THE S THEN E IN ABCX PATTERN TO ALIGN OUR ACFT WITH RWY 28L. WE THEN WERE ALLOWED TO REDUCE OUR AIRSPD. WHILE HEADING E CTLR CALLED OUT TFC, A COMMUTER ACFT APCHING FROM THE E. WE DID NOT SIGHT THE COMMUTER ACFT AND INFORMED THE CTLR. THE CTLR THEN VECTORED US TO THE N AND THEN TO THE W FOR RWY 28L. WHILE IN THE TURN TO ALIGN ACFT WITH THE RWY THE COMMUTER ACFT WAS SPOTTED AT OUR 2 O'CLOCK POS AND ABOVE OUR ALT IN THE TURN FOR RWY 28R. WE INFORMED THE CTLR THAT WE NOW HAD THE COMMUTER ACFT IN SIGHT AND THAT IT WAS ABOVE US AND BEHIND US. CTLR RESPONDED ROGER, MAINTAIN VISUAL WITH THE COMMUTER ACFT AND SWITCH TO TWR FREQ. WE SWITCHED OVER TO SFO TWR CTL AND INFORMED THE CTLR THAT WE COULD NOT MAINTAIN VISUAL WITH AN ACFT THAT WAS ABOVE AND BEHIND US. THE TWR CTLR REPLIED THAT IT WAS NOT A PROB AND THAT WE WERE CLRED TO LAND. WE LANDED ON RWY 28L. I FEEL THAT APCH CTLS ACTIONS IN THIS PARTICULAR EVENT WERE POTENTIALLY DANGEROUS. WE WERE NOT VECTORED TO A POS FROM WHICH A SAFE LNDG COULD BE MADE DURING APCH TO RWY 28R. APCH CTLS DIRECTION TO HAVE A FLC MAINTAIN VISUAL WITH AN ACFT THAT IS ABOVE AND BEHIND THEM WHILE ON FINAL APCH IS NOT ONLY IMPRACTICAL, BUT IMPOSSIBLE AND DANGEROUS IF ATTEMPTED. FURTHERMORE, APCH CTL'S CLRNCS SET THE STAGE FOR THE DEVELOPMENT OF A SERIOUS CONFLICT.

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.