Narrative:

On base leg to final for runway 19L at sfo, bay approach called out traffic at our 12-1 O'clock position. We acknowledged searching as there were 4 aircraft with lights illuminated in that area. The radio was quite busy. Again approach asked if we had the traffic. We responded that we did and approach said to keep visual separation with that traffic and cleared us to intercept the runway 19L localizer. As we turned to intercept the localizer, it became apparent that we were going to turn inside the traffic and lose sight of him as we completed the turn. I remember reading about a pilot recently violated and fined for not keeping visual contact with an aircraft so I was concerned when we were turning inside the other aircraft. That aircraft was going to land on runway 19R. I wanted to tell the controller we couldn't keep that aircraft in sight and did transmit that fact, but the controller never really acknowledged my call. There were few breaks in radio traffic and the controller cleared us for a visual approach, cross 7 DME at 3000 ft, and contact the tower. Since I was still trying to keep the other aircraft in sight, I selected approach mode of the autoflt controls which would make sure we didn't overshoot the localizer and would capture the glide path. I allowed the autoplt to fly down the glide path while still trying to tell the controller about losing sight of the other aircraft. As we intercepted the normal glide path we were below 3000 ft at 7 mi, but on the normal glide path. On short final, I asked tower to call approach and ask what our restr was. Tower said cross 10 DME at 3000 ft. We were just about at that altitude, but we both heard 7 DME, therefore the confusion. Corrective - try to call on radio and check on restr - radio was busy and we were getting closer to runway. Contributing factor - on reserve, up at XA00 am, called at XM00 pm for all night flight msp-sfo-msp....fatigue.

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Original NASA ASRS Text

Title: UNABLE TO MAINTAIN VISUAL CONTACT WITH ANOTHER ACFT ON APCH, PLT TRIED TO NOTIFY CTLR, BUT CONGESTED FREQ PREVENTED COM.

Narrative: ON BASE LEG TO FINAL FOR RWY 19L AT SFO, BAY APCH CALLED OUT TFC AT OUR 12-1 O'CLOCK POS. WE ACKNOWLEDGED SEARCHING AS THERE WERE 4 ACFT WITH LIGHTS ILLUMINATED IN THAT AREA. THE RADIO WAS QUITE BUSY. AGAIN APCH ASKED IF WE HAD THE TFC. WE RESPONDED THAT WE DID AND APCH SAID TO KEEP VISUAL SEPARATION WITH THAT TFC AND CLRED US TO INTERCEPT THE RWY 19L LOC. AS WE TURNED TO INTERCEPT THE LOC, IT BECAME APPARENT THAT WE WERE GOING TO TURN INSIDE THE TFC AND LOSE SIGHT OF HIM AS WE COMPLETED THE TURN. I REMEMBER READING ABOUT A PLT RECENTLY VIOLATED AND FINED FOR NOT KEEPING VISUAL CONTACT WITH AN ACFT SO I WAS CONCERNED WHEN WE WERE TURNING INSIDE THE OTHER ACFT. THAT ACFT WAS GOING TO LAND ON RWY 19R. I WANTED TO TELL THE CTLR WE COULDN'T KEEP THAT ACFT IN SIGHT AND DID XMIT THAT FACT, BUT THE CTLR NEVER REALLY ACKNOWLEDGED MY CALL. THERE WERE FEW BREAKS IN RADIO TFC AND THE CTLR CLRED US FOR A VISUAL APCH, CROSS 7 DME AT 3000 FT, AND CONTACT THE TWR. SINCE I WAS STILL TRYING TO KEEP THE OTHER ACFT IN SIGHT, I SELECTED APCH MODE OF THE AUTOFLT CTLS WHICH WOULD MAKE SURE WE DIDN'T OVERSHOOT THE LOC AND WOULD CAPTURE THE GLIDE PATH. I ALLOWED THE AUTOPLT TO FLY DOWN THE GLIDE PATH WHILE STILL TRYING TO TELL THE CTLR ABOUT LOSING SIGHT OF THE OTHER ACFT. AS WE INTERCEPTED THE NORMAL GLIDE PATH WE WERE BELOW 3000 FT AT 7 MI, BUT ON THE NORMAL GLIDE PATH. ON SHORT FINAL, I ASKED TWR TO CALL APCH AND ASK WHAT OUR RESTR WAS. TWR SAID CROSS 10 DME AT 3000 FT. WE WERE JUST ABOUT AT THAT ALT, BUT WE BOTH HEARD 7 DME, THEREFORE THE CONFUSION. CORRECTIVE - TRY TO CALL ON RADIO AND CHK ON RESTR - RADIO WAS BUSY AND WE WERE GETTING CLOSER TO RWY. CONTRIBUTING FACTOR - ON RESERVE, UP AT XA00 AM, CALLED AT XM00 PM FOR ALL NIGHT FLT MSP-SFO-MSP....FATIGUE.

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.