Narrative:

We were on an sfo 4 SID. The controller gave us traffic, an small aircraft at 11 O'clock 3 mi at 4000'. We replied negative contact. The controller said maintain 3000' (we were out of 3100' at the time). We overshot 2000' to about 3400' and returned to 3000'. At this time we saw light traffic at about 10 O'clock and reported it to the controller. The controller said maintain visibility sep and climb to FL230. We replied negative, we request standard sep. The controller (another voice) said maintenance 3000'and turn left to a 360 degree heading. This clearance would have turned us right into the traffic at 10 O'clock which appeared to be at about our altitude. We delayed the turn and then turned slowly toward 360 degree and the merging traffic. We were then issued a climb to FL230. We then flew right under the small aircraft the traffic at 11 O'clock, moving to 12, at our altitude, was not the sam. We avoided the traffic at 11 O'clock, 3000' and continued our climb. It was a good thing that we did not accept the maintain visibility sep clearance, we would likely have climbed into the small aircraft. Comments: over the past couple of yrs, I have been involved with four or five incidents where the flight crew locked onto traffic which was not the same traffic the controller was issuing, as in this case. For this reason, I make it a practice of not accept 'maintain visibility sep' clrncs during the approach and departure phase of flight. This incidents indicates that is an excellent practice. Additionally, I believe it is a fatal mistake to use 'visibility sep' as a stopgap solution to an overloaded ATC system.

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Original NASA ASRS Text

Title: SCHEDULED ACR HAS WITH SMA.

Narrative: WE WERE ON AN SFO 4 SID. THE CTLR GAVE US TFC, AN SMA AT 11 O'CLOCK 3 MI AT 4000'. WE REPLIED NEGATIVE CONTACT. THE CTLR SAID MAINTAIN 3000' (WE WERE OUT OF 3100' AT THE TIME). WE OVERSHOT 2000' TO ABOUT 3400' AND RETURNED TO 3000'. AT THIS TIME WE SAW LIGHT TFC AT ABOUT 10 O'CLOCK AND RPTED IT TO THE CTLR. THE CTLR SAID MAINTAIN VIS SEP AND CLB TO FL230. WE REPLIED NEGATIVE, WE REQUEST STANDARD SEP. THE CTLR (ANOTHER VOICE) SAID MAINT 3000'AND TURN L TO A 360 DEG HDG. THIS CLRNC WOULD HAVE TURNED US R INTO THE TFC AT 10 O'CLOCK WHICH APPEARED TO BE AT ABOUT OUR ALT. WE DELAYED THE TURN AND THEN TURNED SLOWLY TOWARD 360 DEG AND THE MERGING TFC. WE WERE THEN ISSUED A CLB TO FL230. WE THEN FLEW R UNDER THE SMA THE TFC AT 11 O'CLOCK, MOVING TO 12, AT OUR ALT, WAS NOT THE SAM. WE AVOIDED THE TFC AT 11 O'CLOCK, 3000' AND CONTINUED OUR CLB. IT WAS A GOOD THING THAT WE DID NOT ACCEPT THE MAINTAIN VIS SEP CLRNC, WE WOULD LIKELY HAVE CLBED INTO THE SMA. COMMENTS: OVER THE PAST COUPLE OF YRS, I HAVE BEEN INVOLVED WITH FOUR OR FIVE INCIDENTS WHERE THE FLT CREW LOCKED ONTO TFC WHICH WAS NOT THE SAME TFC THE CTLR WAS ISSUING, AS IN THIS CASE. FOR THIS REASON, I MAKE IT A PRACTICE OF NOT ACCEPT 'MAINTAIN VIS SEP' CLRNCS DURING THE APCH AND DEP PHASE OF FLT. THIS INCIDENTS INDICATES THAT IS AN EXCELLENT PRACTICE. ADDITIONALLY, I BELIEVE IT IS A FATAL MISTAKE TO USE 'VIS SEP' AS A STOPGAP SOLUTION TO AN OVERLOADED ATC SYS.

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.