Narrative:

An A319 was inbound to sfo on the bsr arrival and slow to descend due to his tbm time restriction. I instructed the airbus to fly heading of 030 and to descend to 4;000 ft. After about 5 miles the A319 was still descending out of 075 and I asked the pilot if he needed a vector east bound for his descent; the pilot said that it wouldn't be a problem so I continued his descent to 030. The A319 was told he was going to be vectored across the localizer for spacing because he was following a heavy and he was cautioned for wake turbulence. I gave the A319 a heading of 250 to intercept the localizer and noticed he was a little high; 6;000; for a 13 mile final and asked the pilot if he was able to shoot the approach at that altitude; the pilot said he would be able and I gave him a clearance for the ILS 28R approach and issued reduce speed to slowest practical speed for wake turbulence. Once I cleared him I began a position relief briefing to another controller; the whole time watching the A319's profile on the ILS. When the next controller assumed the position; he again instructed the airbus to slow to final approach speed and shipped communications to sfo tower; a mile later the tower sent the airbus around. When I was notified the day after of the loss of separation; and upon further review of the tapes; I saw that I used a 4 mile bat instead of a 5 mile bat to represent the minimum for wake turbulence. I also saw that when the airbus was shipped; there was at least 5 miles which was required; however; with the A319's speed; the overtake reduced separation to 4.45 miles before the tower sent him around. Recommendation; for this situation I definitely would vector the aircraft for its descent rather than forcing him to fly an unstable approach. I also would recommend using the appropriate size bat when it comes to wake turbulence minima.

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Original NASA ASRS Text

Title: NCT Controller working the final position for SFO described a loss of wake turbulence separation.

Narrative: An A319 was inbound to SFO on the BSR arrival and slow to descend due to his TBM time restriction. I instructed the Airbus to fly heading of 030 and to descend to 4;000 FT. After about 5 miles the A319 was still descending out of 075 and I asked the pilot if he needed a vector east bound for his descent; the pilot said that it wouldn't be a problem so I continued his descent to 030. The A319 was told he was going to be vectored across the localizer for spacing because he was following a heavy and he was cautioned for wake turbulence. I gave the A319 a heading of 250 to intercept the localizer and noticed he was a little high; 6;000; for a 13 mile final and asked the pilot if he was able to shoot the approach at that altitude; the pilot said he would be able and I gave him a clearance for the ILS 28R approach and issued reduce speed to slowest practical speed for wake turbulence. Once I cleared him I began a position relief briefing to another Controller; the whole time watching the A319's profile on the ILS. When the next Controller assumed the position; he again instructed the Airbus to slow to final approach speed and shipped communications to SFO Tower; a mile later the Tower sent the Airbus around. When I was notified the day after of the loss of separation; and upon further review of the tapes; I saw that I used a 4 mile bat instead of a 5 mile bat to represent the minimum for wake turbulence. I also saw that when the Airbus was shipped; there was at least 5 miles which was required; however; with the A319's speed; the overtake reduced separation to 4.45 miles before the Tower sent him around. Recommendation; for this situation I definitely would vector the aircraft for its descent rather than forcing him to fly an unstable approach. I also would recommend using the appropriate size bat when it comes to wake turbulence minima.

Data retrieved from NASA's ASRS site as of April 2012 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.