Narrative:

I was working east and west radar position combined on a moderately busy afternoon. Traffic was a mix of arrs, departures, and overflts. 1 aircraft involved was small aircraft X, IFR, RNAV route northbound through our airspace at 9000 ft. The other aircraft, small aircraft Y was a VFR who had requested flight following through our airspace on a route sug to sot. Small aircraft Y had been at 8500, but requested a VFR climb to 9500 to stay clear of clouds, and was climbing very slowly. At the time of the situation, my attention had been focused on an arrival situation: vectoring a VFR small aircraft to follow an air carrier jet I was vectoring on a surveillance approach. The air carrier jet had been vectored for a visual approach but was unable to see the airport due to haze. I was anticipating that the air carrier jet would be able to see the airport about 3 to 4 mi on final, which he did). My attention was snapped back to the 2 overflts when the ARTS iia collision alert alarmed. The aircraft were about 1 1/2 mi apart, the small aircraft Y indicating 9100. I had sufficient time to vector the aircraft around each other, lateral separation reducing to about 1 mi. The pilots were unable to see each other when I issued traffic advisories. I believe the primary cause of this occurrence was allowing myself to focus on one situation (the arrs) and not maintain awareness of the entire traffic situation. Additional factor: possibly giving less priority to separating the VFR aircraft.

Related reports:

Google
 

Original NASA ASRS Text

Title: SMA X HAD CONFLICT WITH VFR SMA Y. SEE AND AVOID CONCEPT.

Narrative: I WAS WORKING E AND W RADAR POS COMBINED ON A MODERATELY BUSY AFTERNOON. TFC WAS A MIX OF ARRS, DEPS, AND OVERFLTS. 1 ACFT INVOLVED WAS SMA X, IFR, RNAV RTE NBOUND THROUGH OUR AIRSPACE AT 9000 FT. THE OTHER ACFT, SMA Y WAS A VFR WHO HAD REQUESTED FLT FOLLOWING THROUGH OUR AIRSPACE ON A RTE SUG TO SOT. SMA Y HAD BEEN AT 8500, BUT REQUESTED A VFR CLB TO 9500 TO STAY CLR OF CLOUDS, AND WAS CLBING VERY SLOWLY. AT THE TIME OF THE SITUATION, MY ATTN HAD BEEN FOCUSED ON AN ARR SITUATION: VECTORING A VFR SMA TO FOLLOW AN ACR JET I WAS VECTORING ON A SURVEILLANCE APCH. THE ACR JET HAD BEEN VECTORED FOR A VISUAL APCH BUT WAS UNABLE TO SEE THE ARPT DUE TO HAZE. I WAS ANTICIPATING THAT THE ACR JET WOULD BE ABLE TO SEE THE ARPT ABOUT 3 TO 4 MI ON FINAL, WHICH HE DID). MY ATTN WAS SNAPPED BACK TO THE 2 OVERFLTS WHEN THE ARTS IIA COLLISION ALERT ALARMED. THE ACFT WERE ABOUT 1 1/2 MI APART, THE SMA Y INDICATING 9100. I HAD SUFFICIENT TIME TO VECTOR THE ACFT AROUND EACH OTHER, LATERAL SEPARATION REDUCING TO ABOUT 1 MI. THE PLTS WERE UNABLE TO SEE EACH OTHER WHEN I ISSUED TFC ADVISORIES. I BELIEVE THE PRIMARY CAUSE OF THIS OCCURRENCE WAS ALLOWING MYSELF TO FOCUS ON ONE SITUATION (THE ARRS) AND NOT MAINTAIN AWARENESS OF THE ENTIRE TFC SITUATION. ADDITIONAL FACTOR: POSSIBLY GIVING LESS PRIORITY TO SEPARATING THE VFR ACFT.

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.