Narrative:

I was working local/ground control combined. A cold front was moving through the area. WX was in transition: visibility good (10+ mi), ceiling was broken 600 ft, ASOS had just changed to scattered 600 ft broken 1400 ft, however I had not changed the ATIS. Aircraft X had departed runway 34. When I instructed him to contact departure control, he informed me he needed to return to land. I was aware that the ASOS had changed, making the field VFR so that aircraft X could be cleared for a visual approach rather than be vectored for the instrument approach. I asked if he needed assistance or had a problem, and he replied negative. The only other traffic was citation Y on the ILS approach. I asked aircraft X if he could make the visual approach, and he replied that he thought he could keep the airport in sight with the clouds, so I cleared him for a visual approach to runway 34. Aircraft Y was on a 6 mi final, and the cloud cover south of the airport was broken with aircraft breaking out about 2800 ft MSL on the ILS approach. Aircraft X could probably have turned base and landed ahead of aircraft Y, but I was not sure how much maneuvering he would require, so I asked him to extend downwind, or make a right 360 degree turn to follow the other citation. He (aircraft X) said he could maneuver to the southwest of the field to stay clear of clouds. As he maneuvered, I periodically lost sight of him behind clouds. On the d-brite scope, I saw aircraft X tracking toward the final on a base leg, and I advised him to continue circling, which he did. I saw aircraft X, but not aircraft Y yet -- the aircraft were about 1 mi apart, and the collision alert activated. Aircraft Y landed, aircraft X maneuvered around for the base leg behind and landed. Since I was working local control, my thinking was that aircraft X was in the pattern (I treated him as a VFR rather than an IFR aircraft on a visual approach) requiring 3 mi separation until he saw his traffic, or I saw both. More alertness and rapid assessment of the situation is required during unusual sits. Incidentally, the reason aircraft X had to return was to check a warning light. He promptly departed again.

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Original NASA ASRS Text

Title: ATCT LCL CTLR RESEQUENCED A DEP CITATION JET BACK TO THE ARPT WITH ANOTHER ACFT ON AN INST APCH, BUT NOT PROVIDING THE REQUIRED SEPARATION CRITERIA.

Narrative: I WAS WORKING LCL/GND CTL COMBINED. A COLD FRONT WAS MOVING THROUGH THE AREA. WX WAS IN TRANSITION: VISIBILITY GOOD (10+ MI), CEILING WAS BROKEN 600 FT, ASOS HAD JUST CHANGED TO SCATTERED 600 FT BROKEN 1400 FT, HOWEVER I HAD NOT CHANGED THE ATIS. ACFT X HAD DEPARTED RWY 34. WHEN I INSTRUCTED HIM TO CONTACT DEP CTL, HE INFORMED ME HE NEEDED TO RETURN TO LAND. I WAS AWARE THAT THE ASOS HAD CHANGED, MAKING THE FIELD VFR SO THAT ACFT X COULD BE CLRED FOR A VISUAL APCH RATHER THAN BE VECTORED FOR THE INST APCH. I ASKED IF HE NEEDED ASSISTANCE OR HAD A PROB, AND HE REPLIED NEGATIVE. THE ONLY OTHER TFC WAS CITATION Y ON THE ILS APCH. I ASKED ACFT X IF HE COULD MAKE THE VISUAL APCH, AND HE REPLIED THAT HE THOUGHT HE COULD KEEP THE ARPT IN SIGHT WITH THE CLOUDS, SO I CLRED HIM FOR A VISUAL APCH TO RWY 34. ACFT Y WAS ON A 6 MI FINAL, AND THE CLOUD COVER S OF THE ARPT WAS BROKEN WITH ACFT BREAKING OUT ABOUT 2800 FT MSL ON THE ILS APCH. ACFT X COULD PROBABLY HAVE TURNED BASE AND LANDED AHEAD OF ACFT Y, BUT I WAS NOT SURE HOW MUCH MANEUVERING HE WOULD REQUIRE, SO I ASKED HIM TO EXTEND DOWNWIND, OR MAKE A R 360 DEG TURN TO FOLLOW THE OTHER CITATION. HE (ACFT X) SAID HE COULD MANEUVER TO THE SW OF THE FIELD TO STAY CLR OF CLOUDS. AS HE MANEUVERED, I PERIODICALLY LOST SIGHT OF HIM BEHIND CLOUDS. ON THE D-BRITE SCOPE, I SAW ACFT X TRACKING TOWARD THE FINAL ON A BASE LEG, AND I ADVISED HIM TO CONTINUE CIRCLING, WHICH HE DID. I SAW ACFT X, BUT NOT ACFT Y YET -- THE ACFT WERE ABOUT 1 MI APART, AND THE COLLISION ALERT ACTIVATED. ACFT Y LANDED, ACFT X MANEUVERED AROUND FOR THE BASE LEG BEHIND AND LANDED. SINCE I WAS WORKING LCL CTL, MY THINKING WAS THAT ACFT X WAS IN THE PATTERN (I TREATED HIM AS A VFR RATHER THAN AN IFR ACFT ON A VISUAL APCH) REQUIRING 3 MI SEPARATION UNTIL HE SAW HIS TFC, OR I SAW BOTH. MORE ALERTNESS AND RAPID ASSESSMENT OF THE SIT IS REQUIRED DURING UNUSUAL SITS. INCIDENTALLY, THE REASON ACFT X HAD TO RETURN WAS TO CHK A WARNING LIGHT. HE PROMPTLY DEPARTED AGAIN.

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.