Narrative:

Both aircraft were on a base leg (opposite direction) for runway 27. The aircraft on a right base was at 7000 ft. The aircraft on a left base was at 5000 ft. The final for runway 27 was full and on tower frequency. Cvg tower was reported on fire and evacuate/evacuation started. Supervisors advised no more aircraft on final and expect the tower to break out all traffic on final. I climbed the left base aircraft to 6000 ft. I began to coordination with arrival feeder about downwind aircraft at 7000 ft. He was too busy. I then descended the right base aircraft to 6000 ft to avoid downwind. I then tried to coordination with departure for airspace but he was working an emergency. I saw a potential conflict with the 2 base aircraft. I assumed the left base aircraft was descending to 5000 ft. I turned both aircraft; later the conflict alert went off but assumed everything was fine. I later realized I had climbed the left base aircraft to 6000 ft instead of descending him to 5000 ft as I always do in this operation. I then advised the supervisor of a potential loss of separation.

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Original NASA ASRS Text

Title: CVG CTLR EXPERIENCED OPERROR AT 6000 FT WITH 2 ACFT ON OPPOSITE BASE LEGS AS TWR EVACED AND ALL ACFT REQUIRED IMMEDIATE VECTORS.

Narrative: BOTH ACFT WERE ON A BASE LEG (OPPOSITE DIRECTION) FOR RWY 27. THE ACFT ON A R BASE WAS AT 7000 FT. THE ACFT ON A L BASE WAS AT 5000 FT. THE FINAL FOR RWY 27 WAS FULL AND ON TWR FREQ. CVG TWR WAS RPTED ON FIRE AND EVAC STARTED. SUPVRS ADVISED NO MORE ACFT ON FINAL AND EXPECT THE TWR TO BREAK OUT ALL TFC ON FINAL. I CLBED THE L BASE ACFT TO 6000 FT. I BEGAN TO COORD WITH ARR FEEDER ABOUT DOWNWIND ACFT AT 7000 FT. HE WAS TOO BUSY. I THEN DSNDED THE R BASE ACFT TO 6000 FT TO AVOID DOWNWIND. I THEN TRIED TO COORD WITH DEP FOR AIRSPACE BUT HE WAS WORKING AN EMER. I SAW A POTENTIAL CONFLICT WITH THE 2 BASE ACFT. I ASSUMED THE L BASE ACFT WAS DSNDING TO 5000 FT. I TURNED BOTH ACFT; LATER THE CONFLICT ALERT WENT OFF BUT ASSUMED EVERYTHING WAS FINE. I LATER REALIZED I HAD CLBED THE L BASE ACFT TO 6000 FT INSTEAD OF DSNDING HIM TO 5000 FT AS I ALWAYS DO IN THIS OP. I THEN ADVISED THE SUPVR OF A POTENTIAL LOSS OF SEPARATION.

Data retrieved from NASA's ASRS site as of January 2009 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.