Narrative:

Bradley approach control advised traffic at 11 O'clock, a commuter. I was unfamiliar with the description but assumed it was the carrier identify. There was traffic at 11 O'clock and I called it. Problem was there were 2 aircraft at 11 O'clock. I idented/saw the larger of the 2 (which later was idented as air carrier-medium large transport). When I acknowledged what I assumed was the intended traffic, I took up visual separation on it, and the ATC controller relinquished his responsibility for intended traffic. Next came TCASII TA then RA to 'climb climb'. TCASII RA was followed. Twin engine turboprop passed off left wing less than 1000 ft. The TCASII TA/RA seemed to be correct. ATC approach was advised of our deviation and why. Phone conversations were held with ATC and later, the tower. In my estimation, there were 2 contributing factors to this unnecessary TCASII alert. First, the transmission/TA from approach control could have been more specific (ie, paint a picture -- '2 targets at 11 O'clock, air carrier-medium large transport heading southeast at 4000 ft and a twin engine commuter at 5000 ft heading southwest, report the twin engine commuter in sight'). Secondly, because the advisory was not as clear (to me) as it could have been, I called a visual sighting on the aircraft I could see at 11 O'clock. Unfortunately it was an additional aircraft and not the intended one.

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Original NASA ASRS Text

Title: ACR ISSUED TFC, SIGHTED, BUT THERE WERE 2 ACFT IN SAME AREA. RECEIVED TCASII RA.

Narrative: BRADLEY APCH CTL ADVISED TFC AT 11 O'CLOCK, A COMMUTER. I WAS UNFAMILIAR WITH THE DESCRIPTION BUT ASSUMED IT WAS THE CARRIER IDENT. THERE WAS TFC AT 11 O'CLOCK AND I CALLED IT. PROBLEM WAS THERE WERE 2 ACFT AT 11 O'CLOCK. I IDENTED/SAW THE LARGER OF THE 2 (WHICH LATER WAS IDENTED AS ACR-MLG). WHEN I ACKNOWLEDGED WHAT I ASSUMED WAS THE INTENDED TFC, I TOOK UP VISUAL SEPARATION ON IT, AND THE ATC CTLR RELINQUISHED HIS RESPONSIBILITY FOR INTENDED TFC. NEXT CAME TCASII TA THEN RA TO 'CLB CLB'. TCASII RA WAS FOLLOWED. TWIN ENG TURBOPROP PASSED OFF L WING LESS THAN 1000 FT. THE TCASII TA/RA SEEMED TO BE CORRECT. ATC APCH WAS ADVISED OF OUR DEV AND WHY. PHONE CONVERSATIONS WERE HELD WITH ATC AND LATER, THE TWR. IN MY ESTIMATION, THERE WERE 2 CONTRIBUTING FACTORS TO THIS UNNECESSARY TCASII ALERT. FIRST, THE XMISSION/TA FROM APCH CTL COULD HAVE BEEN MORE SPECIFIC (IE, PAINT A PICTURE -- '2 TARGETS AT 11 O'CLOCK, ACR-MLG HDG SE AT 4000 FT AND A TWIN ENG COMMUTER AT 5000 FT HDG SW, RPT THE TWIN ENG COMMUTER IN SIGHT'). SECONDLY, BECAUSE THE ADVISORY WAS NOT AS CLR (TO ME) AS IT COULD HAVE BEEN, I CALLED A VISUAL SIGHTING ON THE ACFT I COULD SEE AT 11 O'CLOCK. UNFORTUNATELY IT WAS AN ADDITIONAL ACFT AND NOT THE INTENDED ONE.

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.