Narrative:

Air carrier X flying on a 330 degree assigned heading to downwind at 7000 ft MSL for runway 20R at bna. My aircraft received a TCASII TA which showed an aircraft at our 0130 O'clock and less than 5 mi. Early morning haziness made it difficult to visually acquire the aircraft. Seconds later, the TCASII RA sounded 'climb, climb!' I immediately climbed at 2000 FPM to satisfy the indicated climb command of 1500 FPM. As I commenced the climb I saw the target visually at 2 O'clock and 200 ft below my altitude (corroborated by the RA symbol minus 200 on TCASII). I climbed to 7600 ft MSL before beginning descent back to 7000 ft MSL when clear of conflict signal from TCASII sounded. I believe the target aircraft Y passed off my right by 1 1/2 mi. After landing, the controller supervisor called me to explain that there never was a loss of separation during the effective encounter. He stated that the aircraft Y was a VFR small aircraft at 6500 ft MSL heading southwest. I told him that I found it hard to believe the target aircraft's altitude since the TCASII showed minus 200 ft as I departed 7000 ft MSL. The controller also explained that the computer assigned altitudes were a part of the TCASII events from his point of view. The TCASII RA I received was valid and helped me avoid a possible collision. The TCASII unit worked exactly as designed!

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Original NASA ASRS Text

Title: ACR X TCASII TA RA CLB NON ADHERENCE TO ATC CLRNC HAD AIRBORNE CONFLICT WITH VFR ACFT Y. PLTDEV. EVASIVE ACTION CLB TAKEN

Narrative: ACR X FLYING ON A 330 DEG ASSIGNED HDG TO DOWNWIND AT 7000 FT MSL FOR RWY 20R AT BNA. MY ACFT RECEIVED A TCASII TA WHICH SHOWED AN ACFT AT OUR 0130 O'CLOCK AND LESS THAN 5 MI. EARLY MORNING HAZINESS MADE IT DIFFICULT TO VISUALLY ACQUIRE THE ACFT. SECONDS LATER, THE TCASII RA SOUNDED 'CLB, CLB!' I IMMEDIATELY CLBED AT 2000 FPM TO SATISFY THE INDICATED CLB COMMAND OF 1500 FPM. AS I COMMENCED THE CLB I SAW THE TARGET VISUALLY AT 2 O'CLOCK AND 200 FT BELOW MY ALT (CORROBORATED BY THE RA SYMBOL MINUS 200 ON TCASII). I CLBED TO 7600 FT MSL BEFORE BEGINNING DSCNT BACK TO 7000 FT MSL WHEN CLR OF CONFLICT SIGNAL FROM TCASII SOUNDED. I BELIEVE THE TARGET ACFT Y PASSED OFF MY R BY 1 1/2 MI. AFTER LNDG, THE CTLR SUPVR CALLED ME TO EXPLAIN THAT THERE NEVER WAS A LOSS OF SEPARATION DURING THE EFFECTIVE ENCOUNTER. HE STATED THAT THE ACFT Y WAS A VFR SMA AT 6500 FT MSL HDG SW. I TOLD HIM THAT I FOUND IT HARD TO BELIEVE THE TARGET ACFT'S ALT SINCE THE TCASII SHOWED MINUS 200 FT AS I DEPARTED 7000 FT MSL. THE CTLR ALSO EXPLAINED THAT THE COMPUTER ASSIGNED ALTS WERE A PART OF THE TCASII EVENTS FROM HIS POINT OF VIEW. THE TCASII RA I RECEIVED WAS VALID AND HELPED ME AVOID A POSSIBLE COLLISION. THE TCASII UNIT WORKED EXACTLY AS DESIGNED!

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.