Narrative:

On descent TCASII TA alerted for aircraft 3 mi and 1000 ft below us and climbing. TCASII changed to RA directing a climb of 1500 FPM to an altitude of 10600 ft. Traffic was sighted passing right side of our aircraft 1/2 mi away at our altitude. RA went away and we descended back to our assigned altitude. Bna approach issued no advisories on traffic and voiced no concern about our altitude deviation. Traffic was climbing east into sun and probably never saw us. Aircraft was orange colored twin propeller with no air carrier markings. TCASII worked! Otherwise a much closer conflict/near miss may have occurred.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION FROM ASSIGNED IN EVASIVE ACTION CLB AFTER TCASII RA.

Narrative: ON DSCNT TCASII TA ALERTED FOR ACFT 3 MI AND 1000 FT BELOW US AND CLBING. TCASII CHANGED TO RA DIRECTING A CLB OF 1500 FPM TO AN ALT OF 10600 FT. TFC WAS SIGHTED PASSING R SIDE OF OUR ACFT 1/2 MI AWAY AT OUR ALT. RA WENT AWAY AND WE DSNDED BACK TO OUR ASSIGNED ALT. BNA APCH ISSUED NO ADVISORIES ON TFC AND VOICED NO CONCERN ABOUT OUR ALTDEV. TFC WAS CLBING E INTO SUN AND PROBABLY NEVER SAW US. ACFT WAS ORANGE COLORED TWIN PROP WITH NO ACR MARKINGS. TCASII WORKED! OTHERWISE A MUCH CLOSER CONFLICT/NEAR MISS MAY HAVE OCCURRED.

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.