Narrative:

While on final approach to runway 10 at tist, an RA was received without previous warning from tower. I initiated an immediate climb and left bank at which time tower was asked about traffic. It was only at that time that stt tower confirmed the presence of the C172 close by, stating it was 'no factor.' I thought differently, as did my first officer. I believe that the tower controller made a mistake in not reporting the traffic, for whatever reason, and that was not normally the case for stt tower. No one was hurt and not one injury occurred as a result.

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Original NASA ASRS Text

Title: FLC OF AN ATR42 CLBED AND TURNED IN RESPONSE TO A TCASII RA. WHEN QUERIED, THE TWR CTLR ACKNOWLEDGED THE PRESENCE OF A CESSNA 172, BUT AS NO FACTOR.

Narrative: WHILE ON FINAL APCH TO RWY 10 AT TIST, AN RA WAS RECEIVED WITHOUT PREVIOUS WARNING FROM TWR. I INITIATED AN IMMEDIATE CLB AND L BANK AT WHICH TIME TWR WAS ASKED ABOUT TFC. IT WAS ONLY AT THAT TIME THAT STT TWR CONFIRMED THE PRESENCE OF THE C172 CLOSE BY, STATING IT WAS 'NO FACTOR.' I THOUGHT DIFFERENTLY, AS DID MY FO. I BELIEVE THAT THE TWR CTLR MADE A MISTAKE IN NOT RPTING THE TFC, FOR WHATEVER REASON, AND THAT WAS NOT NORMALLY THE CASE FOR STT TWR. NO ONE WAS HURT AND NOT ONE INJURY OCCURRED AS A RESULT.

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.