Narrative:

I was vectoring air carrier X, a B737, for a left base entry for a visual approach to runway 35. X was restr to 3000 ft due to PA23 traffic at 2500 ft southeast of X inbound for runway 6. TA's were exchanged between the 2 aircraft. X was assigned a 090 degree heading still at 3000 ft. X advised he was deviating to the right, refused the heading due to a TCASII advisory. Closest traffic was the PA23 still indicating 2500 ft. X said he showed something different. There were 2 other aircraft 4-5 mi from X, all were separated by 1000 ft. Continued to advise me of his TCASII TA's on the frequency. Air carrier X decision to deviate laterally based of TCASII information was totally unexpected. His action caused me to change my arrival sequence. X apparent concern with TCASII advisories made me concerned that he would deviate again with the number of aircraft under my control, safety was compromised because of all the attention and distrs created by 1 aircraft focusing in on TCASII. This is my second experience with a TCASII aircraft deviating laterally based on a TCASII advisory. (Previous occurrence, an ATR42 turned to avoid a target 500 ft below. The pilot advised it was not an RA but a TA.) this appears to be becoming a dangerous trend.

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Original NASA ASRS Text

Title: ACR X TCASII RA WITH VFR C172 REFUSED CLRNC RADAR VECTOR HDG. NONSTANDARD USE OF TCASII EVASIVE ACTION TURN.

Narrative: I WAS VECTORING ACR X, A B737, FOR A L BASE ENTRY FOR A VISUAL APCH TO RWY 35. X WAS RESTR TO 3000 FT DUE TO PA23 TFC AT 2500 FT SE OF X INBOUND FOR RWY 6. TA'S WERE EXCHANGED BTWN THE 2 ACFT. X WAS ASSIGNED A 090 DEG HDG STILL AT 3000 FT. X ADVISED HE WAS DEVIATING TO THE R, REFUSED THE HDG DUE TO A TCASII ADVISORY. CLOSEST TFC WAS THE PA23 STILL INDICATING 2500 FT. X SAID HE SHOWED SOMETHING DIFFERENT. THERE WERE 2 OTHER ACFT 4-5 MI FROM X, ALL WERE SEPARATED BY 1000 FT. CONTINUED TO ADVISE ME OF HIS TCASII TA'S ON THE FREQ. ACR X DECISION TO DEVIATE LATERALLY BASED OF TCASII INFO WAS TOTALLY UNEXPECTED. HIS ACTION CAUSED ME TO CHANGE MY ARR SEQUENCE. X APPARENT CONCERN WITH TCASII ADVISORIES MADE ME CONCERNED THAT HE WOULD DEVIATE AGAIN WITH THE NUMBER OF ACFT UNDER MY CTL, SAFETY WAS COMPROMISED BECAUSE OF ALL THE ATTN AND DISTRS CREATED BY 1 ACFT FOCUSING IN ON TCASII. THIS IS MY SECOND EXPERIENCE WITH A TCASII ACFT DEVIATING LATERALLY BASED ON A TCASII ADVISORY. (PREVIOUS OCCURRENCE, AN ATR42 TURNED TO AVOID A TARGET 500 FT BELOW. THE PLT ADVISED IT WAS NOT AN RA BUT A TA.) THIS APPEARS TO BE BECOMING A DANGEROUS TREND.

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.