Narrative:

TCASII RA generated heading deviation. Cleared by hou to proceed to aus bergstrom and descend to 6000 ft. During descent, directed to turn left 20 degrees and expedite descent through 16000 ft for IFR traffic at 17000 ft. Further clearance was direct to the airport passing 16000 ft. At approximately 16500 ft, we received a TCASII TA with traffic 1700 ft below and at approximately 11 O'clock position. Descent rate at this time was approximately 3000 FPM and airspeed approximately 300 KIAS. At approximately 16000 ft, we got a TCASII RA 'climb, climb.' first officer had just acquired the target visually at approximately 10-11 O'clock position. I had only the TCASII visibility information at this time 10-11 O'clock position and -600 ft. First officer determined that a climb would only result in stopping at the other aircraft's altitude at best and increased the descent rate in conjunction with the previously cleared right turn toward the airport. I concurred verbally based on my analysis of situation from TCASII information. After the conflict was resolved, I advised ZHU and suggested that the 20 degree left turn had really increased the conflict potential, and was then advised that the aircraft we had maneuvered for was not the original IFR traffic, but was known VFR traffic climbing to 17500 ft. We had received no previous callout about this traffic. We also never saw the previously reported IFR traffic. Supplemental information from acn 566288: descending into aus cleared to 6000 ft, asked to turn left 20 degrees and expedite through 16000 ft. Leaving 16000 ft, got TA at -1700 ft, followed quickly by 'climb, climb.' I had acquired the aircraft and felt that if we were to stop descent and try to climb we would have leveled and reversed descent at approximately the other aircraft's altitude. I rolled approximately 45 degrees right bank and increased descent rate. The aircraft passed to our left and slightly high. It appeared to be a beech jet. ATC advised that the aircraft was VFR and not the aircraft we had initially vectored to avoid. As we passed, the other aircraft began a bank to avoid us.

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Original NASA ASRS Text

Title: B737-700 CREW AND A BEECH JET HAD LESS THAN COMFORTABLE SEPARATION IN ZHU CLASS E AIRSPACE.

Narrative: TCASII RA GENERATED HDG DEV. CLRED BY HOU TO PROCEED TO AUS BERGSTROM AND DSND TO 6000 FT. DURING DSCNT, DIRECTED TO TURN L 20 DEGS AND EXPEDITE DSCNT THROUGH 16000 FT FOR IFR TFC AT 17000 FT. FURTHER CLRNC WAS DIRECT TO THE ARPT PASSING 16000 FT. AT APPROX 16500 FT, WE RECEIVED A TCASII TA WITH TFC 1700 FT BELOW AND AT APPROX 11 O'CLOCK POS. DSCNT RATE AT THIS TIME WAS APPROX 3000 FPM AND AIRSPD APPROX 300 KIAS. AT APPROX 16000 FT, WE GOT A TCASII RA 'CLB, CLB.' FO HAD JUST ACQUIRED THE TARGET VISUALLY AT APPROX 10-11 O'CLOCK POS. I HAD ONLY THE TCASII VISIBILITY INFO AT THIS TIME 10-11 O'CLOCK POS AND -600 FT. FO DETERMINED THAT A CLB WOULD ONLY RESULT IN STOPPING AT THE OTHER ACFT'S ALT AT BEST AND INCREASED THE DSCNT RATE IN CONJUNCTION WITH THE PREVIOUSLY CLRED R TURN TOWARD THE ARPT. I CONCURRED VERBALLY BASED ON MY ANALYSIS OF SIT FROM TCASII INFO. AFTER THE CONFLICT WAS RESOLVED, I ADVISED ZHU AND SUGGESTED THAT THE 20 DEG L TURN HAD REALLY INCREASED THE CONFLICT POTENTIAL, AND WAS THEN ADVISED THAT THE ACFT WE HAD MANEUVERED FOR WAS NOT THE ORIGINAL IFR TFC, BUT WAS KNOWN VFR TFC CLBING TO 17500 FT. WE HAD RECEIVED NO PREVIOUS CALLOUT ABOUT THIS TFC. WE ALSO NEVER SAW THE PREVIOUSLY RPTED IFR TFC. SUPPLEMENTAL INFO FROM ACN 566288: DSNDING INTO AUS CLRED TO 6000 FT, ASKED TO TURN L 20 DEGS AND EXPEDITE THROUGH 16000 FT. LEAVING 16000 FT, GOT TA AT -1700 FT, FOLLOWED QUICKLY BY 'CLB, CLB.' I HAD ACQUIRED THE ACFT AND FELT THAT IF WE WERE TO STOP DSCNT AND TRY TO CLB WE WOULD HAVE LEVELED AND REVERSED DSCNT AT APPROX THE OTHER ACFT'S ALT. I ROLLED APPROX 45 DEGS R BANK AND INCREASED DSCNT RATE. THE ACFT PASSED TO OUR L AND SLIGHTLY HIGH. IT APPEARED TO BE A BEECH JET. ATC ADVISED THAT THE ACFT WAS VFR AND NOT THE ACFT WE HAD INITIALLY VECTORED TO AVOID. AS WE PASSED, THE OTHER ACFT BEGAN A BANK TO AVOID US.

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.