B737 captain experiences a TCAS RA while being vectored for a visual approach. ATC called the traffi...

Narrative:

Near mid-air with VFR traffic while vectoring for runway 4 visual approach. First noticed traffic when he was on 10-mile final for runway 4 and 800 ft below us. We were abeam airfield. I initially thought we were following him for landing. Approach gave us descent from 5;000 to 2;500 ft. We started down without delay. Approach called out traffic to follow abeam us at 1;800 ft short final; he was no factor. Approach called out VFR traffic 11 or 12 o'clock and gave us a turn to final. I was confused because it seemed we were descending and turning into traffic per TCAS display. Traffic went from 400 ft below to co-altitude during descending turn. We got 1;500 ft vvi descending RA. On TCAS display; we were co-altitude and co-airspace. It all happened very fast. We never had visual. I think we were close to a mid-air. There was very little traffic in area. After we notified approach of RA; they claimed traffic was 'primary target' with no altitude readout; but he was climbing. We had altitude read out on him the whole time and RA indicates transponders were communicating. I'm not sure what we could have done. We didn't realize a conflict existed until too late because we thought traffic was IFR. I didn't know what approach was planning until they turned us and conflict was upon us.

Original NASA ASRS Text

Title: B737 Captain experiences a TCAS RA while being vectored for a visual approach. ATC called the traffic but claimed no altitude information was available. TCAS saw the traffic with altitude and provided the correct escape maneuver.

Narrative: Near mid-air with VFR traffic while vectoring for Runway 4 visual approach. First noticed traffic when he was on 10-mile final for Runway 4 and 800 FT below us. We were abeam airfield. I initially thought we were following him for landing. Approach gave us descent from 5;000 to 2;500 FT. We started down without delay. Approach called out traffic to follow abeam us at 1;800 FT short final; he was no factor. Approach called out VFR traffic 11 or 12 o'clock and gave us a turn to final. I was confused because it seemed we were descending and turning into traffic per TCAS display. Traffic went from 400 FT below to co-altitude during descending turn. We got 1;500 FT VVI descending RA. On TCAS display; we were co-altitude and co-airspace. It all happened very fast. We never had visual. I think we were close to a mid-air. There was very little traffic in area. After we notified Approach of RA; they claimed traffic was 'primary target' with no altitude readout; but he was climbing. We had altitude read out on him the whole time and RA indicates transponders were communicating. I'm not sure what we could have done. We didn't realize a conflict existed until too late because we thought traffic was IFR. I didn't know what Approach was planning until they turned us and conflict was upon us.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1176553
Time
Date	201405
Local Time Of Day	0601-1200
Place
Locale Reference	SAT.Airport
State Reference	TX
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	Final Approach
Flight Plan	VFR
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 221
Events
Anomaly	Conflict NMAC

B737 captain experiences a TCAS RA while being vectored for a visual approach. ATC called the traffic but claimed no altitude information was available. TCAS saw the traffic with altitude and provided the correct escape maneuver.