Narrative:

On an IFR flight from rbd to hou; in VMC; being controlled by houston TRACON. Arrived via the blubell 2 STAR. Shortly after passing cowzz intersection at 5;000 ft; was given a descent to 3;000 ft and a 135 degree heading; vectors for the hou ILS runway 30L. I did not realize it at the time; but this descent took us out of but underneath class B airspace. Shortly after leveling at 3;000 ft; cruising at about 200 KTS; TCAS indicated traffic at 12 o'clock position; 3 NM; 500 ft below and climbing. I began deviating left (east) but another target appeared about 1/4 miles east of the original target; limiting my ability to maneuver. About that time I acquired visual contact with the original target. It was in a climbing; steep-bank turn toward me. I passed a few hundred ft above and less than 1/4 miles east of it. I never acquired the second target and my TCAS unit indicated that I passed even closer; but west of it. I wonder if it may have been a phantom 'double' of the first target. As I was passing by the traffic; I got a radio call from TRACON suggesting a right turn (I think an earlier call from TRACON may have been blocked). I told them that I had deviated left and was returning to my original 135 degree heading. 'That was close;' I said. 'They are out of the class B and I am not talking to them;' was the response. The frequency was too busy to ask the question that came to mind next: 'why am I out of the class B?' to vector relatively high performance aircraft on approach to a major airport out of class B is bad procedure in my opinion. No higher performance aircraft were in the vicinity. My understanding is that the purpose of class B airspace is to avoid exactly this type of hazardous situation. It should be used for its intended purpose.

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Original NASA ASRS Text

Title: IFR SMT inbound to HOU with I90 experienced conflict at 3000 with unreported traffic; reporter questioned ATC's altitude assignment below Class B.

Narrative: On an IFR flight from RBD to HOU; in VMC; being controlled by Houston TRACON. Arrived via the Blubell 2 STAR. Shortly after passing COWZZ Intersection at 5;000 FT; was given a descent to 3;000 FT and a 135 degree heading; vectors for the HOU ILS Runway 30L. I did not realize it at the time; but this descent took us out of but underneath Class B airspace. Shortly after leveling at 3;000 FT; cruising at about 200 KTS; TCAS indicated traffic at 12 o'clock position; 3 NM; 500 FT below and climbing. I began deviating left (east) but another target appeared about 1/4 miles east of the original target; limiting my ability to maneuver. About that time I acquired visual contact with the original target. It was in a climbing; steep-bank turn toward me. I passed a few hundred FT above and less than 1/4 miles east of it. I never acquired the second target and my TCAS unit indicated that I passed even closer; but west of it. I wonder if it may have been a phantom 'double' of the first target. As I was passing by the traffic; I got a radio call from TRACON suggesting a right turn (I think an earlier call from TRACON may have been blocked). I told them that I had deviated left and was returning to my original 135 degree heading. 'That was close;' I said. 'They are out of the Class B and I am not talking to them;' was the response. The frequency was too busy to ask the question that came to mind next: 'Why am I out of the Class B?' To vector relatively high performance aircraft on approach to a major airport out of Class B is bad procedure in my opinion. No higher performance aircraft were in the vicinity. My understanding is that the purpose of Class B airspace is to avoid exactly this type of hazardous situation. It should be used for its intended purpose.

Data retrieved from NASA's ASRS site as of April 2012 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.