Narrative:

We were given a clearance to descend from 11000 to 4000' from fat approach. At the same time he gave us a traffic advisory of a target at our 11-12 O'clock type and altitude unknown. We were flying in and out of clouds and ground buildups at the time. As we were passing through 9500' I spotted the traffic at our 11:30 position moving southeast at our altitude. Fortunately we both saw each other and made turns to the left to avoid each other. We passed within 500' horizontal. My first officer told approach about the incident and what type of aircraft it was. Approach came back and said he was showing the traffic as a primary target. What I feel caused this problem to occur was that this person was flying in conditions that were close to marginal VFR, and was flying an aircraft that was probably equipped with a transponder and had it turned off. The aircraft in question was an small transport.

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Original NASA ASRS Text

Title: NMAC.

Narrative: WE WERE GIVEN A CLRNC TO DSND FROM 11000 TO 4000' FROM FAT APCH. AT THE SAME TIME HE GAVE US A TFC ADVISORY OF A TARGET AT OUR 11-12 O'CLOCK TYPE AND ALT UNKNOWN. WE WERE FLYING IN AND OUT OF CLOUDS AND GND BUILDUPS AT THE TIME. AS WE WERE PASSING THROUGH 9500' I SPOTTED THE TFC AT OUR 11:30 POS MOVING SE AT OUR ALT. FORTUNATELY WE BOTH SAW EACH OTHER AND MADE TURNS TO THE LEFT TO AVOID EACH OTHER. WE PASSED WITHIN 500' HORIZ. MY F/O TOLD APCH ABOUT THE INCIDENT AND WHAT TYPE OF ACFT IT WAS. APCH CAME BACK AND SAID HE WAS SHOWING THE TFC AS A PRIMARY TARGET. WHAT I FEEL CAUSED THIS PROB TO OCCUR WAS THAT THIS PERSON WAS FLYING IN CONDITIONS THAT WERE CLOSE TO MARGINAL VFR, AND WAS FLYING AN ACFT THAT WAS PROBABLY EQUIPPED WITH A XPONDER AND HAD IT TURNED OFF. THE ACFT IN QUESTION WAS AN SMT.

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.