Narrative:

We were level at 15000 ft on top of an overcast en route to bmi from ord. We were given a discretion descent to 10000 ft but didn't begin descent due to passenger comfort. Later we were given a descent to 6000 ft and while passing 13000 ft the controller said you may want to stop your descent at 11000 ft -- you have traffic at 12-11 O'clock and 3 mi at 10500 ft opposite direction. While leveling at 11000 ft we went IMC and received a TCASII advisory of traffic at 10 O'clock and 500 ft below. Center said it was an small aircraft getting VFR advisories from another controller. We went IMC at 11000 ft, if this guy was at 10500 ft there was no way he was VFR. After clearing the traffic and continuing our descent, we did not get into VFR conditions until 9000 ft. The bottom of the overcast was ragged and it was very hazy. In-flight visibility was 1 1/2-2 mi at best. I hope this guy didn't think that getting VFR advisories from center doesn't take the place of an IFR clearance! If he had not turned on his transponder and been talking to center we would have never seen and he would have been a very weak primary return to a center controller. This is the kind of thing that gets people killed. After talking with the controller via telephone he gave me the tail number of the small aircraft. Someone should have a talk with this guy.

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Original NASA ASRS Text

Title: COMMUTER HAS TCASII ADVISORY ON DSCNT AND CTLR ADVISORY TO LEVEL OFF. RECEIVES ADVISORY AS HE ENTERS IMC. TFC SUPPOSEDLY VFR.

Narrative: WE WERE LEVEL AT 15000 FT ON TOP OF AN OVCST ENRTE TO BMI FROM ORD. WE WERE GIVEN A DISCRETION DSCNT TO 10000 FT BUT DIDN'T BEGIN DSCNT DUE TO PAX COMFORT. LATER WE WERE GIVEN A DSCNT TO 6000 FT AND WHILE PASSING 13000 FT THE CTLR SAID YOU MAY WANT TO STOP YOUR DSCNT AT 11000 FT -- YOU HAVE TFC AT 12-11 O'CLOCK AND 3 MI AT 10500 FT OPPOSITE DIRECTION. WHILE LEVELING AT 11000 FT WE WENT IMC AND RECEIVED A TCASII ADVISORY OF TFC AT 10 O'CLOCK AND 500 FT BELOW. CTR SAID IT WAS AN SMA GETTING VFR ADVISORIES FROM ANOTHER CTLR. WE WENT IMC AT 11000 FT, IF THIS GUY WAS AT 10500 FT THERE WAS NO WAY HE WAS VFR. AFTER CLRING THE TFC AND CONTINUING OUR DSCNT, WE DID NOT GET INTO VFR CONDITIONS UNTIL 9000 FT. THE BOTTOM OF THE OVCST WAS RAGGED AND IT WAS VERY HAZY. INFLT VISIBILITY WAS 1 1/2-2 MI AT BEST. I HOPE THIS GUY DIDN'T THINK THAT GETTING VFR ADVISORIES FROM CTR DOESN'T TAKE THE PLACE OF AN IFR CLRNC! IF HE HAD NOT TURNED ON HIS TRANSPONDER AND BEEN TALKING TO CTR WE WOULD HAVE NEVER SEEN AND HE WOULD HAVE BEEN A VERY WEAK PRIMARY RETURN TO A CTR CTLR. THIS IS THE KIND OF THING THAT GETS PEOPLE KILLED. AFTER TALKING WITH THE CTLR VIA TELEPHONE HE GAVE ME THE TAIL NUMBER OF THE SMA. SOMEONE SHOULD HAVE A TALK WITH THIS GUY.

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.