Narrative:

I cleared air carrier X for the runway 9R ILS to maintain 3000 ft when I noticed VFR traffic 5-6 mi southwest of denna indicating 2700 ft. I issued traffic and told air carrier X to descend to 2500 ft. Air carrier X said he saw the traffic and said it was an small aircraft. He said he made a TCASII descent to avoid the small aircraft. There was an small aircraft that made an ILS at dpa, and other aircraft asking for instructions to schaumburg. The pilot later called and said he was never higher than 2000 ft. I could not track actual target because of 4 targets in schaumburg traffic pattern. However, dpa controller asked him to squawk VFR and noticed his altitude 5 mi east of dpa as 2700 ft, heading eastbound. He tried to contact the pilot and warn him about entering ord TCA but pilot never acknowledged.

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Original NASA ASRS Text

Title: SMA UNAUTHORIZED PENETRATION OF TCA AIRSPACE HAD CONFLICT WITH ACR X TCASII RA DSND. PLTDEV.

Narrative: I CLRED ACR X FOR THE RWY 9R ILS TO MAINTAIN 3000 FT WHEN I NOTICED VFR TFC 5-6 MI SW OF DENNA INDICATING 2700 FT. I ISSUED TFC AND TOLD ACR X TO DSND TO 2500 FT. ACR X SAID HE SAW THE TFC AND SAID IT WAS AN SMA. HE SAID HE MADE A TCASII DSCNT TO AVOID THE SMA. THERE WAS AN SMA THAT MADE AN ILS AT DPA, AND OTHER ACFT ASKING FOR INSTRUCTIONS TO SCHAUMBURG. THE PLT LATER CALLED AND SAID HE WAS NEVER HIGHER THAN 2000 FT. I COULD NOT TRACK ACTUAL TARGET BECAUSE OF 4 TARGETS IN SCHAUMBURG TFC PATTERN. HOWEVER, DPA CTLR ASKED HIM TO SQUAWK VFR AND NOTICED HIS ALT 5 MI E OF DPA AS 2700 FT, HDG EBOUND. HE TRIED TO CONTACT THE PLT AND WARN HIM ABOUT ENTERING ORD TCA BUT PLT NEVER ACKNOWLEDGED.

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.