Narrative:

Flight arriving from phx cleared for 4R ILS approach mdw. On centerline of localizer 5500' descending to 4000' to intercept G/south 17 NM from airport (reference 109.9 localizer DME) in and out of clouds visibility approximately 2-3 mi. Saw blue and white small aircraft at 12 O'clock position, coming out of clouds westbound (right to left) at same altitude, distance between closing rapidly. Took evasive climbing right turn to avoid. Passed within 1000' of other aircraft as he dove to the right. Advised and inquired approach control of small aircraft. Told no aircraft on radar initially, then told just appeared on altitude squawking 1200. No further occurrence.

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Original NASA ASRS Text

Title: CLOSE PROX ACR-MLG GA-SMA IN ORD TCA. SMA PROBABLY A SPILLIN.

Narrative: FLT ARRIVING FROM PHX CLRED FOR 4R ILS APCH MDW. ON CENTERLINE OF LOC 5500' DSNDING TO 4000' TO INTERCEPT G/S 17 NM FROM ARPT (REF 109.9 LOC DME) IN AND OUT OF CLOUDS VISIBILITY APPROX 2-3 MI. SAW BLUE AND WHITE SMA AT 12 O'CLOCK POS, COMING OUT OF CLOUDS WBND (RIGHT TO LEFT) AT SAME ALT, DISTANCE BTWN CLOSING RAPIDLY. TOOK EVASIVE CLBING RIGHT TURN TO AVOID. PASSED WITHIN 1000' OF OTHER ACFT AS HE DOVE TO THE RIGHT. ADVISED AND INQUIRED APCH CTL OF SMA. TOLD NO ACFT ON RADAR INITIALLY, THEN TOLD JUST APPEARED ON ALT SQUAWKING 1200. NO FURTHER OCCURRENCE.

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.