CONFLICT AIRBORNE BETWEEN ACR-MLG ON VECTORS FOR APCH AND GA-SMA; BOTH BELOW FLOOR OF TCA AT BUSY SATELLITE.

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MY ACFT WAS DSNDING TO 1600'. RADAR VECTORS (310 DEGS) TO 4R ILS MIDWAY. BOTH THE CAPT AND I HAD SPOTTED A TOTAL OF 4 SINGLE ENG ACFT. WE WERE UNABLE TO VERIFY POS OF ANY BECAUSE THE CTLR WAS EXTREMELY BUSY POINTING OUT TFC AND DIRECTING ON 2 DIFFERENT FREQS (THE CTLR WAS OVERWORKED AND DOING A GREAT JOB AT HANDLING THE TFC). WE SAW THE CONFLICTING TFC AT 1 O'CLOCK; CONVERGING. THE TFC WAS AHEAD APPROX 180 DEGS. THE CAPT WAS FLYING. HE STARTED HIS DSCNT AT 2600'. THE SMA PASSED BELOW AND AHEAD. THE SMA TOOK NO EVASIVE ACTION AT ALL. AS THE ACFT PASSED BELOW; THE CTLR POINTED OUT 'TFC 12 O'CLOCK LESS THAN A MILE; ALT UNKNOWN.' MY RECOMMENDATIONS ARE THAT THE AIR TFC CTLRS IN APCHS AND DEPS NOT WORK MULTIPLE FREQS. TO INCREASE SAFETY IN THE CHICAGO MIDWAY AREA; LOWER THE O'HARE TCA TO GND LEVEL AROUND MIDWAY APCH CORRIDORS. BETTER COORDINATE AIR TFC; COMBINE AIR TFC CTL SYSTEMS TO PREVENT EARLY DSCNTS TO LOW HIGH DENSITY ALTS WITH VFR UNCTLED TFC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THIS WAS FIRST GOOD DAY OF SPRING AND EVERY SMA IN THE AREA WAS OUT. CTLR WAS DOING GOOD JOB BUT JUST TOO MANY ACFT. FELT THE SMA WAS EITHER OUT OF MDW OR MEIGS AS AT THIS POINT THEY ARE PERFECTLY LEGAL UNDER THE FLOOR OF THE TCA. THERE HAS BEEN SOME TALK OF LOWERING THE FLOOR OF THE TCA IN THIS AREA DUE TO THE LARGE INCREASE OF TURBINE ACFT INTO MDW AND AS IT IS NOW; TRACON HAS TO GET MDW ARRS UNDER THE FLOOR SOME DISTANCE OUT TO INTERCEPT G/S. NOTED IN THE LAST MONTH THERE HAS BEEN AN APPARENT CHANGE IN THE FLOW IN AND OUT OF MDW AS THEY ARE BEING KEPT HIGHER LONGER ON ARR AND CLB QUICKER ON DEP. AN OFFICIAL FAA NEAR MISS RPT WAS FILED; BUT TO DATE NO FOLLOW UP FROM FAA.