C90 controller described a loss of separation event involving arrival traffic into mdw and departure...

Narrative:

Mdw was using a combination of rnp/RNAV Y 13C and visual approach 13C all afternoon. Typically; when 13C is in use; ord protects for the mdw 13C ILS. However; since the ILS was not in use today; ord was operating as normal with their southbound departures off runway 22L. When traffic to mdw was light; it wasn't really a big deal. However; with the evening rush; it became more of a problem. Due to mdw's size and also the vast sea of orange lights that is the metro chicago area; visuals became a bit more difficult to achieve after sunset. Right now; only one airline is certified to use the rnp Y 13C approach; and even then; not all of their aircraft are capable. The evening rush included several GA aircraft along with other air carriers which really forced our hand to use visuals. Earlier in the shift; I had asked a controller in charge to call mdw and see if we could use runway 31C since the winds were fairly light. I saw one air carrier proceeding on a wide base leg; outside of the rnp Y final approach course. I told him to turn right to heading 090 to continue following the traffic; to which he replied; 'roger; we still have our traffic in sight.' I then switched the aircraft to tower frequency about 7 miles from the airport. Just then; I saw an air carrier departing ord runway 22L southbound; climbing slowly; but assigned the ORD6 SID. The line's flm-ic saw what was going on and took action to change the advertised approach in use at mdw to the GPS 4R circle to 13C to avoid further issues. I was later told that separation was lost. Under light traffic; using this combination of visuals and rnp Y 13C approaches works; however; under any real load; it quickly becomes a difficult operation which has no built-in safeguards to protect mdw inbound traffic from ord departure traffic. If runway 13C is required; then ord needs to protect for it.

Original NASA ASRS Text

Title: C90 Controller described a loss of separation event involving arrival traffic into MDW and departure traffic from ORD; the reporter suggesting amending procedures when this combination of runways are required.

Narrative: MDW was using a combination of RNP/RNAV Y 13C and Visual Approach 13C all afternoon. Typically; when 13C is in use; ORD protects for the MDW 13C ILS. However; since the ILS was not in use today; ORD was operating as normal with their southbound departures off Runway 22L. When traffic to MDW was light; it wasn't really a big deal. However; with the evening rush; it became more of a problem. Due to MDW's size and also the vast sea of orange lights that is the Metro Chicago area; visuals became a bit more difficult to achieve after sunset. Right now; only one airline is certified to use the RNP Y 13C Approach; and even then; not all of their aircraft are capable. The evening rush included several GA aircraft along with other air carriers which really forced our hand to use visuals. Earlier in the shift; I had asked a CIC to call MDW and see if we could use Runway 31C since the winds were fairly light. I saw one air carrier proceeding on a wide base leg; outside of the RNP Y final approach course. I told him to turn right to heading 090 to continue following the traffic; to which he replied; 'roger; we still have our traffic in sight.' I then switched the aircraft to Tower frequency about 7 miles from the airport. Just then; I saw an air carrier departing ORD Runway 22L southbound; climbing slowly; but assigned the ORD6 SID. The line's FLM-IC saw what was going on and took action to change the advertised approach in use at MDW to the GPS 4R circle to 13C to avoid further issues. I was later told that separation was lost. Under light traffic; using this combination of visuals and RNP Y 13C approaches works; however; under any real load; it quickly becomes a difficult operation which has no built-in safeguards to protect MDW inbound traffic from ORD departure traffic. If Runway 13C is required; then ORD needs to protect for it.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1031880
Time
Date	201208
Local Time Of Day	0001-0600
Place
Locale Reference	MDW.Airport
State Reference	IL
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	EMB ERJ 145 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Flight Plan	IFR
Person 1
Function	Departure Approach
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

C90 controller described a loss of separation event involving arrival traffic into mdw and departure traffic from ord; the reporter suggesting amending procedures when this combination of runways are required.