Narrative:

Air carrier Z was stationed 2 mi north of mdw at 5500 ft MSL. Ord was landing runway 27L. Mdw was landing runway 22L. Ord ebounds depart ord on a 140 degree heading climbing to 5000 ft and are climbed and turned east reference the runway 27L arrs. Mdw ebounds depart mdw on a 090 degree heading and are climbed to 3000 ft then 4000 ft and handed off to the east departure controller. The TCAS event occurred when the east departure controller was unable to climb the B757 above 5000 ft because of air carrier Z position and a mdw departure (B737) was climbed to 4000 ft under the B757. Traffic was issued to the B737 and they had B757 in sight. As the B757 approached air carrier Z position he responded to an RA and descended to 4700 ft with the B737 under him at 4000 ft. The supervisor on duty in the TRACON made a bad decision and put these aircraft in this position by putting air carrier Z at 5500 ft. Air carrier Z requested altitude was 3500 ft. It was suggested to the supervisor that 3500 ft was a safer altitude and that this situation would occur 10 mins before the event. The supervisor ordered that air carrier Z be climbed to 5500 ft.

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Original NASA ASRS Text

Title: C90 CTLR DESCRIBED TCAS RA INCIDENT BTWN ORD AND MDW TFC WHEN SUPVR DIRECTED SPECIAL OPS TFC AT 5500 FT; REPORTEDLY CAUSING THE INCIDENT.

Narrative: ACR Z WAS STATIONED 2 MI N OF MDW AT 5500 FT MSL. ORD WAS LNDG RWY 27L. MDW WAS LNDG RWY 22L. ORD EBOUNDS DEPART ORD ON A 140 DEG HDG CLBING TO 5000 FT AND ARE CLBED AND TURNED E REF THE RWY 27L ARRS. MDW EBOUNDS DEPART MDW ON A 090 DEG HDG AND ARE CLBED TO 3000 FT THEN 4000 FT AND HANDED OFF TO THE E DEP CTLR. THE TCAS EVENT OCCURRED WHEN THE E DEP CTLR WAS UNABLE TO CLB THE B757 ABOVE 5000 FT BECAUSE OF ACR Z POS AND A MDW DEP (B737) WAS CLBED TO 4000 FT UNDER THE B757. TFC WAS ISSUED TO THE B737 AND THEY HAD B757 IN SIGHT. AS THE B757 APCHED ACR Z POS HE RESPONDED TO AN RA AND DSNDED TO 4700 FT WITH THE B737 UNDER HIM AT 4000 FT. THE SUPVR ON DUTY IN THE TRACON MADE A BAD DECISION AND PUT THESE ACFT IN THIS POS BY PUTTING ACR Z AT 5500 FT. ACR Z REQUESTED ALT WAS 3500 FT. IT WAS SUGGESTED TO THE SUPVR THAT 3500 FT WAS A SAFER ALT AND THAT THIS SITUATION WOULD OCCUR 10 MINS BEFORE THE EVENT. THE SUPVR ORDERED THAT ACR Z BE CLBED TO 5500 FT.

Data retrieved from NASA's ASRS site as of January 2009 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.