An MD83 crew reports a TCAS RA at 5000 ft requiring an evasive descent. Crew did not see the traffic...

Attributes
ACN	700570
Time
Date	200606
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : c90.tracon
State Reference	IL
Altitude	msl bound lower : 4720 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : initial
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	700570
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
ASRS Report	700571
Events
Anomaly	conflict : airborne critical
Independent Detector	aircraft equipment : tcas
Resolutory Action	flight crew : took evasive action flight crew : returned to assigned altitude flight crew : exited adverse environment
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance Airspace Structure
Primary Problem	Ambiguous

Narrative:

Leveled off at 5000 ft to comply with leveloff clearance. Received a descending TCAS RA which I complied with immediately. My first officer advised chicago departure control. I descended until clear of conflict was announced by TCAS system. Descent to 280 ft below assigned altitude (4720 ft) was all that was required to comply with the RA. Never saw the other offending aircraft. Did notice a red RA on the TCAS screen; but do not recall the relative altitude.

Original NASA ASRS Text

Title: AN MD83 CREW RPTS A TCAS RA AT 5000 FT REQUIRING AN EVASIVE DSCNT. CREW DID NOT SEE THE TFC.

Narrative: LEVELED OFF AT 5000 FT TO COMPLY WITH LEVELOFF CLRNC. RECEIVED A DSNDING TCAS RA WHICH I COMPLIED WITH IMMEDIATELY. MY FO ADVISED CHICAGO DEP CTL. I DSNDED UNTIL CLR OF CONFLICT WAS ANNOUNCED BY TCAS SYS. DSCNT TO 280 FT BELOW ASSIGNED ALT (4720 FT) WAS ALL THAT WAS REQUIRED TO COMPLY WITH THE RA. NEVER SAW THE OTHER OFFENDING ACFT. DID NOTICE A RED RA ON THE TCAS SCREEN; BUT DO NOT RECALL THE RELATIVE ALT.

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.