B767 reacted to a TCASII RA and similar call sign confusion while under ZAU control.

Attributes
ACN	586776
Time
Date	200306
Day	Thu
Local Time Of Day	1801 To 2400
Place
Altitude	msl single value : 33000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	B767 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change
Aircraft 2
Controlling Facilities	artcc : zau.artcc
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	586776
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
ASRS Report	586110
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation other anomaly other
Independent Detector	aircraft equipment : tcas other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : took precautionary avoidance action
Consequence	faa : reviewed incident with flight crew
Miss Distance	vertical : 900
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Near bdf VOR under ZAU control we were placed in a conflict situation requiring maneuvering in response to an RA. Center told us to climb 2000 ft when he really meant aircraft Y to climb. There had been a frequency mix-up with aircraft Y while we were on ZKC so we were saying aircraft X before and after our number call for clarity. The controller stated that he had just told the wrong aircraft X to climb. After climbing 1000 ft the traffic alert sounded and I observed the aircraft 10 mi ahead 1000 ft higher and appearing to be headed directly toward us on the TCASII screen. I clicked the autoplt off and started to level when the RA triggered a descent of 1000 FPM nearly simultaneously with a call from the controller to descend. I followed the RA to 1000 FPM down and then to holding level until after passing below the traffic. I doubt that we ever got closer than 900 ft vertically as both of us were responding to the RA. The descent was smooth to the point that the relief pilot in the cabin was not aware that it had occurred. The RA, aircraft, and controller all reacted correctly when the conflict became obvious.

Original NASA ASRS Text

Title: B767 REACTED TO A TCASII RA AND SIMILAR CALL SIGN CONFUSION WHILE UNDER ZAU CTL.

Narrative: NEAR BDF VOR UNDER ZAU CTL WE WERE PLACED IN A CONFLICT SIT REQUIRING MANEUVERING IN RESPONSE TO AN RA. CTR TOLD US TO CLB 2000 FT WHEN HE REALLY MEANT ACFT Y TO CLB. THERE HAD BEEN A FREQ MIX-UP WITH ACFT Y WHILE WE WERE ON ZKC SO WE WERE SAYING ACFT X BEFORE AND AFTER OUR NUMBER CALL FOR CLARITY. THE CTLR STATED THAT HE HAD JUST TOLD THE WRONG ACFT X TO CLB. AFTER CLBING 1000 FT THE TFC ALERT SOUNDED AND I OBSERVED THE ACFT 10 MI AHEAD 1000 FT HIGHER AND APPEARING TO BE HEADED DIRECTLY TOWARD US ON THE TCASII SCREEN. I CLICKED THE AUTOPLT OFF AND STARTED TO LEVEL WHEN THE RA TRIGGERED A DSCNT OF 1000 FPM NEARLY SIMULTANEOUSLY WITH A CALL FROM THE CTLR TO DSND. I FOLLOWED THE RA TO 1000 FPM DOWN AND THEN TO HOLDING LEVEL UNTIL AFTER PASSING BELOW THE TFC. I DOUBT THAT WE EVER GOT CLOSER THAN 900 FT VERTLY AS BOTH OF US WERE RESPONDING TO THE RA. THE DSCNT WAS SMOOTH TO THE POINT THAT THE RELIEF PLT IN THE CABIN WAS NOT AWARE THAT IT HAD OCCURRED. THE RA, ACFT, AND CTLR ALL REACTED CORRECTLY WHEN THE CONFLICT BECAME OBVIOUS.

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.