B777-200 crew took a transmission and clearance for another aircraft in C90 class B.

Attributes
ACN	525891
Time
Date	200109
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : c90.tracon
State Reference	IL
Altitude	msl bound lower : 6600 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B777-200
Operating Under FAR Part	Part 121
Navigation In Use	other other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : c90.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent : approach
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 180 flight time total : 9000 flight time type : 1700
ASRS Report	525891
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far non adherence : published procedure other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued alert controller : issued new clearance flight crew : returned to original clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We're not sure who is to fault. We were descending to 6000 ft as indicated on the MCP (mode control panel). Approach issued a climb clearance back to 7000 ft due to traffic. Approach control had another aircraft with a similar call sign. We or approach could have mixed up the call signs. We had an FAA inspector in the jump seat who thought we did everything right. The inspector thought approach mixed up the call signs. Any number of causes have contributed to the altitude deviation. Possible causes: 1) I could have set the wrong altitude and the captain verified the wrong altitude. 2) the captain could have moved the altitude selector instead of the heading selector. 3) I could have answered for another aircraft's call sign. 4) approach could have gotten similar call signs mixed up and issued the wrong altitude. Corrective recommendations: extra vigilance by everyone.

Original NASA ASRS Text

Title: B777-200 CREW TOOK A XMISSION AND CLRNC FOR ANOTHER ACFT IN C90 CLASS B.

Narrative: WE'RE NOT SURE WHO IS TO FAULT. WE WERE DSNDING TO 6000 FT AS INDICATED ON THE MCP (MODE CTL PANEL). APCH ISSUED A CLB CLRNC BACK TO 7000 FT DUE TO TFC. APCH CTL HAD ANOTHER ACFT WITH A SIMILAR CALL SIGN. WE OR APCH COULD HAVE MIXED UP THE CALL SIGNS. WE HAD AN FAA INSPECTOR IN THE JUMP SEAT WHO THOUGHT WE DID EVERYTHING RIGHT. THE INSPECTOR THOUGHT APCH MIXED UP THE CALL SIGNS. ANY NUMBER OF CAUSES HAVE CONTRIBUTED TO THE ALTDEV. POSSIBLE CAUSES: 1) I COULD HAVE SET THE WRONG ALT AND THE CAPT VERIFIED THE WRONG ALT. 2) THE CAPT COULD HAVE MOVED THE ALT SELECTOR INSTEAD OF THE HEADING SELECTOR. 3) I COULD HAVE ANSWERED FOR ANOTHER ACFT'S CALL SIGN. 4) APCH COULD HAVE GOTTEN SIMILAR CALL SIGNS MIXED UP AND ISSUED THE WRONG ALT. CORRECTIVE RECOMMENDATIONS: EXTRA VIGILANCE BY EVERYONE.

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.