Air carrier inbound to ord initiated a turn to the runway 4R localizer; the turn was issued to anoth...

Narrative:

We were receiving vectors and on a downwind for the ILS 4R at ord and there was another aircraft ahead of us on the approach with a very similar flight number. Both the PF and pm heard a clearance with our flight number to turn to intercept the localizer and the clearance was read back with no correction from the controller. As the turn was being made we heard the other aircraft read back the same clearance and we realized that it was in fact meant for them. The PF immediately disconnected the autopilot and turned back to our original heading. We received a momentary TA as we were turning but it only lasted a few seconds. ATC did not say anything about our deviation and moments later issued the same clearance to us. The other flight read back the same clearance we had just read back and upon receiving the TA we realized that the clearance was in fact not meant for us. We and ATC were confused by the similar flight numbers and there was a breakdown in communication as a result. Autopilot was disconnected and we promptly returned to our original course. Both the flight crew and ATC should be more vigilant when there are similar call signs in use and ATC should should immediately provide clarification when someone accepts the wrong clearance.

Original NASA ASRS Text

Title: Air Carrier inbound to ORD initiated a turn to the Runway 4R localizer; the turn was issued to another preceding aircraft with a similar flight number.

Narrative: We were receiving vectors and on a downwind for the ILS 4R at ORD and there was another aircraft ahead of us on the approach with a very similar flight number. Both the PF and PM heard a clearance with our flight number to turn to intercept the localizer and the clearance was read back with no correction from the Controller. As the turn was being made we heard the other aircraft read back the same clearance and we realized that it was in fact meant for them. The PF immediately disconnected the autopilot and turned back to our original heading. We received a momentary TA as we were turning but it only lasted a few seconds. ATC did not say anything about our deviation and moments later issued the same clearance to us. The other flight read back the same clearance we had just read back and upon receiving the TA we realized that the clearance was in fact not meant for us. We and ATC were confused by the similar flight numbers and there was a breakdown in communication as a result. Autopilot was disconnected and we promptly returned to our original course. Both the flight crew and ATC should be more vigilant when there are similar call signs in use and ATC should should immediately provide clarification when someone accepts the wrong clearance.

Data retrieved from NASA's ASRS site as of April 2012 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	947122
Time
Date	201105
Local Time Of Day	0601-1200
Place
Locale Reference	ORD.Airport
State Reference	IL
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	EMB ERJ 145 ER&LR
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Commercial
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Deviation - Procedural Clearance Deviation - Track / Heading All Types

Air carrier inbound to ord initiated a turn to the runway 4R localizer; the turn was issued to another preceding aircraft with a similar flight number.