Air carrier on final for runway 16C at sea described a confused event when ATC issued directions to ...

Narrative:

Call sign confusion; our call sign was aircraft xxk we were cleared to intercept the localizer 16C. Just as the autopilot captured the localizer; we said: 'localizer captured' in the cockpit; at the same time ATC said: aircraft yyk I need to take you off the localizer; turn right to 060 heading. I selected heading select and started to turn as the copilot answered ATC. As he did aircraft yyk said: 'someone else answered.' ATC then said: 'aircraft xxk stay on the localizer and aircraft yyk turn right to 060.' we had just started to roll into the bank; so I took off the autopilot and rolled back onto the localizer. We only got slightly right of course. I think three things contributed to this situation. First; ATC never informed us of the other aircraft with a similar call sign. Second; we blocked out hearing the word 'yy' when we said 'localizer captured' so we thought he must have said aircraft xxk since we did not know of another (K) on the frequency. We also did not hear him say 'K' again; still thought it was for us thinking he left off the 'K' and we would have corrected it with ATC.

Original NASA ASRS Text

Title: Air Carrier on final for Runway 16C at SEA described a confused event when ATC issued directions to turn off the LOC when in fact the clearance was for another flight with the same number absent the 'K' suffix.

Narrative: Call sign confusion; our call sign was Aircraft XXK We were cleared to intercept the localizer 16C. Just as the autopilot captured the localizer; we said: 'LOC captured' in the cockpit; at the same time ATC said: Aircraft YYK I need to take you off the localizer; turn right to 060 heading. I selected heading select and started to turn as the copilot answered ATC. As he did Aircraft YYK said: 'Someone else answered.' ATC then said: 'Aircraft XXK stay on the localizer and Aircraft YYK turn right to 060.' We had just started to roll into the bank; so I took off the autopilot and rolled back onto the localizer. We only got slightly right of course. I think three things contributed to this situation. First; ATC never informed us of the other aircraft with a similar call sign. Second; We blocked out hearing the word 'YY' when we said 'LOC Captured' so we thought he must have said Aircraft XXK since we did not know of another (K) on the frequency. We also did not hear him say 'K' again; still thought it was for us thinking he left off the 'K' and we would have corrected it with ATC.

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	984627
Time
Date	201112
Local Time Of Day	1201-1800
Place
Locale Reference	S46.TRACON
State Reference	WA
Environment
Flight Conditions	Marginal
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 27000 Flight Crew Type 17000
Events
Anomaly	ATC Issue All Types Deviation - Track / Heading All Types

Air carrier on final for runway 16C at sea described a confused event when ATC issued directions to turn off the localizer when in fact the clearance was for another flight with the same number absent the 'K' suffix.