B747 crew took a clearance for another aircraft.

Attributes
ACN	440880
Time
Date	199906
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : iad.airport
State Reference	VA
Altitude	msl bound lower : 9000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : iad.tracon
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : iad.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 21000 flight time type : 500
ASRS Report	440880
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued alert controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Dulles approach 126.1/vectors and descent for runway 19R. Frequency was congested. We were given 250 degree heading to fly through localizer. We had and acknowledged left turn to 160 degrees and descent to 5000 ft. After beginning left turn and starting descent from 11000 ft to 5000 ft 'confirm heading 250 degrees.' controller then advised there was another aircraft with same call numbers. We turned and stopped and reestablished to 250 degrees. Descent was stopped at 9000 ft as directed. No conflict. Also, vectors were given to intercept localizer without identing which runway (19L or 19R). Radio congestion appears to have caused 2 gaps. 1) failure to advise similar call sign. 2) identify runway in use.

Original NASA ASRS Text

Title: B747 CREW TOOK A CLRNC FOR ANOTHER ACFT.

Narrative: DULLES APCH 126.1/VECTORS AND DSCNT FOR RWY 19R. FREQ WAS CONGESTED. WE WERE GIVEN 250 DEG HDG TO FLY THROUGH LOC. WE HAD AND ACKNOWLEDGED L TURN TO 160 DEGS AND DSCNT TO 5000 FT. AFTER BEGINNING L TURN AND STARTING DSCNT FROM 11000 FT TO 5000 FT 'CONFIRM HDG 250 DEGS.' CTLR THEN ADVISED THERE WAS ANOTHER ACFT WITH SAME CALL NUMBERS. WE TURNED AND STOPPED AND REESTABLISHED TO 250 DEGS. DSCNT WAS STOPPED AT 9000 FT AS DIRECTED. NO CONFLICT. ALSO, VECTORS WERE GIVEN TO INTERCEPT LOC WITHOUT IDENTING WHICH RWY (19L OR 19R). RADIO CONGESTION APPEARS TO HAVE CAUSED 2 GAPS. 1) FAILURE TO ADVISE SIMILAR CALL SIGN. 2) IDENT RWY IN USE.

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.