<< >> NASA ASRS Report 439765, June 1999

Flight crew of an embraer, EMB120 descended from assigned altitude and changed heading during descent in response to another company aircraft similar sounding call sign.

Attributes
ACN	439765
Time
Date	199906
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sfo.airport
State Reference	CA
Altitude	msl bound lower : 6000 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : o90.tracon
Operator	common carrier : air carrier
Make Model Name	Brasilia EMB-120 All Series
Operating Under FAR Part	Part 135
Flight Phase	descent : intermediate altitude descent : vacating altitude
Route In Use	arrival : on vectors
Aircraft 2
Controlling Facilities	tracon : o90.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine pilot : cfi
Experience	flight time last 90 days : 200 flight time total : 7500 flight time type : 1200
ASRS Report	439765
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : cfi pilot : private pilot : multi engine pilot : atp technician : airframe technician : powerplant
Experience	flight time last 90 days : 250 flight time total : 5000 flight time type : 2500
ASRS Report	441234
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : became reoriented
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While en route from smf to sfo and talking to bay approach we accepted a clearance that we found out later was meant for another (company) aircraft. The clearance contained a heading, speed reduction, and descent from 7000 ft to 4000 ft. During our descent we heard company, 'aircraft Y,' confirm that they were cleared to 4000 ft at 180 KTS. At that point we stopped our descent at 6000 ft and queried ATC. Bay approach then cleared us, 'aircraft X' to 4000 ft, and indicated that we had in fact accepted aircraft Y clearance, but it had not caused any traffic conflict. Since air carrier changed its call signs in early june there have been many communication errors committed by both ATC and our air carrier pilots. The change involved going from a 3 digit call sign to a 4 digit call sign, all of which now begin the same. The result is that we all have similar sounding call signs, which we believe is a source of much of the confusion.

Related reports:

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Original NASA ASRS Text

Title: FLC OF AN EMBRAER, EMB120 DSNDED FROM ASSIGNED ALT AND CHANGED HEADING DURING DSCNT IN RESPONSE TO ANOTHER COMPANY ACFT SIMILAR SOUNDING CALL SIGN.

Narrative: WHILE ENRTE FROM SMF TO SFO AND TALKING TO BAY APCH WE ACCEPTED A CLRNC THAT WE FOUND OUT LATER WAS MEANT FOR ANOTHER (COMPANY) ACFT. THE CLRNC CONTAINED A HEADING, SPD REDUCTION, AND DSCNT FROM 7000 FT TO 4000 FT. DURING OUR DSCNT WE HEARD COMPANY, 'ACFT Y,' CONFIRM THAT THEY WERE CLRED TO 4000 FT AT 180 KTS. AT THAT POINT WE STOPPED OUR DSCNT AT 6000 FT AND QUERIED ATC. BAY APCH THEN CLRED US, 'ACFT X' TO 4000 FT, AND INDICATED THAT WE HAD IN FACT ACCEPTED ACFT Y CLRNC, BUT IT HAD NOT CAUSED ANY TFC CONFLICT. SINCE ACR CHANGED ITS CALL SIGNS IN EARLY JUNE THERE HAVE BEEN MANY COM ERRORS COMMITTED BY BOTH ATC AND OUR ACR PLTS. THE CHANGE INVOLVED GOING FROM A 3 DIGIT CALL SIGN TO A 4 DIGIT CALL SIGN, ALL OF WHICH NOW BEGIN THE SAME. THE RESULT IS THAT WE ALL HAVE SIMILAR SOUNDING CALL SIGNS, WHICH WE BELIEVE IS A SOURCE OF MUCH OF THE CONFUSION.

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.