Narrative:

Bay TRACON was southeast confign, which required me at R14 to sequence oak and sfo arrs on same arrival route, at the same time also sequencing sjc arrs. Sfo and sjc arrivals had a 20 mit restriction over bsr and sns, respectively. At the time of the incident, and for approximately 30 mins prior, I was extremely busy sequencing to all 3 major airports (sfo, oak, sjc). I was not aware of similar call signs approaching my airspace. The call signs were air carrier X and air carrier Y. Air carrier Y was at FL260 inbound to sfo in the position a sjc arrival would normally be in. Air carrier X checked on frequency level at FL310. I then cleared X on the preferential route. I looked at air carrier Y's data block and stated Y's altitude (FL260) to air carrier X. X then queried if the altitude assignment was FL290. Thinking that Y was asking and if I meant him to climb, I stated Y 'maintain FL260.' air carrier X did not catch that I said Y company and rogered, 'maintain FL260 and 4 digits.' C/a activated after the aircraft passed. I think between the similarity of call sign number (same digits) and aircraft being so close also contributed to my confusion between the airplanes. Supplemental information from acn 101038: air carrier Z en route sjc-ave-san, FL290. Air carrier X over ave-sns-sjc, FL310. Air carrier Y 20W/ave-bsr-sfo, FL260. Upon initial call by X at ave at FL310, the radar controller cleared X direct sns and to maintain FL260 (was looking at the data block of air carrier Y at FL260). X began descent and conflicted with Z at FL290. Traffic load was very heavy and complex at this time and the rdp notice of C/a between X and Z was the first realization that 2 aircraft with similar call signs were on frequency at the same time and an incorrect altitude had been issued to X.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN 2 ACR. OPERATIONAL ERROR.

Narrative: BAY TRACON WAS SE CONFIGN, WHICH REQUIRED ME AT R14 TO SEQUENCE OAK AND SFO ARRS ON SAME ARR ROUTE, AT THE SAME TIME ALSO SEQUENCING SJC ARRS. SFO AND SJC ARRIVALS HAD A 20 MIT RESTRICTION OVER BSR AND SNS, RESPECTIVELY. AT THE TIME OF THE INCIDENT, AND FOR APPROX 30 MINS PRIOR, I WAS EXTREMELY BUSY SEQUENCING TO ALL 3 MAJOR ARPTS (SFO, OAK, SJC). I WAS NOT AWARE OF SIMILAR CALL SIGNS APCHING MY AIRSPACE. THE CALL SIGNS WERE ACR X AND ACR Y. ACR Y WAS AT FL260 INBND TO SFO IN THE POS A SJC ARR WOULD NORMALLY BE IN. ACR X CHKED ON FREQ LEVEL AT FL310. I THEN CLRED X ON THE PREFERENTIAL ROUTE. I LOOKED AT ACR Y'S DATA BLOCK AND STATED Y'S ALT (FL260) TO ACR X. X THEN QUERIED IF THE ALT ASSIGNMENT WAS FL290. THINKING THAT Y WAS ASKING AND IF I MEANT HIM TO CLB, I STATED Y 'MAINTAIN FL260.' ACR X DID NOT CATCH THAT I SAID Y COMPANY AND ROGERED, 'MAINTAIN FL260 AND 4 DIGITS.' C/A ACTIVATED AFTER THE ACFT PASSED. I THINK BTWN THE SIMILARITY OF CALL SIGN NUMBER (SAME DIGITS) AND ACFT BEING SO CLOSE ALSO CONTRIBUTED TO MY CONFUSION BTWN THE AIRPLANES. SUPPLEMENTAL INFO FROM ACN 101038: ACR Z ENRTE SJC-AVE-SAN, FL290. ACR X OVER AVE-SNS-SJC, FL310. ACR Y 20W/AVE-BSR-SFO, FL260. UPON INITIAL CALL BY X AT AVE AT FL310, THE RADAR CTLR CLRED X DIRECT SNS AND TO MAINTAIN FL260 (WAS LOOKING AT THE DATA BLOCK OF ACR Y AT FL260). X BEGAN DSCNT AND CONFLICTED WITH Z AT FL290. TFC LOAD WAS VERY HEAVY AND COMPLEX AT THIS TIME AND THE RDP NOTICE OF C/A BTWN X AND Z WAS THE FIRST REALIZATION THAT 2 ACFT WITH SIMILAR CALL SIGNS WERE ON FREQ AT THE SAME TIME AND AN INCORRECT ALT HAD BEEN ISSUED TO X.

Data retrieved from NASA's ASRS site as of August 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.