Narrative:

Taxiing out we were sequenced behind an air carrier Y medium large transport. There was some confusion on ground control and the air carrier Y was misidented as an air carrier Z. At one point a supervisor had to come on the frequency to make the right identify. As we approached the end of the runway we were told to go to tower frequency 120.7. This was unusual, since this is the frequency for the short runway that the GA planes use. The tower was using 1 frequency for both runways and the tower operator was overloaded, as well as the frequency. We were #1 for takeoff at the end of the runway, runway 30L. There was no one in front of us since air carrier Y had been cleared for takeoff. We could hear the tower calling out the number of another aircraft, clearing them for immediate takeoff. The tower called the # at least 2 times possibly 3, calling for immediate takeoff. Since we were #1 and there was no other aircraft in sight and there already had been confusion with call signs and no one in front of us, I asked the first officer to ask if they were calling us and did they mean that we were cleared for takeoff. At this point the tower operator apparently thought the other aircraft had called and said 'yes, cleared for takeoff.' I took the runway and as I lined up rolling towards the centerline I looked up the field and noted that there was another company aircraft at the intersection holding short of the runway. He was the other number that they had been calling, but had just come over to the frequency. I instructed the first officer to verify that we were the one cleared for takeoff. The tower responded by cancelling the other aircraft's takeoff clearance and once again cleared us to go. Initially we were called bdef and then correctly bcef. I have been flying out of sjc since that early 1960's, I have never seen an air carrier takeoff from that intersection. We were never informed of him or made aware that there would be someone else departing ahead of us. The entire problem could have been avoided, I believe, by using different frequencys or at least informing us there would be a downfield departure.

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Original NASA ASRS Text

Title: ACR MLG UNAUTH TKOF FROM SJC IN RESPONSE TO WRONG CALL SIGN.

Narrative: TAXIING OUT WE WERE SEQUENCED BEHIND AN ACR Y MLG. THERE WAS SOME CONFUSION ON GND CTL AND THE ACR Y WAS MISIDENTED AS AN ACR Z. AT ONE POINT A SUPVR HAD TO COME ON THE FREQ TO MAKE THE RIGHT IDENT. AS WE APCHED THE END OF THE RWY WE WERE TOLD TO GO TO TWR FREQ 120.7. THIS WAS UNUSUAL, SINCE THIS IS THE FREQ FOR THE SHORT RWY THAT THE GA PLANES USE. THE TWR WAS USING 1 FREQ FOR BOTH RWYS AND THE TWR OPERATOR WAS OVERLOADED, AS WELL AS THE FREQ. WE WERE #1 FOR TKOF AT THE END OF THE RWY, RWY 30L. THERE WAS NO ONE IN FRONT OF US SINCE ACR Y HAD BEEN CLRED FOR TKOF. WE COULD HEAR THE TWR CALLING OUT THE NUMBER OF ANOTHER ACFT, CLRING THEM FOR IMMEDIATE TKOF. THE TWR CALLED THE # AT LEAST 2 TIMES POSSIBLY 3, CALLING FOR IMMEDIATE TKOF. SINCE WE WERE #1 AND THERE WAS NO OTHER ACFT IN SIGHT AND THERE ALREADY HAD BEEN CONFUSION WITH CALL SIGNS AND NO ONE IN FRONT OF US, I ASKED THE F/O TO ASK IF THEY WERE CALLING US AND DID THEY MEAN THAT WE WERE CLRED FOR TKOF. AT THIS POINT THE TWR OPERATOR APPARENTLY THOUGHT THE OTHER ACFT HAD CALLED AND SAID 'YES, CLRED FOR TKOF.' I TOOK THE RWY AND AS I LINED UP ROLLING TOWARDS THE CENTERLINE I LOOKED UP THE FIELD AND NOTED THAT THERE WAS ANOTHER COMPANY ACFT AT THE INTXN HOLDING SHORT OF THE RWY. HE WAS THE OTHER NUMBER THAT THEY HAD BEEN CALLING, BUT HAD JUST COME OVER TO THE FREQ. I INSTRUCTED THE F/O TO VERIFY THAT WE WERE THE ONE CLRED FOR TKOF. THE TWR RESPONDED BY CANCELLING THE OTHER ACFT'S TKOF CLRNC AND ONCE AGAIN CLRED US TO GO. INITIALLY WE WERE CALLED BDEF AND THEN CORRECTLY BCEF. I HAVE BEEN FLYING OUT OF SJC SINCE THAT EARLY 1960'S, I HAVE NEVER SEEN AN ACR TKOF FROM THAT INTXN. WE WERE NEVER INFORMED OF HIM OR MADE AWARE THAT THERE WOULD BE SOMEONE ELSE DEPARTING AHEAD OF US. THE ENTIRE PROB COULD HAVE BEEN AVOIDED, I BELIEVE, BY USING DIFFERENT FREQS OR AT LEAST INFORMING US THERE WOULD BE A DOWNFIELD DEP.

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.