Narrative:

When we started our long taxi at XA30L from the gate, we were instructed to taxi to runway 1R for our departure to fat on the SFO8 departure. At XB00L (approximately) we were next for takeoff. Tower said air carrier XXX hold short of runway 1R for wake turbulence avoidance. I, the first officer, read back the instructions. 15-20 seconds later, I heard 'air carrier XXX taxi into position and hold runway 1R.' I read back the instructions 'taxi into position and hold runway 1R.' we started our taxi, clearing right and left into position on runway 1R. Sfo tower said, 'air carrier XXX you were not instructed to taxi into position, you were instructed to hold short runway 1R.' my captain said to the tower 'we read back the instruction to taxi into position, and sorry about that.' the sfo tower came back and said 'air carrier XXX continue holding in position on runway 1R.' we held in position on the runway until we were cleared for takeoff. The captain and I talked about what happened during our cruise to fat. I believe I mistook the call sign of company same air carrier xx for the call sign of company air carrier XXX. The tower probably said 'same air carrier xx taxi into position and hold runway 1L' and I heard 'air carrier XXX taxi into position and hold runway 1R.' I was wrong in what I heard. Contributing factors: a long taxi, busy airport, busy radio traffic, similar company call signs, same air carrier xx to air carrier XXX. Crew needs to pay closer attention to the frequency. How it was discovered: sfo tower saw us taxi into position runway 1R. Corrective action: we apologized to the controller. I called and asked for the tower supervisor, but spoke to a controller ab. He said that they (controllers) listened to the tapes and they heard me read back 'air carrier XXX, taxi into position and hold runway 1R.' so the controller at the time did not hear our transmission. Ab told me that there was not any problem and asked us to listen more carefully when the radio gets real busy. I told him thank you and I was sorry for the mistake. The captain and I both agreed that in our future communications we will talk slower. Sometimes controllers are very busy and begin to talk fast and as pilots we begin to do the same. This is when important information can get lost in the radio communication. As a pilot, I will slow down and ask for clarification when not absolutely sure.

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Original NASA ASRS Text

Title: E120 CREW TAXIED INTO POS WITHOUT CLRNC.

Narrative: WHEN WE STARTED OUR LONG TAXI AT XA30L FROM THE GATE, WE WERE INSTRUCTED TO TAXI TO RWY 1R FOR OUR DEP TO FAT ON THE SFO8 DEP. AT XB00L (APPROX) WE WERE NEXT FOR TKOF. TWR SAID ACR XXX HOLD SHORT OF RWY 1R FOR WAKE TURB AVOIDANCE. I, THE FO, READ BACK THE INSTRUCTIONS. 15-20 SECONDS LATER, I HEARD 'ACR XXX TAXI INTO POS AND HOLD RWY 1R.' I READ BACK THE INSTRUCTIONS 'TAXI INTO POS AND HOLD RWY 1R.' WE STARTED OUR TAXI, CLRING R AND L INTO POS ON RWY 1R. SFO TWR SAID, 'ACR XXX YOU WERE NOT INSTRUCTED TO TAXI INTO POS, YOU WERE INSTRUCTED TO HOLD SHORT RWY 1R.' MY CAPT SAID TO THE TWR 'WE READ BACK THE INSTRUCTION TO TAXI INTO POS, AND SORRY ABOUT THAT.' THE SFO TWR CAME BACK AND SAID 'ACR XXX CONTINUE HOLDING IN POS ON RWY 1R.' WE HELD IN POS ON THE RWY UNTIL WE WERE CLRED FOR TKOF. THE CAPT AND I TALKED ABOUT WHAT HAPPENED DURING OUR CRUISE TO FAT. I BELIEVE I MISTOOK THE CALL SIGN OF COMPANY SAME ACR XX FOR THE CALL SIGN OF COMPANY ACR XXX. THE TWR PROBABLY SAID 'SAME ACR XX TAXI INTO POS AND HOLD RWY 1L' AND I HEARD 'ACR XXX TAXI INTO POS AND HOLD RWY 1R.' I WAS WRONG IN WHAT I HEARD. CONTRIBUTING FACTORS: A LONG TAXI, BUSY ARPT, BUSY RADIO TFC, SIMILAR COMPANY CALL SIGNS, SAME ACR XX TO ACR XXX. CREW NEEDS TO PAY CLOSER ATTN TO THE FREQ. HOW IT WAS DISCOVERED: SFO TWR SAW US TAXI INTO POS RWY 1R. CORRECTIVE ACTION: WE APOLOGIZED TO THE CTLR. I CALLED AND ASKED FOR THE TWR SUPVR, BUT SPOKE TO A CTLR AB. HE SAID THAT THEY (CTLRS) LISTENED TO THE TAPES AND THEY HEARD ME READ BACK 'ACR XXX, TAXI INTO POS AND HOLD RWY 1R.' SO THE CTLR AT THE TIME DID NOT HEAR OUR XMISSION. AB TOLD ME THAT THERE WAS NOT ANY PROB AND ASKED US TO LISTEN MORE CAREFULLY WHEN THE RADIO GETS REAL BUSY. I TOLD HIM THANK YOU AND I WAS SORRY FOR THE MISTAKE. THE CAPT AND I BOTH AGREED THAT IN OUR FUTURE COMS WE WILL TALK SLOWER. SOMETIMES CTLRS ARE VERY BUSY AND BEGIN TO TALK FAST AND AS PLTS WE BEGIN TO DO THE SAME. THIS IS WHEN IMPORTANT INFO CAN GET LOST IN THE RADIO COM. AS A PLT, I WILL SLOW DOWN AND ASK FOR CLARIFICATION WHEN NOT ABSOLUTELY SURE.

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.