Narrative:

After our flight was cleared into position to hold runway 1L, the controller issued a takeoff clearance for aircraft #1 on runway 1L. The first officer called the controller, asking for verification that aircraft #1 was cleared for takeoff runway 1L. The controller responded 'cleared for immediate takeoff.' observing that we were the only aircraft in position for takeoff, we concluded that a frequency block had covered the first part of the controller's takeoff clearance. After starting our takeoff roll, the tower frequency was again blocked by simultaneous xmissions. After which the tower controller stated, 'aircraft #1, disregard, continue your takeoff.' the controller's last remark induced doubt as to whether a proper takeoff clearance had been issued in the first place, and as to the nature of this transmission during our takeoff roll. Obviously, the better course of action on our part would have been to hold in position until we had a clear readout of our call sign in the takeoff clearance, even though all circumstances pointed to the conclusion that the clearance was issued to us. I don't believe safety was compromised in this instance, but communications broke down badly. A large part of the problem at sfo seems to stem from the requirement for the local controller to work the arrival as well as departure runways. This leads to frequent blockage of the frequency as aircraft and controller try to get a word in. The situation is made even worse by the increasingly burdensome requirements for the controller to issue advisory information to holding traffic regarding traffic on final and vice versa. Much of this chatter seems to be useless, and just adds to frequency congestion. Supplemental information from acn 412300: the tower did not reply with our call sign when we asked him to confirm. High traffic volume in sfo was a prime factor in this incident.

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Original NASA ASRS Text

Title: MLG ACR FLC ATTEMPT, BUT DO NOT CLARIFY WITH TWR LCL CTLR, IF TKOF CLRNC IS FOR THEM, AND DEPART. PIC ACKNOWLEDGES THERE WAS A NEED FOR CONFIRMATION, BUT APPLIED TKOF PWR ANYWAY. FLC CONCERNED WITH TWR FREQ CONGESTION, AND CHALLENGE THE NEED FOR ALL THE TFC COORD EXCHANGE REQUIRED BY LCL CTLR.

Narrative: AFTER OUR FLT WAS CLRED INTO POS TO HOLD RWY 1L, THE CTLR ISSUED A TKOF CLRNC FOR ACFT #1 ON RWY 1L. THE FO CALLED THE CTLR, ASKING FOR VERIFICATION THAT ACFT #1 WAS CLRED FOR TKOF RWY 1L. THE CTLR RESPONDED 'CLRED FOR IMMEDIATE TKOF.' OBSERVING THAT WE WERE THE ONLY ACFT IN POS FOR TKOF, WE CONCLUDED THAT A FREQ BLOCK HAD COVERED THE FIRST PART OF THE CTLR'S TKOF CLRNC. AFTER STARTING OUR TKOF ROLL, THE TWR FREQ WAS AGAIN BLOCKED BY SIMULTANEOUS XMISSIONS. AFTER WHICH THE TWR CTLR STATED, 'ACFT #1, DISREGARD, CONTINUE YOUR TKOF.' THE CTLR'S LAST REMARK INDUCED DOUBT AS TO WHETHER A PROPER TKOF CLRNC HAD BEEN ISSUED IN THE FIRST PLACE, AND AS TO THE NATURE OF THIS XMISSION DURING OUR TKOF ROLL. OBVIOUSLY, THE BETTER COURSE OF ACTION ON OUR PART WOULD HAVE BEEN TO HOLD IN POS UNTIL WE HAD A CLR READOUT OF OUR CALL SIGN IN THE TKOF CLRNC, EVEN THOUGH ALL CIRCUMSTANCES POINTED TO THE CONCLUSION THAT THE CLRNC WAS ISSUED TO US. I DON'T BELIEVE SAFETY WAS COMPROMISED IN THIS INSTANCE, BUT COMS BROKE DOWN BADLY. A LARGE PART OF THE PROB AT SFO SEEMS TO STEM FROM THE REQUIREMENT FOR THE LCL CTLR TO WORK THE ARR AS WELL AS DEP RWYS. THIS LEADS TO FREQUENT BLOCKAGE OF THE FREQ AS ACFT AND CTLR TRY TO GET A WORD IN. THE SIT IS MADE EVEN WORSE BY THE INCREASINGLY BURDENSOME REQUIREMENTS FOR THE CTLR TO ISSUE ADVISORY INFO TO HOLDING TFC REGARDING TFC ON FINAL AND VICE VERSA. MUCH OF THIS CHATTER SEEMS TO BE USELESS, AND JUST ADDS TO FREQ CONGESTION. SUPPLEMENTAL INFO FROM ACN 412300: THE TWR DID NOT REPLY WITH OUR CALL SIGN WHEN WE ASKED HIM TO CONFIRM. HIGH TFC VOLUME IN SFO WAS A PRIME FACTOR IN THIS INCIDENT.

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.