Narrative:

We were beginning a flight from sfo to sbp. Sfo was departing runway 1L and 1R. Winds were generally out of the west at 10-15 KTS. We were cleared to 'taxi into position and hold,' which was done. Several seconds alter the tower advised us what we thought was winds 320 at 15, and if we could accept a takeoff clearance. Since this was well within our crosswind limitation, we advised in the affirmative and were then cleared for takeoff. We proceeded with a normal takeoff and climb out. At this time the aircraft behind us was given a wind check of 220 at 14. If this was the same wind direction given to us, we realized that instead of large headwind component, we had a large tailwind component which exceeded our 9 KT limitation for takeoff by approximately 4 KTS. Since we were already in the climb phase we continued with the flight to our destination. I feel this occurrence was caused because we misunderstood the wind direction given to us by the tower controller. The wind may have changed after we were instructed to taxi into position, but if not, then I feel that this important piece of information should have been given to us while we were still holding short of the runway. At that point we weren't engaged in checklists or the movement of the aircraft and would have a better chance of understanding the call and have the time to see how it effects our aircraft.

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Original NASA ASRS Text

Title: PIC OF COMMUTER SMT SUSPECTS THEY MADE A TKOF DOWNWIND IN WIND VELOCITY IN EXCESS OF MAXIMUM ALLOWABLE.

Narrative: WE WERE BEGINNING A FLT FROM SFO TO SBP. SFO WAS DEPARTING RWY 1L AND 1R. WINDS WERE GENERALLY OUT OF THE W AT 10-15 KTS. WE WERE CLRED TO 'TAXI INTO POS AND HOLD,' WHICH WAS DONE. SEVERAL SECS ALTER THE TWR ADVISED US WHAT WE THOUGHT WAS WINDS 320 AT 15, AND IF WE COULD ACCEPT A TKOF CLRNC. SINCE THIS WAS WELL WITHIN OUR XWIND LIMITATION, WE ADVISED IN THE AFFIRMATIVE AND WERE THEN CLRED FOR TKOF. WE PROCEEDED WITH A NORMAL TKOF AND CLBOUT. AT THIS TIME THE ACFT BEHIND US WAS GIVEN A WIND CHK OF 220 AT 14. IF THIS WAS THE SAME WIND DIRECTION GIVEN TO US, WE REALIZED THAT INSTEAD OF LARGE HEADWIND COMPONENT, WE HAD A LARGE TAILWIND COMPONENT WHICH EXCEEDED OUR 9 KT LIMITATION FOR TKOF BY APPROX 4 KTS. SINCE WE WERE ALREADY IN THE CLB PHASE WE CONTINUED WITH THE FLT TO OUR DEST. I FEEL THIS OCCURRENCE WAS CAUSED BECAUSE WE MISUNDERSTOOD THE WIND DIRECTION GIVEN TO US BY THE TWR CTLR. THE WIND MAY HAVE CHANGED AFTER WE WERE INSTRUCTED TO TAXI INTO POS, BUT IF NOT, THEN I FEEL THAT THIS IMPORTANT PIECE OF INFO SHOULD HAVE BEEN GIVEN TO US WHILE WE WERE STILL HOLDING SHORT OF THE RWY. AT THAT POINT WE WEREN'T ENGAGED IN CHKLISTS OR THE MOVEMENT OF THE ACFT AND WOULD HAVE A BETTER CHANCE OF UNDERSTANDING THE CALL AND HAVE THE TIME TO SEE HOW IT EFFECTS OUR ACFT.

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.