ACR ACFT WAS RELEASED FROM THE GATE WITH INSUFFICIENT FUEL FOR THE TRIP.

Narrative

THE FLT RELEASE INDICATED A GATE RELEASE FUEL LOAD OF 50300 LBS WHICH APPEARED TO BE A NORMAL FUEL LOAD FOR OUR 5 HR PLUS FLT TO LAX; WITH ONT/SAN AS ALTERNATE ARPTS. THE CAPT INDICATED THAT WE WOULD HAVE A 'LIGHT' LOAD FOR THIS FLT; WHICH I INTERPRETED AS MEANING NOT VERY MANY PAX; SO THE FUEL LOAD SEEMED VERY APPROPRIATE; AS WE WOULD BE ABLE TO CLB TO FL390 FOR MUCH OF OUR FLT W. AS IS TYPICAL; JUST PRIOR TO CLOSING UP AND PUSHING BACK OFF THE GATE; THE CUSTOMER SVC AGENT INFORMED US OF OUR PAX COUNT OF 143 PAX. I DID NOT THINK THAT THIS WAS A VERY 'LIGHT' LOAD; BUT CONTINUED ON WITH THE PREFLT PROCS. OUR FINAL WT AND BAL FIGURES WOULD BE SENT TO US OVER OUR ACARS AND WE WOULD BE ABLE TO VERIFY ALL OF THE FINAL FIGURES WHEN WE RECEIVED THIS INFO. IT IS TYPICAL FOR US TO LEAVE THE GATE AND TAXI OUT PRIOR TO RECEIVING THIS INFO. AT THIS TIME; WE HAD OUR REQUIRED GATE RELEASE FUEL (50300 LBS) ON BOARD THE ACFT; IN ACCORDANCE WITH THE FLT RELEASE. AS WE TAXIED OUT FOR TKOF ON RWY 27L AT PHL; WE WERE ABOUT #15 OR SO FOR TKOF AND WERE STATIONARY ON THE TXWY; AWAITING OUR WT AND BAL INFO. WHEN WE RECEIVED OUR FINAL WT AND BAL INFO OVER THE ACARS; IT INDICATED A TKOF WT OF APPROX 220000 LBS WHICH WAS CONSIDERABLY HIGHER THAN WHAT OUR DISPATCHER HAD CALCULATED ON THE FLT RELEASE AND I TOLD THE CAPT THAT WE WERE ABOUT 24000 LBS HEAVIER THAN PREVIOUSLY PLANNED FOR TKOF AND THAT WE WOULD HAVE TO TAKE A LOOK AT THE FUEL REQUIRED FOR THIS HEAVIER WT. AFTER I ENTERED THE DATA INTO THE FMC; IT ALSO ADVISED US THAT WE HAD 'INSUFFICIENT FUEL.' (THE FMC HAD CALCULATED MORE FUEL BURN BASED ON HEAVIER WTS; AND LOWER CRUISE ALT.) I THEN CALLED OUR LOAD PLANNERS ON THE RADIO AND ASKED THEM TO CALL OUR DISPATCHER AND HAVE HIM FIGURE A NEW FUEL LOAD FOR THIS HEAVIER TKOF WT. WE HAD ALREADY FIGURED OUT THAT BECAUSE OF THIS 24000 LB INCREASE IN OUR GROSS WT; THAT WE DID NOT HAVE SUFFICIENT FUEL FOR THE FLT AS PREVIOUSLY PLANNED WITH OUR ALTERNATES AS INDICATED. OUR DISPATCHER FIRST SENT US A REVISED FUEL BURN FOR OUR NEW WT AND THEN SENT US A NEW GATE RELEASE FUEL; AND A NEW TKOF MINIMUM FUEL. THE NEW GATE RELEASE FUEL WAS 55700 LBS AND I THINK THE TKOF MINIMUM FUEL WAS ABOUT 53700 LBS; WHICH WAS MORE THAN WE THEN HAD ON BOARD THE ACFT. IT WAS DETERMINED THAT ADDITIONAL FUEL MUST BE ADDED FOR OUR FLT; AND THAT WE NEEDED TO TAXI BACK TO THE GATE. WE THEN INFORMED THE TWR THAT WE NEEDED TO RETURN TO THE GATE FOR ADDITIONAL FUEL; RECEIVED TAXI CLRNC FOR THIS AND RETURNED TO THE GATE. AT THE GATE; THE ACFT WAS THEN REFUELED; AND WE THEN LEFT FOR OUR UNEVENTFUL FLT TO LAX.