Narrative:

It became evident early in the flight that our current philosophy of running with minimum fuel was going to leave us about 1000 pounds short for a safe arrival in las. Dispatched fuel was based on landing with 3500 pounds at our psp alternate and no delays. A west departure ate up the little extra fuel we had; and developing thunderstorms in and around las suggested holding and arrival delays that would exceed our available fuel. Coordinated with dispatch via ACARS and suggested stopping in rno for extra fuel. Dispatch suggested flying at .65 M; but this was below our minimum controllable speed at FL390. We explained to dispatch we were already operating at lrc at optimum altitude; so any changes would only increase our fuel burn. Dispatch said we could legally delete our alternate and use that fuel; but we did not think this was wise with thunderstorms surrounding las. Ended up declaring minimum fuel with center about halfway through our flight. In addition; dispatch coordinated with lax TRACON to give us priority handling in las. Center gave us a great shortcut direct to las from bty and the thunderstorms cooperated; which allowed us to land in las with fuel to spare. This flight fit the trend of next generation flight plans with long; direct legs between fixes and strong winds aloft. The flight planning program apparently makes assumptions about the wind model between waypoints and comes up with an unrealistically low fuel burn. This problem does not appear on more traditional routings with shorter legs between check points because there are more fixes to accurately account for the wind. Lesson learned: an extra 1000 - 1500 pounds over what we had would have given us the fuel to deal with the winds aloft and developing WX around las and reach our destination without receiving traffic priority.

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Original NASA ASRS Text

Title: FLT CREW OF B737-700 DECLARE MINIMUM FUEL ENRTE TO LAS WHEN PLANNED RESERVES APPEAR INADEQUATE.

Narrative: IT BECAME EVIDENT EARLY IN THE FLT THAT OUR CURRENT PHILOSOPHY OF RUNNING WITH MINIMUM FUEL WAS GOING TO LEAVE US ABOUT 1000 LBS SHORT FOR A SAFE ARR IN LAS. DISPATCHED FUEL WAS BASED ON LNDG WITH 3500 LBS AT OUR PSP ALTERNATE AND NO DELAYS. A W DEP ATE UP THE LITTLE EXTRA FUEL WE HAD; AND DEVELOPING TSTMS IN AND AROUND LAS SUGGESTED HOLDING AND ARR DELAYS THAT WOULD EXCEED OUR AVAILABLE FUEL. COORDINATED WITH DISPATCH VIA ACARS AND SUGGESTED STOPPING IN RNO FOR EXTRA FUEL. DISPATCH SUGGESTED FLYING AT .65 M; BUT THIS WAS BELOW OUR MINIMUM CONTROLLABLE SPD AT FL390. WE EXPLAINED TO DISPATCH WE WERE ALREADY OPERATING AT LRC AT OPTIMUM ALT; SO ANY CHANGES WOULD ONLY INCREASE OUR FUEL BURN. DISPATCH SAID WE COULD LEGALLY DELETE OUR ALTERNATE AND USE THAT FUEL; BUT WE DID NOT THINK THIS WAS WISE WITH TSTMS SURROUNDING LAS. ENDED UP DECLARING MINIMUM FUEL WITH CTR ABOUT HALFWAY THROUGH OUR FLT. IN ADDITION; DISPATCH COORDINATED WITH LAX TRACON TO GIVE US PRIORITY HANDLING IN LAS. CTR GAVE US A GREAT SHORTCUT DIRECT TO LAS FROM BTY AND THE TSTMS COOPERATED; WHICH ALLOWED US TO LAND IN LAS WITH FUEL TO SPARE. THIS FLT FIT THE TREND OF NEXT GENERATION FLT PLANS WITH LONG; DIRECT LEGS BETWEEN FIXES AND STRONG WINDS ALOFT. THE FLT PLANNING PROGRAM APPARENTLY MAKES ASSUMPTIONS ABOUT THE WIND MODEL BETWEEN WAYPOINTS AND COMES UP WITH AN UNREALISTICALLY LOW FUEL BURN. THIS PROBLEM DOES NOT APPEAR ON MORE TRADITIONAL ROUTINGS WITH SHORTER LEGS BETWEEN CHK POINTS BECAUSE THERE ARE MORE FIXES TO ACCURATELY ACCOUNT FOR THE WIND. LESSON LEARNED: AN EXTRA 1000 - 1500 LBS OVER WHAT WE HAD WOULD HAVE GIVEN US THE FUEL TO DEAL WITH THE WINDS ALOFT AND DEVELOPING WX AROUND LAS AND REACH OUR DEST WITHOUT RECEIVING TFC PRIORITY.

Data retrieved from NASA's ASRS site as of January 2009 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.