Narrative:

The problem occurred because I learned how to override our flight planning software's taxi out fuel estimation function. During the earlier part of my shift (XA00-XC00) the chief dispatcher called me out to challenge me on the practice of upping taxi fuel. In his opening shot; the chief dispatcher revealed only that some unidented PIC of one of my flts had called to mention a 300 pound taxi fuel figure. The normal taxi out fuel number for an SF340 turboprop in our operation is 200 pounds. What was this additional 100 pounds all about? On the defensive; I tried to make my case for the practice -- the fuel planning function of our flight planning software allows us the ability to 'tweak' up the taxi out fuel. I knew for a fact -- from direct; first-hand observation -- that an SF340 at a busy hub during a push can easily burn several hundred pounds getting from the gate to the runway. In other words; the 200 pound taxi out 'allowance' the computer automatically calculated might be enough -- but often it was not. One of the other dispatchers had shown me how this could be accounted for; and; at the same time; one could take deliberate advantage of the difference between maximum ramp weight (29;300 pounds) and maximum structural takeoff weight (29000 pounds). As the chief dispatcher pointed out; this works -- and is perfectly legal -- so long as the aircraft does in fact burn off the additional fuel prior to taking the runway for takeoff. Actually; technically; it's legal so long as the aircraft is down to takeoff weight sometime prior to brake release. His question was whether or not I was telling pilots when I 'invoked' this procedure. Given my current understanding of the practice; there is no doubt in my mind that at least some of the flts I dispatched prior to this conversation with our chief dispatcher could very possibly have taken off overweight (since the load control function is not in our hands; we dispatchers normally do not know what the final weight and balance numbers are prior to pushback and pilots are not specifically encouraged to review the taxi fuel figures on their releases; either coming or going; especially since they aren't used to seeing them changed). However; I have since integrated into my routine the practice of instructing the PIC in question to contact me prior to pushback; as well as inserting a remark onto the release that indicates both what I've done to taxi out fuel and why. If I don't hear from the PIC; I make an attempt to contact him or her at the departure gate; or via radio prior to pushback.

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Original NASA ASRS Text

Title: DISPATCHER FOR OPERATOR OF SF340 ACFT FEARS SOME OF HIS FLTS MAY HAVE TAKEN OFF IN EXCESS OF MAX TKOF GROSS WT DUE TO HIS PRACTICE OF ADDING 100 LBS OF ADDITIONAL TAXI FUEL OVER THE COMPANY STANDARD DURING PEAK TFC PERIODS.

Narrative: THE PROB OCCURRED BECAUSE I LEARNED HOW TO OVERRIDE OUR FLT PLANNING SOFTWARE'S TAXI OUT FUEL ESTIMATION FUNCTION. DURING THE EARLIER PART OF MY SHIFT (XA00-XC00) THE CHIEF DISPATCHER CALLED ME OUT TO CHALLENGE ME ON THE PRACTICE OF UPPING TAXI FUEL. IN HIS OPENING SHOT; THE CHIEF DISPATCHER REVEALED ONLY THAT SOME UNIDENTED PIC OF ONE OF MY FLTS HAD CALLED TO MENTION A 300 LB TAXI FUEL FIGURE. THE NORMAL TAXI OUT FUEL NUMBER FOR AN SF340 TURBOPROP IN OUR OP IS 200 LBS. WHAT WAS THIS ADDITIONAL 100 LBS ALL ABOUT? ON THE DEFENSIVE; I TRIED TO MAKE MY CASE FOR THE PRACTICE -- THE FUEL PLANNING FUNCTION OF OUR FLT PLANNING SOFTWARE ALLOWS US THE ABILITY TO 'TWEAK' UP THE TAXI OUT FUEL. I KNEW FOR A FACT -- FROM DIRECT; FIRST-HAND OBSERVATION -- THAT AN SF340 AT A BUSY HUB DURING A PUSH CAN EASILY BURN SEVERAL HUNDRED LBS GETTING FROM THE GATE TO THE RWY. IN OTHER WORDS; THE 200 LB TAXI OUT 'ALLOWANCE' THE COMPUTER AUTOMATICALLY CALCULATED MIGHT BE ENOUGH -- BUT OFTEN IT WAS NOT. ONE OF THE OTHER DISPATCHERS HAD SHOWN ME HOW THIS COULD BE ACCOUNTED FOR; AND; AT THE SAME TIME; ONE COULD TAKE DELIBERATE ADVANTAGE OF THE DIFFERENCE BTWN MAX RAMP WT (29;300 LBS) AND MAX STRUCTURAL TKOF WT (29000 LBS). AS THE CHIEF DISPATCHER POINTED OUT; THIS WORKS -- AND IS PERFECTLY LEGAL -- SO LONG AS THE ACFT DOES IN FACT BURN OFF THE ADDITIONAL FUEL PRIOR TO TAKING THE RWY FOR TKOF. ACTUALLY; TECHNICALLY; IT'S LEGAL SO LONG AS THE ACFT IS DOWN TO TKOF WT SOMETIME PRIOR TO BRAKE RELEASE. HIS QUESTION WAS WHETHER OR NOT I WAS TELLING PLTS WHEN I 'INVOKED' THIS PROC. GIVEN MY CURRENT UNDERSTANDING OF THE PRACTICE; THERE IS NO DOUBT IN MY MIND THAT AT LEAST SOME OF THE FLTS I DISPATCHED PRIOR TO THIS CONVERSATION WITH OUR CHIEF DISPATCHER COULD VERY POSSIBLY HAVE TAKEN OFF OVERWT (SINCE THE LOAD CTL FUNCTION IS NOT IN OUR HANDS; WE DISPATCHERS NORMALLY DO NOT KNOW WHAT THE FINAL WT AND BAL NUMBERS ARE PRIOR TO PUSHBACK AND PLTS ARE NOT SPECIFICALLY ENCOURAGED TO REVIEW THE TAXI FUEL FIGURES ON THEIR RELEASES; EITHER COMING OR GOING; ESPECIALLY SINCE THEY AREN'T USED TO SEEING THEM CHANGED). HOWEVER; I HAVE SINCE INTEGRATED INTO MY ROUTINE THE PRACTICE OF INSTRUCTING THE PIC IN QUESTION TO CONTACT ME PRIOR TO PUSHBACK; AS WELL AS INSERTING A REMARK ONTO THE RELEASE THAT INDICATES BOTH WHAT I'VE DONE TO TAXI OUT FUEL AND WHY. IF I DON'T HEAR FROM THE PIC; I MAKE AN ATTEMPT TO CONTACT HIM OR HER AT THE DEP GATE; OR VIA RADIO PRIOR TO PUSHBACK.

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.