I have been researching accurate fuel planning for flights operated by commercial aircraft, with particular focus on the Boeing 737NG series. The information available on the web along with some discussions are quite insightful, though some questions have remained for me. Maybe someone can shed some light on them? Since knowing something in theory often proves difficult when applied in practice, I have added a case example for better understanding. These are random even numbers (that hopefully make sense!) on a flight from airport A to airport B with airport C as alternate.
0200 TAXI FUEL
3000 TRIP FUEL
0150 TRIP CONTINGENCY FUEL (5% of TRIP FUEL)
1200 ALTERNATE FUEL
0060 ALTERNATE CONTINGENCY FUEL (5% of ALTERNATE FUEL)
1000 MINIMUM RESERVE FUEL
5610 FOB (fuel on board) **all weights in Kilograms (Kg), aircraft Boeing 737-800*
Basic question: Would this fuel planning be approvable? The way I see it, if everything goes well en-route, the fuel consumption on this flight would be +/- 3200 Kg (taxi+trip+factoring in contingency), so the FOD (fuel over destination) = 2410 Kg. So far, so good. However, not everything goes well in aviation all the time. There are weather-related delays, sudden airport closures (as we have seen at LHR yesterday), and so on. For that reason, I would like to consider the worst case. I.e. using all the taxi fuel, trip fuel + contingency due to stronger winds than expected, a go-around to due to bad visibility at airport B, a subsequent holding over airport B using the minimum res fuel, and finally a diversion to airport C that also consumes the contingency. That would mean the tanks would be pretty much empty having arrived at airport C – quite a worrisome thought! Would it therefore the acceptable/recommendable to take on some extra fuel just to avoid that situation, even when weather or lots of inbound traffic are likely not going to be a factor?
My second concern is how to set up the FMS (flight management system) properly. The PERF INIT page allows the entry of a "reserve fuel" value. My take is that the system warns the pilot when the computed fuel at DEST (rather than ALTN DEST) falls below that value. My question is, what should I enter here? Logically, I would say that (at least) 2260 Kg would be applicable (min res + alternate + cont fuel). These reserves should not be touched beforehand, so to speak. Should, for example, a holding be expected, maybe it would be good to put some extra fuel in the tanks right away.
I realize that flight planning including fuel calculation is a wide field occupying whole departments at airlines, so any insight is greatly appreciated!