Based on the data you supply for your aircraft, autorouter calculates the required fuel for the route as well as the minimum surplus according to current EU/EASA rules set out in Part-CAT for commercial flights and Part-NCO for non-commercial flights. The following criteria are used:
- Trip fuel
Required fuel for the planned route according to the aircraft’s climb, cruise and descent model and the flight plan’s route and levels; - Alternate fuel
Fuel for a direct (great circle) course from the destination to the farthest alternate in cruise level with a climb and descent. Cruise level refers to the highest level found in the flight plan. If a route to alternate is set, the fuel for this route will be used instead of a direct approximation; - Contingency fuel
Another item is added as a percentage of the trip fuel, usually 5%. This value can be adjusted in the aircraft setting. If the configured percentage of the trip fuel amounts to less than 5 minutes of cruise, the fuel for 5 minutes is used instead. - Holding fuel
For the holding above the alternate, a distinction is made based on the type of flight. If the the flight type is scheduled commercial (“S”) or non-scheduled commercial (“N”), the holding time is 30 minutes, otherwise 45 minutes. For the holding, the altitude with the least fuel burn is considered. - Taxi fuel
The sum of the fixed taxi fuel (required to startup the engines) and the time dependent taxi fuel which is the taxi fuel flow multiplied by the taxi time as obtained from the Eurocontrol taxi time database. The fixed and time dependent taxi fuel factors are part of the aircraft model. In the absence of a taxi time, 5 minutes are used. To use a custom taxi time, edit the flight plan’s TAXI: value in the RMK section.