ICAO Fuel Calculations vs. FAA

There are significant difference in how ICAO determines the fuel required for a 91/GA flight. These calculations are very similar to what the commercial players are having to comply with. The Annex 6, Part II reference is paragraph 2.2 but is reads VERY dry and is without description or insight. The ICAO Flight Planning and Fuel Management Manual Doc #9976 is commercial operations centered but, provides more detailed explanations to the definitions and is a better description of what this standard (and SAFA regulation) is trying to get to.

TAXI FUEL
The amount of fuel expected to be consumed before take-off which typically takes into account “local conditions” at the departure aerodrome and auxiliary power unit (APU) fuel consumption. Practically speaking, this includes the fuel required for engine start and to move an aircraft under its own power considering the route to the departure runway based on known taxi times (when available) for specific airports and runway configurations.

For the purpose of taxi fuel calculations “local conditions” must typically also be taken into account and refer to conditions or occurrences that would contribute to increased fuel consumption prior to take-off including but not limited to “foreseeable” occurrences such as:

a) ground holding;
b) ATC metering programmes;
c) remote de/anti-icing;
d) aircraft engine and wing anti-ice use;
e) single runway operations; and
f) any other occurrence with the potential to increase taxi time.

TRIP FUEL
Tfuel required to fly from the departure aerodrome or from the point of in-flight re-planning to the destination aerodrome, taking into account the aeroplane specific or manufacturer data specified fuel consumption specifications and operating conditions

In actual practice, however, the calculation of trip fuel is typically a complex process that is dependent on numerous underlying and interdependent activities. In the end, however, the intent of every trip fuel calculation is to ensure, to the greatest practical extent, that the planned fuel burn is equal to or greater than the actual fuel burn.

Base flight plans and trip fuel on lengthy IFR departure and arrival routing procedures (longest RNAV SID to longest RNAV STAR). In the real world, these routings may rarely occur, thus introducing some conservatism into the trip fuel calculation. Conversely, those operators capable of assessing the probability of which SID/STAR combination will be used on a given city pair, including the likely track miles to be flown, may account for some or all of the fuel for such procedures as part of discretionary fuel or extra fuel.

CONTINGENCY FUEL
This is the fuel required to compensate for factors that cannot be foreseen during flight planning. This is no less than 5% of the trip fuel. Such factors include, but are not necessarily limited to, deviations from flight plan that could influence the total fuel consumed en route to the destination such as:

a) deviations of an individual aeroplane from the expected fuel consumption data;
b) unforeseen meteorological conditions;
c) extended delays (on the ground or in the air); or
d) deviations from planned routings and/or cruising levels/altitudes.

ALTERNATE FUEL
Alternate fuel is intended to mitigate the safety risks associated with the unavailability of the destination, first destination alternate or isolated aerodrome, as applicable. This is very specific in that the calculation must include a missed approach at the destination aerodrome THEN...

1. Climb to the expected cruising altitude
2. Fly the expected ATC routing
3. Descend to the point where the expected approach is initiated
4. Conduct the approach and landing at the destination alternate aerodrome

FINAL RESERVE FUEL
This is a preflight calculation based on based on the estimated aeroplane weight on arrival at the destination alternate aerodrome. For a turbine-engined aeroplane, the amount of fuel required to fly for 30 minutes at holding speed 1,500ft above aerodrome elevation in standard conditions.

ADDITIONAL FUEL
This is the required to protect against the very unlikely event of an engine failure or depressurization at the most critical point in the flight and presumes that the majority of the fuel used in basic fuel planning will be available for use in proceeding to the en-route alternate aerodrome. Basically, it is the supplementary amount of fuel required to enable the aircraft to descend as necessary and proceed to land at an alternate aerodrome in the event of engine failure or loss of pressurization based on the assumption that such a failure occurs at the most critical point along the route.

DISCRETIONARY FUEL
This is the extra amount of fuel to be carried at the discretion of the PIC. While contingency fuel is typically defined early during pre-flight fuel planning in order to account for unforeseeable occurrences, discretionary fuel may be loaded later in the process by the PIC or as directed by the operator.

"MINIMUM FUEL"
Remains the same as an pilot report to ATC. This is defined as, having committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance to that aerodrome may result in landing with less than the planned final reserve fuel.

"MAYDAY FUEL" 
Remains the same as an pilot report to ATC. This is defined as, when the calculated usable fuel estimated to be available upon landing at the nearest aerodrome where a safe landing can be made is less than the planned final reserve fuel.

BOTTOMLINE
1. 5% Contingency fuel is a new requirement to USA operators
2. "Trip Fuel" contains fuel for known holding vice a holding fuel calculation
3. "Destination Reserve" is 30 mins vice the 45 common to USA operators 
4. These fuel calculations are recent findings on SAFA checks for US operators
5. Compare these to 91.151, 91.167 135.225 Annex 6,Part 2 Paragraph 2.2.3.6.1
6. ATC reports of "MINIMUM FUEL" and "MAYDAY FUEL" remain unchanged