The intent of the following lines is to clarify Airbus recommendations in term of fuel factor for flight planning preparation.
3.1. Effect of the fuel factor on Flight Planning
The following picture illustrates the different fuel quantities and associated flight phases of a typical trip.
The fuel factor defined in flight planning will modify (except fixed values of course):
- the trip fuel -the contingency fuel (generally a percentage of the trip fuel) -the alternate fuel -the final reserve (holding at alternate fuel) -the additional fuel
3.2. Keys for defining the fuel factor
Basically, the nominal performance level that is used in flight planning systems is the same as the Airbus book level (or IFP level, see A-1.The book level).
This performance level may not be representative of the actual aircraft performance level. Amongst the airlines information required to feed any flight planning system, a fuel factor must be defined in accordance with the airline fuel policy (see chapter G-Policy for updating the Fuel Factor).
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
USING THE MONITORED FUEL FACTOR
The following points must be emphasized:
1.
When determining an operational flight plan at fixed speed (FMS selected or manual mode), the flight planning fuel factor must be the same as the one measured with an appropriate aircraft performance monitoring method. In other words, the fuel factor for flight planning is equal to the monitored fuel factor.
2.
When determining a flight plan (or a part of it) at Cost Index ECON speeds,
.
the ECON speeds must be calculated taking into account the FMS PERF FACTOR
.
the flight plan must be calculated with the pre-calculated ECON speeds, using a method consistent with the standard IFP algorithm and taking into account the monitored fuel factor.
Note: Read paragraph 4. Airbus Tools and Fuel Factor to have more information on the capabilities of the Airbus tools covering that subject.
3. The Fuel Lower Heating Value is included within airline information pertaining to Flight Planning. The FLHV should be the same as the one used for the cruise performance analysis. If not, a correction will be applied on the monitored fuel factor. If the FLHV for cruise performance analysis is 1% higher than the FLHV used in the flight planning system, decrease the monitored fuel factor by 1%.
For example, if :
1.
the cruise performance analysis is performed with a FLHV equal to 18590 BTU/LB, and
2.
the flight planning is calculated based on a FLHV equal to 18400 BTU/LB, and
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