Sep-01 Oct-01 Nov-01 Dec-01 Jan-02 Feb-02 Mar-02 Apr-02 May-02
Month

Actual Monitored Fuel Factor
Retained Monitored Fuel Factor
Figure G3 - Smoothed Fuel Factor method
In September 2001, the first available monitored fuel factor is retained. In October 2001, the monitored fuel factor is 2.5%. Averaging this factor with the September one gives 2.45%, which is rounded up to 2.5%. The retained fuel factor is 2.5%. In November, the average is performed over the past three months. 2.4% in September, 2.5 in October, and 2.7% in November. The retain fuel factor is the average of the three, 2.6%. In December, the average of the actual fuel factors over October, November and December results in a 2.7% fuel factor being retained.
Using this technique is a little bit more sophisticated than the previous. The advantage of the method is that it minimizes possible errors and allows to really stick to the fuel factor trend line.
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring

POLICY FOR UPDATING THE FUEL FACTOR
Of course, this smoothing technique is a quite simple (but efficient) one, and one could imagine developing a specific smoothing technique based on polynoms or the like. Airbus is prepared to share its view with any airline interested, and for the sake of airline operations improvement.

5. WHO CHANGES THE FUEL FACTOR(S)?
The intent of this paragraph is to give the Airbus view on who must be informed of a change of fuel factor on one hand, and who should have the authority to do so. It does not impose any way of working neither aim to substitute to any airline practice.
Airline Flight Operations staff members should define the different fuel factor(s) based on an aircraft performance monitoring method. For routine aircraft performance monitoring, the Specific Range method and the use of the APM program will facilitate recurrent analysis.
Note: The AMM does not provide any procedure to change this factor.
Airline Flight Operations will trigger a change in fuel factor(s) and provide the relevant figures to supervisory management and to operational teams: -in charge of the flight planning system update (Flight Planning Office) -in charge of updating of the FMS PERF FACTOR on board the aircraft
(Maintenance, Avionics…)
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
POLICY FOR UPDATING THE FUEL FACTOR

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Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring

APPENDICES

H. APPENDICES
This chapter gathers additional material dealing with aircraft performance
monitoring. 
Appendix 1 : High Speed Performance Software  P134 
　
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