RESULTS APPRAISAL
4. As a reminder, the analysis performed with the Airbus tools is based on aircraft models or databases called IFP databases or High Speed Performance databases. These databases are valid for cruise analysis in the expected usual operational conditions. Should not-expected conditions be encountered, the cruise performance analysis could be biased due to an aircraft database effect. For instance, points recorded below 20000 feet (it sometimes occurs even though the systems for automatic retrieval are configured not to record such points), should be disregarded. However a range of altitudes above 20000 ft should be recorded to have a spectrum of different wing loading (W/δ) so as to assess the consistency of any positive or negative SR deviation.
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
RESULTS APPRAISAL
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Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
USING THE MONITORED FUEL FACTOR
F. USING THE MONITORED FUEL FACTOR
1. INTRODUCTION
Airline Flight Planning systems are based on a reference aircraft performance level (book level or IFP level, see paragraph A-1. The book level). In order to establish a fuel policy, an adjustment of this level is required by most of the regulations (e.g. JAR-OPS) in order to get scheduled flight planning consistent with the actual aircraft performance level.
Furthermore, airlines flight operations are usually in charge of performing route studies both for operational and commercial purposes. These studies are usually conducted with the Airbus high speed performance calculation software. This software allows to get aircraft performance relevant for the book level. As a consequence, tuning the different fuel studies by means of the monitored fuel factor is mandatory for day-to-day flight operations.
On the other hand, the FMS onboard the aircraft also performs fuel consumption predictions based on a reference model: the FMS performance database. The PERF FACTOR entered in the MCDU helps to the FMS predictions.
Implementing aircraft performance monitoring aims to determine the monitored fuel factor. The intent of this paragraph is to correlate the factors required in the various fields of application on one hand with the monitored fuel factor on the other.
In the following, the term "fuel factor" will be applied to both mathematically factor (ie the modified fuel flow is the reference fuel flow times the fuel factor) or arithmetic deviation (in percent, ie the modified fuel flow is the reference fuel flow, times the fuel factor plus 1). The same terminology will be used and the symbol % will be added to deviations in percentage.
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
USING THE MONITORED FUEL FACTOR
2. FMS PERF FACTOR
2.1. Purpose
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