2.2. FMS Perf Data Base (PDB)
The main FMS aircraft performance predictions deal with:
- fuel consumption, time,
-climb and descent path,
-recommended maximum altitude, and
-optimization of speeds and cruise altitude taking into account economic criteria
defined by the airline Cost Index.
The PDB is derived from the IFP aircraft databases, which is consistent with the book level (see also A-1. The book level). Slight simplifications were taken into account because of the limited size of the FMS memory. For example, only one air conditioning setting is available (LO/ECON as appropriate).
The FMGEC/FMC contains an integrated aircraft performance database. This database is used by the FM part of the FMGEC/FMC to compute the predictions. The airlines cannot modify any data in the aircraft performance database. Fuel predictions can be adjusted by using a PERF FACTOR (see below) or an IDLE FACTOR (A330/A340 only). Per design, the aircraft performance databases are stored in the FMS Perf Data Base (PDB). There is only a single PDB per family of aircraft. The activation of the right model in the PDB is done when the FMGEC/FMC is installed on the aircraft by a pin program setting.
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
USING THE MONITORED FUEL FACTOR
The corresponding aircraft model identification is then displayed on the MCDU A/C STATUS page.
2.3. Update of the PDB
For aircraft not fitted with FMS2, the FMS PDB is part of the FM hardware. Update of the Perf Data Base can be done, on current FMS, only at the opportunity of a new FMGEC standard certification.
For aircraft fitted with FMS2, the FMS PDB is part of the FM software. Its update is subject to a Service Bulletin and installation of a new PDB part number.
2.4. PERF FACTOR definition
2.4.1. General
The FMS PERF FACTOR is used for fuel prediction computation within the Flight Management part of the FMGS. The PERF FACTOR is a positive or negative percentage that is used to tune the predicted fuel flow used for fuel prediction computation. In other words, the PERF FACTOR is used to adjust the FMS aircraft performance level to the actual aircraft performance capability.
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