FMS GENERAL DESCRIPTION
4 FMGS OPERATION
Performance factors can be modified prior to flight, based on actual
aircraft performance to refine profile and fuel predictions.
See Part II FLIGHT PHASE PROCEDURES for further information.
Data for the flight, inserted manually or by datalink (when installed),
include e.g. route to be flown, cost index, expected cruise altitude,
forecast winds and temperatures, weight, CG and fuel.
Using these data the FMS can then:
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Construct an optimum vertical profile to be used for vertical
guidance, and for time, fuel, altitude predictions at waypoints.
−
Compute flight parameters used for lateral and vertical guidance,
and for display on the EFIS.
The flight plans which can be entered into the FMGC are:
−
The ACTIVE flight plan (PRIMARY /ALTERNATE flight plans), which is
used for guidance,
−
The TEMPORARY flight plan, when revisions of the ACTIVE flight
plan are made,
−
The SECONDARY flight plan, which allows preparation (and review)
of alternative flight plan. The secondary flight plan can be copied into
the ACTIVE flight plan and vice versa.
The FMGCs are supplied by the aircraft electrical power.
The FMSs contain batteries which can maintain power supply and allow
to keep entered data in the memory for at least 10 mn, in the event of
lost of normal electrical power supply.
The two FMGCs, and their associated MCDUs, operate together to
cross-check navigation accuracy and provide redundancy. The normal
mode of operation is Dual, with two degraded modes - Single and
Independent – after certain failures or data anomalies.
DUAL Mode
In DUAL mode (the normal mode of operation) each FMGC makes its
own calculations and exchanges the processed data with the other
FMGC by "cross-talk" for comparison and validation.
Data entered via either MCDU is fed to both FMGCs. However, since
each FMGC receives data from the systems (e.g. ADIRS, navaids) on
its own side, the predictions of each FMGC may differ slightly.
During operation in DUAL mode, one FMGC is selected as the "master"
and the other as the "slave". This ensures that prime navigation
functions are synchronized and that guidance commands to A/P, FD,
A/THR, are provided by the same source.
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© THALES AVIONICS S.A.
AIRBUS A318/319/320/321
Summary of Contents for FMGS
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