Thales FMGS, Pilot'S Manual

Page: 57 / 703

FMS GENERAL DESCRIPTION
FMGS OPERATION 7
3.3. NAVIGATION/FLIGHT MANAGEMENT
Navigation
FMGC position
The prime function of the FMGC is to compute an accurate position and
ground speed based on the navigation data available.
FMGC1 uses IRS1/IRS2/IRS3, GPS1, VOR1/DME1/LOC1/MLS1,
FMGC2 uses IRS1/IRS2/IRS3, GPS2, VOR2/DME2/LOC2/MLS2,
GPS is an airline option and may be installed with the 2 following
architectures :
a) Hybrid - the GPS output data are acquired and processed by the
ADIRS, then transmitted to the FMGCs.
b) Autonomous architecture - the GPS output data are directly acquired
and processed by the FMGC.
Each IRS is subject to its own variable
drift error.
Using GPS reference (or Navaids
reference when GPS is not available),
both FMGCs continuously monitor each
IRS to determine and update an IRS
error model. This computation is done by
a Kalman filter and provides a BEST
position/speed for each IRS.
The estimated IRS drift error is shown in
the MCDU POSITION MONITOR page.
GPS provides an accurate position but may be affected by lack of
satellite coverage or temporary interruption.
Radionavaids used by the FMGCs to compute the position are DME,
VOR/DME, VOR, LOC or MLS. Accuracy is variable depending on type of
navaid and its position relative to the aircraft.
POSITION MONITOR
FMGC1 5019.1N/00130.8E
3IRS/GPS
FMGC2 5019.2N/00130.7E
3IRS/GPS
GPIRS 5019.1N/00130.7E
MIX IRS
5019.4N/00130.1E
IRS1 IRS2 IRS3
NAV 2.5 NAV 4.0 NAV 1.0
SEL
<FREEZE NAVAIDS>
AIRBUS A318/319/320/321
© THALES AVIONICS S.A.
J43126AA 00