FMS GENERAL DESCRIPTION
FMGS OPERATION 9
EPE (Estimated Position Error)
The FMGC position is estimated with 95% probability to be within a
circle of uncertainty.
The ESTIMATED circle radius is shown on the PROGRESS page.
By comparison of REQUIRED value with ESTIMATED value, the system
determines a HIGH/LOW accuracy level .
To provide the best accuracy, the FMGC position is derived by using the
navigation systems in the following order of priority:
All phases, except approach:
1. 3IRS/GPS
2. 3IRS/DME/DME
3. 3IRS/VOR/DME
4. IRS only
On approach:
95%
robabilit
RADIUS
CRUISE AEC001
CRZ OPT REC MAX
FL350 FL380 FL398
<REPORT
UPDATE AT
*[ ]
BRG /DIST
---° /----.- TO [ ]
PREDICTIVE
<GPS GPS PRIMARY
REQUIRED ACCUR ESTIMATED
2.0NM HIGH 0.08NM
1. 3IRS/GPS/LOC or MLS
2. 3IRS/GPS
3. 3IRS/DME/LOC or MLS
4. 3IRS/VOR/LOC or MLS
5. 3IRS/LOC or MLS
More details are given in Part III: POSITION MONITOR page and
Part IV: FMS Degraded Operation.
Radio navaids
The FMS auto-tunes the radio navaids contained in the Navigation Data
Base:
− to determine the best RADIO position, as stated above,
− for reference when part of the flight plan, or approach aid.
The auto-tuned navaids can be manually changed through the MCDU -
RAD NAV page or the RMP.
Navaids selected may be displayed on EFIS with ident and/or
frequency.
See Part III – MCDU – NAVAIDS / RAD NAV pages for more
information.
AIRBUS A318/319/320/321
© THALES AVIONICS S.A.
J43126AA 00
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