MULTI PHASE
NAVIGATION management & monitoring 53
POSITION DISCREPANCY
FMS1/FMS2 POS DIFF
CHECK IRS (1)(2)(3)/FM POSITION
Scratchpad messages (amber)
See Part IV: Degraded operations
MAP-SHIFT
Map shift may occur in the following situation.
Non GPS A/C at take-off:
If the RWY used for take-off is different from the entered in ACTIVE
F-PLN, updated position will be erroneous. After takeoff FMGC position
will be updated based on radio position availability and will generate
map-shift.
Coordinates reference for update at take-off
are associated landing runway threshold
coordinates. If a significant difference exists
between the two values, an error is
introduced at updating which is corrected
gradually after take-off as FMGC position is
updated.
Non GPS A/C in flight:
When navaid coverage is not sufficient, radio position is not available
and FMGC position is no longer automatically updated.
FMGC position is then based on the mixed IRS position; FMGC accuracy
depends on IRSs accuracy.
Once a radio position is regained FMGC position is progressively
updated; pilot may observe on ND a gradual map-shift.
All A/C:
Map-shift may be due to erroneous navaid(s) data in the NAVdb.
This type of error may introduce:
LANDING THRESHOLD
AKE-OFF THRESHOLD
− Wrong position of the navaid display on ND, and or,
− Incorrect radio position which, if used by FMGC, will generate
incorrect FMGC position.
In this case:
− Cross-check and use raw data references,
− Identify erroneous navaid and check coordinates,
Navaid data may be checked via DATA INDEX 2/2 as described in
Ch 7.1.
− Deselect erroneous navaid via SELECTED NAVAIDS page as
described above.
AIRBUS A318/319/320/321
© THALES AVIONICS S.A.
J43126AA 00
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