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The calculation can also be made in degraded mode, from
inertial data alone.
During approach, the LOC information is used for the lateral
re-alignment of the aircraft position.
An information about the accuracy of the position, as
calculated by the system, is supplied to the crew.
3_ Follow-up of the flight plan
The use of the autopilot or of the flight director and the
selection of the lateral autocontrol function (push action on
HDG/TRK selector knob on the FCU) make this follow-up
possible.
Flight segments can be guided in VOR mode (selection by the
crew on the MCDU).
4_ Selection of navaids
The FMGC normally ensures the selection of navaids (ADF, ILS)
:
- automatically as a function of geographical criteria
depending on the planned route and on the aircraft position.
- manually from the MCDUs.
For information displayed on the ND, the selection of VOR and
ILS automatically causes the selection of DME.
The selection of DME frequencies for the calculation of
position is fully automatic.
In standby mode, the pilot can take control of the navaid
selections side after side, through action on the RMP.
(Ref. Fig. 009)
Consequently, any FMGC selection is overridden and in
particular, the management of DME frequencies is cancelled for
the calculation of position by the FMGC.
(d) Performance data
1 Calculation of optimum speed
_ The flight management system enables to minimize the flight cost through the optimization of the speed. The calculations are dependent on :
-
the flight plan,
-
the aircraft weight entered by the crew,
-
the various models of aircraft and engines stored in the
mass memory. Wind and temperature models are also taken into account for the calculations. The crew can modify these models.
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AFS - Selection of Navaids
Figure 009
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3
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4
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Calculation of predictions throughout the flight plan The vertical profile is sequenced in flight phases :
-takeoff
-climb
-cruise
-descent
-approach.
The system defines a certain number of pseudo waypoints which
are integrated in the flight plan.
These are :
-
waypoints corresponding to climb, level or descent phase,
-
waypoints corresponding to change of speed.
The system automatically adapts the aircraft performance :
-
to time constraints at a waypoint (in the flight plan there can only be one constraint at a waypoint entered by the pilot), or
-
to speed constraints and/or altitude constraints at various climb or descent waypoints (defined by the flight plan or entered by the pilot).
The system uses the constraints to calculate the speed, altitude, time and fuel when overflying each waypoint. The system also calculates a geographic profile for the climb and approach.
Follow-up of vertical profile
The use of the AP or FD enables follow-up of the vertical
profile on condition that a vertical speed has not been
imposed by the pilot via the FCU.
The follow-up of the optimum speed is made by the AP/FD or by
the thrust control system on condition that the pilot has not
imposed the speed to be followed.
The follow-up of the vertical profile and of the optimum speed
can be simultaneous or independent.
During final approach, if a non-precision approach has been
selected, the vertical profile is defined up to the minimum
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