-Radio nav station tuned by the FMS for display or position calculation. They are located on the ND in accordance with the aircraft position and the flight plan.
-Self-elaborated message in case of disagreement between the radio nav frequency as selected by the FMS and the frequency actually tuned by the receivers.
-All the data base waypoints, VOR stations, NDB or airport in the displayed area following the selection of the various options on the FCU.
-Cross track error and transition turns of the flight plan.
-Some important messages elaborated in the FMS.
-Pseudo waypoints computed by the vertical functions for vertical
guidance aid. Finally, two other instruments are used to display FMS information. The PFD as main guidance instrument displays the data computed or inserted on the MCDU such as ECON speed targets and target altitudes in automatic guidance modes, V1 and V2, DH or MDA in approach. The ECAM is used to display the aircraft gross weight. The installation of the whole system is dual, following the architecture described in figure (Ref. Fig. 001) The FMS works then normally in DUAL mode based on the master/slave principle; the master FMS is the one associated with the autopilot engaged. If no autopilot is engaged, the side 1 is master. Based on this principle, all the data entered by a pilot on any MCDU are transmitted to both FMGCs through the intersystem bus. The computations in each side are made independently of the other side. However, the results are either synchronized (e.g. lateral/vertical flight plan) by the master side or compared (e.g. aircraft position). In the latter case, a miscomparison will lead to a message or even to the disengagement of the dual mode. The comparisons which may lead to disengage the dual mode, during power up, are the following:
-Data base incompatibility
-Operational program
-Aircraft/engine model section. In this case, both systems work in independent mode. This means that the entry of data on one MCDU applies only on the same FMS side. The MCDU, ND and PFD display is linked to the own side FMS. A long-term power-up is required to intend to revert to dual mode. Each FMGC will tune its own side radio nav receiver. The crew has to tune the left side radio nav on the left MCDU, the right side radio nav on the right MCDU. This applies also to ILS selection.
A particular case of operation is when one FMS has failed. The alive FMS then reverts to SINGLE mode. The operations on the MCDUs are exactly similar to the DUAL mode except that the response time may be longer. If the ND modes and ranges are synchronized on both sides (FCU), then both sides will display the same information. If not, only the ND of the alive FMS side will display the FMS data. The other ND will display a specific message. The radio navigation selection can be performed exactly in the same conditions as in DUAL mode.
R **ON A/C 106-149, 151-199, 211-299, 301-399, 401-499,
Post SB 22-1089 For A/C 151-199,211-212,
FLIGHT MANAGEMENT SYSTEM (FMS) - DESCRIPTION AND OPERATION
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1. General
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The Flight Management System (FMS) performs various functions to help the crew in the management of the flight. These functions are all constructed from a lateral and a vertical flight plan. The pilot can select this flight plan from a data base stored in the system and can modify it at any time. (Ref. para. 3.A.).
In the lateral plan, the FMS performs:
-navigation computation (aircraft position),
-radio navigation aid selection (automatically or by pilot selection),
-lateral guidance to maintain the aircraft along the flight plan from R takeoff to approach (Ref. para. 3.B.).
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