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FLIGHT MANAGEMENT SYSTEM (FMS) - DESCRIPTION AND OPERATION
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1. General
_______ 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 aids selection (automatically or by pilot selection),
-lateral guidance to maintain the aircraft along the flight plan from
takeoff to approach (Ref. para. 3.B.).
In the vertical plan, it computes:
-an optimum speed at each point,
- other characteristic speeds,
-the aircraft weight and center of gravity.
Then it computes predictions along the flight plan based on these speeds and
weight. It performs vertical guidance referenced to these predictions. Other
miscellaneous performance computations are also made (Ref. para. 3.C.).
The crew can insert various data or select function modes through two MCDUs
(Multipurpose Control and Display Unit) linked to the FMGCs (Flight
Management and Guidance Computer).
The MCDUs, both NDs, and, for some parameters, the PFDs are also used by the
system to display information related to the above-mentioned functions (Ref.
para. 3.D.).
2. System Description
__________________ The FMS general architecture which shows the two FMSs incorporated in the FMGCs, with the two MCDUs and the DMCs for display is given in figure. (Ref. Fig. 001) It has to be noted that the navigation data base must be loaded once every 28 days by a loader (type ARINC 603) which is plugged to the FMS in the cockpit (Ref. 22-83-00). The navigation data base can be loaded from one FMGC to the other FMGC through the intersystem bus. This function is called "Nav data base crossload". The conditions required to activate the crossload function are as follow:
-pin related to this function activated
-aircraft in PREFLIGHT or DONE phase
-different data base cycle in each FMGC/MCDU status.
FMS - General Architecture
Figure 001
When the three conditions are all met, the ACTIVATE CROSSLOAD indication comes into view on the aircraft status page of both MCDUs. To transfer any nav data base, push the line key (4L) adjacent to the ACTIVATE CROSSLOAD indication on the MCDU related to the transmitting FMGC. The CONFIRM CROSSLOAD indication comes into view on the line adjacent to the key 4L of the transmitting MCDU. This line is blanked on the receiving MCDU. If you push the line key adjacent to the CONFIRM CROSSLOAD indication, the NAV DATA BASE CRASSLOAD IN PROCESS message and the percentage progress come into view on both MCDUs. The FMS navigation, radio navigation and lateral guidance architectures are shown in the following figures. (Ref. Fig. 002, 003, 004, 005) The architecture for weight and speed calculation and for vertical guidance/ predictions is given in the following figures. (Ref. Fig. 006) The MCDUs are also shared between other systems : CFDIU, AIDS, ACARS. However, the FMS has priority. This means that when the power is set up after a long-term interrupt, the MCDUs are linked to the FMS automatically. The displayed page is the A/C STATUS page which gives the FMS configuration. A specific procedure allows access to the other systems. If the MCDUs are already working when the FMGCs are powered, the display is not modified. The crew has then to press any page key (except MCDU MENU) to be coupled to the FMGC. The initialization will be briefly described in next section. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：A320飞机维护手册 AMM AUTO FLIGHT 自动飞行2(51)
