Flight Management System (FMS) Explained

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Flight Management System (FMS)

The flight management system (FMS) was introduced on modern aircraft to bring data and information gathered from electronic flight instruments, aircraft monitoring, and navigation systems together and provide outputs that can be used for automatic control of the aircraft from take-off to final approach and landing.

Main Components of FMS

The components of Flight Management Systems (FMS) are:

  • Flight Management Computer (FMC)
  • Automatic Flight Control (AFCS)/Automatic Flight Guidance System (AFGS)
  • Aircraft Navigation System
  • Electronic Flight Instrument System (EFIS)

How FMS Works?

A Flight Management Computer (FMC), Control & Display Unit (CDU), IRS, AFCS, and a system of data buses that permits data interchange with the other digital and computerised systems and equipment installed to the aircraft are all important components works together to form a Complete  FMS (Flight Management System). One for the captain and one for the first officer FMS control unit are fitted on Central Pedestal for. During regular operation, the two systems share the data that comes in. In the event of a failure, however, each system can be configured to function separately.  It is feasible to discover flaws within the system and avoid erroneous indications by automatically comparing (on a continuous basis) the indications and outputs supplied by the two systems. The IRS, EICAS, engine thrust management computer, and air data computer are among the systems that provide input to the FMC.

Advanced flight planning and navigation capabilities are provided by modern Flight Management Systems (FMS). To provide En-Route, Terminal, and Non-Precision Approach Navigation Guidance, existing combinations of avionics equipment such as GPS, VOR/DME, Inertial Reference/Navigation Systems (IRS/INS), and dead reckoning data are used.

The FMS uses sensor inputs to calculate factors including fuel consumption, airspeed, position, and predicted arrival time while in flight (ETA). Vertical flight limitations are maintained by the aircraft's autopilot system and the Vertical Navigation (VNAV) system. VNAV keeps track of the correct speed and altitude limitations (as specified in the flight plan) and ensures that they are met at waypoints. From the initial takeoff until the last touch down, a flight can be made almost totally automatic by integrating various automatic operations.

Features of FMS

Typical features of flight management systems include:

  • Integrated Automatic Multi-Sensor Navigation
  • Sensor Monitoring & Control
  • Display/Radar Control
  • Moving Map Data Display
  • Steering/Pitch Commands to Autopilot
  • Multiple Waypoint Lateral Navigation (LNAV)
  • Optimised Vertical Navigation (VNAV)
  • Time/Fuel Planning & Predictions based on the aircraft flight data
  • Data Based Departure Procedures (DP) Standard Terminal Arrival Routes (STAR) and approaches
  • Integrated EFIS and Radar Control
  • System Integrity & Monitoring
  • Flight Maintenance & Execution

The FMS, like other flight safety important systems, can have a Dual System, Each system calculates the position of the aeroplane. Cross-checks across systems verify the authenticity and quality of flight data, giving aircrews the peace of mind of dual-redundant position and navigation systems. Waypoints (including those of the origin and destination) are entered into the FMC through the Control Display Unit (CDU) before to departure to define the route (as many as 100 waypoints in some systems). FMS initialization also entails inputting operational flight characteristics such as aircraft weight and fuel load into the FMS.

FMS Navigation Database Updates

The FMC ( Flight Management Computer) Navigational Database, which contains airports and ground beacons, requires to be updated with latest Databases on a regular basis (every 28 days with 13 update cycles per annum). The update is normally supplied on CDROM, but most aircraft require a floppy disc for installation ( modern system may have USB drive).

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