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FLARM (short for FLight Alarm) is a collision avoidance instrument designed to assist in the "See-and-Avoid"-Practice used during VFR flights. Originally being designed for gliders, it is now often used in light aircraft, especially when often operating in areas where there is a lot of glider activity.

Working principle

A small computer predicts the future flightpath of the aircraft it is installed in based on GPS data. This predicted flightpath is then transmitted regularly using radio signals similar to the ones used for example for garage remote controls. These signals are received by other FLARM devices (inside a range of typically 3-5 km.[1] If a collision risk is calculated, there is a warning emitted.[2]


Earlier FLARM devices ("Classic FLARM") had a simple 16-led vertical and horizontal display that showed a broad direction to look for the traffic. Today, FLARM devices are only core modules and can be combined with a variety of displays. FLARM signals can also be included for example on soaring computers like the LX8000/9000.[3][4]

Status in FlightGear

Since June 2020, a basic FLARM simulation is available in FGData. It can be included and placed in any aircraft. See the README file for more information.

Current Status:

  • Available Devices:
    • FLARM Classic,
    • FLARMv3 display
    • (TRX-2000 as included in the DR400-Ecoflyer)
  • Algorithm: very simple time-to-collision prediction based on closure rate. Improvements are very welcome, but please keep it light! 20}% completed
  • Obstacle Database and Warning: Not done Not done


Please contact D-ECHO if you wish to contribute to the FLARM implementation so that there can be a coordinated effort.


  1. Operating Manual, FLARM Collision Avoidance System, Version 242 (pdf), pages 2-3. Published by FLARM Technology, Ltd. Retrieved 26 July 2020.
  2. The Affordable Collision Avoidance Technology for General Aviation and UAV (pdf). Published by FLARM Technology, Ltd. Retrieved 26 July 2020. - General Description
  3. Displays. Published by FLARM Technology, Ltd. Retrieved 26 July 2020. - Third party FLARM displays
  4. Integrated systems. Published by FLARM Technology, Ltd. Retrieved 26 July 2020. - Manufacturers with FLARM devices integrated into a display, EFIS other avionics

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