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Interior of an ASW 19 glider showing an older Classic FLARM device on top of the instrument panel

FLARM is an electronic device to selectively alert pilots to potential collisions between aircraft. It is not formally an implementation of ADS-B, as it is optimised for the specific needs of light aircraft, not for long-range communication or ATC interaction.

FLARM (the name being a portmanteau of 'flight' and 'alarm') obtains its position and altitude from an internal GPS and a barometric sensor and then broadcasts this together with forecast data about the future 3D flight track. At the same time, its receiver listens for other FLARM devices within range and processes the information received. Advanced motion prediction algorithms predict potential conflicts for up to 50 other aircraft and alert the pilot using visual and aural warnings. FLARM also has an integrated obstacle collision warning system together with an obstacle database. The database includes both point obstacle and segmented obstacles, such as split power lines and cableways.

Unlike conventional transponders in aircraft, FLARM has a low power consumption and is relatively inexpensive to purchase and install. Furthermore, conventional Airborne Collision Avoidance Systems (ACAS) are not very effective in preventing light aircraft from colliding with each other as light aircraft can be close to each other without being in danger of collision. ACAS would issue continuous and unnecessary warnings about all aircraft in the vicinity, whereas FLARM will only issue selective warnings that pose a collision risk. Versions are sold for use in light aircraft, helicopters, and gliders. The newer PowerFLARM models extend the FLARM range to over 10 km. They also have an integrated ADS-B and transponder Mode-C/S receiver, making it possible to also avoid mid-air collisions with large aircraft.

Newer devices can also act as authorized flight recorders by producing files in the IGC format defined by the FAI Gliding Commission. Through an interface, all FLARM devices can be connected to FLARM displays or compatible avionics (EFIS, moving map, etc.) to give visual and aural warnings and also to show the intruder's position on the map. Licensed manufacturers are also producing integrated FLARM devices in different avionics products. There are also FLARM devices that can issue spoken warnings similar to TCAS.

FLARM Protocol[edit]

The FLARM radio protocol version 4 is public,[1] but FLARM changes the protocol on regular basis to ensure no other vendors can build competing products using the FLARM protocol.

The FLARM serial data protocol, which provides the output from a FLARM device, is also public, while the prediction engine of FLARM is patented by Onera (France)[2] , proprietary and licensed to manufacturers by FLARM Technology in Switzerland.

FLARM Company[edit]

FLARM[3] was founded by Urs Rothacher and Andrea Schlapbach in 2003, joined by Urban Mäder in 2004.[4] First sales were made in early 2004. Currently there are over 25,000 FLARM-compatible devices (around half of them produced by FLARM Technology, the rest by licensed manufacturers who have now overtaken FLARM in current sales) in use mainly in Switzerland, Germany, France, Austria, Italy, UK, the Benelux, Scandinavia, Hungary, Israel, Australia, New Zealand and South Africa.

FLARM's technology is also used in ground-based vehicles, e.g. for all sorts of vehicles in surface-mining such as trucks, dozers etc. These products are designed and produced by the Swiss company SAFEmine.


  2. ^ US patent 6438492, Claude Le Tallec & Boris Gravier, "Device for improving the security of aircraft in visual flight regime", issued August 20, 2002, assigned to Onera 
  3. ^ FLARM
  4. ^ FLARM Company History

External links[edit]