Gliders need to be electronically visible to motor-powered aircraft. This can be achieved with either ADS-L or ADS-B. It is recommended to keep an existing Mode S transponder and if possible, upgrade to ADS-B out.
There are thousands of FLARM installations in gliders. This is a great solution for collision awareness among gliders, e.g. in thermals. The recommendation focuses on the interoperability, to be visible to other aircraft categories.
FLARM is ideal for use among gliders. To improve interoperability with motor-powered aircraft, it is recommended to use a FLARM device with the ability to receive ADS-B and Mode S signals. For best interoperability, it is recommended to combine it with either ADS‑B out or ADS-L in/out.
If ADS-L in/out is used as a standalone device without FLARM, there may be disadvantages for collision awareness with other gliders (e.g. in thermals). This is because the collision awareness protocols in apps like Foreflight, Skydemon etc. are not built for gliders.
ADS-B out is recommended due to the inherent benefits of a permanent installation (e.g. known reliability, range, diversity). It ensures interoperability with traffic warning systems in motor‑-powered aircraft.
Last modification 23.05.2025
