FANET and FLARM: who actually sees you in the air

Every pilot who looks at a FANET device asks the same fair question: this is nice, but will the gliders see me? The answer takes more than one word, because three different protocols are involved and they do three different jobs.

What FANET actually gives you

FANET is pilot to pilot. You appear on the instruments of everyone around you who speaks it, and they appear on yours. Ground stations of the Open Glider Network pick you up too, so your track is visible from the ground. Because the protocol also carries climb rate, a screen full of nearby pilots doubles as a map of where the lift is.

There is more in it than position. FANET can broadcast your name, share a thermal you have found, declare what you are doing — paraglider, sailplane, walking — and send an SOS. That last one is a distress beacon already sitting in the radio you are carrying.

One detail matters in a crowded thermal: FANET slows itself down as the sky fills up. The more neighbours around you, the less often each device transmits, so the shared channel stays usable. Hobby firmwares that beacon at a fixed rate work fine on a quiet hill and choke the channel in a gaggle of fifteen. Ours follows the spec.

Why there is no FLARM in our devices

FLARM is what gliders and powered aircraft carry, and the line here is legal rather than technical.

Receiving and decoding FLARM is fine — that is how every OGN ground station works. Transmitting a FLARM packet is what requires a commercial licence and an assigned radio ID. Our radio could physically send those packets; we choose not to. A hobby build with nobody carrying liability is one thing, a flight instrument sold in the EU is another.

The legal route exists: buy the licensed FLARM OEM module and embed it. That is what several European manufacturers do, and it brings a second chip with its own firmware on an update schedule we would not control. Devices with two update paths, one of them out of your hands, age badly.

So the gap people keep pointing at — a cheap standalone FLARM — is a legal gap, not an engineering one. Better firmware cannot close it.

What this means for you

If you fly where FLARM is effectively mandatory, carry FLARM. FANET does not make you visible to a glider that listens only to FLARM, and we have never claimed it does. What FANET gives you is the other half of the sky: the pilots around you, the lift they are finding, and a distress call that does not need a phone. ADS-L, below, covers part of the rest.

For most paraglider pilots that is exactly the half that matters, because the traffic you actually share a thermal with is other paragliders.

ADS-L: shipping, both directions

ADS-L is the protocol meant to make everyone interoperable, and it is no longer a plan here. The FANET Vario transmits and receives it in the firmware it ships with, on the same radio that carries FANET.

ADS-L Out puts your position on air. OGN ground stations across Europe already decode ADS-L, and so does any aircraft carrying an ADS-L receiver — including FLARM modules that have bought the extension. Nothing goes through our server: it is radio, so range depends on terrain, antenna and transmit power. Transmitting needs a GNSS fix and a clock synchronised to UTC, because ADS-L frames are tied to the UTC second. The app keeps that clock in sync itself. The frame goes out once a second, at that fixed rate, whatever else the radio is doing: a burst that short takes a negligible share of airtime, and nothing you set for reception slows it down.

ADS-L In gives the radio a share of its listening time to ADS-L instead of FANET. Aircraft heard that way appear on your map, tagged ADS-L, and they never leave your phone.

What is divided is reception, and only reception. The chip is single-channel: it sits on one frequency with one modulation at a time, and FANET and ADS-L use different ones, so it has to take turns. The split is yours to set in the app. The more of that listening time goes to ADS-L, the less is left for FANET, so the paragliders around you see you less often. Listening is sampling, not monitoring — a target may only refresh every ten to thirty seconds. Treat it as awareness, not separation.

The full reasoning, including how we read the licence and why LoRa keeps FANET from ever becoming the European standard, is written up in detail on our workshop blog: FLARM, FANET and ADS-L — where the line actually is.