ADS-L is the electronic conspicuity standard designed to bring lightweight, affordable surveillance to the widest possible range of GA aircraft in European airspace. If you fly a glider, ultralight, or vintage aeroplane that will never carry a certified transponder, ADS-L is built for you. If you already have full ADS-B Out, ADS-L still matters because it determines who else shows up on your traffic display.
This post covers what ADS-L actually is at a technical level, how it differs from certified ADS-B Out, which organizations are building the coalition behind it, and what the Conspicuity Declaration launched at AERO 2025 means in practice.
What Makes ADS-L "Light"
The "L" stands for Light, and the name is deliberate. Full ADS-B Out requires a certified Mode S Extended Squitter transponder broadcasting on 1090 MHz, installed by an approved workshop, with a certified GNSS position source feeding it. That installation typically runs several thousand euros for parts and labour, requires aircraft downtime, and demands an approved maintenance release before you fly again. For a Cessna 172 on an IFR ticket, that's a reasonable investment. For a Scheibe Falke motor glider or a Rotax-powered ultralight, it can exceed the aircraft's annual operating budget.
ADS-L strips the standard down to its essential safety function: broadcasting your position so other aircraft and ground systems can see you. It does this with significantly relaxed requirements across four dimensions.
Cost. An ADS-L device targets a price point an order of magnitude below a certified transponder installation. Portable units in the 500 to 800 euro range can meet the standard, putting electronic conspicuity within reach of student pilots and flying clubs.
Power. Full ADS-B Out transponders draw substantial power from the aircraft electrical bus. ADS-L devices operate on battery power for multiple hours, which matters enormously for gliders with minimal electrical systems and ultralights with weight-limited wiring.
Weight and installation. ADS-L devices are portable by design. No panel cutout, no wiring loom, no STC. You place the unit in the cockpit with a clear sky view, switch it on, and fly. Move it to a different aircraft the next day.
Certification pathway. Rather than requiring full ETSO certification, ADS-L operates under a declaration-based compliance model. Manufacturers declare conformity to the published technical standard, which dramatically reduces the time and cost to bring devices to market.
The trade-offs are real. ADS-L devices transmit at lower power than certified transponders, so their air-to-air range is shorter. They use GNSS-derived position rather than pressure altitude from a certified encoder, introducing slightly different accuracy characteristics. And they are explicitly not a replacement for a Mode S transponder in airspace where one is required. ADS-L fills the gap everywhere else.
ADS-L vs Full ADS-B Out: The Technical Differences
Understanding where ADS-L sits in the surveillance hierarchy helps clarify what it can and cannot do.
Full ADS-B Out on 1090 MHz Extended Squitter broadcasts aircraft position, velocity, identification, and integrity data at intervals defined by EUROCAE ED-102A. It is designed for the entire ATM system. Air traffic controllers use it. TCAS queries it. Other aircraft receive it directly. The transmitted power level, antenna performance, message format, and position accuracy are all tightly specified to ensure system-wide interoperability.
ADS-L retains the core concept of broadcasting position and identity, but with a simplified message set and lower transmission power. It is designed for cooperative traffic awareness between nearby aircraft, not for integration into the surveillance infrastructure that supports IFR separation services. Think of it as peer-to-peer visibility rather than system-wide surveillance.
This distinction matters practically. A Pilatus PC-12 on an IFR flight plan at FL180 needs full ADS-B Out because ATC depends on that data for separation. A Jodel D.11 pottering around a grass strip at 1,500 feet in Class G needs to be visible to nearby traffic and to show nearby traffic on the pilot's display. ADS-L serves that second mission at a fraction of the cost and complexity.
The ADS-L Coalition: Who Is Building This
Standards succeed or fail based on adoption, and adoption in aviation depends on getting manufacturers, service providers, regulators, and pilot organisations pulling in the same direction. The ADS-L coalition exists precisely for this purpose.
The coalition brings together device manufacturers producing portable and installed EC equipment, traffic aggregation platforms like SafeSky and the Open Glider Network (OGN), airspace service providers, and pilot associations across multiple European states. EASA participates not as a coalition member in the traditional sense but as the regulatory body providing the framework and encouraging industry-led standardisation.
What makes the coalition distinctive is its emphasis on interoperability across existing protocols. European GA already has multiple electronic conspicuity technologies in use. FLARM dominates the gliding community with over 50,000 devices deployed. ADS-B 1090 MHz serves IFR traffic and an increasing number of VFR aircraft. OGN provides open-source ground-station coverage across much of Europe. SafeSky aggregates data from dozens of sources into a unified traffic picture. The ADS-L coalition's task is not to replace any of these systems but to define a common electronic conspicuity standard that allows them to work together.
This interoperability model is critical for pilots flying in mixed-equipage airspace. On any given summer afternoon at a busy uncontrolled aerodrome, you might share the circuit with a glider broadcasting FLARM, a Cessna with a Mode S transponder, an ultralight with an OGN tracker, and a visiting French Robin with a SafeSky-connected tablet. The ADS-L standard aims to make all of these aircraft visible to each other through a shared data layer, regardless of which specific technology each one carries.
The Conspicuity Declaration at AERO 2025
At AERO Friedrichshafen in April 2025, the coalition launched the Conspicuity Declaration. This is not a regulation. It is a voluntary commitment by manufacturers, service providers, and pilot organisations to adopt shared principles for electronic conspicuity in GA.
The declaration establishes four commitments. First, inclusivity: every aircraft type should be able to participate in electronic conspicuity, from a high-performance turboprop to a paramotor. Second, interoperability: devices must exchange data across protocol boundaries, so a FLARM-equipped glider appears on an ADS-B receiver's display and vice versa. Third, affordability: the coalition explicitly commits to keeping device costs accessible for individual pilots, not just airlines and corporate operators. Fourth, safety culture: the declaration frames EC adoption as a proactive safety measure rather than a compliance burden, encouraging pilots to equip voluntarily rather than waiting for mandates.
The declaration matters because it creates industry alignment ahead of regulation. EASA's roadmap for electronic conspicuity envisions harmonised standards by 2027, with potential mandates in certain airspace classes to follow. By establishing consensus on interoperability requirements now, the coalition reduces the risk of fragmentation where different countries or aircraft communities adopt incompatible solutions.
What This Means for Pilots Flying Different Aircraft Types
The practical impact of ADS-L varies by what you fly and where.
Glider pilots gain the most immediate benefit. Gliders have relied on FLARM for traffic awareness for two decades, but FLARM is invisible to ADS-B-equipped powered aircraft. An ADS-L device that bridges both protocols means a glider thermalling near an active approach path becomes visible to the Cirrus on a GPS approach, and the Cirrus becomes visible to the glider pilot.
Ultralight and microlight pilots in countries like France, Germany, and the Czech Republic represent a huge segment of European GA flight hours. Many of these aircraft have electrical systems too limited for a certified transponder. ADS-L's low-power, battery-operated design fits this community perfectly.
Vintage and homebuilt aircraft often face certification barriers that make transponder installation impractical or prohibitively expensive. A portable ADS-L device sidesteps those barriers entirely.
Powered GA pilots who already have Mode S transponders benefit indirectly. More aircraft broadcasting position data means a fuller traffic picture on your receiver. The ultralight that was previously invisible at your 10 o'clock now shows up on your display, giving you time to look outside and confirm visual contact.
For a deeper look at how Europe's broader push for electronic conspicuity fits together, that post covers the regulatory momentum and preparation steps.
Where SkyRecon Fits
SkyRecon is built around the ADS-L philosophy: portable, affordable, interoperable. It receives dual-band ADS-B on both 1090 MHz and 978 MHz, integrates SafeSky Inside for access to 30+ supplemental traffic sources including FLARM and OGN data, and outputs GDL90 to EFB apps like SkyDemon, EasyVFR, and ForeFlight. The built-in 3.4-inch display provides traffic awareness without depending on a tablet, and the whole unit moves between aircraft in seconds.
As the ADS-L standard matures and EASA's conspicuity framework solidifies, devices built around interoperability and portability will be best positioned to keep pilots compliant and visible. For more on how portable ADS-B receivers are reshaping GA safety, see our parent guide.
The Road Ahead for ADS-L
The ADS-L coalition's work is not finished. Technical specifications continue to evolve as real-world deployments reveal edge cases around message formatting, position update rates, and interference management in dense traffic environments. Ground infrastructure for receiving ADS-L transmissions is expanding across Europe, with OGN stations providing much of the backbone.
For pilots, the actionable takeaway is straightforward. Electronic conspicuity is shifting from optional extra to expected baseline for responsible GA flying in Europe. ADS-L makes that shift affordable and practical for aircraft types that were previously left out. Equipping now means building familiarity with the technology, contributing to the traffic picture for everyone around you, and being ready when voluntary adoption becomes regulatory expectation.