From three gliders, a worldwide system is created
The history of FLARM begins in the early 2000s in Switzerland. The engineers and glider pilots Urban Mäder, Urs Rothacher and Andrea Schlapbach were looking for a cost-effective way to warn pilots in time before dangerous approaches.
The timing was favorable. GPS became significantly more accurate for civilian users, while radio and microelectronics became ever smaller and more affordable.
In 2004, the first approximately 500 devices were put on the market. Today, the product range includes both fixed and portable collision warning devices as well as components that other avionics manufacturers can integrate into their systems.
Especially in glider flight, FLARM practically became the standard. From there, the technology gradually spread to motor aircraft, ultralight aircraft, and helicopters.
FLARM was more than just a position transmitter from the very beginning
The basic technical principle is relatively elegant.
Each device knows its position, altitude, speed, and direction of movement via GPS. This information is then transmitted locally to other FLARM devices.
However, the most important factor is the forecast. FLARM not only considers the current distance between two aircraft, but also calculates, based on their motion vectors, whether a dangerous conflict could develop within the next few seconds.
Only when the flight paths actually become collision-critical does the pilot receive a warning.
This distinguishes the system from a pure traffic display, which merely shows all the aircraft that have been received.
Why „See and Avoid“ alone is not enough
In VFR flight, visual air space surveillance remains indispensable. Nevertheless, it has physical limitations.
An oncoming aircraft can appear almost motionless in the field of vision for an extended period of time. It is precisely this lack of relative motion that makes perception particularly difficult, especially when the aircraft is directly on a collision course.
In addition, there are dead angles due to wing surfaces or cockpit structures, glare, mist, a restless background, and the constant need for attention to instruments and navigation.
Electronic collision warning systems are therefore not intended to replace visual scanning, but to specifically draw attention to areas where searching should be conducted.
FLARM and ADS-B follow different approaches
Parallel to FLARM, ADS-B has developed.
In Europe, ADS-B Out on certified aircraft is usually based on Mode S Extended Squitter at 1090 MHz. A properly equipped aircraft regularly transmits its GNSS position, altitude, identity, and other data.
The essential difference: An ADS-B out system does not necessarily have to have an ADS-B receiver.
Therefore, an aircraft can be visible to others without actually being a source of traffic. Similarly, a pilot can use an ADS-B receiver even though his own aircraft is not transmitting an ADS-B position.
In FLARM, however, sending and receiving are fundamentally connected.
This is particularly important for glider flights, because aircraft often move very close to each other and quick warnings are needed.
The problem of fragmented electronic visibility
However, the future of electronic collision avoidance will not consist of a single system.
Today, several technical worlds already exist side by side:
Mode S transponders without ADS-B, ADS-B, FLARM, various portable systems, and increasingly technologies for drones and unmanned aerial vehicles.
In addition, there are aircraft that do not emit any electronic signals at all.
This creates an important misunderstanding for pilots: A traffic sign in the cockpit never automatically shows the entire traffic.
Even a modern system with ADS-B and FLARM can miss aircraft if they do not transmit compatible signals.
PowerFLARM connects several worlds
FLARM is therefore increasingly trying to combine different technologies into one device.
Products such as PowerFLARM can receive ADS-B signals in addition to FLARM traffic. Depending on the system and configuration, additional transponder signals can also be analyzed.
The goal is to obtain the most complete picture of the traffic situation, without the pilot having to monitor several separate displays.
This combination is particularly interesting for motor aircraft that operate both in conventional GA traffic and in regions with intensive glider flight activity.
Drones change the requirements
One of the biggest future challenges is unmanned aerial vehicles.
The number of professionally operated drones is expected to increase significantly. This includes inspection flights, surveying, logistics, government operations, and, in the long term, possibly regularly operated unmanned aerial vehicles outside the direct line of sight of the pilot.
This increases the need to make manned and unmanned aviation mutually visible electronically.
The remote ID used today on many drones serves a different purpose than a classic collision warning system. It is primarily intended to enable the identification of a drone in its surroundings and is not designed as a comprehensive air-to-air traffic warning system for manned aviation.
ADS-L as a possible European component
The EASA is therefore working on concepts for so-called iConspicuity.
An important approach is ADS-L – Automatic Dependent Surveillance Light.
The basic principle is to equip even very light aircraft with an inexpensive and energy-saving means of electronic visibility.
This is particularly relevant for participants for whom a classic fashion S-transponder would be hardly useful due to weight, energy requirements or costs: for example, sailplanes, gliders or certain drones.
FLARM plays an interesting role in this development because many of the technical requirements – compact devices, low power consumption and direct communication between road users – have been part of the core of the system for years already.
FLARM opens its radio protocol
A further development is therefore noteworthy.
FLARM was long criticized for the fact that essential parts of the system were proprietary and manufacturers needed license agreements for certain integrations.
Now the company has published parts of the radio protocol for position and identification data.
For FLARM, this is a fundamental change in strategy.
Originally, the closed architecture was intended to ensure that safety-critical functions were not replicated using unverified software or unsuitable hardware.
With the opening, a larger ecosystem is now apparently set to be enabled to a greater extent.
Mobile telephony is not the only solution
It is repeatedly proposed to simply exchange future traffic information via mobile networks.
For certain applications, this makes sense. Weather data or strategic traffic information does not necessarily need to be updated within fractions of a second.
With immediate collision warning, things are different.
An air-to-air system works regardless of mobile phone coverage and external infrastructure. Two aircraft equipped accordingly can be recognized immediately.
This is particularly advantageous at higher altitudes or in remote regions.
Mobile telephony is therefore likely to become more of an adjunct to rather than a sole technology for electronic collision avoidance.
The goal: as many signals as possible on one display
Ultimately, it is less crucial for pilots which radio protocol another road user uses.
What is crucial is that its position is recognized and displayed on a common display as much as possible.
The technical development is therefore increasingly moving away from the question „FLARM or ADS-B?“ towards multi-system solutions.
Modern traffic warning systems attempt to combine information from various sources and generate a unified picture of the situation.
This development is expected to continue to accelerate with the growth of drone traffic.
Electronic visibility does not replace looking outward
Despite all the technological developments, one principle remains unchanged.
FLARM, ADS-B and future systems support „See and Avoid“, but they do not replace it.
Not every aircraft transmits electronic position data. Antenna shadowing, range limitations, faulty installation, or technical failures can also cause a target not to be displayed.
An empty traffic sign therefore never automatically means an empty airspace.
The greatest safety effect is achieved when electronic traffic information and consistent visual airspace monitoring are combined.
Conclusion
FLARM has developed from a Swiss glider project into a significant component of European general aviation in just over two decades.
However, the coming years are likely to be more characterized by integration than by individual technologies. ADS-B continues to spread; ADS-L is intended to make lighter aircraft electronically visible, and with the increasing traffic of drones, another group of airspace users is added.
FLARM responds to this with devices that can receive multiple signal types, and with a greater openness to its proprietary technology.
This could change the role of the system: from a classic glider collision warning system to a component of an increasingly interconnected European airspace.
Source references:
Aviation magazine
