The light:guard Aircraft Detection Lighting System (ADLS)

Wind turbines, officially known as wind turbines, flash to make them visible to air traffic in the dark. This is intended to prevent collisions with airplanes and helicopters. In Germany, this obstacle marking is regulated by the “General Administrative Regulation on the Marking of Aviation Obstacles” (AVV marking for short). According to the AVV, wind turbines must be marked from a height of 100 meters. To ensure that they no longer flash all night, the use of an Aircraft Detection Lighting System will be mandatory from 2025.

Wind turbines flash red at night in order to be visible. This night-time marking is carried out by means of so-called hazard lights, fire W red or blade tip lighting. The color and light intensity are prescribed. Daytime marking is also mandatory on wind turbines. However, this mainly includes the stripes on the turbine (see question after next). In some cases, wind turbines also flash white light during the day, but this is the exception.

The flashing pattern, color and intensity are prescribed by the aviation authority. It depends on the type of lighting installed. Fire W red, for example, flashes in the specified sequence 1s on/0.5s off/1s on/1.5s off.

The stripes on wind turbines are part of the daily marking. The day markings are usually made using colored markings. These can be attached to the mast and rotor blades.

An orange or red stripe six meters wide is required on the rotor blades from a total height of 100 meters.

The mast must be marked at a height of 40 ± 5 meters above the ground. An orange or red colored ring three meters wide (six meters for lattice masts) should be used. This is required if the total height exceeds 150 meters. It is also required if the total height exceeds 100 m and the machine house is not marked. In this case, the second orange or red stripe on the rotor blades is also dispensed with.

Aircraft Detection Lighting Systems (ADLS) offer several advantages:

Reduced light pollution: less night-time lighting means less disturbance for residents and nature.

Increased acceptance of wind power: Residents are more willing to accept wind turbines in their vicinity if night-time lighting is minimized.

Energy savings: Lighting is only used when it is really needed, which saves energy.

Precise predictions with percentage values are difficult to make across the board. In some wind farms, the light:guard system achieves light-off times of almost 100%. However, it depends very much on the location and the region. Next to an airport, the reduction in lighting is not nearly as significant. The flight activity is simply too high here. In general, of course, the safety of air traffic must be guaranteed. For this reason, it does not make sense to state or interpret percentages regardless of location. 

An example of an ideal case is the wind farm Groen in the Netherlands. Here, the light:guard system was able to reduce flashing by over 97%, despite high flight activity. The exact results can be found in this case study.

There are two approaches to this: Multilateration and Single Receiver Approach.

Multilateration: With this method, the position of an aircraft is determined by receiving transponder signals at several receivers. The signals are received at different locations and the time differences are used to calculate the exact position of the aircraft. This method is very precise and can also accurately determine the altitude of the aircraft. However, it requires several receivers, which increases the costs and installation effort.

Single Receiver Approach: This method uses only one receiving station to receive the signals from transponders. The position of the aircraft is estimated based on the strength and direction of the received signal. This method is less accurate than multilateration and can have difficulties in determining the exact altitude. However, it is cheaper and easier to install as only one receiving station is required.

Multilateration (MLAT) is a well-known and proven method in aviation. The position of a flying object is calculated by measuring the different arrival times of the same radio signal at different receivers. The light:guard system for Aircraft Detection Lighting System works at most locations by means of multilateration and can therefore achieve particularly accurate results. Multilateration requires the following elements:

Transponder receiver (Light:Guard receiver): There are several transponder receivers at known locations with synchronized clocks. These receivers receive the transponder signals transmitted by airplanes.

Time measurement: When an aircraft transmits a transponder signal, this is received by the various transponder receivers. Each transponder receiver measures the time it takes for the signal to reach it.

Triangulation: Positions can be calculated using the time differences in the transponder signals between the various transponder receivers. This is done by triangulation. The position of the aircraft is determined by the intersection of the time measurements from different receivers.

Error correction: As the transponder signals require a certain amount of time to reach the receivers, a number of factors must be taken into account. These factors are the transit time of the signal, possible reflections and atmospheric conditions. Algorithms correct the errors and calculate the exact position of the aircraft.

A transponder is an electronic device that is installed in aircraft. It emits a signal that is received by radar systems on the ground. This allows the position and altitude of the aircraft to be precisely determined. In aviation, transponders are used to make the position and altitude of an aircraft visible to air traffic controllers on the ground.

Since there is no regulation on the topic in English language, a number of synonyms are being used, Aircraft Detection Lighting System (ADLS) being the most common one.

Others include:

• Radar-Activated Lighting System
• Aircraft Proximity Lighting System
• Demand-Controlled Lighting System
• Aircraft Detection Obstruction Lighting
• Smart Obstruction Lighting System
• Dynamic Lighting Control System
• Aircraft-Triggered Lighting System
• Obstacle Detection and Lighting System
• Adaptive Aviation Lighting System

Transponder-based ADLS: With these systems, the position of flying objects is determined by the transponder signals they emit. Only flying objects equipped with a transponder are recognized. These systems are very accurate and require less infrastructure on the ground.

Radar-based ADLS: These systems use radar signals to detect aircraft in the vicinity of wind turbines. They can detect all flying objects, regardless of whether they have a transponder or not. However, radar ADLS requires more technical infrastructure and can be more expensive to install and maintain.

Active and passive radar are two different types of radar systems.

Active radars actively emit signals that are reflected by an object and then received by the radar. The time it takes for the signal to return is measured to determine the distance and speed of the object.

In contrast, passive radars receive signals emitted by other sources, such as radio or television transmitters. Based on the interference or changes in these signals, a passive radar can detect objects without emitting signals itself.

Both types have their own advantages and disadvantages, such as the stealth characteristics of passive radar, which can make it more difficult to be detected by traditional active radar systems.

The Light:Guard receivers cover almost all of Germany with their reception radius. 50,000 km² of this area has already been surveyed and certified in accordance with AVV. New ADLS systems can be put into operation very quickly in this area.

Wind farms in one of the surveyed areas can receive ADLS in eight weeks. If the systems are ADLS-compliant, we guarantee installation and certification within eight weeks. By sending us a brief inquiry, we can quickly find out whether your wind farm is eligible.

In other countries this is different of course. To find out how fast we can bring ADLS to your wind farm please contact our representative for your country.

Over the past few months, the German Wind Energy Association (BWE) has been working with the Federal Ministry of Transport (BMV) to discuss the long-standing issue of the operating time of Aircraft Detection Lighting Systems (ADLS). As a result, a coordinated position has been reached on this issue.

The discussions focused on the question of whether transponder-based ADLS systems must be activated during civil twilight or whether continuous lighting (red light) must be operated throughout this period.

After intensive consultation between the BWE and the BMV, agreement has now been reached:

• During civil twilight in the evening and morning, no ADLS signal should be active.
• During these periods, the continuous lighting remains activated.
• The ADLS is activated exclusively during the night, i.e., between the end of civil dusk and the beginning of civil dawn, in accordance with the definitions of the European Safety Rules (SERA).

This ensures that aviation obstacles remain visible at dusk, even if aircraft are flying in the airspace without active transponders. Premature activation of ADLS during dusk could otherwise lead to unlit installations and thus to a safety risk.

Depending on the season and geographical location, civil twilight lasts approximately 30 to 40 minutes in summer and 20 to 30 minutes in winter.

During these times, lighting is therefore continuously activated:

1. Dusk: Continuous lighting mandatory
2. Night: Activation of the Aircraft Detection Lighting System
3. Dawn: Continuous lighting mandatory again

This three-part model ensures continuous visibility of the installations in all transition phases between day and night.

There can be many reasons for active firing despite the ADLS system being in place. The most common reasons include

Flight activity in the airspace:

• The effective area of the wind farm is flown through
• Flying object at a greater distance (the light:guard system detects from 6 km on the ground at the latest)
• Flight activity further away than 6 km
• A flying object on standby (e.g. rescue helicopter) is in the vicinity. As long as the transponder is switched on, the lighting in the wind farm is activated

In this case, Light:Guard can carry out an extended airspace analysis that identifies the transponder that led to the activation. Of course, we cannot switch it off.

Signal interference:

• Failed internet connection
• Excessive latency in the internet connection (e.g. LTE in rural areas)
• Power failure in the wind farm or grid shutdown
• Failure of the transponder receiver in the wind farm (e.g. during maintenance work)
• Server failure

• Different ADLS signal providers in the wind farm
• Transmission of the suppression signal via radio or cable is disrupted
• Lamp or lighting cabinet defective
• Power failure at individual WTGs

The better the signal quality of the ADLS system, the more light emissions can be reduced by flashing. Light:Guard is continuously working to improve airspace monitoring by

• Installing more Light:Guard receivers in surrounding wind farms
• Optimizing the algorithms to determine the transponder position more precisely
• Improving the hardware
• Filtering interference signals
• Analysis programs to monitor the activation times in the wind farm

These analysis programs are of course also made available to customers.

Yes, Light:Guard is a certified and tested provider of Aircaft Detection Lighting Systems. Our systems are type-tested and therefore meet all legal requirements for a safe and reliable ADLS solution. In addition, our company is certified according to both ISO 9001 (quality management) and ISO 27001 (information security management).

These certifications guarantee you the highest standards in quality, data security, and process stability—from development and operation to support for our ADL systems.

The NIS 2 Directive (Network and Information Systems) is a binding EU regulation designed to strengthen cybersecurity, which was transposed into German law in December 2025. It requires companies in the critical infrastructure sector (KRITIS) to comply with higher security standards and reporting obligations. This also includes many wind farm operators. The directive also obliges these companies to comply with cybersecurity standards for suppliers and service providers.

After review, Light:Guard does not itself fall under the criteria of the NIS2 regulation and is therefore not subject to NIS2 reporting requirements.

Regardless of this, as a service provider in a KRITIS-related environment, we are certified according to ISO 27001 – as the only provider of Aircraft Detection Lighting System (ADLS).

As part of our ISO 27001-certified information security management system (ISMS), we implement the following measures, among others, so that NIS 2-affected operators and plant managers can continue to plan with us:

Technical measures

✔ Access controls

✔ Patch and update management

✔ Backup and recovery strategies

✔ Defined incident response processes

Organizational measures

✔ Regular training

✔ Existing emergency and recovery plans

✔ Structured supplier evaluation

In addition, we have established a clearly defined reporting process for security-critical incidents.

With these measures, we meet the requirements relevant for service providers in the NIS2 environment and support you as an operator in fulfilling your own NIS2 obligations and demonstrating compliance to authorities and audit bodies.

These certifications guarantee you the highest standards in quality, data security, and process stability—from development and operation to support for our ADL systems.