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Hearing the words ‘Wind turbine clutter’ is enough to send shivers down the spine of any wind developer or Air Traffic Controller (ATC). For many years, the wind and aviation industries have been trying to solve the problem that has held up or prevented many wind developments, as well as affecting radar and its technical capabilities. So what exactly is ‘clutter’, how does it affect radar and what is the effect of multiple turbines? This article presents an overview of the issue with a summary of possible mitigation solutions.

This could be… • Give avoiding action and pass on the traffic information

• Pass on the traffic information and give avoiding action if requested

In controlled airspace, ATC operators are often able to disregard wind turbine clutter.

If a wind development consists of multiple turbines, then the radar may interpret the multiple clutter sources as a ‘track’. A track is initiated by a contiguous set of three or more individual blips on a radar screen. This means that the radar displays a track

Blanking – in some instances, it is possible to remove the area of clutter from the radar operator’s screen in the form of a blank. The blank removes the area of clutter but also prevents new tracks or continued tracks from being shown in this area of airspace. This solution is therefore not viable in areas of operationally sensitive airspace.

Radar Infill – this solution involves taking the feed from another radar which cannot detect the returns from the wind turbine. This feed can then be ‘patched’ in over the top of the affected radar’s display, showing the now unaffected airspace. Aircraft returns can now be detected and continued through this area of airspace.

Clutter Tolerant Radar or Software/ Hardware Updates – some current radar and those in development have or will have the ability to distinguish the difference between wind turbine returns and those from real aircraft in the surrounding airspace. Using this data, the radar can then present the information in various ways.

THIS INCLUDES… • Blanking the radar returns whilst showing aircraft returns

• Dimming the clutter associated with the wind turbines whilst also showing aircraft returns


Wind turbine clutter is the appearance of unwanted radar returns on the operator’s screen that are caused by detectable wind turbines. On standard primary surveillance radar (PSR), this clutter could be interpreted as a hovering helicopter, or an aircraft flying in and out of the radar’s detectable range. Clutter is also sporadic in nature and the detectability of wind turbines will depend on a number of factors including wind speed and direction, turbine size and the intervening terrain to name just a few.

TAKING APPROPRIATE ACTION In accordance with CAP 493- Manual of Air Traffic Services Part 1, it is stated that a ‘a position symbol which cannot be associated with an aircraft known by the controller to be operating within the airspace concerned shall be considered to represent an unknown aircraft.’ The action taken by a radar operator will vary based on the category of airspace and its proximity to known aircraft. In general, ATC may consider the area of clutter, alert a pilot and then decide on appropriate action.

that, to a radar operator, looks like that an aircraft transiting airspace. In this instance, some radar will estimate bearings and speeds for several rotations of the radar even if the turbines cease to be detectable. Again, a radar operator may choose to take or offer appropriate action to pilots in the vicinity of the clutter.


In some instances, mitigation can be applied to remove the clutter from the radar screen. Both technical and non-technical solutions exist, all with various benefits and drawbacks. The main solutions are presented briefly below. It is important to consider that not all solutions will be viable for a proposed wind development.

Layout Optimisation – by assessing the intervening terrain and landscape obstructions, it may be that a turbine can be re-located to remove it from line of sight to a radar. Alternatively, a reduction in tip height may also produce the same result. A combination of these techniques can be used to ensure that the largest possible turbine can be developed without affecting the surrounding radar infrastructure.

• Showing the clutter returns from the radar at a very high resolution, thus less of the radar operator’s screen is subjected to wind turbine clutter, allowing for a clearer picture of the airspace

There are number of wind turbine radar mitigation technologies being developed that are likely to be the next technological milestone for the mitigation of new wind developments on existing radar. These technologies however are yet to gain approval from the Civil Aviation Authority (CAA). If this were to happen, then it is likely that the wind turbine radar issue would become less of a problem in the UK.


Wind turbines can produce clutter, an intermittent distraction for air traffic controllers and potential safety hazard to aviation. There are a number of mitigation solutions available to wind developers and aviation stakeholders – these will become increasingly relied upon as the number of appropriate site locations without radar constraints reduces.

Pager Power


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