13 Jun The dangerous relationship between wind turbines and aviation

Wind turbines are becoming increasingly popular as sources of renewable energy. And just as with airports, the preferred locations are far enough away from populated areas to minimise nuisance. If placed too close to airports, however, they create hazards to aviation, only some of which can be mitigated. Here we examine four issues, other than the widely discussed issue of interference with airport radar and radio, that are central to the topic.

The problems are greatest for general aviation and at heliports

Growing trend

Around the globe, governments are placing more and more wind farms to help meet renewable energy targets. Not only is their number multiplying; as the technology develops, wind turbines are also growing taller.

Only some of the hazards of wind turbines placed too close to airports can be mitigated. If their location means air traffic operating to and from the airport cannot be handled safely, the only option is placing the wind turbines elsewhere.

What exactly are the issues?

For large airports, where proper spatial planning provides for a correct application of obstacle limitation surface regulations, hazards from wind turbines nearby are relatively minor. The problems are greatest for general aviation and at heliports.

Wind turbines are obstacles

The low-level airspace around an airport’s runway or at a heliport that is needed for aircraft to climb or descend must be protected from obstacles, especially in case of engine loss. Like buildings, wind turbines are obstacles and should, as a rule, not be permitted to penetrate the obstacle surface.

Obstacle Limitation Surfaces (Source: CAA UK)

Wind turbines create turbulence

As the blades turn to generate power, they create turbulence downwind. For large, heavy transport aeroplanes, this turbulence is not a great threat. For smaller general aviation aeroplanes and helicopters, passing behind a wind turbine introduces turbulence that can, in extreme cases, cause an unsafe flight.

With turbulent air being produced only when the wind turbine is operating, this hazard is easier to mitigate at a low-intensity heliport, for example, than a busy airport. The jury is still out as to what is a safe distance for aircraft to avoid turbulence from wind turbines in operation. Conservative estimates currently prescribe up to six times the turbine’s diameter.

Wind turbines can just be in the way

A wind turbine that does not penetrate an obstacle surface or introduce turbulence may still present a special hazard for helicopters and general aviation due to its position. For example, wind turbines placed close to the point of a turn in an approach flight path might block critical visibility for the pilot during a manoeuvre close to the ground.

Whilst this specific hazard is admittedly subjective, case-by-case safety solutions could be defined with good communication between aviation and wind energy stakeholders.

Wind turbines are bright lights at night

This issue is complicated by the interests of a third party: the local community. Aviation stakeholders expect wind turbines to be marked with lights as per international requirements, but the wind energy sector is very conscious that local communities find the lights a nuisance.

Automatic detection systems that activate obstacle lights only when aircraft are in the vicinity are probably the best technological solution available today. However, balancing aviation safety and the wishes of local communities is something all parties, including regulatory authorities, must work on further.

Working out obstacles

When planning wind farms and turbines near airports, it is critical that planners and energy companies work together with the airport and air traffic management to analyse each individual issue for aviation operations and to find ways to avoid or mitigate them.

Using a tool such as OLET, for example, can help determine workable obstacle limitation levels around the airport, and airspace analysis and planning can help pinpoint critical points under flight paths to avoid or change.

About To70. To70 is one of the world’s leading aviation consultancies, founded in the Netherlands with offices in Europe, Australia, Asia, and Latin America. To70 believes that society’s growing demand for transport and mobility can be met in a safe, efficient, environmentally friendly and economically viable manner. To achieve this, policy and business decisions have to be based on objective information. With our diverse team of specialists and generalists to70 provides pragmatic solutions and expert advice, based on high-quality data-driven analyses. For more information, please refer to www.to70.com.

Adrian Young

Combining safety and efficiency in civil aviation is a key part of our work. With a passion for aviation and aviation safety, I have contributed to safety improvements for airlines and at airports in Europe, Africa, Asia and Australia. Projects range from major hub airports to remote operations from dirt runways. When relaxing, I can be found in the artist’s studio, where I sculpt in stone.