Offshore Wind Farm Helicopter Search and Rescue Trials

2 Radar cross section of turbines

The wind turbine generators (WTG) are very large structures in the vertical plane and significantly so in the horizontal plane. Although the towers are cylindrical, their diameter of about 5 metres and height above the water – around 70 metres - is such that they have a comparatively large reflecting surface area. This is compounded by the reflecting surfaces of the platforms, ladders and other structural features of the towers, an average total of about 80 square metres at any time and from any direction. The three bladed rotors have a total reflecting area of around 200 square metres when their plane is at right angles to the direction of the radar scanner, and around half that when in line with it. The nacelle and boss have reflecting areas of up to 16 square metres. Thus in the vertical plane the North Hoyle WTGs, similar to most other types, may from a particular direction have a radar reflecting area of around 300 square metres.

Fig 4 : North Hoyle Vestas turbine