Aviation has had to accept wind farms are a vital part of our future
Airports use radar to monitor – and where necessary control – aircraft in their vicinity. For a long time there have been two main types of radar: primary and secondary.
Primary radar is what most people think of when they visualise radar systems: a pulse of electronic energy is sent out, the reflected “return” from an aircraft is received, and the aircraft’s position displayed as a “blip” on a screen.
Secondary radar, on the other hand, sends out an interrogative signal that is received by a transponder in the aircraft, and the transponder replies with a signal that reveals not only the aircraft’s position, but its
identification, and other information like its altitude and destination. Airports such as Prestwick usually have both types.
Radar works well with aircraft, because when airborne they are the only large objects up in the sky, so they can be seen distinctly.
If aircraft are close to the ground, primary radar picks up “clutter” caused by reflection from hills, buildings, or even trees and flocks of birds, and this can obscure the aircraft’s “blip” return on the radar display.
That includes reflections from wind farm turbines. Indeed, the latter are a particular
problem because they are big, very high, and their moving blades confuse conventional radar, causing on-screen clutter that can obscure aircraft returns at low altitude.
Radar signals work in line of sight. They cannot “see” anything over the horizon – or beyond a hill – any more than the human eye can. If large objects such as wind turbines are close to a radar installation, they can render it almost useless, but many miles away they are much less of a problem.
Wind turbines are not allowed to be built close to airports because they are a collision risk to aircraft taking off or approaching to land.
Aviation has had to accept wind farms are a vital part of the world’s future, so the industry is being forced to adapt to this new status quo. Fortunately, new types of radar – generically referred to as “smart radar” because installed software distinguishes between useful returns and clutter – have been developed and are becoming increasingly widely used by airports all over the world.
Prestwick itself is installing a smart radar called Scanter, which can mitigate radar returns from wind farms and other ground clutter, but it also provides additional surveillance capabilities that bring benefits for airport management.