Wind Power in the UK (PDF). - Sustainable Development Commission

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Wind Power in the UK (PDF). - Sustainable Development Commission

Annex C: Aviation and communicationEffects on SSRBecause SSR operates on the basis oftransmissions both from the radar to the aircraftand from the aircraft back to the radar, thereturned signal is much stronger than in thecase of PSR. It is therefore much less vulnerableto interference from wind turbines. Beamdistortion, caused by scattering of the signal bythe wind turbines and leading to target positionerrors or false interrogations, is another effect.Studies in the Netherlands, Ireland and the UKhave found that wind turbine effects on SSR arenegligible for a wind farm located 5km or morefrom an SSR station. NATS En Route, whichoperates SSR at all of its radar stations (repeated)is also notable that the impacts of wind turbineson SSR have been found to be generated by theturbine towers, not the rotating turbine blades. Inthis respect the impact of wind turbines on SSR isno different in form to that of other tall structuressuch as chimneys or high buildings. 1ATC around airfieldsMost military airfields and commercial airportsare equipped with PSR, which is used bycontrollers to guide aircraft after take-off, toguide incoming aircraft to the runway, and tomaintain separation for aircraft operating in thevicinity of the airfield.For these radar systems, a wind developmentlocated beneath the departure track or the finalapproach track, or in an area where aircraft arefrequently routed (vectored), may createparticular problems for controllers. Aircraftvectored across the wind farm area may not bedistinguishable from the radar returns producedby the wind turbines. Depending on the level ofradar service being provided, aircraft may haveto be vectored away from the radar returnsproduced by the wind turbines.This can result in aircraft having to fly longerdistances, inability to maintain the standardseparations between aircraft and, in severecases, may preclude the provision of a radarservice altogether.These difficulties are most likely to occur whenthe wind farm is located in uncontrolledairspace, that is, airspace where any aircraft mayfly without obtaining permission from ormaintaining contact with any ATC agency. This isbecause in this type of airspace it is more likelythat an unknown primary radar return – forexample from a wind turbine – could be a realaircraft, and therefore may require radarcontrollers to vector aircraft around it. Mostmilitary airfields and the smaller civil airportsand airfields are in uncontrolled airspace.Airport radars typically provide services out to arange of approximately 40nm (74km) but anyimpacts from wind farms are likely to be limitedto projects within a significantly closer range.Statutory safeguarding arrangements are inplace around most commercial airports. Most ofthese require pre-planning consultation for anywind farm proposal within 30km. However,objections from airport operators may beencountered at greater ranges when the windfarm is in a key area of ATC operational interest.In addition, because responsibility for civilairport safeguarding has been transferred fromthe central regulatory authority, the CAA, toindividual airports, policy and practice on windfarms can vary significantly from one airport toanother.En route ATCControl of aircraft in the en route phase of flightis carried out by controllers employed byNational Air Traffic Services (NATS), based at fourcentres at Swanwick, West Drayton, Manchesterand Prestwick. In addition, en route controllersprovide radar services to military aircraft, often140 Wind Power in the UK sustainable development commission

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