The assessment of the impact of wind turbines on the electronic infrastructure required to operate an air traffic service is complex and dependent on a wide range of factors – many of them statistical rather than fixed in nature. When NERL (NATS En-Route PLC) carry out an assessment as to the potential impact of proposed developments this is done using the latest understanding of industry best practise and a range of in-depth analysis tools are employed.
It is not possible to replicate this process in a simple diagrammatic format; however the following maps have been designed as an aid to developers in understanding where interference with NERL infrastructure is likely. They do not represent an exhaustive list of the areas where there is a potential impact to NERL’s infrastructure nor do they represent no-go areas where NERL will automatically object to proposed wind turbines.
For each of the 54 air-ground-air (AGA) communication stations, 55 navigation aids and 20 secondary surveillance radar operated by NERL a consultation zone has been provided; 10km for the air-ground-air communication stations and navigation aids and, in line with CAA publication CAP764, 15 nautical miles (nm) for the secondary surveillance radar. Upon receiving a turbine planning application these are the ranges within which NERL would carry out an in-depth assessment for equipment of these types.
CAP764 Appendix 2 details a simple line-of-sight method to assist in determining whether a further more detailed assessment needs to be carried out in relation to primary surveillance radars. To aid developers with this task, a number of maps have been produced corresponding to turbines with tip heights from 20 to 200m describing the areas where turbines of the relevant height would be within line-of-sight of at least one of the primary surveillance radars operated or used by NATS En-Route.
Please note that in some cases, NATS take a data feed from an airport radar to provide an en-route service from one of its centres. An example of this is Glasgow radar providing data to the NATS Prestwick centre, as well as serving the airport itself. It is important to appreciate that this can give rise to the situation where two stakeholders can make conflicting statements based on the same asset. For example, Glasgow airport may state that there is no impact upon its airport radar due to a specific development, but NATS may object to that same development based on the impact on Glasgow radar.
This can happen because the radar’s coverage is used by the Air Traffic Control units to provide a service in different areas; as such a specific turbine may impact one but not the other operator. Obviously, the converse situation is also possible, whereby NATS states there isn’t an issue, while Glasgow airport objects.
These maps are made available in order for applicants to ascertain whether their proposed development is anticipated to have an impact upon NATS En-Route’s infrastructure and operations. It does not consider airports. Although some airport radar cover is included in these maps, such as Glasgow and Edinburgh, it is only because these radars are fed into a NATS centre.
Whether the impact upon an airport is acceptable or not, can only be determined by consulting the airport in question. Where the airport has agreed provision of a pre-planning service with NATS, this information can be obtained by undertaking a pre-planning assessment (refer to the pre-planning page).
Please note that when producing the maps, the earth’s radius was extended by a factor of 2 in order to take into account simple ‘over the horizon’ effects as discussed in section 5 of the appendix. No attempt however was made to take into account the detailed diffraction geometry of any specific locations.