Wind Turbines & Aviation
One of the most common difficulties in finding suitable places for building wind turbines is overcoming concerns that they will cause a problem for military and civilian aircraft. This is why aviation is one of the first issues to be investigated when assessing whether or not a wind turbine can be built in a particular location. To do this, the views of the Ministry of Defence, the Civil Aviation Authority, National Air Traffic Services and individual airport operators are always sought very early in the lifetime of the development of a site.
Broadly speaking turbines can potentially cause a problem for both military and civilian aviation in two ways: either (a) by affecting radar, or (b) by being in the way of aircraft taking off and landing.
In the UK there are two types of radar – primary and secondary. Primary radar identifies aircraft from a radar signal bouncing back from the aircraft and secondary radar identifies the aircraft by an electronic ‘tag’ on the airplane. It is only primary radar which may be affected, because as the turbine blades go round, the radar sometimes confuses the turbines with aircraft. This can be a problem for some military radar, since they are tasked with preventing terrorist attacks and for civilian radar because they are used to control and direct the movement of air traffic.
All landing strips and airports in the UK have to keep certain areas around the runway clear of tall structures, so that there are no obstacles for aircraft landing and taking off. The heights and locations of obstacles which may cause a problem vary between the different types of airstrips and airports in the country. Generally though, it is a misconception that because of their height turbines will be in the way of airplanes, since unless they are taking off and landing, airplanes need to keep around 400m above ground level – way above the 125m maximum height of a turbine.
Aside from choosing sites which aviation authorities consider will not be a problem for radar or aircraft, there a number of measures which can be taken to ensure that turbines can be built and aircraft safety is not compromised.
Such measures include:
- Reducing the overall height of the turbine, so that the radar cannot see it due to high ground hiding the turbine
- Reducing the number or orientation of turbines so that the radar display picture is not cluttered with as many unknown images
- Providing the radar with some computer software so that the turbines are not shown on the radar display and changing aircraft movements to avoid overflying the turbines
The following statutory consultees are consulted during the development of wind farms to ensure that aviation issues are fully considered during the development process:
- Civil Aviation Authority
- National Air Traffic Services
- Ministry of Defence
- Local airports
The most user-friendly document looking at wind energy and aviation was produced by the Wind Energy, Defence and Civil Aviation Interests Working Group in 2002. The document 'Wind Energy and Aviation Interests - Interim Guidelines' aims to do the following:
- Provide a clear, readable, single source of information on all aspects of the impact of wind turbines on aviation, both civil and military
- Identify the range of interactions between wind energy and aviation interests
- Outline the measures adopted to address the issues which are likely to arise from such interactions
- Identify the organisations involved in these processes
Alenia Marconi Systems Ltd produced a report in 2003, paid for by the Department for Trade and Industry (now BIS), called 'Feasibility of Mitigating the Effects of Wind Farms on Primary Radar'. This report is an in-depth study on the effect of wind turbines on radar systems and considers mitigation measures.
QiniteQ also produced a report in 2003 for the Department of Trade and Industry (now BIS). This report 'Wind Farms Impact on Radar Aviation Interests - Final Report' provides a technical discussion on wind farms and radar.
An overview of the practices adopted by various European countries in relation to wind farms and aviation is provided in 'Wind Turbines and Aviation Interests - European Experience and Practice'. This report was produced for the Department of Trade and Industry (now BIS) by STASYS Ltd in 2002.