In my post on Safeguarding aeronautical communications from windfarms, I said that I would try and understand more on significant work and report back, because the official guidance was quite limited and it It was clear to me from my own projects that work had been done but frustratingly nothing published.

The Aviation Management Board Meeting held at MOD, Eskmeals on Thursday, 18 July 2013 gave a hint of the work in progress. The public minutes from the meeting contain a reference regarding work done:

“NATS was funding this £1.8m research programme over two years. It has five aims: to build on earlier work; to develop scientifically credible evidence on detrimental effects; to determine operational impacts; to develop guidance material; and for NATS to develop software tools to assess wind farm applications. QinetiQ and Pipehawk were the main contractors and the work would be undertaken at the Shooters Bottom and Red Tile sites. The research was due to start in August and run until the end of September 2013. The software would be developed by January 2015. The guidance document would need to be timed to fit in with CAA’s CAP schedule.”

So nothing tangible yet, although it turns out that NATS have published some of the trial data in an FAQ in relation to a windfarm planning application, but it is a little obscure as it only seems to appear on the Preston Council planning portal rather than being more prominent on NATS website. The FAQ confirms a little on the nature of issues and notes whilst measurements have been done, notably at Shooter Bottom Farm 2009 and Goonhilly in 2007, that there are no concrete criteria, and more work needs to be done.

Since this post was created in 2014 the FAQ link to Preston City Council planning portal in respect of AGA impact no longer functions, so I attach a copy of the FAQ from my archives. This cites a NATS internal report from December 2009 concerning Shooters Bottom Farm Field Trial which yielded an RCS of 48.6 dBm² in the back scatter region and 54.9 dBm² in the forward scatter region at VHF for a turbine of hub height 65 m and tip height 100 m.

Finally in 2019 CAP670 was updated in a more comprehensive way and now contains “Appendix A to GEN 02: Methodology for the Prediction of Wind Turbine Interference Impact on Aeronautical Radio Station Infrastructure”, which is what I presume is the culmination of this work that was due in 2015. This section includes specific methods and planning figures that can be used in make safeguarding assessments. The RCS planning figure for a large industrial turbine is 41 dBm² at VHF in the back scatter region and 51 dBm² in the forward scatter region. These figures are significantly lower than the Shooters Bottom trial, so presumably reflect other data perhaps of a more statistical nature.