Interferance From Wind Farms
 

Hi Guys & Girls,

Could someone please explain to me why a wind farm could interfere with the ATC systems, the only thing I could think of was a possible interference to radar, possibly some EMF interference or line of sight communications?

It’s been a long time since I sat my exams and I fly rotary so it’s not an area of aviation I deal with. Could someone else please shed more light on this?

I am asking because a planning application has been made to build a wind farm with in 500 meters of the village I live in, naturally the people from the village are against it but also BAA opposed it about a year ago, since then revised plans have been re-submitted for this wind farm. I just wanted to get my head around the reasons why it could interfere with ATC systems etc.

Thanks in advance TTTE.

BAA has nothing to do with ATC technical matters so far as I am aware but, as always, I stand to be corrected. The only thing I can possibly think of is if a radio or radar station was located very close by the phenomena of propellor modulation might occur, although I very, very much doubt it... and this would be no concern of the BAA. If you fly choppers you'll know more about prop-mod than me!

http://www.bwea.com/aviation/radar.html

There are links to the report at the bottom of the page. I've worked in a couple places where wind farms are a problem for radar.

That's very interesting - thanks av8boy.

You are most welcome, sir.

This too
http://www.caa.co.uk/docs/33/Cap764.pdf

Airport operators will oppose Windfarm proposals on the advice of NATS (if they are the airport ATC provider) if it is likely to affect airport ATC operations. NATS are only operating ATC on behalf of the airport authority so can't oppose.

NATS will oppose proposals themselves if the site is likely to affect Primary Radar used for enroute services.

Rather than links, why not say
"the rotation of the blades on a wind turbine and its associated structure appear on radar as a stationary, or slow moving primary radar return, thus being very difficult to disinguish between a primary return from a moving aeroplane or a permanant echo".

That said, BAe have developed new technology for radar which assists in precluding the above problems.

My understanding is not all the effects of windfarms on radar are fully understood, especially SSR where you have effects like backscatter and shadowing, so there is a zone around radars within which any windfarm application will be objected to. As for the BAE solution this is still some way off and will need to have some money thrown at it, although the Americans have just placed a mighty big order with Raytheon for primary radar so it could be that a solution comes from that (red)neck of the woods.

"the rotation of the blades on a wind turbine and its associated structure appear on radar as a stationary, or slow moving primary radar return, thus being very difficult to disinguish between a primary return from a moving aeroplane or a permanant echo".

Would the old-fashioned MTI not take them out?

Unfortunately wind turbine blades have a similar RCS (radar cross section) as a small plane and the blades move at a similar speed, so there is no way to get the MTI to filter them out.

what about RAG maps?? they would work....

What are RAG maps please?

Range (or Radar) azimuth Gain. You could specify areas of adjusted gain on the Watchman radar for certain areas that were known to give PEs in certain met conditions. We had 5 'RAG maps' I seem to recall for differing situations. They took out things like wind farms, I'm sure

I actually did consider saying "MTI can't cope with multiple wind turbines," but opted for the links because there was much more info and I didn't want to try to reduce this to something more simple than it deserved.

The returns don't just show as slow moving....I've witnessed, several times, windfarm reflections on a Watchman primary which showed as a large, solid contact appearing out of our overhead and tracking away at huge speed...we measured the intervals and worked it out as Mach 5 or so - most unsettling the first time, and we were wondering if the US Mil were doing something scary!!! When the engineers explained the real reason it was a bit of an anti-climax...

Thanks for all your help guys.

The concern with windfarms is that they absorb radar energy, creating a shadow within which the radar signature of any plane is reduced/removed.

But you might say so do all reflective surfaces? True, the problem comes as said above, the turning of the blades means the windfarm turbines break through the MTI supression (after all if windfarms didn't show up then neither would a hovering helicopter?). These primary returns present clutter on the screen that can hide the return of a real aircraft; so ATC have to limit any radar service being provided to an aircraft in their vacinity (because you cannot tell if a conflicting track is about to pop out from the clutter)... a wise controller might give this clutter a wide berth, or put another way ATC delays!

There is circuitry that will remove these returns (e.g. RAG Maps as mentioned) but this is done at the degradation of the radar picture (which may or may not be a localised effect?) and again the service should be limited i.e. NOT as good as it MIGHT be!

So, within the world in which we live, ask yourself this question. If you were given the responsibility of signing off an application for another windfarm close to your airfield, in the knowledge that this might mean you have to reduce the service you are providing to aircraft, whose companies might sue if there is an accident (not to mention the hundreds of bereaved families of those onboard)... do you; or would you raise an objection against the planning proposal (which is logged as "we didn't want it, but someone else forced it upon us")...

What do you think?

hehehe so the cover story is still working then :}

Wind Farm Interference
 

Hi

The main issue is interference with Primary Radar.

Wind Turbines can create clutter because the blade tips are travelling at speeds of around 100 knots which mean that they get through the filters that remove static objects.

Other concerns relate to physical obstructions, potential interference to SSR and a few other things like Nav Aids and ILS.

In general concerns can be overstated - I have to declare a bias - I work for a consultancy that helps wind farm developers overcome these issues.

Hope this Answers your question.

You can find out more at www.pagerpower.com and www.bwea.com/aviation

Regards

Windfarmer