There needs to be some sensible policy guidance on this, if objections are raised at the planning permission stage it is far too late.

There is likely to be a tolerable interference level which can be filtered out or localised, acceptable from the perspective of the air defence system.....multiple radars, E3 gap filling etc can cover when needed...add to that operator training, to watch for that suspicious plot entering the wind farm zone!

Of more concern would be interference in overland and low flying training areas. There is a case for keeping wind farms distant from these areas for very understandable flight safety reasons!

Is there further information in the public domain? I think I grasp how the interference or spoofing would occur, but to what extent? How similar is the doppler shift from a rotating wind turbine blade to a fast moving jet aircraft, for exampe? How big are these blind spots? What is the position of the CAA? As I understand it they require consultation on windfarms within 30km of an aerodrome.

I thought the most interesting bit was...

"This obscuration occurs regardless of the height of the aircraft..."

Presumably this also applies to civilian radar ?

Civilian radars predominantly work in a co-operative environment, namely the aircraft squawk mode 3A/mode S etc. The effects of wind turbines or other factors affecting primary radar are of supreme indifference to them.

Which is one reason why the AD system cannot solely rely on the ATC system - if you want to know why read the 911 report.

This issue is being looked at on this side of the pond too. Site below has some info and interesting links.

http://www.eere.energy.gov/windandhy...terference.asp

hope the link works. If not type it in :}

Cheers, Bob C

The CAA have been working on this problem for quite some time, so it shouldn't be a surprise to government. The following document is dated July 06:

CAA Policy and Guidelines on Wind Turbines

Chapter 2 spells out the impact of wind turbines on aviation and given the fact that civilian aviation is now more widespread than military aviation (even low level radar coverage over the sea for oil rig operations is important), it's strange that just military objections are being noted.

Perhaps the problem for the military isn't detecting aircraft but also cruise misiles and the like.

I wonder if they've tried radar absorbing paint on the blades?

Edit: Seems the Americans are... "Coating equipment with absorbent or reflective materials to minimize the turbine's radar signature"

The CAA will not (generally) protest against windfarms; they will mitigate any potential risk by providing dispensation to allow aircraft to be controlled on SSR only. Fine for the UK military if the Queens enemys only operate in controlled airspace and cooperate by transmitting an SSR code.............. :}

Whoever designs the first Stealth wind turbine will be quids in!

A raw doppler displayed on a radar screen displays the speed of the contact relative to the receiver. An F4 on an AWG12 radar would show as a largish and solid return (IIRC) but there would be a line of contacts on the same bearing in front and behind as each turbine blade as a given instant would have a higher or lower doppler shift in relation to the aircraft in which it was mounted.

Modern processing presents the doppler return as the correct range and as a single blip in the same way as the traditional image you might have of early pulse radars as beloved by film producers and the like.

The processing algorithyms can filter unwanted echoes, such as that from known windfarms, but also filter out wanted echoes that match the filter criteria.

The doppler return from a target flying tangential to a radar receiver will have exactly the same doppler value as a static target on the ground.

Doppler and filters are not, in thenselves, as complete answer.

If turbine blades (is windmill too old fashioned?) didn't follow the wind around, the problem would be more containable. A turbine pointing axially at the RADAR head would return negligible doppler shift whereas one presented at 90 deg would return the maximum for the rotation rate.

Depending on spacing, do blades reflect and return from each other, thus multiplying shift values?

MoD lifts wind farm objections
 

Looks like the wind farm developers have bought the RAF a new Air Defence radar for Trimmingham. Only another dozen needed!

BBC News - MoD drops opposition to Norfolk offshore wind farms