Wind Turbine Plan at East Midlands Airport!
 

I could not believe my eyes when I read this:-

Wind Turbine

AOPA have I believe in the recent past objected (successfully) to a plan to install wind turbines in the circuit of a general aviation airfield on the grounds that the turbulence in the lee of wind turbines pose a hazard to aircraft nearby which are in the critical stages of take and landing.

Do wind turbines generate turbulence? I would have thought that as they are driven by the wind rather than driving the wind, there wouldn't be any (very little) turbulence. I stand to be corrected though.

Hachet Harry,
turbines certainly do produce turbulence. I believe it takes around 10 blade diameters downwind for the freestream windspeed to recover, so the turbulence caused would probably extend a similar distance. don't quote me on that though! 31.5m height doesnt sound very much though - large (~2MW) turbines are something like 80m blade diameter, with the tips reaching to around 100 or 110m above ground . so these are relatively small. Which suggests that they've perhaps done their homework? Flip side of small turbines, of course, is do they produce enough electricity to make them worthwhile? But if they don't pose a hazard to operations, i'd say support them - even if they only make a small practical contribution, they may be valuable to the industry from a PR point of view.

A wind turbine blade is essentially a wing - with the wingtip typically travelling at some 200 knots.
Wind turbines normally have to be separated by 6 rotor diameters otherwise there is a severe risk of the turbulence from one causing sufficient blade flex in the next to hit the supporting column.

Has anyone at EMA even considered the effect of aircraft wake on the turbines? :uhoh:

s&r: they state 13.5m blades - a 27m diameter rotor could produce around 200kw at peak. This does not make much sense with a height of 31.5m though - could it be that the 31.5m is height to hub?

They are supposedly 460m from runway. The 10D figure you mention is not the limit for turbulence - it is the generally accepted breakeven distance for loss of power due to turbulence and the extra cost of cabling for greater separation.

BillS, you're right - the 10D was for power loss considerations, the turbulence was just a guess based on that.

the airport's proposal's at http://www.eastmidlandsairport.com/d...ne-handout.pdf

shows 31.5 as hub height, 45m ground to blade tip. looking at the location, i'd guess they're unlikely to cause turbulence problems in a southwesterly, given the hangars to the northeast. but there appears to be nothing between them and the western end of the runway (17 diameters away), so in a southerly/southeastery wind it would depend on how far the turbulence lasts downstream.

The CAA's advice is that turbulence is unlikely to be an issue for any aircraft remaining 500ft+ away from turbines.
NS

I'd be more interested in knowing what the implications are for radio navaids at the airport, bearing in mind that the rotating blades of turbines are known to disrupt the normal path of radio signals. In some cases it has been necessary to build TV relay stations due to the effect on TV transmission, and MoD have objected to some developments due to concerns over radar blocking.

Beam bending's far more of a problem with static objects than moving ones. You'll probably find the control tower at EMA has more impact on navaids than wind turbines. And they won't have got this far without investigating all of that closely.
NS

No! It is the moving field due to the rotation that causes the problems. There are many references for this, e.g.
http://ieeexplore.ieee.org/iel5/6373/17053/00788348.pdf
quote:
"To a receiver of electromagnetic signals in the vicinity of a WT [wind turbine], the rotating blades act as a time varying multipath source. As a result of the scattering from the blades the total signals received are generally amplitude and phase (or frequency) modulated. The former being more dominant for slow moving WTs. These extraneous modulations of the desired signal, if sufficiently strong, can adversely affect the performance of an electromagnetic system."

But read on in that very same paper you quote and you will find, in the discussion of effects on VORs:
The CAA has also advised in CAP 764 that navaids are reckoned to be sufficiently protected from wind turbines by applying the normal CAP 670 site safeguarding criteria for static objects. The most stringent of these are for localisers, extending to 1500m from the aerial. But EMA will have done all this in finding a suitable site for their turbines.

NS

I'm rather surprised that radar is not affected - I understand that NCL (along with NATS & MoD) have objected to turbines over 10km from the airport.
OK on effect of the turbine turbulence - but what of the effect upon the turbine?

MoD have objected to certain wind farm developments that would interfere with their radar, and last year there was a formal objection from Bournemouth airport to the development of wind turbines on the Isle of Wight for the same reason.

Now I aint an engineer but this is the way it was explained to me.
A pure radar picks up on anything solid that is within the path of the radio beams.
The majority of what a Radar picks up is not normally required for air traffic control (buildings, bridges,weather etc).
The pure Radar picture is therefore filtered by a processor which picks up particularly on angular velocity ( ie how quickly a target moves within its scope.)
This means that an Air traffic controller can sit at their Radar screen and be confident that the returns that they view are aircraft moving around the airfield.

The angular velocity of a wind turbine confuses the processor into believing it might possibly be an aircraft and so produces a radar return, it cannot be disregarded because the return received might actually be an aircraft.
Anyone still following me???
The effect, I believe is not just around where the wind farm is situated but due to reflections could be for many miles around.
This is the most likely reason for an objection to a wind farm being placed close to an airport.
My apologies to the engineers on this thread but this is the way the teccies I work with explained it to a simpleton like myself.
Ps. as a result of this sort of thing, Glasgow airport is having to get a second radar to "fill in" the bits its normal radar is now missing.

Fact is, it displays the collosal stupidity of those who even consider the idea of placing these turbines anywhere near an airport. With any of the previously mentioned risks being possible, why are the planning authorities even thinking about allowing these inefficient monstrosities to be installed there.
Another problem installation is currently with the planners on the Island of Lewis, where they are planning one of the largest windfarm developments in Europe, with turbines around 400 feet high!
Guess where they'll be situated? Immediately below the procedure for Rwy 18 at Stornoway.
Do the planners worry about this? No - not if it creates 3 jobs and produces enough power to boil Mrs. Mcleod's kettle once a week!
Unfortunately the whole culture of windfarms has become a runaway train fed by the combination of the greed of the power companies for huge subsidies, and the PC Greenies who have no interest in any facts asscociated with these things.
End of rant!

Relevant pages on the BWEA website (beware industry bias),

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

IMHO, the daft proposals get squashed early on by CAA/MOD/SRG etc, etc. Reading the links in this thread it does appear that East Midlands have consulted on the aviation issues before going public.

Has anyone actually tried landing an airliner down wind of a turbine, or is speculation all we have?

Some of you are getting a bit carried away here. No inside info on this one but I suspect EMA have discounted effects on their radar because (a) no aircraft would normally be getting a radar service immediately around the location of the turbines except possibly some transiting through the overhead and (b) they would disappear in the radar overhead anyway; (c) the turbines are well away from the approaches and climb-outs and (d) they're well inside controlled airspace so the chances of them representing pop-up traffic or infringers are virtually zero. They'll probably just blank out those cells of the radar just like they would if, for example, they had persistent road traffic clutter in a location like that.
NS

I would just like to highlight a few facts i found after careful research into scientific journals.

A. The turbines are more likely to be affected by wind turbulance from the planes than the otherway round, but this is not a significant risk to turbine performance.
B. A responce to 'BILLS' comment; turbines are seemingly not required to be placed 6 rotor diameters apart but more like 4.5-5, and this overcompensates for any wind disturbance anyway.
C. Army Radars will be affected yes, obviously. Although with the volume of radars dotted all over the country one area affected will easily be covered by about 2 more radars from other angles.
D. Turbines situated at the stated areas of the airport are almost more safe than any others further away. Planes will not fly along the sides of the runway or the airport - only down the actual runway and so will have less chance of contact even with them being closer.

Obviously this is a biased opinion as i feel wind energy is one of the few ways we can develop without the need for building more nuclear power stations (which won't even be ready untill about 2020 - and what will we use untill then - more dirty coal stations, oil which is running out and gas from russia???)

Just an opinion which i hope people will recognise.

Dave.

There are many Wind Farm proposals held up by aviation objections (I've been quoted 80% of all objections are aviation based). MoD deals with approx 1000 enquiries each year, they are generally pragmatic, but the process is slowed by Defence Estates who are a nightmare. NATS are pretty good, and mainly concerned with En-route radars. Most airports are concerned about anything that falls inside their 30km safeguarded area. The impact on PSR is significant, clutter, false plots etc.

I believe that NEMA have put a significant amount of energy into the technical aspects of this application.