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fireflybob
5th Sep 2007, 08:25
I could not believe my eyes when I read this:-

Wind Turbine (http://news.bbc.co.uk/1/hi/england/leicestershire/6979032.stm)

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.

Hachet Harry
5th Sep 2007, 14:24
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.

stick&rudder
5th Sep 2007, 14:38
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.

BillS
5th Sep 2007, 14:39
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:

BillS
5th Sep 2007, 15:01
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.

stick&rudder
5th Sep 2007, 15:49
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/documents/wind-turbines/ema-wind-turbine-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.

NorthSouth
5th Sep 2007, 17:59
The CAA's advice is that turbulence is unlikely to be an issue for any aircraft remaining 500ft+ away from turbines.
NS

Sallyann1234
5th Sep 2007, 18:24
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.

NorthSouth
5th Sep 2007, 21:07
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

Sallyann1234
5th Sep 2007, 21:39
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."

NorthSouth
5th Sep 2007, 22:17
But read on in that very same paper you quote and you will find, in the discussion of effects on VORs:
The analytical procedures employed are logical extensions of those the FAA (Federal Aviation Administration) found acceptable in the case of static scatterers and showed that the interference when the WT blades are rotating is less troublesome than when the blades are stationary.

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

BillS
5th Sep 2007, 22:30
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?

Sallyann1234
5th Sep 2007, 22:37
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.

Bagheera
6th Sep 2007, 05:29
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.

Bigscotdaddy
6th Sep 2007, 09:19
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!

dontpickit
6th Sep 2007, 09:42
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.

ZeBedie
6th Sep 2007, 10:41
Has anyone actually tried landing an airliner down wind of a turbine, or is speculation all we have?

NorthSouth
6th Sep 2007, 17:25
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

dave10101
8th Sep 2007, 03:41
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.

danieloakworth
26th Sep 2007, 10:11
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.

GOLF_BRAVO_ZULU
26th Sep 2007, 12:06
Bagheera, you explained the Moving Target Indicator principle quite well and that is the problem with mill blades and primary RADAR in line of sight.

dave1010;

your para C. Primary RADARs don't cross reference with other RADAR heads. The display shows what the head sees (Army!?).

your para D. Had there been a non frangible windmill on Phuket aerodrome, it may well have stopped OG 269 from veering into the embankment.

cwatters
26th Sep 2007, 12:50
I suspect that the MOD are worried about their radar not detecting very low flying aircraft and missiles. Perhaps not a problem in this case because radar dish could be placed the other side of the WM?.

aviate1138
26th Sep 2007, 12:55
The point is, Wind turbines are a Political Sop and generate little energy and cost a fortune [offset by our Taxpayers subsidy via the Labour Government] and are an eyesore to boot. If ever we needed a sign that the country is losing its marbles then it is the Greens insistence that renewable energies are so much better than Coal, Oil and Nuclear power sources. Modern Coal powered plants would enable energy at the flick of a switch [ for those cold nights that will inevitably come, usually accompanied by still air [so no pathetic wind power output then?] and if history confirms Climate Change as a natural event and not Man Made, then all those squillions of pounds in Carbon Offset/Trading/Claptrap will have been thrown down the proverbial drain - instead of making roads smooth, building new houses, educating our children, cleansing our hospitals etc.
There is no Political Party for those who think "Global Warming" is a con and that we should remember that the Middle Ages rejoiced in much warmer weather than we have now
and no one was driving cars or flying 747's!!!!
CO2 is not a poison - trees/plants die without it.
Final point - removal of 24 hour "Breaking News" would be a huge bonus and would help avoid the scaremongering to which we are now subjected.
Yesterdays "Tornadoes"??? [Squall line] had cameras Zooming in on 6 tiles laying on grass as proof of a 'disaster in the Midlands'
When will the hysterical madness fade away and sense and sensibility return? :rolleyes:

Skycop
17th Feb 2011, 23:18
I understand that the EMA wind farm construction is now well under way.

How badly will this affect the locally based air ambulance unit? A little bird tells me their helipad is less than 200 metres downwind (i.e. of the prevailing wind) of the turbines and they aren't happy bunnies. A no-fly zone has apparently been declared (yes, at an airport!) and this will prevent their normal Class A departure path. :confused:

Piltdown Man
18th Feb 2011, 11:43
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.

I totally agree. A short time ago we were approaching AMS over Flevoland (to the East of PAM) where each "new" farm appears to have it's own turbine. The whole of Flevoland was covered in dense but shallow fog and we could plainly see the wind turbines poking through the top. What was interesting was that each turbine not only disturbed the air directly downwind but the entire downwind quadrant. The distance affected appeared to be approx. 10 blade diameters. How much the air was disturbed I don't know, but you could clearly see the effect of the turbines on the fog and by implication, the surrounding air.

PM

DERG
18th Feb 2011, 12:01
aviate1138

Right on!

BillS
18th Feb 2011, 17:43
The real scandal is the NIMBYs.
Not the ones you would imagine.

The Dept Energy & Climate Control ministers; Chris Huhne (lives in Hampshire) Charles Hendry & Greg Barker (who live in East Sussex)

The big scandal is the DECC NIMBYs, the three DECC ministers.

We are all told we must get 30% of our electricity from renewable sources - most from on-shore wind.

So Hampshire uses 682MW but 0MW approved from wind
East Sussex - uses 224MW, approved less than 3MW

But compare that with others:
Northumberland - uses 172MW - approved 272MW of wind
East Yorks - uses 184MW - approved 108MW
Cornwall - uses 307, approved 156
Cumbria - uses 315, approved 133
Lancashire - uses 589, approved 136
Lincolnshire - uses 395, approved 84
Northamptonshire - uses 386, approved 83
Cambs - uses 367, approved 153
Durham - uses 231, approved 147

And these counties have much more in the pipeline - nothing where DECC ministers are living!

Using their own statistics (https://restats.decc.gov.uk/cms/welcome-to-the-restats-web-site)

Clearly the message is NIMBY - or Not In My County!
But they'll force them in everywhere else and accuse others of harming children's futures.
So much for Climate Change responsibility.