The perils of wind turbines to aviation

The (usually invisible) turbulence from wind turbines is a serious aviation hazard.

By Paul Hayes, Director of the Canadian Owners and Pilots Association (COPA), Canadian Plane Trade Magazine

A matter of increasing concern to our members is the almost uncontrolled spread of wind turbines across many areas of our country with, in many cases, little or no concern for the impacts on aviation.

These structures, nominally over 400 feet in height above ground, are being established either individually, in small groups or in much larger farms of over 20 or more units. In virtually every instance, there is no requirement for the proponent or authorizing authority to carry out any form of an aeronautical assessment to ascertain the potential impacts on aviation resources or local flight operations, and yet the aviation safety impacts include obstacles in the vicinity of aerodromes, wake turbulence and the lack of effective aeronautical marking and lighting in accordance with the appropriate Canadian Air Regulations and Standards.

A particularly aggressive approach to wind turbines occurred in Ontario when the government established the Green Energy Act. Prior to the passage of the legislation, COPA appeared before the committee holding hearings and petitioned to have a requirement included in the Act that wind turbine proponents or approving authorities conduct an aeronautical study to assess the aviation impacts of a proposed development and to develop appropriate setbacks and other mitigating measures.

COPA’s petition was not accepted and the final version of the Act also removed the ability of municipalities and other lower forms of government from controlling the development of these types of clean energy projects in their backyards.


The typical traffic pattern (or circuit) flown by light aircraft when maneuvering in the vicinity of aerodromes is to an international standard and pilots are expected to adhere to it when flying to and from these aerodromes.

The prescribed standard pattern is normally left hand.  This results in the pattern being both sides of the runways to allow for take-offs and landings in opposite directions.

The normal dimensions of the pattern are two km off both ends of a runway and two km abeam the runway when in the downwind.

As a variation to the standard left hand turns in the pattern, at numerous aerodromes a right hand circuit is used under various circumstances to avoid such factors as obstacles and noise sensitive areas in the vicinity of an aerodrome.

Where a circuit pattern using right hand turns is required, it must be specified in the CFS.  This, of course, requires that the aerodrome is registered and therefore is listed by Transport Canada in the CFS. The appropriate provision for the use of right hand patterns or circuits is found in Canadian Air Regulation 602.96, paragraph (3) (c).

Of note is that frequently in wind turbine development proposals, proposed sites are inside the normal boundary of a traffic pattern at the aerodromes – that is, they would be between the normal downwind leg of the pattern when an aircraft would be flying abeam the runway, as well as inside the climb out and approach patterns.

In this regard, the standard usually assumed is that, if possible, there should not be any tall obstacles between in aircraft flying in the circuit pattern and its access to the runway in the event of an urgent need for a landing. In the case of turbines located between the downwind, climb out and approach and the runway, this principle is violated, and it is therefore not a safe situation.


For some certified aerodromes (airports) that have registered zoning in effect in accordance with the provisions of the federal Aeronautics Act, the airspace around them is protected from penetration by such obstacles. For many other airports and all registered and unregistered aerodromes, there is no such protection.

Any obstacle erected in the approach or departure paths or in the circuit at these aerodromes may result in the raising of IFR minimum approach altitudes and overshoot or departure restrictions, modifications to circuit procedures or even prohibition of the use of one or more runways.

In the worst case scenario, Transport Canada could prohibit any aviation activity at the aerodrome.

It is important to emphasize that Transport Canada’s only interest in wind turbines is that these obstacles are appropriately lit and in fact they have backed away from any marking requirements, which is why you only see white turbines in Canada.

Protection of our aviation infrastructure from encroachment is not of interest to Transport Canada, other than to restrict operations when a wind turbine has been assessed as a safety issue. Wind turbines pose an additional hazard compared with other obstacles because they produce wake turbulence that can extend a considerable distance downwind.

Additional precautions are necessary compared with other obstacles such as antennas in order to avoid this silent killer. Although there has been some research into wind turbine turbulence, no setbacks have been established by regulation to ensure aviation safety in the vicinity of wind turbines.


The only TC guidance is contained in the certification guideline in trying to provide an adequate level of obstruction clearance, Transport Canada refers proponents to use the obstacle limitation surfaces for a Code 1 non-instrument runway that are outlined in Transport Canada document TP 3 12 Aerodrome Standards and Recommended Practices, Chapter 4, paragraph 4.2.2 and Table 4.1. The standard that can be most specifically applied is the takeoff approach surface as the principle obstacle clearance criterion.

This surface is 2,500 meters long and diverges at 10 percent from the ends of the runway strip. At its outer limit, the surface is 560 m wide, and at the specified 1:20 slope, it would be 125 m above the elevation of the end of the runway.

In using just the 2,500 m long take-off/approach surface and the specified 1:20 slope, the height above ground at the outer limit of this surface would be 125 m or 410 feet. In addition, looking at this from the perspective of aircraft performance, and using a representative climb or descent angle of three degrees and a speed range of 70 to 90 miles per hour, aircraft might typically be expected to be in the order of 400 to 500 feet above ground at the 2,500 m outer end of the approach surface.

When allowance is made for the effects of aerodrome altitude and air temperature during summer operations, the altitudes attained in the climb will be expected to be not as great – for example, with reference to the Koch chart in the planning section of the CFS, based on an aerodrome elevation of about 1,500 feet above sea level and a typical summer day temperature of 30 degrees C, the rate of climb for an aircraft may be reduced by in the order of 35 percent, so that the 400 to 500 feet above ground of the height of a representative turbine at the 2,500 m point would not be reached.

As the wind turbines could be in the order of at least 400 feet in height, it is concluded that the 2,500 m distance alone would not provide sufficient safety protection if a turbine were to be located in the vicinity of the end of the take-off/approach surface. As well, the effects of the wake and turbulence from a turbine if the wind is blowing toward the runway would be most pronounced on an aircraft just at this height.

For the above calculations, the Cessna 150 and 172 types, as well as the Aeronca Champ and Piper 53 Cub, have been used as representative aircraft types. However, as mentioned above, ultra light aircraft are also operated at many of the aerodromes. These aircraft, which are much lighter, typically climb after takeoff and descend for landing at a steeper angle. Because they are lighter and often climb and cruise at lower airspeeds it is understood that there may be potential for controllability issues in turbulent conditions. The matter of the wake turbulence from the wind turbines could therefore be of more concern with these aircraft.

If the TP 312 standard for the outer surface is included in the consideration, then any obstacle higher than 45 m (150 feet) above the elevation of the aerodrome within a four km radius of the aerodrome centre point would not be acceptable. This surface is intended to protect aircraft maneuvering in the vicinity of an aerodrome. However, to test if even the four km distance from the ends of a runway would provide adequate safety protection, an assessment was completed based on aircraft performance characteristics, suitable minimum obstacle clearance of at least 300 feet above the top of the turbines, and the possible wake and turbulence effects of the turbines.

Using the same 70 to 90 mph light aircraft climb speed and the associated 300 to 400 feet per nautical mile (160 to 2 15 ft/km) climb gradient, the representative aircraft would be expected to be in the order of 700 to 850 feet above ground at the four km point. This should place the aircraft at least 300 feet above the top of a 400 foot high wind turbine, most likely to avoid the effects of the expected wake and turbulence.

From this analysis, it might be concluded that at four km from the runway ends and along the extended runway centre line there would be adequate clearance.

Information on the potential effects on aircraft of wake turbulence generated by wind turbines is quite variable. Some information suggests that at three rotor diameters behind a turbine the turbulence may be largely dissipated, while other sources suggest it may still occur at a greater distance, as much as 10 rotor diameters or more. Information available to us suggests that wind turbine companies may generally rely on a downwind distance of five rotor diameters in setting up the spacing between individual turbines so as to avoid the effects of wake turbulence on adjacent turbines.

This standard can be applied in suggesting how far a turbine should be from a low level aircraft flight path.  For example, using a five rotor diameter downwind allowance and a nominal rotor diameter of 100 m, this would mean a separation distance of at least 500 m. This would suggest that no turbine should be located any closer than 500 m outside the 2 km outer boundary of the aerodrome air traffic or circuit pattern.


In addition to COPA’s efforts to convince the Ontario government to consider the effects of wind turbines on aviation when the Green Energy Act was developed and attempts to engage Transport Canada in developing standards to minimize the safety impact on aerodromes, COPA’s Freedom to Fly Fund is being employed to investigate legal aspects to determine if there is some basis to prevent encroachment on aerodromes or provide compensation for the loss of use.

Our recent win at the Supreme Court level on federal jurisdiction is being examined to see if it is applicable to wind turbine encroachment on aerodromes. The Fund is also being used to conduct a formal safety risk assessment, in which the wind generation industry, the governments and others will be invited to participate.

The end point of this exercise will be to determine the safety risks associated with wind turbines and develop risk mitigation measures that can be employed, either voluntarily or by regulation, to minimize the risks and continue aerodrome operation.

Until a firm direction is established, members whose aerodromes are being impacted by wind turbine installations are advised to get involved early in the development process to make your concerns known. You can use the calculations from this article to point out the safety issues and encourage the proponents to minimize their liability by keeping the turbines a suitable distance away from the approach, departure and circuit areas.

15 thoughts on “The perils of wind turbines to aviation

  1. Those siting Industrial Wind Turbines in Ontario seem to believe that air space belongs to them first. So many tall structures in one area would need to be sited and contained in a city, but now plots of land and areas of water are being designated industrial expressly for these machines.
    There is a large amount of freedom of our open air spaces given up to a very few. The smaller this world becomes, the more important industrial siting becomes. It is a matter of respect and acknowledgment that we share.
    Migrating bird patterns appear to be of no concern, no any other claim to any other businesses requiring open air space.
    Dalton McGuinty has allowed reckless industrial siting to run rampant in Ontario. This is a person whose vision is clearly tunnel vision with little care or understanding for other people and wildlife.

  2. In Essex County Boralex was allowed to site turbines too close to a runway that belonged to a WW2 decorated pilot despite his objections. Many people spoke out against this travesty, the wind industry is Ontario’s dictator

  3. When one local wind industry employee was asked why wind turbines can’t be on a separate piece of land, away from any residents and lined up in rows like most people would imagine a wind “farm”, his reply was that they cannot be lined up in rows. The turbulence from the first one would cause terrible damage to the one situated behind it.
    Evidently it is of higher honour for developers and government to protect their almighty equipment rather than to worry about the homes, humans and animals in their path.

  4. Oh ya, and when he was asked what about the homes behind the turbines?… he didn’t have an answer.

  5. I shudder when I think of all the private planes and airstrips. The rural countryside is dotted with them but Sick Turbines is right – the government and turbine companies seem to think the airspace is theirs and theirs alone.

  6. Yes, and what about the birds that get sucked into the wind turbine turbulence?

    Wind developers and eco-nuts don’t care as it’s more important to save planet earth.

  7. Lets’ break this down to very simple terms: Wind Turbine Policy is based on LIES. They are supposed to save the World from Fossil Fuel Generation that contributes to Global Warming with the release of C02 emissions.

    “Global Warming” is a LIE.
    “C02 emissions cause harm to the Environment” is a LIE
    “Wind Turbines is a Free Clean and Green way to generate electricity” is a LIE

    I’ll stop there and just state categorically that when a Policy is based on LIES then it is a LIE!

    Enough said!

  8. I’m guessing this will change once a passenger aircraft is impaled on a wind turbine.

    The resulting lawsuits all around should do the trick!

    As for our government(s)’s continuing bowing to the industry… Well we all know who really governs us and it sure as hell isn’t who get elected!

    Looks like Dalton and Tim are now trying to “out-stupid” each other…

    Just what we need!

    We’re screwed!


  9. Often a wind turbine can create the turbulence of a 747 jet aircraft. Just what will happen to the birds when Ontario is covered like a carpet with ~7,000 turbines?

    Would the wind developers and the eco-nuts who back these turbines care to explain this to Ontarians?

  10. And the biggest ECO nut of all?

    Staff of the Ministry of Transportation (MTO) are being celebrated today in a ceremony held at Queen’s Park by Gord Miller, the Environmental Commissioner of Ontario. This is to recognize their Alternative Power project at Summer Beaver Airport, Canada’s first remote airport powered entirely by renewable energy. Commissioner Miller is presenting his 2009/10 ECO Recognition Award to MTO staff for their exemplary work in developing and implementing the program.

    Somehow I doubt they consulted COPA on that lunatic exercise.

  11. “Summer Beaver Airport, Canada’s first remote airport powered entirely by renewable energy.”

    I hope it’s powered by more than just wind, solar and batteries.
    Experiencing a little turbulence in on the approach would be a good thing. You at least know the air traffic control systems should be up and online.


  12. “Looks like Dalton and Tim are now trying to “out-stupid” each other…”

    Yeah, or trying to outsmart the electorate. What better way to win over Ontarians than to promise lowering the price of beer. Heck Tim, while you’re at it, why not mention lowering the price of Internet and Cable and maybe promise that the Leafs will win the cup on your watch! That’ll be a lock.

    You know, it wouldn’t surprise me if Tim and Dalton slurp oysters together at the country club and discuss who can come up with the most cockamamie way to fool the public.

  13. It is too bad none of the upper political circles, have enough balls to stand up for us in rural Ontario

  14. We had a small aircraft fly dangerously close to the ground during the snow squall on saturday afternoon. The plane was zig zagging as though it was lost. It wasn’t twice the height of the 80 foot hydro towers along the road. This was within a 1 km radius of the HAF energy project proposed for West Lincoln, on the border of Glanbrook, in the flight path to the Hamilton International Airport, in Tim Hudak’s riding…..
    This wasn’t a first, it won’t be the last.
    Maybe they are plotting the turbines in the flight path to the airstrip kind of like those driveway markers with the reflectors that are supposed to keep people out of the ditch?

  15. Oh that’s right, the planes don’t fly that low. According to the airport regs they fly at 2500 feet over here. Its amazing how I can’t tell if the flag is up on my mailbox at 80 feet away, but I can walk outside at night and see the rivots on the belly of the cargo planes flying over head at 2500 feet. My eyes must be better at 2AM.

Comments are closed.