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There are at least 2 critical dangers for flyers created by these things: 1) air turbulence – generated by a sea of 50-60m blades with their outer tips travelling at around 400km/h – interfering with the ability of the pilot to control their kite (see our post here); and 2) slamming into them – with reasonably predictable results.
As to 1) here’s a report submitted last year to the Civil Aviation Safety Authority by Ted McIntosh (a highly experienced agricultural pilot from NSW):
Date: 18-03-2013
Local time: 0730
State: NSW
Location: 9kms WNW of Gunning Wind Farm, Gunning NSW. Damage to aircraft: nil Most serious injury: nil
Summary:
Whilst on descent to my operating airstrip near Biala NSW, I suddenly experienced severe turbulence at about 500-600ft AGL. The wind at this time had been approx. 5-8 knots from the SE. After landing I ascertained that there was only a slight breeze at ground level. I suspected that the turbulence was caused by the wind turbines at the Gunning Wind Farm but was amazed that the effect could be felt 9kms away.
After the next take-off I confirmed that the turbulence was indeed caused by the turbines.
There are many fixed wing & helicopter aircraft which operate at or below 500 ft AGL legitimately from hundreds of airfields around Australia.
CASA & the Dept. of Infrastructure & Transport have released a study, the National Airports Safeguarding Framework Guidelines D (Wind Turbines) to protect major airports, but it should be apparent that the greater threat to air safety from wind turbine turbulence lies around country airports, both public & private, which threat CASA & the Dept of Infrastructure & Transport have glossed over or ignored.
For aircraft trying to stay aloft or take-off and land safely, weather related turbulence is an unseen menace that often strikes without warning. But it’s hard to envision turbulence being generated by turbines troubling a skilled flyer over 9 km away. So here’s a picture for the uninitiated:
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As to 2) here’s a tragic report from South Dakota, where a light plane slammed into a turbine in foggy conditions. And here’s a picture of the culprit:
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4 dead as plane crashes at South Dakota wind farm
SFGate (Associated Press)
Dirk Lammers
28 April 2014
SIOUX FALLS, S.D. (AP) — A small airplane heading back to South Dakota after a Texas cattle sale crashed into a wind farm in foggy weather, killing the pilot and three passengers.
Elizabeth Cory, a spokeswoman for the Federal Aviation Administration, said the Piper 32 was traveling from Hereford, Texas, to Gettysburg, South Dakota. The single-engine plane was registered to Donald J. “D.J.” Fischer of Gettysburg, according to the FAA.
The National Transportation Safety Board is investigating, but authorities have not released any details on the crash.
Authorities have not released the names of the victims, but Luce Funeral Home confirmed that Fischer, the 30-year-old pilot, died. Lien Funeral Home confirmed the deaths of cattlemen Brent Beitelspacher, of Bowdle, and Logan Rau, of Java.
The funeral home handling arrangements for the fourth victim said it could not release any information.
The three passengers were in Hereford to attend a sale of live cattle and embryos, primarily for the production of show steers, said Mike Mimms, a veterinarian who runs the annual event.
Mimms, who performs cattle embryo transfers, said he has probably bought 3,000 cows from Beitelspacher through telephone calls but hadn’t had the opportunity to meet him until this past weekend.
“I got a Christmas card from him this Christmas,” Mimms said. “It was the first time I even knew what he looked like, and he’s standing there with his family with young kids. And I can’t get that image out of my mind.”
Fischer, a crop sprayer for Air Kraft Spraying Inc., followed in his father’s footsteps into the aerial business and was extremely involved in his community, said state Rep. Corey Brown, R- Gettysburg.
Brown, a longtime family friend, said Fischer had just gotten married in March and was a volunteer emergency medical technician who was often out on calls.
“This is one of those things that’s going to hit the community pretty hard, because I would venture to say there are probably are not many people here who D.J. didn’t touch their life in some way,” Brown said.
Fischer attended South Dakota State University and played defensive tackle for the school’s football team from 2002-2005.
John Stiegelmeier, SDSU’s head football coach, described Fischer as a gifted athlete who was a great friend to his teammates.
“I’m a small school guy and he was the same — phenomenal work ethic, phenomenal loyalty to the coaching staff and his teammates,” Stiegelmeier said. “Whatever you asked D.J. to do, he did it, with a smile on his face, too. He didn’t hesitate.”
Mimms said the three cattlemen noted that they had a rough flight down to Texas due to high winds, and conditions were similar in Hereford when they left Sunday morning.
“They made it through the windy weather, and the fog was the problem when they got there,” he said.
The wreckage was found Monday at the South Dakota Wind Energy Center, a site south of Highmore with 27 turbines that are about 213 feet tall, plus the length of the blade.
Steve Stengel, a spokesman with Florida-based NextEra Energy Inc., said there was damage to a turbine but he couldn’t say what part of the tower was hit.
“It’s been so foggy up there and we haven’t had a chance to investigate,” Stengel said Monday.
Fog and low clouds combined for reduced visibility in the Highmore area on Sunday night, and winds were out of the east at about 15 to 25 mph, said Renee Wise, meteorologist with the National Weather Service office in Aberdeen. There were also scattered showers across region Sunday night, and some might have been heavy at times, she said.
Mimms, said the news has sent shock and sadness through the close-knit ranching community.
“There are a lot of people out there who feel like they lost one of their best friends,” Mimms said.
Similar conditions contributed to a 2008 crash in southeast Minnesota. Federal investigators concluded the pilot of a 1948 Cessna 140 lacked proper instrument training for the day’s foul weather. The National Transportation Safety Board’s probable cause report also noted the pilot’s failure to maintain control of the airplane while maneuvering around a wind farm.
Associated Press SF Gate
This may be the first time this has happened, but it won’t be the last. Stick a line of obstacles taller than the Sydney Harbour Bridge on top of elevated ridgelines and it’s a matter of when (and how many) not if.
For flyers just trying to get from A to B the additional (and unnecessary) risk created by these things is bad enough. But spare a thought for those called on to fly among these things on routine basis – eg, crop dusters and fire-fighters involved in water-bombing (see our post here).
Just another reason to can the fans.
STOP THESE THINGS 
Reblogged this on gottadobetterthanthis and commented:
The fans cause problems with radar too.
Some aircraft stay well clear but I’m losing count of the number of times small aircraft, including a helicopter, flying at what appears to me to be very low altitude over our roof and the 110m high turbines of the Cape Bridgewater wind farm. There needs to be more warnings and information for these pilots and tourists on the sightseeing flights out of the Portland Airport, about the up and the down drafts and the dangers of flying too close. Even in the daylight it seems risky to me and when I hear them fly over, race outside with the phone and camera, just in case. To hear an aircraft at 800 or so metres and closer to the wind farm…that’s too close. I dread the likelihood of a tragic collision. Disastrous and preventable impacts of wind farms; how the hell can amends be made to this South Dakota Community or any community enduring this unnecessary loss of life?