Potential hazards to small aircraft concern area pilots





A recent University of Kansas study identifying potentially serious safety hazards for small aircraft from wind turbulence generated by wind farms has caused some concern among area pilots and aviation officials.

According to the study, the turbines on a wind farm can set up a circular vortex as far away as 3 miles, which can catch a small plane and spin it around if it gets too close.

Kansas has about 140 public-use airports and many more private-use airports. The state also has 16 operational wind farms and a proposal for an additional 58, with some planned in close proximity to existing airports.

"More work is needed, but we have raised a red flag of the problems wind farms can have on small airports and aircraft in close proximity," said Tom Mulinazzi, professor of civil, environmental and architectural engineering at KU, who led the study.

Mulinazzi also added that a "wind shear" could cause small aircraft to slam to the ground on landing attempts. Wind shear refers to a rapid change in wind speed or direction with height, or a rapid change in wind speed over a short horizontal distance. That can cause a sudden change in lift and altitude for a small aircraft.

Weston Thompson, airport manager and pilot with the Scott City Regional Airport, said he hasn't experienced wind turbulence or vortices, but for crop dusters, wind turbines can create dangerous situations.

"From a turbulence aspect, it's incredibly minor for passenger planes," Thompson said. "But for sprayers, anytime you're that low to the ground near the turbines, I would think they get a great amount of turbulence," he said.

Doug Chanay, owner and pilot of Chanay Aircraft Services at the Garden City Regional Airport, is a sprayer, and he has flown over wind farms in Spearville, Cimarron, Haskell County and Montezuma. He has experienced turbulence created by the turbines.

"I've flown up against it in the spray fields, and it's a lot of turbulence out there," he said. "If you get too close and get behind a strong gust, there is enough turbulence to cause the plane to roll. If you are aware of it, you can fly around it, but it does create a hazard."

In addition, cross winds greater than 12 mph can be created, which are higher than such craft typically encounter during landing or take-off, according to the study. Cross winds refer to the wind component that is blowing at right angles to the aircraft's line of flight. Since they are perpendicular to the plane, their force is increased. Chanay described this as friction by stating that unstable wind currents, plus the winds generated by the turbines, would push against the plane, causing difficulties landing safely.

Previous research by the university into turbulence generated by wind farms had shown that airplanes could briefly disappear on radar when flying near a turbine, because radar interprets the movement of the blades as precipitation, which can mask the radar return of an aircraft. Chanay said the generated condensation from the turbines shows how much turbulence is in the area.

The wind farm study was prompted after pilots complained about turbulence causing a "roll upset" near public airports in Pratt and Rooks counties, Mulinazzi said.

In the final study by Mulinazzi, a professor and a graduate student, the amount and pattern of the turbulence from a single wind turbine was examined, as was the amount and pattern of wind turbulence from a wind farm, both in a horizontal and a vertical direction. The information from the study will be used to develop recommendations for the location of wind farms and the safe operation of airports and other aviation activities.

"The problem comes if they are built too close to us," Corey Keller, airport manager at Dodge City Regional Airport, said. "Most airports try to stay within 10 to 15 miles of wind farms, but more are being built."

There are are three operational wind farms in Ford County, as well as six proposed, and there are three operational wind farms in Gray County, one operational wind farm in Wichita County, two proposed in Hamilton County, four proposed in Scott County, and one each in Stevens, Haskell and Kearny counties.

A 3-D model was used to demonstrate the effect of winds from 10 to 40 mph. The study found that the higher the wind speed, the further the turbulence reached — stretching nearly three miles from a single turbine before dissipating.

Jesse Romo, director of the Kansas Department of Transportation's aviation division, said the university may have jumped the gun on its findings, meaning that there is more research to be done.

"The creation of the turbulence is real, but the next question is the true impact, and that remains to be seen," Romo said.

There have been evaluations in Kansas of towers that don't meet the required height, and there have been hundreds of cases examining the potential hazardous effect of proposed construction on air navigation, Romo said.

Along with the wind generated by the turbines, Chanay and Thompson both said the structure itself, and meteorological towers (MET towers), also pose a threat.

"MET towers create an obstacles for us because they are not lit because they are not tall enough," Thompson said.

MET towers are used to gather wind data for site evaluation and development of wind energy projects. Any tower less than 200 feet does not have to have lights, and that includes wind turbines, according to the Federal Aviation Administration.

"Of course, everybody likes renewable energy," Chanay said. "They will continue to be built, and I don't think anybody is against them. I just think they are a hazard."

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