A study from the University of Kansas School of Engineering sheds light on a potential safety hazard that could affect hundreds of airports across the country and calls for updated guidelines to improve aviation safety. At issue is the proximity of wind farms to general aviation airports, and how the small aircraft that use them could be affected by the turbulence generated by wind turbines.
“We’re really looking at two potential threats,” said Tom Mulinazzi, professor of civil, environmental and architectural engineering. “These turbines can set up a circular vortex that can roll a plane if it gets in there. And they can increase crosswind speeds above what’s expected, which can be a real danger to small aircraft, which don’t typically take off and land with crosswinds stronger than about 12 miles per hour.”
Mulinazzi, Professor of Aerospace Engineering Z. Charlie Zheng and his graduate student Anpeng He co-authored the report for the Aviation Division of the Kansas Department of Transportation.
By using advance computational aerodynamics modeling, the KU research team studied the effect of winds from 10-40 miles per hour. They found the higher the wind speed, the farther the turbulence reached – stretching as far as nearly three miles from a single turbine – before dissipating.
The KU team studied proposed wind farms that would be constructed near airports, one in Rooks County and the other in Pratt. At both airports, within nearly three miles of the runway, pilots could potentially encounter a crosswind or a “roll upset” generated from a wind turbine.
Mulinazzi and Zheng presented their findings at the inaugural Kansas Aviation Expo in Wichita. Mulinazzi said it appears this study is the first of its kind in the United States. Current Federal Aviation Administration guidelines only evaluate vertical structures from a static perspective within an airport zone. However, wind farms are dynamic with spinning blades that can create rotational vortices.
“The FAA reviews the potential hazard of the physical height and location of any structure, but not any of the emissions from that structure,” said Tiffany Brown, state aviation engineer with KDOT’s Aviation Division. “This research points out a shortcoming in the current evaluation process and that is why this is so important.”
KU is at the leading edge of studying this potential hazard.
“We found no research that looked at the impact of wind generated by wind farms on general aviation,” Mulinazzi said. “But KDOT tells us they’ve been getting complaints from pilots about unexpected turbulence as they approach airports near wind farms, so we felt like the study was worthwhile, especially with the boom in wind farms and wind farm proposals in Kansas.”
Kansas has about 140 public-use airports and many more private-use airports. There are 16 wind farms operating in Kansas today, but there are proposals for an additional 58, with some planned in close proximity to existing airports.
“So as state and local leaders consider these proposals for new wind farms, we’re hoping to provide them with specific information they can use to create guidelines to ensure aircraft safety. Right now, there’s really nothing on the books,” Mulinazzi said.
Previous research 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. No previous research had analyzed the actual impact of this turbulence on aircraft handling and performance, Mulinazzi said.
The report has been submitted to KDOT and is designed to serve as a resource for Kansas cities and counties as they consider potential regulations that govern airport airspace and safety.
“Additional research is required to draw the true correlation between wind turbine vortices and aircraft performance,” said Jesse Romo, director of KDOT Aviation. “This study proves that the concern is real but we need to take it to the next level to enact change in the FAA’s evaluation process and to properly plan the location of wind farms that don’t create an environment that compromises the safe and efficient operation of aircraft at an airport.”