The future of travel is green, and aircraft manufacturers are looking for energy savings for in-flight operations, including during harsh freezing conditions. Whether it be for a jet, helicopter, or drone, the aircraft industry wants to ensure passenger safety while reducing costs and environmental footprint. As companies look to replace or supplement traditional thermal de-icing technologies that require high power, passive de-icing methods—ones that require no energy—are gaining steam. Material scientists heeded the call with a brand new area of research: icephobic coatings.
Icephobic coatings are passive, ice-resistant materials like paints or lacquers that can be applied to the surface of an object, changing the surface properties. Without a need to be "plugged in," the coatings could act as viable replacements for active de-icing systems, ultimately saving energy and cost. But any new technology needs a viable testing method, prompting the National Research Council of Canada (NRC) to find a solution.
Assembled spin rig at the National Research Council of Canada. During testing, icephobic coatings are secured to the ends of the rig's arms.
"With the field of ice-resistant veneers still in its nascent phase, there is no standardized method worldwide to test how well such materials repel ice particles. Using our unique blend of airborne icing facilities and aerospace expertise, the NRC took on the challenge to bridge this testing gap," said David Orchard, leader of the NRC's Reducing Aviation Icing Risk research program.
The NRC has developed a one-of-a-kind, in-situ rotating ice adhesion rig, where researchers are able to measure the adhesion properties of ice to various icephobic coatings in controlled and repeatable conditions. The "spin" rig—designed and built at the NRC, and installed in the NRC's Altitude Icing Wind Tunnel—works by securing coated specimens to the ends of its retaining arms. The wind tunnel accretes ice on the specimens and the spinning is then gradually accelerated to 9,000 RPM until the ice sheds. The shedding is measured by accelerometers, where shear force is calculated using the time it takes the ice to shed and the mass of accreted ice. The less force it takes to shed the ice, the better the coating.
Similar rigs worldwide have produced unreliable results as specimens had to be moved from the location where ice was applied to the spin rig's location, producing variability in temperature and time. The NRC test method mitigates these issues by conducting the entire test in the Altitude Icing Wind Tunnel.
The NRC tests icephobic coatings for drones
Operating a vehicle in icing conditions is a challenge at the best of times, but imagine the difficulties that are compounded when the vehicle is unmanned, in the air, and weighs less than 25 kg. Unmanned aerial vehicles (UAVs) are in danger of failing due to ice adhesion, leading to unsafe conditions for Canadians living in the fly zones, and the loss of a drone can be costly and could mean losing valuable data. As more and more UAVs hit the airspace, and do so in freezing conditions, the need for lightweight, passive icing solutions has arisen.
Innovators creating these ice-resistant veneers see their potential application on drones as a match made in heaven, as UAVs' limited onboard power and payload means a passive ice-prevention method is preferable.
"The NRC ice-adhesion test method and spin rig could be used to test any type of icephobic coating. Currently, Canadians' most pressing need is to test for drone safety. As of yet, there are no commercially available UAV icephobic coatings on the market and we are proud to be able to supply a reliable test mechanism for Canadian innovators to develop their technologies" said Iraj Mantegh, leader of the NRC's unmanned aircraft systems research program.
Using our unique method and rig, the NRC has tested 12 icephobic coatings from Canadian small- and medium-sized businesses, three of which show great potential for passive protection of UAVs against in-flight icing. To verify and demonstrate its findings for UAVs in realistic icing environments, in early 2018 the NRC plans to test the three viable coatings on drone wings in its Altitude Icing Wind Tunnel.
This project is part of the unmanned aircraft systems program at the NRC's Aerospace Research Centre. For more information about the National Research Council of Canada, its aerospace programs, capabilities and facilities, click on the links below.
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