Preventing the dangerous formation of ice on aircraft
Ice and airplanes are a dangerous mix. Ice accretion on aircraft presents a severe problem: even a barely-visible layer of ice can seriously limit the functioning of vital utilities such as wings, propellers, windshields, antennas and vents. Ice forms as large, cold droplets land and freeze on contact with the chilled surface of the aircraft. Aviation data suggest icing has been responsible for 35 % of weather-related plane accidents (the largest cause) and around a fifth of weather-related fatalities in the past century (the second largest after turbulence). “Icing also increases fuel consumption of aircraft, by increasing weight and drag, while decreasing thrust and lift,” explains Professor Jolanta Sapieha from Polytechnique Montreal, team leader responsible for coating development. This means any solution to the problem will be environmentally-friendly, and will eliminate the costs of frequent de-icing procedures on the ground. In 2016, an international consortium of experts from across Europe and Canada created the PHOBIC2ICE project, taking off on an ambitious challenge to develop and test technologies to prevent and reduce ice formation on aircraft. Creating antifreeze The team developed several types of polymeric, metallic and hybrid coatings designed to repel ice formation. These icephobic coatings focussed on five materials: aviation aluminium and titanium alloys, stainless steel, carbon-epoxy composite and polyamide. Research was split into three categories: basic research including tests on material surface topography and adhesion, advanced testing in ice-forming conditions, and practical tests on the durability of the new coatings in view of natural effects such as corrosion and UV exposure. “The most effective coatings worked to repel as much water droplets as possible before freezing (superhydrophobicity), or by reducing the adhesiveness of formed ice to the surface,” says Dr Elmar Bonaccurso, from Airbus in Germany, PHOBIC2ICE team leader responsible for the development of industry requirements (use cases) and testing protocols. “Specific treatments and coatings can prevent water drops from freezing, by reducing water adhesion and slowing down the ice nucleation, so that water drops can be removed by the sheer force of airstream,” says Mr Antonio Miraglia, R&D Director at DEMA Aeronautics in Montreal, responsible for droplet impact modelling in the PHOBIC2ICE project. Testing the mettle Large-scale wind tunnel and flight tests were carried out in Canada and Spain respectively, to probe and develop the proposed solutions. This was coupled with advanced computer modelling simulations, carried out at three scales: the level of atom interactions, micrometre scale and macro scale. The models were used to simulate the behaviour of rain droplet streams on wing profiles at three scales – at the level of interactions between single atoms, at the micrometre scale and at the macro scale (larger portions of the surface). There were additional benefits to the new surface designs beyond ice repellence: several coatings or surface modification techniques outperformed bare metals in resistance to rain and sand erosion, corrosion and aircraft maintenance chemicals. The coatings were created with existing aircraft in mind, as well as potential future models. “All of the surface modification techniques were designed to be compatible with existing components, so they could be applied to current airplanes or integrated directly into the design of new ones,” says Prof. Sapieha. A successful team effort The intercontinental research team consisted of nine partners, and all members expressed how beneficial and enjoyable it was to work as a team, drawing on each other’s expertise. “We proved that patience and respect develop trustful cooperation and relationships,” says Mr Leo Turno from Warsaw, Poland, and PHOBIC2ICE project coordinator. “It is also worth mentioning that the presence of highly dedicated people from industry makes the whole project much easier to manage, since all scientists feel much more motivated to stretch their capabilities beyond their usual limits.” Professor Ali Dolatabadi from Concordia University in Montreal, work package leader responsible for modelling and coating development and project co-ordinator for the Canadian partners adds: “It was the most enjoyable project that I had the pleasure to work on in the past 15 years.”
Keywords
PHOBIC2ICE, ice, planes, accretion, formation, innovation, prevention, design, fuel consumption, aviation, coatings
