Up there where the big planes fly, it gets very cold indeed: outside temperatures of -50°C are nothing special. Droplets of water suspended in the air can freeze to aircraft instantly, accumulating into layers of ice. A number of systems are used to tackle this gelid build-up, which constitutes a safety hazard. EU-funded researchers are developing new solutions.
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The Jedi Ace project is striving to improve on current techniques designed to keep the wings of flying aircraft free of ice. It has developed new coatings that will make it harder for freezing water to adhere, and designed innovative sensors that will help to detect any ice that has begun to form. It has also looked into ways to improve on current approaches for heating systems designed to keep wings clear.
By the time this innovative endeavour ends in April 2016, the researchers are hoping to combine these innovations into an energy-efficient integrated solution and produce an outline of further R&D needed in view of commercialisation. The project was funded jointly by the European Commission and by the Japanese Ministry of Economy, Trade and Industry.
Have things in your wings, you must
“Ice accumulating on flying aircraft is a huge problem. It has caused a number of accidents in the past, and so planes need special technology to avoid it,” says project manager Nadine Rehfeld of Fraunhofer Institute for Manufacturing Technology and Advanced Materials in Bremen, Germany. Aircraft on the ground obviously can and do also ice over, but this is a different type of challenge — notably because it can be tackled by maintenance crews prior to take-off.
One of the main risks associated with icing is that it can change the aerodynamics of the plane, potentially with dramatic consequences. Rehfeld and her Jedi colleagues set out to find better ways to tackle the phenomenon, which they considered more specifically with regard to the wings.
Flying in the face of frost
“We had three technical objectives,” Rehfeld notes. “One of these is developing an improved active heating system, i.e. one where the fuel consumption is reduced significantly compared to the conventional approach, which uses bleed air.”
Bleed air, she explains, is hot air generated by the engines, which have to work harder to produce it. It is pumped into the wing to warm the surface and melt off any ice that has accumulated. Jedi Ace is proposing to replace this kind of system with one that combines electric heating devices and coatings designed to avoid icing in the first place.
The team has developed two types of coating for this purpose, which it is putting forward for use on different parts of the wing. The first, intended for the leading edge, is an elastomeric substance that makes it harder for ice water and particles to adhere, and also shields this component from abrasive agents such as rain or sand carried in the air.
The second, says Rehfeld, is meant for application a little further back on the wing. It repels moisture, and so helps to avoid so-called runback ice forming when meltwater from the leading edge is driven back by the airflow and cools.
“Our second technical objective is developing a new generation of ice sensors. These are optical sensors that can detect the ice on surfaces very rapidly, and that also control the anti-icing function of the ice protection systems,” Rehfeld explains. The sensors make it easier to detect icing early on and to switch the heating system on and off accordingly.
“And the third objective — our overall aim, in fact — is then to produce an integrated wing ice protection system,” Rehfeld adds. The first two objectives have already been met, she reports, and the partners are now putting the final touches to their concept for the combined system.
Rehfeld notes that there is still a lot to do to develop these advances into a deployable solution, and that the partners are hoping to launch a follow-on project that would enable them to pursue this task together. The ice-busting force is strong with this alliance, and Rehfeld reports that the chance to cooperate across continents has emerged as a great asset. “It’s a great opportunity to learn from each other,” she concludes.