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Methods Developed to Detect, Remove Ice from Aircraft Wings

Liverpool Airport landing (ChronowerX_GT/Flickr)Engineers at two Fraunhofer Institutes in Germany are devising new solutions for dealing with ice accumulating on aircraft wings in flight, a serious safety concern. The technologies developed by the Fraunhofer Institute for Structural Durability and System Reliability in Darmstadt and Institute for Manufacturing Technology and Advanced Materials in Bremen will be discussed at the ILA Air Show in Berlin, 11-16 September.

The solutions developed by the Fraunhofer teams deal with ice accumulating on an aircraft’s wings during flight, which can happen at high altitudes in any weather. Current methods involve directing heat from the engines to open spaces in the wings, or inflating rubber mats on the wings to dislodge the ice. These methods, say the engineers, require exorbitant amounts of energy and are difficult to implement on wings made of newer types of carbon fiber composite materials.

The Darmstadt solution uses nanoscale compounds integrated into the wing materials that generate an electrically conductive layer and thus can heat the wing. Since the conductive layer is integrated into the basic wing material, it is protected by the overlying fabric. Also, because the nanomaterials are built into the basic wing material, this solution avoids weak points that can result from connecting different types of metal.

“Since we are combining like with like,” says Darmstadt’s deputy department head Martin Lehmann, “the material does not fatigue quickly.” Tests at ground level show this method makes it possible to heat aircraft wings up to 120 degrees Celsius.

In wind tunnel tests, at temperatures of -18 Celsius and at realistic wind speeds, the researchers sprayed a wing with water, let an ice crust form, and then turned on turned on the integrated heater. In a second wind-tunnel test, the Darmstadt team started the heater at the same time they sprayed the wings to prevent ice from forming, an approach called anti-icing, as opposed to de-icing done after ice accumulates.

Lehmann and colleagues report both tests worked successfully, and with different wing models where the heated zones were configured differently. “We were able to maximize heat output this way,” says Lehmann, “because the heater needs to keep the wings reliably free of ice, and yet consume as little energy as possible.”

The Bremen solution is still in development, but involves developing new shape-memory materials where the materials can change their shape or volume, when sensing a change in temperature or in response to an electric current, and thus dislodge the ice off the wing’s surface. Bremen’s Stephan Sell who specializes in paint technology says, “We expect energy savings from this to reach up to 80 percent compared to conventional heating methods.”

A related effort in Bremen will develop a new type of sensor to monitor and report on ice accumulations in real time, as opposed to current methods that use indirect measurements. This integrated sensor would make it possible to alert the crew to wing icing as it happens, and monitor the the de-icing process as well.

Researchers at Bremen already developed a product that could help keep ice from forming on wings, namely water-repellant coatings to protect against the melted ice running back from the wing’s leading edge. Once the heaters melt the ice back into water, it flows down to the lower part of the wing as melt water, where it freezes again and turns back into ice.

The task is to make sure the melted water runs off instead of sticking to the wing. “We can achieve that by blending certain additives into the paint, such as fluorinated compounds,” says Sell. “The main challenge is figuring out how to produce water-repellant coatings so that they remain stable for several years, resisting the effects of UV radiation and high erosion stresses.”

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Photo: ChronowerX_GT/Flickr

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