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NO-ICE ROTOR - a greener way to protect aircraft from icing

An innovative lightweight heatable coating technology that will enable tilt-rotorcraft to operate safely in icy weather is the subject of Clean Sky’s NO-ICE ROTOR project. Having just passed the halfway point in its 48-month timeline the project is progressing through its technical milestones, leading to enhanced operational safety, energy savings and a reduction in emissions in the future of European aviation.

“Icing conditions are a major safety concern in aviation and most commercial aircraft have to be equipped with an ice protection system in order to operate safely during tough icing conditions. Clean Sky’s NO-ICE ROTOR is all about developing and manufacturing an ice protection system for the rotor blades of Leonardo’s Next Generation advanced tilt civil rotorcraft” says Alexander Baumann of Villinger GmbH, the Austrian company leading Clean Sky’s NO-ICE ROTOR project. The project is supported by Austrian entities CEST Kometenzzentrum fur Elektrochemische Oberflachentechnologie GmbH; AIT Austrian Institute of Technology; and RTA Rail TEC Arsenal Fahrzeugversuchsanlage GMbH; as well as Italy’s SIA Aviatest Ltd.

The specific technical objectives of the Clean Sky NO-ICE-ROTOR project are to perform structural and environmental test substantiation of ultra high reliability heater layers which can be embedded into the rotorcraft’s composite structures to provide anti-icing and de-icing capability, while operating in high strain and vibration conditions. Structural and environmental testing are being conducted on representative test items (also known as ’coupons’) consisting of functional heater layers embedded in the prop-rotor blade and airframe sections of a tilt-rotor configuration intended for civil certification.

But this ambitious undertaking presents a couple of very substantial hurdles to overcome: ”In the NO-ICE ROTOR project there are two very major challenges,” explains Andrzej Podsadowski, Project Officer at Clean Sky. ”Firstly is the amount of energy needed to de-ice the affected areas, and this places very heavy loads on the Next Generation advanced tilt civil rotorcraft’s electrical systems. And the second challenge is with the material. The rotorcraft’s propeller blades are manufactured out of carbon fibre, so you cannot overheat them otherwise there’s a risk that their structural properties will be affected. However, if you under-heat them then they don’t de-ice properly, so determining and applying the right amount of heat is critical”.

To address these complex issues Villinger has developed a unique semi-conductive coating that is applied as an ultra-thin heater layer of less than 0.2mm thickness. It’s lightweight (at less than 150g per square metre), and works as an electrical resistor layer, providing smooth, full-face heating. It is also able to transmit homogeneous radiation heat, if required. The technology can output temperatures of 130°C continuously during flight, with a maximum possible temperature output of 200°C.

Although some details of how the technology operates are at this stage confidential, Baumann was at liberty to reveal that ”it relies on a new kind of heating science which – rather than based on metallic wires – is based on a heatable coating which is embedded between the rotor blade base and the metallic rotor shield. It’s a full-face heating technology that brings a lot of advantages compared to the conventional approach. For example, it’s very light in weight and much more reliable than existing technology which is why we think this project can really serve as a starting point for further development of rotor de-icing technologies, because if the industry sees how this technology brings so many advantages compared to conventional heaters hopefully there will be a switch to our technology”.

”The first third of the project is pretty much completed and what we’ve achieved so far includes thermal analysis of the interaction between the propellor blade and our technology and we’ve defined how it would be laid out in terms of deicing zones. We’ve also calculated the power demands and the power density of the heater layers, so this is all fixed now, and we’ve defined what level of power and what range of temperature is required to de-ice the rotor-blades properly” says Baumann.

Villinger also made environmental ’coupon’ tests in the laboratory where they produced samples that are representative of the layer system where each layer is applied with the protective top coatings.

”What we’ve achieved so far is that we tested the coupons in the laboratory for humidity, vibration liquid resistance and adhesion, to ensure that the material used for our heater layer can be used for the NO-ICE ROTOR system and will be on track for certification later on” adds Baumann.

Soon Villinger will receive the first materials from Leonardo to make a first prototype for the system and see how that works, and towards the end of the project the intention is to equip a complete section of the rotor blade with the NO-ICE ROTOR system which will be tested in an icing wind tunnel to assess how the coating performs at different spin rates. Additionally there will also be operational ice wind tunnel testing towards the end of the project.

Though the project continues until the end of 2020, from the Clean Sky perspective, all of this bodes well for the future: ”There are savings because this is quite a clever system and does not need as much energy as existing systems. The NO-ICE ROTOR system could be deployed to the places where you really need to deploy the energy” says Clean Sky’s Podsadowski.