Breaking the ice: progress in rear-end anti-icing coatings and design
Ice build-up on aircraft structures poses serious dangers – increasing weight and drag, reducing efficiency and affecting safety, especially when flying in cold weather. The answer lies in advancing icing-tolerant designs and anti-icing technologies to improve overall aircraft design while maintaining uncompromised flight safety. Focused on this, a consortium of ten partners has worked on the EU-funded IMPACT(opens in new window) project. The goal included advancing state-of-the-art ice accretion simulation capabilities, scouting ice-phobic coatings and optimising the shape of the rear fuselage and empennage, accounting for aerostructural, aeroelastic and icing conditions, ultimately contributing to the Clean Sky 2’s(opens in new window) Large Passenger Aircraft programme. “IMPACT has successfully covered an ambitious set of scientific and technical objectives relevant for the design of highly efficient next-generation commercial aircraft rear ends,” states Michele De Gennaro, IMPACT project coordinator.
Calculating how ice builds up
Through 3D icing simulation, the project developed industry-level methods and tools for accurate calculation of ice accretion swept empennages. Experts were able to develop a model that helps predict how liquid droplets impact and flows on the aerodynamic surface, forming rivulets and turning into ice, while considering complex multi-physics interactions and accounting for surface ice-phobic properties. The project computed the aerodynamics of ice accretion on large passenger aircraft horizontal stabiliser surfaces, enabling this to be included in the overall aircraft’s design process. “Various innovations were developed in terms of meshing and computational fluid dynamics set-up to enable tackling ice accretion as an integral part of the aircraft’s multi-objective optimisation,” says De Gennaro.
Innovations in anti-icing solutions
IMPACT analysed a large range of anti-ice coatings available on the market, including some in an R&D phase. The goal was to understand their performance and durability and to gather information on anti-ice and anti-erosion properties. A selection of the best technologies was tested in a state-of-the-art, large climatic wind tunnel in Vienna, Austria, on straight and undulated leading edges of a benchmark aerofoil section. The tests contributed to creating the most advanced and complete database on coatings ever produced(opens in new window), shedding light on the performance of coating technology for rear-end applications and becoming a reference for validating 3D ice accretion codes. “In addition, groundbreaking work was carried out in the implementation of low-level physical icing models that will consider real physical properties of surfaces in the ice accretion simulations, this being a problem of great industrial significance,” asserts De Gennaro. The effect of reduced ice accretion from the application of a hydrophobic coating on the leading edge of a straight swept wing can be seen in the photo above.
Aerodynamic and aero-structural optimisation
To make the fuselage rear end and empennage lighter, IMPACT worked on an innovative concept based on a forward-swept horizontal tail plane. The result was an optimised rear end layout with the same aerodynamic performance of the baseline design, but with a 5 % reduction of the tailplane area and an ice-tolerant design. This was achieved with the addition of a leading-edge extension device, specifically created to work with a forward-swept tail. By using advanced techniques, the team further optimised the tail’s structure, unveiling the potential for an additional weight reduction of 6 % at the tailplane level, which can result in a total weight reduction of 10 %. “This, in turn, leads to a potential fuel saving of 1 % at the aircraft level when compared to a 2020 state-of-the-art large passenger aircraft baseline, such as the Airbus A320neo,” adds De Gennaro. The work carried out by IMPACT advances methodologies needed by the aviation industry and is likely to continue to consolidate the results achieved.
