GKN delivers innovative wing leading edge demonstrator for Clean Sky

The new natural laminar flow (NLF) concept is part of the European Clean Sky Smart Fixed Wing Aircraft program, aimed at maturing wing technology for the next generation of low-emission, high-performance aircraft.

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GKN Aerospace (Redditch, Worcestershire, U.K.) has delivered an innovative wing leading edge demonstrator to the Clean Sky program, helping bring an ultra-high performance, natural laminar flow (NLF) wing closer to reality. The integrated NLF wing leading edge has been produced through the GBP2.5m Ground Based Structural and Systems Demonstrator (GBSSD) phase of the Clean Sky Smart Fixed Wing Aircraft program, which is maturing NLF wing technology for the next generation of low emission, high-performance aircraft.

Rich Oldfield, technical director for GKN Aerospace explains, “The NLF wing promises a substantial improvement in aerodynamic performance and reduction in drag when compared to a modern turbulent wing. Achieving these performance improvements will be a significant step towards reaching the ACARE goals for 2020, which include a 50 percent reduction in carbon dioxide emissions and an 80 percent reduction in nitrogen oxide emissions.”

GKN Aerospace’s ground based demonstrator (GBD) is a 4.5m-long by 1m wide section of flight-representative wing leading edge attached to a partial wing box assembly. The leading edge accommodates a Krueger flap in two sections. This split has allowed GKN Aerospace engineers to investigate two very different design philosophies.

The first ‘baseline’ section applies a monolithic composite skin to the traditional rib design seen on the majority of metallic leading edges today. The second "innovative" section has applied a more radical design to address issues experienced in meeting NLF tolerances with the baseline design. This section comprises a lightweight leading edge sandwich panel incorporating electro-thermal wing ice protection technology with an integrated erosion shield and fastener-free outer surface. Additive manufacturing processes have been used to create a novel support structure for the Krueger mechanism, replacing the aluminium ribs in the baseline design. This allows the leading edge panel to be supported by just three composite ribs: a single central rib and two closing ribs. These maintain the correct leading edge aerodynamic profile over the complete range of operating temperatures. This innovative section has a lower component and fastener count, is significantly lighter and has a greatly improved performance predictions compared to the baseline section, says GKN.

The project is a collaboration between three GKN Aerospace technology centers in the UK: a team at the UK’s National Composites Centre, at GKN Aerospace in Luton and at the GKN Aerospace additive manufacturing centre (AMC) in Bristol.

The project was performed in close cooperation with Airbus; Airbus will manage the assembly of the leading edge components at the Manufacturing Technology Centre (MTC), Coventry and the integration of the Krueger flaps and deployment mechanism at the Airbus facility in Bremen.

The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for the Clean Sky Joint Technology Initiative. Clean Sky is the most ambitious aeronautical research program ever launched in Europe. Its mission is to develop breakthrough technologies to significantly increase the environmental performance of airplanes and air transport, resulting in less noisy and more fuel efficient aircraft, hence bringing a key contribution in achieving the Single European Sky environmental objectives.