GKN Aerospace has delivered a wing leading-edge demonstrator to the Clean Sky program, part of an effort to bring an ultra-high performance, natural laminar flow (NLF) wing closer to reality.

The integrated NLF wing leading edge has been produced through the Ground Based Structural and Systems Demonstrator (GBSSD) phase of the Clean Sky Smart Fixed Wing Aircraft program. Clean Sky is a public private partnership between the European Commission and the aerospace industry.

Rich Oldfield, technical director, GKN Aerospace says the NLF wing promises an 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 Advisory Council for Aeronautics Research in Europe (ACARE goals) for 2020, which include a 50% reduction in carbon dioxide emissions and an 80% 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 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 applied a more radical design to address issues experienced 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 support structure for the Krueger mechanism, replacing the aluminum ribs in the baseline design. This allows the leading edge panel to be supported by t 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 section has a lower component and fastener count, is lighter and has an improved performance predictions compared to the baseline section.

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 and at the GKN Aerospace additive manufacturing centre (AMC).

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