Design and Testing a Full Scale Laminar Wing Leading Edge High-Lift System

The feasibility of laminar flow control technology for future wing is bound to the development of a leading edge high-lift system that complies with the requirements on smooth surfaces to enable maintaining the laminar boundary layer flow. Classical leading edge high-lift devices like slats are not suitable as they introduce disturbances in the very sensitive upper surface leading edge area. Krueger flaps, which are deflected from the lower side of the wing, are a good alternative as they additionally offer the capability to shield the wing against contamination by insects, water or dirt. Already in 1985, Boeing proposed a concept of a vented Krueger forming a gap flow between main wing and Krueger flap together with a folding bull nose. Although in principle the aerodynamic performance of a Krueger flap is less than for a slat, Rudolph proposed to further develop this kind of Krueger device to provide aerodynamic characteristics comparable to a slat device. Within the EC project DeSiReH a vented foldable bull nose Krueger was designed that showed comparable high-lift aerodynamics. Within the European AFLoNext project, a full scale HLFC leading edge demonstrator was designed and built that incorporated the vented foldable bull nose Krueger. In summer 2018 this demonstrator was wind tunnel tested in the CIRA Icing Wind Tunnel facility. Within this test the aerodynamic design was verified. Additionally, it was tested whether the Krueger device would need a distinct de-icing system. The contribution summarizes the design of the Kruger device together with the findings from the full scale wind tunnel test of the Krueger flap configuration