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Starting point of this work was the question, to what extent it is possible and reasonable to improve the high lift behavior of thin and long fowler flaps by improving their deformation behavior with a stiffness optimized design. Due to undesired large deviations of the flaps elastic line from the elastic line of the wing there is a significant lift reduction during take off and landing. This lift reduction is caused by an uneven gap between wing and extended flap. The gap is necessary to accelerate the airflow and prevent it from separating from the upper side of the flap. Furthermore, the trailing edge of the flap is simultaneously the trailing edge of the wing during cruise flight. Due to the elasticity of the material there is an upward bending of this trailing edge, leading to an increased aerodynamic drag in cruise flight. Therefore, the goal of this work was the stiffness oriented re-design of such a flap under consideration of necessary strength criteria.

Drag reduction technologies in aircraft design are the key enabler for reducing emissions and for sustainable growth of commercial aviation. Laminar wing technologies promise a significant benefit by drag reduction and are therefore under investigation in various European projects. However, of the established moveable concepts and high-lift systems, thus far most do not cope with the requirements for natural laminar flow wings. To this aim new leading edge high-lift systems have been the focus of research activities in the last five years. Such leading edge devices investigated in projects include a laminar flow-compatible Kruger flap [1] and the Droop Nose concept [2, 3] and these can be considered as alternatives to the conventional slat. Hybrid laminar flow concepts are also under investigation at several research institutes in Europe [4].