NASA’s Langley Research Center developed a simple, deployable, flap side edge main element link that reduces airframe noise while still enabling a clean cruise configuration. Termed the FLEXSEL (flexible side edge link), this flexible structural link design makes use of hyperelastic materials to provide a smooth geometric transition of minimal spanwise extent between the flap side edge and the main wing. The comparatively small spanwise dimension of the FLEXSEL enables it to achieve the noise reduction without detriment to, and with possible improvement of, other aerodynamic characteristics.

FLEXSEL-integrated airframe in deployed configuration. (Image: NASA Langley)

The invention is an approach to mitigate the airframe noise originating at the side edges of aircraft trailing edge flaps. The link consists of an elastomeric foam core bounded by a homogeneous elastomeric skin. The unloaded shape of the link can be chosen to correspond to an intermediate configuration between the retracted and deployed end states, thereby reducing force requirements and optimizing shape control throughout flap articulation. Also, the link cross-section can subtend on partial flap chord and/or flap thickness dimensions.

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