Design and Test of an Active Pneumatic Trailing Edge Flap for High-Speed Rotorcraft

As part of the High-Speed, Highly Efficient Rotor (HSHER) program, a novel trailing-edge flap concept is evaluated. A finely tuned internal laminate topology, coupled with a lightweight pneumatic actuation system, enable a performant trailing-edge flap technology that does not require electronic or mechanical actuators within the rotor blade. The trailing-edge flap is experimentally shown to provide a 12-degree range of motion between the downward and upward deflected configurations under pressures which can be generated passively by the rotation of the rotor blade. The structure is shown to be sufficiently stiff against aerodynamic pressures and moments, is resilient to strains resulting from large blade deflections, and can hold its shape in the event of pneumatic actuator failure. Additionally, the test data confirmed the strong predictive capability of the finite element analysis for highly-compliant laminate designs such as this. The design is highly customizable and can accommodate a wide variety of airfoils, flap parameters, and loading scenarios. Details of the design, fabrication, and testing of the trailing-edge flap are presented.