Active Flap System for an Advanced CH-47 Rotor

With ever increasing efforts to maximize range and payload in addition to minimizing noise and vibration for rotorcraft, the US Army has invested in research and development that seek to define active rotor systems and mature the underlying technology to a higher readiness level. Numerous active devices can be used on rotor blades such as flaps, slats, trim tabs and other active control mechanisms. This present study describes the design of an advanced CH-47 rotor blade incorporating twin active flaps, each with a span of 10% rotor radius and actuated by electro-mechanical actuators (EMA). The blade/flap system was designed with the goal of achieving 90% reduction in rotor induced vibration, reducing acoustic detection range by 50% and increasing rotor cruise efficiency (isolated rotor Lift/Equivalent drag) by 8%. Analysis was performed using a single 20% rotor radius span flap per blade on both forward and aft rotors. A 60 inch demonstration full-scale blade section with a 10% rotor radius span, 0.2 chord length trailing edge flap was designed and selected components were fabricated. This paper describes the trade studies required to implement an active flap as well as a description of potential benefits of a flap installation. This research was partially funded by the Government under TIA No. W911W6-11-2-0002. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon.