Tiltrotor/Tiltwing Performance Enhancement Via Active On-Blade Flaps

Rotors for tiltrotor or tiltwing aircraft are required to operate in flight conditions ranging from hover and low speed edgewise flight to high speed cruise. Even with a tilting nacelle and/or wing configuration, it is not possible to achieve optimal performance in all flight conditions with rotor blades that have a fixed twist distribution, and thus design compromises are inevitably required. This paper summarizes the major results of an assessment of an on-blade camber control system via trailing edge flaps that effectively allows in-flight adjustment of the blade twist distribution to optimize performance. Validated rotor performance optimization software was used to determine performance improvements possible for representative flight conditions as well as to quantify the nature and amplitude of flap deflection required. Demonstration of prototype versions of on-blade active control devices using smart materials technology - specifically Shape Memory Alloy (SMA) actuators – was also undertaken, building on prior demonstrations of airfoil and wing shape control via SMAs. In addition, key features of these devices were also demonstrated in benchtop tests, wind tunnel experiments, and hover stand demonstrations. Finally, power consumption, sizing, and weight calculations were conducted for notional actuator designs.