“Digital” SMA-Based Tracking Tabs for One-Per-Rev Vibration Reduction

A novel approach for providing one-per-rev vibration reduction using collections of discrete active tab devices was recently tested under an Army-sponsored research program. Each tab incorporates a patented bistable design that uses SMA wires for transitioning between one of two deflection positions, thereby providing a localized perturbation to the blade aerodynamics at the location of the trailing edge tab. By arranging several such tabs spanwise along the rotorblade, incremental adjustments may be made using these tabs to perform tracking adjustments on the blades, while in flight, avoiding the typical maintenance cycle of fly-measure-land-adjust-repeat for manual blade tracking. The device has been prototyped, and has been designed so that it may be retrofit on existing rotor blade systems, thereby providing active in-flight tracking capability to both existing and future rotorcraft.