Flutter Assessment of a Rotor Blade with Innovative Layout in Hover using Indicial Aerodynamics

The double-swept ERATO blade layout is assessed for flutter stability in hover flight and compared to the straight 7AD reference blade. Used numerical methods comprise multibody dynamics together with an unsteady aerodynamic model based on Wagner’s function and related enhancements for the general motion of an airfoil section considering heave and pitch motion. The numerical solutions for flutter onset are gained from simulations in both, frequency and time domain. According flutter results are compared and observed aeroelastic couplings of the rotor blades are discussed. The two layouts exhibit the classical bending-torsion coupling as known for articulated rotor blades. An additional coupling is found with the ERATO blade. A dominant flutter mode develops with rotor harmonics of 3/rev for increasing rotor speed. The observed mechanism is composed of two flap bending modes that carry shares in blade twist as a result of the double-swept rotor blade shape.