Dynamic Stability Of A Bearingless Circulation Control Rotor Blade In Hover

The aeroelastic stability of flap bending, lead-lag bending and torsion of a bearingless circulation control rotor blade in hover is investigated using a finite element formulation based on Hamilton's principle. The flexbeam, the torque tube and the outboardblade are discretized into beam elements, each with fifteen nodal degrees of freedom. Ouasisteady strip theory is used to evaluate the aerodynamic forces and the airfoil characteristics are represented either in the form of simple analytical expressions or in the form of data tables. The unsteady aerodynamic effects are introduced approximately through dynamic wake induced inflow modeling. The nonlinear equations of motion are solved for steady blade deflections using an iterativee procedure. The flutter solution is calculated assuming blade motion to be a small perturbation about the steady solution, and the normal mode equations are used to reduce the number of equations. A correlation study of analytical results with the experimental data is attempted for selected bearingless blade configurations with conventional airfoil characteristics . Then stability results are obtained for circulation control beari ngless configurations consisting of a single flexbeam with a wrap-around type torque tube and the pitch links located at both the leading edge and the trailing edge of the torque tube. The stability is examined at various thrust levels and collective pitch settings.