Analysis of Flap-Lag-Torsion Aeroelastic Stability at High Advance Ratios

The aeroelastic stability of rotor blades in the flap, lag, and torsion degrees of freedom is analyzed in preparation for high-advance ratio wind tunnel testing of Mach-scaled rotors. A wide range of advance ratios (0 ≤ μ ≤ 3) are evaluated for articulated and hingeless rotor configurations. Linearized equations of motion in the rotating frame are derived, which consider periodic coefficients, reverse flow, pitch-flap and pitch-lag coupling, and control inputs. The steady state trim is compared with wind tunnel data. Floquet theory is used to evaluate the stability of the equations of motion in response to perturbations from trim. Results are compared to past analyses and expanded to higher advance ratios. Damping and frequency response behavior are evaluated, and rotor stability boundaries are presented.