Aeroelastic Stability for Straight and Double Swept Rotor Blades in Forward Flight

Double-swept blades can effectively reduce helicopter rotor blade vortex interference noise. However, they can lead to the deviation of the aerodynamic center and center of gravity of the blade section relative to the pitch axis, and this can pose a risk to aeroelastic stability during high-speed forward flight. Therefore, it is necessary to investigate this issue in depth. Based on the straight blade of a star flexible rotor, a double-swept blade structure was designed and the dynamic characteristics and aeroelastic stability of the straight blade and double-swept blade were compared and analyzed. The effects of parameters such as sweep-forward angle, sweep-backward angle, sweep-forward station, and sweep-backward station on aeroelastic stability were studied. The analysis results showed that the double-swept structure, compared to the straight blade, can reduce the third flap frequency and first torsional frequency of the blade. Additionally, the double-swept blade can improve aeroelastic stability during forward flight when the double-swept blade beam is strengthened. Increasing the sweep-backward angle is beneficial to aeroelastic stability. However, when the sweep-backward station is closer to the blade tip, the aeroelastic stability becomes worse.