Multibody Dynamics Model of a VTOL Teetering Rotor

This paper presents the development of a multibody dynamics model of a VTOL teetering rotor. The developed model includes a teetering hub, containing a flexure and torque tube, rotor blades, pitch links, and swashplate system. A non-teetering rotor configuration, which modified the baseline teetering rotor by removing the teetering hinge, is also developed, and its aeromechanics characteristics compared to those of the baseline teetering design. The rotor aeroelastic responses and loads are studied under various flight conditions including the conversion flights. The rotor natural frequencies are calculated for two blade pitch angles, which represents respectively the rotor operating in helicopter and airplane modes. The MBDyn predictions of aerodynamics loading of the teetering rotor are compared with those of OVERFLOW in both helicopter and airplane modes. The comparison shows overall good agreements. The blade responses and loads in conversion flight are then compared between the baseline teetering rotor and the modified non-teetering version. Similar aeromechanical characteristics are shown for the two rotor configurations, such as the blade response, steady hub loads, and steady and oscillatory blade shear forces. However, the non-teetering rotor displays a much larger blade bending moments, both the mean and oscillatory components. Overall, the study shows that the multibody analysis has the capability to model complex rotor configurations, and helpful in establishing the requirement and criteria applied to VTOL proprotor load analysis in supporting the aircraft design.