Dynamic Properties of Some Gimbal and Teetering Two-Blade Helicopter Rotor Heads

The primary aim of the paper is the characterization of the dynamic behaviour of an innovative two-blade main rotor design under cyclic perturbations. The consequent 'wobbling' motion, i.e. the 2/rev precession of the hub with respect to the mast, is known as a significant drawback of typical current two-blade rotor realisations, based on a teetering mount, as it induces considerable oscillating loads to the fuselage. As an alternative capable to alleviate this problem, the proposed design is based on a constant-speed gimbal mount. The performance of this solution is contrasted with a pure teetering one, as well as with intermediate architectures retaining only a part of the innovative elements of the new gimbal rotor, in order to appreciate their effects separately. All models are simulated within a high-fidelity finite element multibody framework. The results confirm the superior characteristics of the constant-speed architecture. The study is completed with a sensitivity analysis of the dynamic response of the proposed rotor model with respect to some important design parameters.