Dynamics of Helicopters with DVA Under Structural Uncertainties

This paper evaluates the effects and effectiveness of a dynamic vibration absorber (DVA) designed for mitigation of unstable oscillations of helicopters when it is on the ground, i.e.: ground resonance phenomenon. For this purpose, firstly, a parametric analysis shows the stability charts obtained for helicopters without and with DVA as function of the fuselage and rotor damping levels. Also, the present paper is interested on determining the influence of designed DVA devices on the stability robustness of the aircraft once uncertainties are considered in the blade’s hinge stiffness. In this sense, \(\mu \)-analysis is used to predict the smallest stiffness perturbation that leads the helicopter to instability. Indeed, it is not possible to assure the same properties of mechanical components which may alters the effectiveness of the designed DVA. Therefore, the assessment of stability robustness is verified and compared between both aircrafts (without and with DVA). The results showed for both helicopters, if proper combination of fuselage and rotor damping is considered, stability robustness is verified. Also, the inclusion of DVA device on helicopters does not affect the aircraft stability robustness.