Abstract: Based on complex modulus of elastomeric lag dampers obtained from bench mark test undergoing symmetrical and single frequency excitations, nonlinear Voigt-Kelvin Solid (VKS) model parameters are identified. An improved nonlinear VKS model is presented accounting for frequency modifications so as to be appropriate for both single and dual frequency cases. The improved model is then verified by correlating with test data. The updated model can capture the nonlinear characteristics of complex modulus of elastomeric lag dampers. Hence the model is applicable to the predictions of complex modulus for single and dual frequency situations. The improved model is applied in helicopter air resonance stability analysis. Result shows that the regressive lag modal damping decreases by about 37% as helicopter flies from hovering toforward flight.