Dynamic stability equations of bearingless rotor blades were investigated using a simplified model.The aerodynamic loads of blades were evaluated using two-dimensional airfoil theory.Perturbation equations were obtained by linearization of the perturbation.A normal-mode approach was used to transform the equations expressed by nodal degrees of freedom into equations expressed by modal degrees of freedom

which can reduce the dimension of the equations.The stability results of rotor blades were presented using eigenvalue analysis.The shape function matrix was obtained using spline interpolation

which simplified the analysis and made assembly of the inertial matrix

damping matrix

and stiffness matrix a simple mathematical summation.The results indicate that the method is efficient and greatly simplifies the analysis.