Abstract: The aeroelasticity of helicopter composite rotor blades with elastic coupling is analyzed. The st ructuralmodel in this analysis includes the effect s of t ransverse shear deformation , out-of-plane warping and aeroelastic coupling. A 21-DOF beam finite element , including t ransverse shear DOF and warping DOF , is developed for analysis.The governing differential equations of motion for a hingeless rotor are derived using the Hamiltonps principle.Three different composite blade configurations are conducted for comparison. The result s show that changes in bladef requencies are very small , however , the mode shapes are significantly changed considering elastic coupling. Theblade stability in hover is st rongly affected by the ply-induced composite couplings. Positive flap -torsion couplinghas a stabilizing effect on the lag mode damping. Negative flap-torsion coupling has a destabilizing effect on the lagstability.