A time-accurate procedure to model fluid/structure interactions of helicopter blades is presented. The Navier-Stokes equations in conjunction with the one-equation Spalart-Allmaras turbulence model are used to compute the flow. Structural dynamics is modeled using the modal equations. The aerodynamic and structural dynamic equations are coupled time-accurately using the linear acceleration method of Newmark (direct integration scheme). Effects of time accuracy on the computed results are investigated. Results are compared with experimental data for a full rotor blade system.