A formulation to determine the aeroelastic response of a rotor in forward flight is presented. The aerodynamic forces arising in the steady periodic state have been calculated using a frequency domain based CFD analysis in multiblade coordinates. The CFD model is coupled with a nonlinear finite element model of a rotor also in multiblade coordinates. The formulation is quite general and any fluid model governed by equations such as RANS, Euler or Hybrid can be used in the computations. The transformation to multiblade coordinates leads to the cancellation of harmonics except at the blade passage frequencies, thereby increasing the efficiency of the technique. The formulation is being implemented in a computer code and as of today the CFD solution in the frequency domain has been validated by comparing with the available experimental and numerical results.