The NLR 7223-62 airfoil is a high speed airfoil with peaky leading edge contour. The high lift performance needed for helicopter applications is achieved by an inverse camber at the trailing edge. In this paper, unsteady ∞ow flelds of this airfoil are computed using CFD based on RANS. Several turbulence models are investigated for Mach numbers up to 0:7. The CFD results are compared with experimental results. I. Introduction Analyses of unsteady aerodynamics are important for ∞utter, gust response and maneuver studies of flxed wing aircraft. These analyses for three dimensional conflgurations are computationally intensive and therefore two dimensional results are used employing strip and lifting-line theories. Usually unsteady aerodynamics calculations are performed for small perturbations about steady state. Unlike flxed-wing aircraft, the steady forward ∞ight of a helicopter is unsteady. This is due to the need for cyclic pitch to trim the helicopter. Therefore, unsteady aerodynamics of helicopters involve both large disturbances as well as small perturbations. The tip Mach number of advancing blade approaches high subsonic levels and hence compressibility efiects are important.