The present work deals with the sensitivity of aerodynamic force to variations in viscous coefficients and chemical reaction rates in thermochemical nonequilibrium flow over HB2 model. Within this scope, numerical simulations are conducted by varying the viscous coefficients and chemical reaction rates over their uncertainty range. The numerical method uses Park's two-temperature model for the description of thermochemical nonequilibrium processes and solves the full N-S equations for a multicomponent reacting gas mixture. The effect of variations in viscous coefficients and chemical reaction rates on pressure coefficient on the flare skirt part shows a big difference. The thicker boundary layer is not the reason for pressure becoming higher on the flare part. It is found that the main contribution to the pressure increase in the nonequilibrium case is the change of temperature due to chemical nonequilibrium, but not the increase of viscous coefficient.