In this paper, the L ₁ adaptive control theory is used to design a high bandwidth inner loop controller to provide attitude and velocity stabilization of an autonomous small-scale rotorcraft in the presence of wind disturbances. The nonlinear model of the vehicle is expressed as a linear time-varying system for a predefined region of operation, for which an L ₁ adaptive controller is designed. The L ₁ adaptive controller ensures that an uncertain linear time-varying system has uniformly bounded transient response for system's input and output signals, in addition to stable tracking. The performance bounds of L ₁ adaptive controller can be systematically improved by increasing the adaptation rate without hurting the robustness of the system. The performance achieved with the L ₁ controller is compared with that obtained via a linear state feedback controller for demanding reference signals in the presence of wind disturbances. Simulation results show that the performance of the L ₁ surpasses that of the linear controller illustrating the advantages of fast adaptation.