This article proposes simultaneous helicopter and control system design and illustrates its advantages. First, the traditional, sequential approach in which a satisfactory control system is designed for a given helicopter is applied. Then, a novel approach, in which the helicopter and control system are simultaneously designed, is applied to redesign the entire system. This redesign process involves selecting certain helicopter parameters as well as control system parameters. For both design procedures the key objectives are to minimize control energy and satisfy prescribed variance constraints on specific outputs. In order to solve the complex optimization problem corresponding to the simultaneous design approach, an efficient solution algorithm is developed by modifying the simultaneous perturbation stochastic approximation method to account for limits on optimization parameters. The algorithm is applied to redesign helicopters using models generated in straight level as well as maneuvering flight conditions. The performance of the designs obtained using the sequential and simultaneous design approaches is compared and the redesign process is thoroughly investigated. Finally, the robustness of the redesigned systems is also studied.