Expensive and time-consuming flight tests are required to evaluate different helicopters and flight control systems in terms of handling and ride qualities. If gusts occur during these flights, they can distort the flight crew's perception of the handling and ride qualities. Therefore, it is desired to quantify the influence of gusts on these criteria. This requires the determination of gusts that occur during the flights. Indirect methods are favored for quantification of the gusts to avoid the complex mounting of expensive measuring devices. Existing gust reconstruction approaches rely on gust models in addition to dynamic models of the vehicle, so the quality of these approaches depends on the validity and quality of the gust models. Hence, an approach that is only bound to the model validity of the vehicle dynamics is preferred. Unfortunately, such an approach is currently not available. This paper addresses this gap by deriving an observer using the closed-loop shaping method. The proposed observer reconstructs gusts from measured accelerations considering the gust rejection properties of the helicopter. Consequently, it works independently of any gust model and provides an easy-to-use alternative to existing methods. The quality of the approach is evaluated with simulation data under various flight conditions.
