Effects of vehicle dynamics on small UAS-gust encounters

Abstract

This study investigates the relative impacts of different gusts on representative small Uncrewed Air Systems through the use of a simple analytical model. The model uses basic vehicle characteristics, including planform area and mass, to account for the altitude gained during gust interactions. This is a missing component from most current fundamental gust studies, both experimental and numerical. The results show that the induced negative effective angle of attack created by the vertical motion of the vehicle has a significant countering effect on the gust and suggests that this effective angle of attack should be accounted for in future gust studies. Efforts are undertaken to determine the relative importance of accounting for this motion. This is done by investigating the impact of the induced negative angle of attack on the altitude trajectory. An equation is found using gust and vehicle characteristics to determine the critical gust ratio at a given gust development rate, which is the minimum gust ratio which will lead to vehicle stall. Lastly, an empirical relationship is derived to allow for the effective gust ratio conversion between fixed-model experiments and flying-vehicle gust interactions.