In-flight deployment of morphing UAVs: A method to analyze dynamic stability, controllability and loads

Several morphing unmanned aircraft systems which can be deployed in-flight are currently being developed for a variety of missions. Key to a successful in-flight deployment of these aircraft is that they enter a stable and controllable flight phase following a potentially highly dynamic transition phase without exceeding structural limitations. The aim of the current study is to develop a new physics-based methodology which can be used to assess under which flight conditions an unmanned morphing aircraft can be safely deployed in terms of stability, controllability and dynamic flight loads. The method is based on a Monte Carlo Simulation of the deployment phase with a multibody dynamics simulation model. As test case, the Dash X UAV is analyzed in combination with different deployment scenarios. Parameters to be varied are initial flight conditions such as body angular rates and the morphing strategy. The model is validated against a limited set of flight test data in its deployed state. Example results of the aircraft motion and loads are presented for safe deployments with a highly dynamic transition phase. The procedure to construct stability limits and deployment load envelopes is presented. The deployment load envelopes are a natural extension to the V-n diagram typically used for structural design. The stability limits can be used to determine the operational limits under which a UAV can be deployed safely without the risk of entering an unstable or uncontrollable flight regime. Ultimately, this method can be used to support the design of in-flight deployable morphing UAVs and the related operational procedures. It is demonstrated that the Dash X UAV can be safely deployed under realistic conditions with acceptable structural loads.