Abstract
Modern advancements of Unmanned Aerial Vehicles (UAVs) indicate designs that are more flexible than conventional aircraft. Though accurate models of flexible aircraft have been generated to examine flutter during steady-level flight, there is much to understand regarding the impact maneuvers have on the stability of flexible UAVs. To explore the stability of a generic UAV, the critical flutter speeds and frequencies are calculated using coupled aeroelastic analytic methods. The mathematical model applied for steady-level flight conditions combines rigid body and elastic dynamics to generate sufficiently accurate flutter speeds and frequencies. Using a similar model modified for steady maneuvers, this study will examine the impact the maneuvers have on stability by comparing results to that of steady-level flight. Time invariant maneuvers, such as steady climbs and steady-level turns, will be examined at various altitudes. Extracted from existing work for maneuvering aircraft, the expectation is that the UAV will be less stable during both maneuvers. Results for both maneuvers examined indicate that a climb ranging from a decline of eight degrees to an incline of eight degrees has minimal impact on critical flutter speeds. However, trends largely suggest that the aircraft becomes marginally more stable as the climb angle increases. For example, at 20 kilometers, at a climb angle of eight degrees, the flutter speed is calculated to be 63.97 meters per second – a flutter speed larger than steady-level flight conditions. As for steady-level turn scenarios observed, trends in flutter speeds generally indicate that the aircraft becomes less stable as the turn radius reduces. This can be observed at an altitude of 20 kilometers, where with a turn radius of 500 meters, the flutter speed is approximately 63.906 meters per second – a flutter speed smaller than steady-level flight conditions at the same altitude.