Abstract
A relatively low-order linear dynamic model is developed for the longitudinal flight-dynamics analysis of a flexible flying-wing research drone, and results are compared to previously published results. The model includes the dynamics of both the rigid-body and elastic degrees of freedom, and the subject vehicle is designed to flutter within its flight envelope. The vehicle of interest is a 12–lb, unmanned flying-wing aircraft with a wingspan of 10 ft. In the modeling, the rigid-body degrees of freedom are defined in terms of motion of a vehicle-fixed coordinate frame, as required for flight-dynamics analysis. As a result, the state variables corresponding to the rigid-body degrees of freedom are identical to those used in modeling a rigid vehicle, and the additional states are associated with the elastic degrees of freedom. Both body-freedom and bending–torsion flutter conditions are indicated by the model, and it is shown that the flutter speeds, frequencies, and genesis modes suggested by this low-order model agree very well with the analytical predictions and flight-test results reported in the literature. The longitudinal dynamics of the vehicle are characterized by a slightly unstable phugoid mode, a well-damped pitch-dominated elastic-short-period mode, and the stable or unstable aeroelastic modes. A classical rigid-body short-period mode does not exist.
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