Aeroelastic Stability of an Aerial Refueling Hose–Drogue System with Aerodynamic Grid Fins

In this work, the aeroelastic stability of an aerial refueling system is investigated. The system is formed by a classical hose and drogue, and the novelty of our work is the inclusion of a grid fin configuration to improve its stability. The unsteady aerodynamic forces on the grid fins are determined using the concept of a unit grid fin (UGF). For each UGF, the unsteady aerodynamic forces are computed using the Doublet-Lattice Method, and the forces on the complete grid fins are calculated using interfering factors obtained from wind tunnel measurements for the steady case. The static equilibrium position of the system influences the linearized perturbed unsteady motion of the ensemble. This effect, together with the phase lag angle introduced to account for the unsteady aerodynamic forces in the hose, makes the flutter computation of the complete system a non-typical one. The results show that, by adding the grid fins, the stability of the refueling system is improved, delaying or annulling flutter occurrence.