Variable flight velocity contributions to elastic/ viscoelastic lifting surface control effectiveness

The paper reports on analyses regarding control effectiveness of viscoelastic wings and control surfaces, such as ailerons, flaps, horizontal and vertical tail surfaces, etc. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [1]. Such elastic analyses are here extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings the critical parameter is the velocity at which control reversal takes place. Since elastic formulations constitute viscoelastic initial conditions, viscoelastic reversal may occur at speeds, but furthermore does so in time at 0 < t_cr ≤ ∞. Variable flight velocities that may occur during rolling maneuvers are also taken into account.