Flight dynamics and stability of a tethered inflatable kiteplane

Abstract

The combination of lightweight flexible-membrane design and favorable control characteristics renders tethered inflatable airplanes an attractive option for high-altitude wind power systems. This paper presents an analysis of the flight dynamics and stability of such a kiteplane operated on a single-line tether with a two-line bridle. The equations of motion of the rigid-body model are derived by Lagrange's equation, which implicitly accounts for the kinematic constraints due to the bridle. The tether and bridle are approximated by straight line elements. The aerodynamic force distribution is represented by four discrete force vectors according to the major structural elements of the kiteplane. A case study comprising analytical analysis and numerical simulation reveals that the amount and distribution of lateral aerodynamic surface area is decisive for flight dynamic stability for the specific kite design investigated. Depending on the combination of wing dihedral angle and vertical tail plane size, the pendulum motion shows either diverging oscillation, stable oscillation, converging oscillation, aperiodic convergence, or aperiodic divergence. It is concluded that dynamical stability requires a small vertical tail plane and a large dihedral angle to allow for sufficient sideslip and a strong sideslip response. © Copyright 2010.