Dynamics of Towed Payload System Using Multiple Fixed-Wing Aircraft

The payload capability of many aircraft is typically limited by the maximum takeoff weight. However, when in flight, many aircraft can handle larger loads, but this capability is rarely exploited. The possibility of using an aircraft cable system to lift large payloads is studied in this paper. This concept has been studied previously for single-aircraft, single-cable systems in some detail. The major limitation of such systems is the need to fly very tight circles at high-lift coefficients. This limits the size of the payload that can be retrieved with such a system. To overcome this, it is possible to employ a multiple-aircraft, multiple-cable system to allow greater control of the payload position as well as allowing a much wider choice of aircraft speed and lift coefficient. In this paper, an object-oriented cable modeling approach is used to study the relative equilibria of such a system. Parametric studies of different payload masses and aircraft orbit parameters are presented, and the dynamic stability is analyzed. Collision-free transition trajectories that take the multiple-aircraft system from circular flight into straight and level flight are derived.