Dynamics and Equilibrium of a Twin-Aircraft-Cable System for Payload Retrieval

Abstract

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 utilizing an aircraft cable system to lift large payloads is studied in this paper. This concept has been studied 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 multi-aircraft-multi-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 model is used to study the relative equilibria of a twin-aircraft-twin-cable system. Parametric studies of different payload masses and aircraft orbit parameters are presented, and the dynamic stability is analyzed. The dynamics of the system during different towpoint maneuvers is also presented.