Dynamic characteristics analysis of towed decoy during release based on Kane's equation

A study is presented of the dynamic characteristics of an aeronautic towed decoy during its release from an aircraft. The releasing process is divided into a falling stage, a releasing stage and a towing stage. A multi-body dynamic model is built for the towed decoy system based on Kane's equation. In this instance, the cable is discretized into an arbitrary number of segments. The decoy is considered as a rigid body hanging from the cable. The cable and decoy's airloads are considered in the dynamic model, as well as the effects of the cable's motion. Numerical simulations of the dynamic characteristics in different conditions are conducted, and the results show that when the towed decoy is released at a high flight speed or altitude, the amplitude of the decoy's pitching angle decreases and the relative position of its gravity center varies smoothly. When the cable releasing speed rises, the amplitude of the decoy's pitching angle decreases and a longitudinal plunging motion of the gravity center occurs, but the releasing time is shortened. When the towed point is far away from the gravity center, the amplitude of the decoy's pitching angle increases. The rate of convergence becomes slow when the towed point is near the gravity center. This study may provide some reference for the design and working of towed decoys.