Helicopter Transportation As A Sling Load With Another Rotorcraft: Dynamic Behavior Study And Stabilizing Parachute Sizing

Abstract

This paper details a novel methodology for determining parachute dimensions to ensure stable sling load operations between two rotorcrafts. We present a comprehensive approach encompassing analytical and multibody dynamic modelling to address the critical challenge of maintaining stability during this complex operation. Initially, we analytically evaluated the neutral yaw static stability of the carried helicopter fuselage, vertical tail, and parachute, establishing an initial parachute area estimation. Subsequently, a single-degree-of-freedom dynamic system (yaw motion only) was employed to validate these results. A detailed multibody model simulating the complete system - including the carrier and transported rotorcrafts with the stabilizing parachute - was developed to account for environmental factors, cable lengths, and inter-axis coupling effects. Furthermore, the dynamic behavior of the transported helicopter without the parachute was assessed. Finally, structural load calculations, adhering to CS-29.865 (Ref. 1), were performed to determine the forces acting on the system, ensuring safe operational parameters.