Research On Stability Of The Flight Of Helicopters With Sling Loads

This paper works on the aircraft dynamics and stability of the helicopter with a sling load.Forest fires are serious natural disasters that threaten the environments and the security of human’s life and property,but there aren’t efficient ways to put them out. Fire-fighting missiles casted by the equipment which is slung by the helicopter are useful tools to quench the forest fires. Compared with the helicopters that hang nothing, the slung-load flight has additional gravity and aerodynamic resistance. In addition to the extra forces, the condition above the forest-fire field is severe. Therefore it’s essential to research on the aircraft dynamics and stability of the helicopter with a sling load.In the beginning of the paper, the slung-load system of the helicopter is introduced. The application and research status both at home and abroad of the helicopter with a sling load are also studied and analyzed. Accordingly, the essentiality of this paper is obvious.In the main part of this paper, the slung-load technology is studied through three aspects—flight performance, slung-load system and implementing technology. After that, the mathematical models of the sling load, the sling and the helicopter are founded separately.According to the relationships between the three parts, the dynamic model of the entire system is built. The dynamic model is composed by a series of mathematical equations needed to be trimmed. With the help of MATLAB, the attitude angles and manipulated variables of the balanced state can be got. With the trimming results, the state and control matrixes which are used as the theoretical basis for the subsequent analysis of the stability of the whole system can be got,too.After establishing the mathematical models, some certain factors that will influence the system’s stability are analyzed. These factors include the helicopter’s flight speed,the slung-load spot, the length of the sling, the weight of the sling load and the aerodynamic characteristics of the slung load. These research can do a great help to the practical flight and the design of the slung load.