Results of the Study of the Influence of External Cargo Parameters on the Helicopter Controllability

Helicopters are widely used for air transportation and aerial work with cargo on external cables, one of the most challenging and dangerous uses. The main reason for the flight complication is the change in the controllability characteristics of the helicopter because of the presence of cargo. As of today, flight tests are mainly conducted to determine the feasibility of aerial transportation and aerial work involving external cargo. In addition, they are conducted to determine safe flight regimes when performing such operations. From a flight safety perspective, it is always desirable to know the changes in the control parameters before flight tests are performed. A proposal was made to use theoretical methods, including numerical simulations, to solve these problems. At present, work is progressing to isolate the effects of different cargoes on the external cable suspension and its direct effects on the static and dynamic characteristics of the helicopter’s control and stability. The effect of cargo mass and sail weight on the control efficiency is expressed by the helicopter’s angular acceleration, which is gained by deviating the cyclic pitch handle—a static control and stability indicator. When considering dynamic control and stability, the influence of the length of the external suspension cable on the transition time was investigated. The results obtained were refined for inclusion in all flight manuals for Mi-8 helicopters concerning flights with cargoes attached to the external suspension cables, the size and weight of the suspension cables as well as the methods of instruction and for preparing the crew for flights with upgraded cargo, including instruction via flight simulators.