Simulation of coupled helicopter-slung load-pilot dynamics

A nonlinear simulation of a helicopter carrying a fin-stabilized underslung load was developed. Simulation predictions were validated using comparisons to flight-test results. A human pilot model was incorporated in the simulation to study the dynamics and stability of the helicopter-slung load-pilot system. Simulation results and their subsequent analysis show that the underslung load is stabilized by the helicopter. These results confirm observations from flight tests regarding the critical role of the piloting technique in determining the stability of the system. Pilot attempts to counteract load lateral oscillations by applying lateral stick commands cause the system to become unstable and result in pilot-induced oscillations. Freezing the lateral stick causes load oscillations to completely decay or damp down to very low residual amplitudes. The effect of piloting technique diminishes at high airspeeds due to the increase in load stability.