FLIGHT DYNAMICS OF AN ARTICULATED ROTOR HELICOPTER WITH AN EXTERNAL SLUNG LOAD

The paper presents a study of the flight dynamics of an articulated rotor helicopter carrying a suspended load. The aircraft model includes rigid body dynamics, individual flap and lag blade dynamics, and inflow dynamics. The load is a point mass with a single suspension point. The load affects trim primarily through the overall increase in the weight of the aircraft, both in straight and in turning flight. The influence of cable length is negligible. Substantial coupling can occur between the Dutch roll and the load modes. Because of this coupling, the Dutch roll damping can decrease with a deterioration of handling qualities. The effects on the phugoid are very small. A suspended load modifies the roll frequency response by adding a notch to the gain curves and a 180-degree jump in the phase curves at the pendulum frequencies of the load. The changes in bandwidth and phase delay are small.