AN INVESTIGATION OF HELICOPTER DYNAMIC COUPLING USING AN ANALYTICAL MODEL

Many attempts have been made in recent years to predict the off-axis r esponse of a helicopter to control inputs, and most have had little su ccess, Since physical insight is limited by the complexity of numerica l simulation models, this paper examines the off-axis response problem using an analytical model, with the goal of understanding the mechani cs of the coupling, A new induced velocity model is extended to includ e the effects of wake distortion from pitch and roll rate, It is shown that the inclusion of these effects results in a significant change i n the flap response to a steady angular rate. The proposed inflow mode l is coupled with the full rotor/body dynamics, and comparisons are ma de between the model and flight test data for a UH-60 in hover, Result s show that inclusion of induced velocity variations due to shaft angu lar rate improves correlation in the off-axis response to cyclic input s.