THE EFFECT OF INFLOW MODELS ON THE PREDICTED RESPONSE OF HELICOPTERS

This paper examines in detail some modifications to main rotor aerodyn amic modeling that will affect the off-axis response of a helicopter. Three different approaches are examined: a version of momentum theory extended to include wake distortion, a first-order aerodynamic lag mod el, and an aerodynamic phase correction, It is shown that all three ap proaches result in similar changes to the off-axis response when appli ed to a simplified linear model of the coupled pitch-roll dynamics in hover, Numerical values for the inflow parameters are determined using system identification and are compared to theoretical predictions and previously identified values, Comparisons are also made between a non linear simulation model incorporating the extended momentum theory and flight test data for a UH-60 in hover, demonstrating considerable imp rovement in the off-axis response prediction.