SCISSORS ROTOR CONCEPT: NEW RESULTS OBTAINED

The paper presents the analysis of the results obtained from the 4-bladed experimental scissors rotor tests conducted on the whirl tower in the flight condition corresponding to hovering. The rotor blades had a variable scissors angle. The influence of the chordwise angular blade position as well as the distance between the blades along the rotor shaft on the rotor performance is shown. Essential difference in rotor aerodynamic characteristics depending upon the fact which blade, the upper or the lower one, is the leading one is presented. Optimal combinations of parameters required to obtain the maximum increase in hovering thrust and figure of merit of the rotor in comparison with the conventional rotor configuration have been defined. Flight test results of a scissors tail rotor and those of a three-bladed conventional one installed on one and the same helicopter are compared, changes in the load level in rotor structural members and pitch trim are presented. Using comparative flight test results, changes in the sound pressure spectrum and external noise level are shown when a scissors rotor is used instead of a three-bladed conventional one.