Numerical investigations on radar cross-section of helicopter rotor with varying blade pitch

Abstract

A calculation method is presented to study the radar cross-section (RCS) of the rotating rotor at different blade pitches. Based on blade pitch control, grid matrix transformation, and instantaneous RCS calculations, the electromagnetic scattering characteristics of the blade, rotor, and helicopter are obtained by the presented method. The pitch angle of each blade of the main rotor is regulated in fixed control mode, linear control mode and smooth control mode. The surface scattering characteristics of the blade in the fixed mode, the RCS of the blade and the rotor in the linear mode, and the effects of different control modes on the RCS of the rotor and helicopter are investigated. When the azimuth is 80°, the pitch of blade 1 is 9.6° in linear mode, and the RCS of some facets near the leading edge is reduced to −65 dBm2 under the given observation conditions. In the fixed control mode, the minimum period of the rotor RCS is equal to the basic passage time of the blade, while in linear control mode and smooth control mode, the minimum period of the rotor RCS is increased. Compared with the fixed control mode, the linear control mode can reduce the RCS peak of the helicopter at the given moment, and the smooth control mode is beneficial to reduce the RCS average of the rotor and helicopter at the given azimuth. The presented method is effective to analyze the dynamic RCS of the rotor and helicopter under different blade pitches, and has important engineering value for the stealth design of helicopter rotors.