Influence of Rotor Dynamic Scattering on Helicopter Radar Cross-Section

Abstract

With the continuous improvement and development of armed helicopters, the research on their stealth characteristics has become more and more in depth. In order to obtain the complex effect of stealth characteristics caused by the high-speed rotation of rotor-like components, a dynamic scattering method (DSM) is presented. Rotation speed, azimuth, elevation angle, pitching angle, and rolling angle are studied and discussed in detail. The results show that the electromagnetic scattering characteristics of the main rotor and tail rotor are dynamic and periodic. This period characteristic is related to the rotation speed and attitude angle of the rotor. The radar cross-section (RCS) of the helicopter varies greatly at different observation angles and attitude angles, but the dynamic electromagnetic scattering effect caused by the main rotor and tail rotor cannot be ignored. The presented DSM is effective and efficient for studying the dynamic RCS of the rotor-type parts of a helicopter or the whole machine.

X-Band Radar Cross-Section of Tandem Helicopter Based on Dynamic Analysis Approach

“…The helicopter consists of two main rotors and a fuselage; thus, its initial model can be expressed as follows: where t is time, m h is the model of the tandem helicopter, m r1 is the model of rotor 1, m r2 is the model of rotor 2, m f is the model of the fuselage [ 3 , 15 ]. In the current coordinate system, when rotor 1 rotates, its dynamic model can be updated to: where M r1 is the grid coordinate matrix of rotor 1, superscript x represents the translation along the x -axis, superscript xz represents the rotation around the z -axis in the current operation, X r1 is the distance between the axis of rotor 1 and the z -axis in the initial state.…”

“…The validation of DAA is presented in Figure 2 , where f RH refers to radar wave frequency and horizontal polarization, rotating speed of rotor 1 n r1 = 1200 r/min. The PO + method of the moment (MOM)/multilevel fast multipole method (MLFMM) in FEKO is used to calculate the RCS of the target and compare it with the result of DAA [ 3 ]. For the case of t = 0.0058 s, it can be seen that the two RCS curves are generally similar, including peak size, peak position and overall trend.…”

“…As a uniquely configured aircraft, the tandem helicopter has the advantages of heavy load, small space size and high hovering efficiency, which makes it widely used in transportation, passenger transportation and rescue tasks. Hence, studying the electromagnetic scattering characteristics of tandem helicopters has important academic significance and engineering value [ 1 , 2 , 3 ].…”

“…Unlike the conventional layout of a helicopter, the tandem helicopter has two large main rotors, which are installed on the lower tower at the nose and the higher tower at the tail, noting that this design allows the two main rotors to affect the aircraft’s RCS within the circumferential azimuth range. According to the core idea of the dynamic scattering method [ 3 ], we apply this approach to the tandem helicopter and expand the independent calculation of the influence of the rotor disk tilt and the analysis of the Doppler characteristics. Therefore, this paper attempts to present a dynamic analysis approach (DAA) to determine the RCS of a tandem helicopter.…”

Keen Investigation of the Electromagnetic Scattering Characteristics of Tiltrotor Aircraft Based on Dynamic Calculation Method

“…Unlike the radar signature of fixed-wing aircraft and birds, the aerodynamic and electromagnetic scattering characteristics brought by tilting rotors are more complex [8][9][10]. Changes in incident wave frequency, rotor rotation speed and attitude angle will all affect the dynamic RCS of conventional helicopters [11][12][13]. It is worth noting that the tilt rotor aircraft can adjust the rotor shaft from the horizontal position to the vertical position while keeping the posture of the fuselage unchanged [14].…”