A Dynamic RCS and Noise Prediction and Reduction Method of Coaxial Tilt-Rotor Aircraft Based on Phase Modulation

Abstract

For tilt-rotor aircraft with coaxial rotors (coaxial rotor aircraft), reduction of radar cross section as well as acoustic noise can be essential for stealth design, and the rotation of the coaxial rotors can have an influence on noise and dynamic radar cross section (RCS) characteristics. In this paper, an approach to the prediction of both the sound pressure level (SPL) of noise and the dynamic RCS of coaxial-tilt aircraft is carried out, based on the theories of the FW-H equation, the physics optics method (PO) and the physical theory of diffraction (PTD) method. In order to deal with the rotating parts (mainly including coaxial rotors), a generated rotation matrix (GRM) is raised, aiming at giving a universal formula for the time-domain grid coordinate transformation of all kinds of rotation parts with arbitrary rotation centers and rotation axis directions. Moreover, a compass-scissors model (CSM) reflecting the phase characteristics of coaxial rotors is established, and a method of noise reduction and RCS reduction based on the phase modulation method is put forward in this paper. The simulation results show that with proper CSM parameter combinations, the reduction of noise SPL can reach approximately 3~15 dB and the reduction of dynamic RCS can reach 1.6 dBsm at most. The dynamic RCS and noise prediction and reduction method can be meaningful for the radar-acoustic stealth design of coaxial tilt-rotor aircrafts.

A Comparative Study of a Hybrid Experimental–Statistical Energy Analysis Model with Advanced Transfer Path Analysis for Analyzing Interior Noise of a Tiltrotor Aircraft

“…This means the excited subsystem has a higher response than other subsystems. (3) The subsystems are assumed to be uncoupled.…”

“…Tiltrotor aircraft, known for their vertical take-off and landing capabilities, have gained popularity in both military and civilian applications. However, this distinctive configuration introduces novel challenges related to noise generation [1][2][3]. In recent years, some studies have proposed new methods or designs to reduce the structureborne noise inside an aircraft or helicopter.…”

“…It achieves this by decomposing the output signal into distinct contributions originating from each input signal. Additionally, ATPA can effectively analyze the interconnections between input and output signals within the black box, revealing the inherent structure of the mechanical system, including the paths through which signals propagate [3]. Consequently, when a comprehensive examination of the mechanical system is required, ATPA proves to be a valuable tool.…”