###### Abstract  
Fluid-structure interaction (PSI) is prevalent in aircraft hydraulic pipes due to high-pressure fluid pulsation, complex pipe path routing and boundary constraints, which pose a serious threat to the safety and reliability of the aircraft hydraulic system. This paper focuses on the FSI response of aircraft hydraulic pipes with complex constraints. A comprehensive fourteen-equation model for describing the FSI of pipe conveying  
[PERSON] [11]. The following representative research works are summarized: [PERSON] [12] presented the classical four-equation model, where the water hammer model was extended and combined with the axial stress model of the pipe and the friction coupling and damping effect were ignored. Then, the four-equation model was extended by [PERSON] et al. [13] and [PERSON] et al. [14], where Poisson coupling was taken into account. Based on the work of [PERSON], [PERSON] and [PERSON] [15] presented the six-equation model containing the radial deformation of the pipe and the added mass of the fluid. An eight-equation model considering axial movement of the free end of the pipe for the vibration analysis of the two-dimensional pipe had been built by [PERSON] [16]. Based on the fluid wave equation and Timoshenko beam model, a fourteen-equation model was firstly proposed by [PERSON] [17], where the pulsation of fluid, the axial deformation, transverse shear deformation, bending deformation of the pipe and the torsional deflection of the pipe wall were considered. After that, considering the friction coupling, Bourbon and junction coupling, the fourteen-equation model was extended and followed by a majority of researchers [9; 10; 18; 19]. The establishment of a more applicable and comprehensive FSI model awaits further study. Solution methods and experimental validations of FSI in the fluid-filled pipe mainly focused on the time domain and frequency domain. The time domain methods are usually used for the transient response analysis of the fluid and pipe, and in the frequency domain the free vibration and forced vibration response are paid much attention [17]. This paper places emphasis on time domain methods and verification; the literature of the main frequency domain solution methods is summarized briefly: the Transfer Matrix Method (TMM) [9; 10; 18; 19; 20; 21], Component Synthesis Method (CSM) [22], wave propagation method [23] and Laplace transform method [9; 10; 18]. The common methods of the time domain solution include: the Method of Characteristics (MOC), Transfer Matrix Method (TMM) [24; 25; 26], Finite Element Method (FEM) [27; 28; 29] and MOC-FEM [30; 31]. As an approximate method for solving hyperbolic partial differential equations, the MOC has become the most commonly used method in the time domain. TMM is a classical method of analyzing the system dynamics, simple solution process and high accuracy; these are the main advantages of this method. The representative research works are summarized: [PERSON] et al. [13; 32] used the MOC to simulate a fluid-filled copper pipe under pulse excitation, and verified experiments were carried out. The concrete steps and common simple boundary conditions for solving the fourteen-equation model through MOC were discussed in detail by [PERSON] [33]. [PERSON] et al. [34] used the MOC to analyze the fluctuating pressure of the two-dimensional aircraft hydraulic pipe. In practical usage, the time step and the length of the pipe segments must conform to the characteristic equation, which causes some limitations in the scope of application, calculation efficiency and calculation accuracy of the MOC. Other time domain solution methods based on the TMM were developed and received satisfactory results. Based on the TMM, [PERSON] [35] presented an appropriate set of dynamic equations and analytical methods, which is applicable to simple segments and complex tubing systems.