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Landing Gear Aerodynamic Noise Prediction Using Building-Cube Method  [PDF]
Daisuke Sasaki,Deguchi Akihito,Hiroshi Onda,Kazuhiro Nakahashi
Modelling and Simulation in Engineering , 2012, DOI: 10.1155/2012/632387
Abstract: Landing gear noise prediction method is developed using Building-Cube Method (BCM). The BCM is a multiblock-structured Cartesian mesh flow solver, which aims to enable practical large-scale computation. The computational domain is composed of assemblage of various sizes of building blocks where small blocks are used to capture flow features in detail. Because of Cartesian-based mesh, easy and fast mesh generation for complicated geometries is achieved. The airframe noise is predicted through the coupling of incompressible Navier-Stokes flow solver and the aeroacoustic analogy-based Curle’s equation. In this paper, Curle’s equation in noncompact form is introduced to predict the acoustic sound from an object in flow. This approach is applied to JAXA Landing gear Evaluation Geometry model to investigate the influence of the detail components to flows and aerodynamic noises. The position of torque link and the wheel cap geometry are changed to discuss the influence. The present method showed good agreement with the preceding experimental result and proved that difference of the complicated components to far field noise was estimated. The result also shows that the torque link position highly affects the flow acceleration at the axle region between two wheels, which causes the change in SPL at observation point. 1. Introduction Great progress has been made in Computational Fluid Dynamics (CFD) in the past several decades, and nowadays it plays an important role in the design and analysis for aircraft development. The emerging problem for the commercial aircraft development is how to reduce the airframe noise from high lift device and landing gear. CFD has been widely used to predict the flow around the high lift device to reduce the aerodynamic noise, whereas the application of CFD to the landing gear is still limited [1–6]. The landing gear is constructed with many bluff components, and thus the noise source is not singular but many and thus complicated. To predict the noise from the real landing gear geometry precisely, all the components need to be modeled in the computation to treat all the interaction effect. Japan Aerospace Exploration Agency (JAXA) has developed a research landing gear model with detailed components based on the current two-wheel landing gear to understand the noise generation mechanism by experiments and numerical analysis. The model, Landing gear Evaluation Geometry model (LEG), includes all the components even with pins, tubes, and cavity as shown in Figure 1 [4–6]. To analyze the flow and acoustic field of the landing gear, the
FEA Based Analysis of Composite Torque Link for a Passenger Aircraft Landing Gear  [PDF]
R. Arravind,R. Mohamed Rijuvan,R. Mohamed Rijuvan
International Journal on Theoretical and Applied Research in Mechanical Engineering , 2013,
Abstract: In the implementation of a composite landing gear technology program was started, a composite torque link for transport airplane landing gear applications was developed. The torque link was designed by finite element analysis and analysis for maximum stress condition. The torque link was fabricated by Resin Transfer Moulding (RTM) for which a tooling concept was developed. Static tests demonstrated the load carrying capabilities in undamaged and damaged condition of the torque link since all specimens failed beyond their Design Ultimate Load level for that case we are hereby carryout the analysis process in order to find the ultimate load and yield stress for the torque link.
An Effective Safety Analysis Method of Civil Aircraft Landing Gear

- , 2016,
Abstract: 以满足民机起落架全寿命周期的安全使用为目标,结合结构、机构、系统可靠性理论,提出了一套完整的民机起落架安全性分析方法。以某型民机前起落架不能放下或放下未锁定故障模式为例,进行了安全性分析,当分析结果不满足安全性指标要求时,则需通过安全性灵敏度分析,开展民机起落架的安全性设计改进。该分析方法适用于飞机设计全过程,可指导起落架设计优化,并可为民机适航取证提供技术支持。
The goal of this paper is to meet the safe use of the whole life cycle of civil aircraft landing gear. Based on the theory of structure, mechanism and system reliability, a complete analysis method of safety of civil aircraft landing gear is given. Taking the nose landing gear failure to extend and down-lock as an example, the safety analysis is performed. When the results do not meet the requirements of the safety indicators, improved safety design of civil aircraft landing gear need to be made using sensitivity analysis. This method is application to the whole process of aircraft design. The method can guide the optimal design of landing gear and provide support for airworthiness
A Simplified Flexible Multibody Dynamics for a Main Landing Gear with Flexible Leaf Spring  [PDF]
Zhi-Peng Xue,Ming Li,Yan-Hui Li,Hong-Guang Jia
Shock and Vibration , 2014, DOI: 10.1155/2014/595964
Abstract: The dynamics of multibody systems with deformable components has been a subject of interest in many different fields such as machine design and aerospace. Traditional rigid-flexible systems often take a lot of computer resources to get accurate results. Accuracy and efficiency of computation have been the focus of this research in satisfying the coupling of rigid body and flex body. The method is based on modal analysis and linear theory of elastodynamics: reduced modal datum was used to describe the elastic deformation which was a linear approximate of the flexible part. Then rigid-flexible multibody system was built and the highly nonlinearity of the mass matrix caused by the limited rotation of the deformation part was approximated using the linear theory of elastodynamics. The above methods were used to establish the drop system of the leaf spring type landing gear of a small UAV. Comparisons of the drop test and simulation were applied. Results show that the errors caused by the linear approximation are acceptable, and the simulation process is fast and stable. 1. Introduction Automatic takeoff, landing, and taxiing are very important parts of completely autonomous flight of UAV, and taxiing tests on UAVs are obviously expensive and risky as it is easy to bring about accidents under high-speed taxiing. Simulation on the other hand is particularly important before the prototype taxiing experiment. During the development of control systems, real-time simulations such as man-in-the-loop (MIL) and hardware-in-the-loop (HIL) are also used to take place between design level simulations and costly experiments with the real plant [1–3]. Obviously accurate and efficient computer simulations of UAV on-ground models play an important role in the control system design, performance evaluations, and dynamics analysis of such vehicle systems. Meanwhile research on ground dynamics in the past decades has achieved significant results, and the design of these dynamics traditionally relies on mathematical model. Ro [4] has studied aircraft-runway dynamics in detail. In general mathematical equations of ground dynamics are complex, highly coupled, and nonlinear; their derivation and numerical implementation demand considerable time and computer cost. In recent years, the accuracy and computational efficiency of flexible multibody has been the focus of research [5, 6]. The simplified flexible multibody method enables the dynamic response to simulate effectively, even be used in many real-time simulations [7–9]. Nonretractable type landing gear has been widely used in

DENG Yangchen,

力学与实践 , 2008,
Abstract: In the light weight design of truss-like landing-gear structure, the related specification on strength is considered. The bars' strength and critical loads are used as constraints and the minimum structural weight design is achieved by shape and size optimization. The data obtained from an example agree with the results of static force test. Theoretical analysis and the flight of model planes carrying load show that the approach is not only feasible but also effective. It can be used to design the landing-gear structure of a small or super light-weighted vehicle. %Finally, three conclusions have been drawn from this paper.
Analysis on Brake Induced Vibration of Aircraft Main Landing Gear

- , 2018,
Abstract: 建立了飞机刹车滑跑刚柔耦合动力学模型,采用控制变量法分析了单一因素对起落架抖振现象的影响规律,结果表明,当刹车力矩变化的频率接近起落架系统共振频率时,抖振现象非常剧烈;刹车力矩最大值越大,刹车力矩波动值越大时,抖振的振幅变化范围越大。在此研究基础上,分别对施加了减速率控制或滑移率控制的飞机起落架抖振进行研究,结果表明,相比于减速率控制方式,带PID控制器的滑移率刹车控制法不仅可提高刹车系统效率,而且可有效降低起落架抖振,提高飞机着陆安全性。
Rigid-flexible coupling dynamics models for taxi and brake analysis are established. In order to analyze the influence factors of brake torque on gear buffeting in this model, the control variable method is applied. Simulation analysis is carried out on this model by changing only one parameter at a time. The simulation results show obviously that:when the frequency of brake torque variation gets close to the resonance frequency, gear buffeting phenomenon is very intense. When the maximum value of the brake torque rises, the gear buffeting phenomenon becomes acute. If the magnitude of gear buffeting fluctuation rises, the range of gear buffeting amplitude is larger in response. Based on previous conclusions, the slip rate braking control strategy and deceleration control strategy are applied for anti-skid braking control respectively, the further research on gear buffeting phenomena under two control cases is conducted, and the response under two different ways of anti-skid braking control strategy are compared. The results show that:the slip rate braking control method with PID controller are much better than the braking control method of deceleration control type, it can improve main gear brake efficiency, slow down gear buffeting, and also improve landing safety
Research on Noise Characteristics for a Nose Landing Gear

- , 2016,
Abstract: 采用仿真与试验的手段对不同来流速度下某型飞机前起落架1/6缩比模型的噪声特性进行了研究。仿真基于"CFD+CAA"混合方法,气动噪声试验在声学风洞中进行。计算与试验结果的对比表明:特征平面的流场分布十分吻合,起落架下游产生大量的涡结构;低频噪声源位于机轮后缘附近,中高频噪声位于减振支柱与防摆支架之间;起落架噪声频谱呈现为宽频特性,计算结果与试验结果基本吻合;远场噪声呈现为典型的偶极子指向性,偶极子长轴与轮轴方向平行。
Experiment and simulation are launched to study the aeroacoustic characteristics of a 1/6 scale aircraft nose landing gear in this paper. Simulation is based on the "CFD+CAA" hybrid method. And the flow and noise field is measured in an aeroacoustic wind tunnel. Comparing the results of the simulation with experiments indicate that, the flow field of the simulation agree with the experiment well. Low frequency noise source located around the wheels, and the middle and high frequency noise sources appear between the shock strut and Anti-twist bracket. The sound pressure spectrum curves are almost consistent in low and middle frequency range, and the spectrum of the far field noise is broadband, the dipole and monopole dominate the landing gear noise, and the directivity has a form of dipole
Design Method of Shimmy Plank for Nose Landing Gear

- , 2018,
Abstract: 本文给出了激励板设计标准之后,对扭转、侧向、纵向扰动的初始载荷进行了理论分析,包括尺度效应、延迟效应、形状效应,研究了激励板的安装角、横截面形状和尺寸等主要设计参数的影响作用。然后,通过带有柔性体的起落架多体建模仿真方法,验证了不同安装角下前起落架扭转、侧向和前后方向的激励效率,以及不同高度和宽度组合设计的激励板激励出的轮胎载荷及轮轴加速度响应。最后,摆振试验数据分析结果表明,设计的3种规格的激励板是安全有效的。
After providing plank design criteria, the loads in yaw, lateral and longitudinal directions for initiating the shimmy were theoretically analyzed, considering the scaling effect, delaying effect, and form effect. Influence of the main parameters in plank design on initial loads was researched, such as installation angle, cross-section shape and size. Then, applying the multi body modeling and simulation method of landing gear with flexible body, confirmed excitation efficiency of nose landing gear with different installation angles in yaw, lateral and longitudinal directions, as well as tire loads and acceleration responses on axle, which were generated by the planks designed with different height and width. At last, the shimmy test results show that the three planks are safe and effective
Multiple Failure Simulation and Health Evaluation of Aircraft Landing Gear Hydraulic Retraction/Extension System

- , 2016,
Abstract: 起落架不能正常收放严重威胁飞行安全,迫切需要掌握其健康状态以便提前预防故障发生。以典型支线客机的起落架收放系统为研究对象,探索了对不同故障模式下的健康程度进行评估的方法。利用AMESim软件建立了该系统的仿真模型,研究液压回路中元件参数性能变化对系统工作性能的影响。选取系统输出参数,提取故障特征,利用神经网络算法实现了系统的健康评估。结论表明该方法是可行的,为新一代飞机起落架液压收放系统的健康评估提供了思路。
Abnormal landing gear retraction/extension(R/E) will make the aircraft unable to land and endanger the flight safety. It is necessary to prevent the failure and avoid the accident by knowing its health condition. A multiple failure modes based health evaluation of aircraft landing gear hydraulic R/E system is developed. For typical regional aircraft, a simulation model of this system is built by AMESim software. The effects of degradation of different component parameters in the hydraulic loop are calculated and fault characteristics are extracted. Health evaluation is performed through neural network algorithm. Simulation and calculation results show that the fault characteristics are reasonable and this method is feasible, which provide a way for health evaluation of new generation aircraft landing gear hydraulic R/E system
Dynamics Analysis and Testing of an Aircraft′s Landing Gear Retraction System

- , 2016, DOI: 10.16450/j.cnki.issn.1004-6801.2016.04.005
Abstract: 采用虚拟仿真及物理试验相结合的方法对飞机起落架收放系统性能进行研究。基于收放系统工作原理,推导了动力学数学模型,建立了结合起落架动力学和液压系统的多学科协同仿真模型,通过试验结果对虚拟样机模型进行验证。基于虚拟模型和试验平台对液压系统阻尼特性进行了分析,结果表明,联合仿真模型的压力曲线与试验实测数据吻合良好,为起落架收放系统提供了准确的设计方法。仿真及试验表明,阻尼孔径的缩小使压力变化缓慢同时振荡较严重,液压缸作动滞后较为明显。
In order to study landing gear retraction performance, research on an aircraft′s landing gear retraction system was carried out that combines a simulation and laboratory test. The working principle of the system was analyzed, and the dynamic mathematics model were derived in detail. A simulation model was established that combines the landing gear dynamics with the hydraulic system, and a laboratory test was carried out to verify the accuracy of the simulation model. Then, the damping characteristic of the hydraulic system were analyzed based on the simulation model and the test. The results show that the pressure curves of the co-simulation model agree with the test data, which verifies the accuracy of the co-simulation model. Moreover, both the simulation and test show that narrowing the damping hole makes the pressure change slowly and oscillate violently, leading to an obvious lagging stroke.
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