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Analysis of Landing-Gear Behavior

TL;DR: In this article, a theoretical study of the behavior of the conventional oleo-pneumatic landing gear during the process of landing impact is presented in a general form and treats the motions of the landing gear prior to and subsequent to the beginning of shock-strut deflection.
Abstract: This report presents a theoretical study of the behavior of the conventional type of oleo-pneumatic landing gear during the process of landing impact. The basic analysis is presented in a general form and treats the motions of the landing gear prior to and subsequent to the beginning of shock-strut deflection. The applicability of the analysis to actual landing gears has been investigated for the particular case of a vertical landing gear in the absence of drag loads by comparing calculated results with experimental drop-test data for impacts with and without tire bottoming. The calculated behavior of the landing gear was found to be in good agreement with the drop-test data.

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Proceedings ArticleDOI
10 Aug 2009
TL;DR: In this article, the authors focused on modeling of a MR damper for landing gear system and analysis of semi-active controller to attenuate dynamic load and landing impact, and developed a PID controller to reduce the acceleration of the system.
Abstract: Depending on the different sink speeds, angles of attack and masses; aircraft landing gears could face a wide range of impact conditions which may possibly cause structural damage or failure. Thus, in hard landing scenarios, the landing gear must absorb sufficient energy in order to minimize dynamic stress on the aircraft airframe. Semi-active control systems are the recent potential solutions to overcome these limitations. Among semi-active control strategies, those based on smart fluids such as magneto-rheological (MR) fluids have received recent attraction as their rheological properties can be continuously controlled using magnetic or electric field and they are not sensitive to the contaminants and the temperature variation and also require lower powers. This thesis focuses on modeling of a MR damper for landing gear system and analysis of semi-active controller to attenuate dynamic load and landing impact. First, passive landing gear of a Navy aircraft is modeled and the forces associated with the shock strut are formulated. The passive shock strut is then integrated with a MR valve to design MR shock strut. Here, MR shock strut is integrated with the landing gear system modeled as the 2DOF system and governing equations of motion are derived in order to simulate the dynamics of the system under different impact conditions. Subsequently the inverse model of the MR shock strut relating MR yield stress to the MR shock strut force and strut velocity is formulated. Using the developed governing equations and inverse model, a PID controller is formulated to reduce the acceleration of the system. Controlled performance of the simulated MR landing gear system is demonstrated and compared with that of passive system

8 citations


Cites background from "Analysis of Landing-Gear Behavior"

  • ...The part of the fuselage on each gear can be considered as a rigid mass since the main gears of the aircraft are mostly located near the nodal points of the wing bending modes and consequently landing gear performance is not affected by the elastic deformation of the aircraft structure [10]....

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Journal ArticleDOI
TL;DR: The model developed is accurate sufficiently and very suitable for real-time flight simulation to represent complex ground reaction behavior under various conditions and occasions and would have cause to decrease the cost for developing a flight simulator with higher fidelity in future.

8 citations

Journal ArticleDOI
TL;DR: In this article, a complete system of the main landing gear of a transport aircraft landing gear was mapped as a deformable 3D numerical model for dynamic analysis with the use of LS-Dyna code.
Abstract: Dynamic analyses of a transport aircraft landing gear are conducted to determine the effort of such a complex system and provide capabilities to predict their behaviour under hazardous conditions. This kind of investigation with the use of numerical methods implementation is much easier and less expensive than stand tests. Various 3D models of the landing gear part are defined for the multistage static FE analysis. A complete system of the main landing gear was mapped as a deformable 3D numerical model for dynamic analysis with the use of LS-Dyna code. In this 3D deformable FE model, developed in a drop test simulation, the following matters were taken into consideration: contact problems between collaborating elements, the phenomena of energy absorption by a gas-liquid damper placed in the landing gear and the response of the landing gear during the touchdown of a flexible wheel with the ground. The results of numerical analyses for the selected drop tests and the results from the experiments carried out on a real landing gear were used for verification of FE models and a methodology of the landing gear dynamics analysis. The results obtained from the various simulations of the touchdown have proved the effectiveness of the 3D numerical model and how many problems can be solved in the course of only one numerical run, e.g. geometric and material nonlinearities, a question of contact between the mating components, investigation of the landing gear kinematics, investigation of the energy dissipation problem in the whole system and the stresses influence on the structure behaviour, which can appear in some elements due to overload.

8 citations


Cites methods from "Analysis of Landing-Gear Behavior"

  • ...The research of aircraft landing gear operation with an oil-pneumatic (oilgas) damper is also described in work [28]....

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References
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01 May 1948

5 citations


"Analysis of Landing-Gear Behavior" refers background or methods in this paper

  • ...In addition to the total fo,'ce on the upper mass, figure 4 Ca) presents calcLdatcd time histories of the hydraulic and pneumatic components of the shock-strut force, as determined from equations (2) and (3), respectively....

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  • ...Equation (2) can be nlade applicable to both tile compression and elongation strokes by introducing tlle factor 7; to indic....

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