• Advances in aircraft and spacecraft science
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• v.3 no.2
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• pp.211-224
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• 2016

The present study aims to investigate the shimmy stability behavior of a single wheeled nose landing gear system. The system is supposed to be equipped with an electromechanical actuator capable to control the shimmy vibrations. A Proportional-Integrative-Derivative (PID) controller, tuned by using the Particle Swarm Optimization (PSO) procedure, is here proposed to actively damp the shimmy vibration. Time-history results for some test cases are reported and commented. Stochastic analysis is last presented to assess the robustness of the control system.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.13 no.3
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• pp.97-109
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• 2005

A canard type aircraft, which has good wing stall and stall/spin-proof characteristics, is under development. The aircraft prototype has full-depth core sandwich type wing and fixed landing gear, and has been built for test flights. Newly developing aircraft will be equipped with retractable landing gear and conventional foam core sandwich laminate structures and multi-rib wings. In this study, we present the structural test procedure and result for aircraft Firefly.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.19-28
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• 2007

In this study, a nonlinear 2 degree of freedom mathematical model has been developed for impact analysis of the nose landing gear of a light aircraft which is composed of an wheel & tire, an Oleo-pneumatic shock strut and the castering wheel fork for the differential braking steering, and then the response of impact is computed using a numerical method. The mathematical model of a nose landing gear contains nonlinear characteristics which are an impact load - deflection property of a tire and internally frictional forces between an inner surface of an upper cylinder and a bearing of a lower rod due to side forces like the declined angle of strut, the moment due to an wheel fork, the side drag due to a steering and it is computed using the 4th-order Runge-Kutta method. The comparison process between analytical results and experimental results of the other proven nose landing gear is carried out to verify the mathematical model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.12
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• pp.1037-1044
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• 2014

In this study, we designed a drop test system considering lunar surface environment and tested landing gear of experimental lunar lander. The lunar lander would be landed at soil place for soft landing. When the lunar lander touches down, the acceleration of the lander is largely affected by mechanical characteristics of the lunar soil. Accordingly, a drop test using lunar soil is needed to verify the performance of the lunar landing gear. Because the lunar soil is not available generally, we developed a lunar simulant KAUMLS(Korea Aerospace University Mechanical Luna Simulant) based on mechanical properties of the lunar soil of NASA's LUNA PROJECT. In addition, drop tests on steel plate and dry sand are performed to evaluate impact characteristics by the surface environment.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.3
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• pp.394-406
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• 2015

In this work, an efficient aircraft landing simulation strategy is proposed to develop an efficient and reliable hard-landing monitoring procedure. Landing stage is the most dangerous moment during operation cycle of aircraft and it may cause structural damage when hard-landing occurs. Therefore, the occurrence of hard-landing should be reported accurately to guarantee the structural integrity of aircraft. In order to accurately determine whether hard-landing occurs or not from given landing conditions, full nonlinear structural dynamic simulation can be performed, but this approach is highly time-consuming. Thus, a more efficient approach for aircraft landing simulation which uses a hierarchical aircraft landing model and an extended inertia relief technique is proposed. The proposed aircraft landing model is composed of a multi-body dynamics model equipped with landing gear and tire models to extract the impact force and inertia force at touch-down and a linear dynamic structural model with an extended inertia relief method to analyze the structural response subject to the prescribed rigid body motion and the forces extracted from the multi-body dynamics model. The numerical examples show the efficiency and practical advantages of the proposed landing model as an essential component of aircraft hard-landing monitoring procedure.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.5
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• pp.330-336
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• 2000

This study deals with the characteristic of refrigerant for heat-treatment deformation control of SM45C steel. The control of heat-treatment deformation must need the progress of production parts for a landing gear. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for landing gear by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on thermal deformation and fatigue strength are also investigated.

• Journal of Aerospace System Engineering
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• v.14 no.4
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• pp.10-17
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• 2020

When an aircraft is taxiing, excitation force is applied according to the shape of the road surface. The sprung mass acceleration caused by the excitation of the road surface negatively affects the feeling of boarding. This paper addresses the verification process of the semi-active control method applied to improve the feeling of boarding. The Magneto-Rheological damper landing gear model is employed alongside the control method. It is a Oleo-Pneumatic damper filled with a fluid having the characteristics of increasing yield stress when subjected to a magnetic field. The control method involves verifying Skyhook Control Type2 developed by Skyhook control. The Sinozuka white noise model that considers runway characteristics was employed for the road surface in the simulation. The runway road surface obtained through this model has stochastic characteristics, so the dynamic characteristics were analyzed by applying Monte-Carlo simulation. A dynamic analysis was conducted by co-simulating the landing gear model made by RecurDyn and the control method designed by Simulink. Simulation results show that the Skyhook Control Type2 method has the best control effect in the low speed range compared to the passive type (without control) and skyhook control.

• Advances in aircraft and spacecraft science
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• v.7 no.5
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• pp.459-473
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• 2020

The aircraft nose landing gear (NLG) can suffer of an unstable vibration called shimmy that is responsible of discomfort and of fatigue stress on the gear strut components. An adaptive controller is proposed in this paper to cope with the aforementioned problem. It is based on a method called Modified Simple Adaptive control (MSAC) which is able of governing the NLG motion by using a feedback signal that relies on just one output of the plant. The MSAC only asks for the passivity of the controlled plant. With this aim, a parallel feedforward compensator is employed in this work to let the system satisfies the almost strictly passivity (ASP) requirements. The nonlinear equations that govern the aircraft NLG shimmy vibration behavior are used to analyzed the controlled system transient response undergoing an initial disturbance and taking into account different taxiing speed values.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.519-520
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• 2012

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.5
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• pp.805-811
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• 2011

Aircraft MLG and wing structures have been recognized as fatigue critical structures and exposed to the risk of fatigue crack initiation and propagation. Furthermore, these structures are frequently subjected to serious dynamic loading condition during a Hard Landing which may lead to their failure. Especially, structural integrity of MLG and wing components is decreased as the flight time increased because of the fatigue damage accumulated on the aircraft. In this study, the effects of Hard Landing on the MLG and wing components of aging aircraft were evaluated by using numerical approach. To achieve the aim, a finite element model has been developed and simulations were conducted by varying the landing conditions. As a result, it was revealed that the high stress concentration phenomenon was occurred at the lower Side Brace of MLG. Thereby, the intensified inspection for the lower Side Brace should be considered to prevent unexpected aircraft mishap.