Dissertations / Theses on the topic 'Main landing gear'

This diploma thesis deals with the landing gear design of the small two-seat aircraft. The introduction focuses on the conceptual gear design and shock absorber computational dynamic characteristic model. The practical part is focused on the landing gear construction according to the selected parameters based on the conceptual and computational model. The diploma thesis ends with strength calculations and production documentation.

Experimental measurements and numerical simulations were conducted on a simplified main landing gear model that consists of a leg-door, and a main strut in a parallel configuration. The effects of varying the leg-door angle of attack, and the gap distance between the two elements, were initially studied by two-dimensional and low-order numerical simulations, using the unsteady Reynolds-Averaged Navier-Stokes equations. The strut diameter was specified to the same diameter as a full-scale main landing gear, and simulated under a free-stream Mach number of 0.2, and a Reynolds number based on the cylinder diameter of 1:7 x 106. Further three-dimensional and high-order numerical simulations were conducted on models with a constant gap distance of 8.7% of the cylinder diameter. The high-order solver evaluates the three-dimensional Navier-Stokes equations in the full-conservation form, with the Zonal Detached-Eddy Simulation model. The fidelity of the numerical solver was improved in two parts. Firstly, an Eigenvalue analysis for a multiple-block environment was developed to optimise the combination of spatial and filtering schemes for maximum grid resolution that is numerically stable. Secondly, a grid quality metric, which correlates strongly to the solution accuracy, was developed. A validation database of experimental measurements on a tripped 26% scale interaction model, at a free-stream Mach number of 0.09, and a Reynolds number based on the cylinder diameter of 2 x 105, was developed at the 2:1 m x 1:5 m wind tunnel at the University of Southampton. The experimental and numerical results show that the wake generated by the interaction model is dominated by low frequencies that correspond to the vortex shedding modes of the cylinder, and the door. As the door angle is increased from 0 to 10.7 degrees, the intensity of the cylinder shedding mode decreased. The sound pressure levels of the radiated noise were calculated using the FW-H method. The dominant noise source is a compact dipole, which reduced in strength as the door angle was increased.

This thesis presents a bifurcation and numerical continuation study into the occurrence of shimmy instability in an aircraft main landing gear (MLG) of single side-stay, dualwheel design. The dynamics are expressed in terms of three rotational degrees of freedom (Dofs) aligned with the side-stay plane, and a fourth translational DoF representing compression of the main strut. These DoFs are modelled by oscillators that are coupled directly through the geometric configuration of the system, as well as through the tyre/ground interface. Using this representation of the MLG system we focus in this thesis on the nonlinear effects of geometric orientation and mechanical freeplay employing bifurcation analysis techniques to highlight their effects on the MLG stability. First, a changing side-stay orientation angle is investigated. Shimmy is studied by means of a two-parameter bifurcation analysis in terms of the landing gear forward velocity and loading force. For this a three-DoF model is used that does not include axial compression. This formulation along with suitable parameters allows for comparison with the existing literature, and an agreement is demonstrated with previous results for a zero side-stay angle. Subsequent variation of this angle is explored and a consistent picture presented, capturing the (transition of the two-parameter bifurcation diagram us a function of this angle. This shows a considerable increase in the complexity of the dynamics for intermediate side-stay angles. The appearance of an additional shimmy mode is observed and a region of tri-stability found where three distinct shimmy types coexist. For the study of freeplay the MLG model is extended to include axial compression; this axial DoF is required to accurately represent freeplay, introduced to the torque links of the system. Parameter values are chosen here to represent a typical mid-range civil aircraft MLG. The addition of freeplay is shown to result in shimmy oscillations that occur within the MLC operating envelope; their properties depend on both the size and 'shape' of freeplay. Freeplay and geometric coupling arc also considered together via consideration of a non-zero side-stay angle. Here, additional dynamic complexity is introduced in the presence of freeplay and, again , this coincidence with the appearance of a new shimmy mode. Further complex phenomena also appear, including multiple- frequency and chaotic-type oscillations, as well as complex transients. The non-zero geometry produce asymmetry and this results in a great sensitivity of the small-amplitude MLG behaviour to the exact shape of freeplay. Therefore, geometric orientation and freeplay a.re found to have significant effects and, when combined, they work together to produce additional complex phenomena, not otherwise observed when considered in isolation.

The aim of this master thesis is modification of landing gear for accomplishment CS-23 regula-tion from that purpose, because landing gear in the use can't pass this type of certification. The first part examines the alternatives of landing gear with consideration optimal technical and eco-nomical difficulty. After finding optimal type of landing gear with shock absorber is there part of designing and computing the load. Last part of thesis is about stress analysis of whole con-cept and reconsidering final changes.

The goal of following master thesis is to design variety of configuration and retraction options of VUT200 TwinCobra landing gear. For each option are a wheel base and a gauge set up by possibility of main landing gear retraction. Next, CS 23 demands and stress analysis are followed. There is a view of twin engine aircraft landing gear disclosed as well.

Aerodynamic measurements were taken over models of the Boeing 777 high fidelity isolated landing gear in the 6- by 6-foot Virginia Tech Stability Wind Tunnel (VT-SWT) at a free-stream Mach number of 0.16. Noise control devices (NCD) were developed at Virginia Tech [9] to reduce noise by shielding gear components, reducing wake interactions and by streamlining the flow around certain landing gear components. Aerodynamic measurements were performed to understand the flow over the landing gear and also changes in the flow between "Baseline" and "NCD" configurations (without and with Noise Control Devices respectively). Hot-film, Pitot-static measurements and flow visualization using tufts were performed over an isolated 26% scale-model high fidelity landing gear for the "Baseline" and "NCD" configurations. Contours of turbulence intensity, normalized wake velocity and normalized total pressure loss for both configurations are compared. The "Baseline" configuration was also compared with the NASA Ames study conducted by Horne et al [7]. Hot-film measurements are also compared to Microphone Phased Array results which were acquired at Virginia Tech by Ravetta [8]. A novel technique for processing hot-film measurements by breaking turbulence into octave bands as acoustic measurements is presented. Particle Image Velocimetry (PIV) measurements were taken at six different locations over the 13% scale-model landing gear with no door and at a truck angle of zero degrees. Results are compared to PIV measurements taken over the wheels of a four-wheel landing gear by Lazos [10-12]. PIV results such as average velocity contours and vectors, streamlines and instantaneous velocity contours and vectors are presented. Results presented from PIV and flow visualization are in good agreement with results from Lazos [10-12].
Master of Science

This master thesis is about stress analysis of landing gear for accomplishment CS-23 regulation. The first part examines all alternatives of landing gear regarding for accomplishment of regulation. Next part is stress analysis of main and nose landing gear using FEM analysis in MSC Nastran software. Last part of master thesis describes topology optimization of two parts of landing gear.

In this thesis, we deal with the design of a shock absorber variant for the type of main landing gear design of the aircraft WT10 Advantic. Then we focus on the design of the selected variant of the main landing gear. Next, we follow regulation CS-23 demands to calculate the load cases for the selected main lending gear. Then we design shock absorber based on the load during landing. We compile the equation of motion of the aircraft, which describes motion of the aircraft during landing, then we compute the equation. Finally, we focus on a stress analysis of the main landing gear and the shock absorber.

This study investigates the flow field and acoustics of a generic four wheel main landing gear. The landing gear is an important airframe noise source during the approach phase. The characteristics of the flow field around the bogie area of the main landing gear are largely unknown. CFD simulations using the DES turbulence model have been used to calculate the unsteady flow field around a generic landing gear model. The surface pressure data has been sampled and used in a FW-H solver to determine far field noise levels. Two different landing gear models have been used, a simplified geometry and a more realistic complex geometry. Three different bogie angles have been simulated: horizontal bogie aligned with the flow, 10⁰ toe up and 10⁰ toe down. Strong streamwise vortices are generated at the front wheels of the landing gear. The trajectory of these vortices determines where the turbulent flow interacts with the downstream components. This interaction leads to surface pressure fluctuations which are a major noise source. The flow field of the simplified configurations shows a consistent trend of the trajectory of the streamwise vortices with respect to changes in bogie angle. The far field noise levels generated by the different components of the simplified configurations are related to the distance at which the streamwise vortices pass. The additional components of the complex landing gear geometry change the characteristics of the flow field. The strong streamwise vortices persist but they do not show the same trend as for the simplified configurations. The wake of the articulation link generates a turbulent in flow for the other components. The different characteristics of the flow field of the complex configurations lead to significant changes in the far field noise levels of the components compared to the simplified configurations.

This thesis studies the design of an electro-hydraulic landing gear and brakes control system of a trainer aeroplane. In the first part there is a basic draft of the landing gear kinematics and its loads during gear retraction, flight and landing. Braking conditions are also analysed. The thesis then focuses on the design of hydraulic circuits and their control. Simulations for studying the dynamic characteristics of the braking proportional valve and the course of plane braking were created in Simulink. There is also a brief section about reliability of the proposed system.

碩士
淡江大學
航空太空工程學系碩士班
98
The application of composite material on the aerospace industry begin WWII, the percentage from not more than 1% to the newly aircraft Boeing 787 nearly 50% of aircraft structure using the composite material. Recently, cause of the fuel price increased, the aircraft manufacture to search for the new method decrease the aircraft fuel consumption. Using composite material is the method one of the method to solve the question. Decrease the fuel consumption is mean that the airliner can carry more passengers and more cargos, make the airliner cut down the expenses of fuel consumption. Thus, the using composite material is an important of future aerospace industry. This research is focus on the light sport aircraft main landing gear structural analysis, by change the material from using the 6061-T6 aluminum to the S-Glass fiber composite material. Using finite element method to analysis the difference material of the main landing gear on the static and dynamic condition. And study the relative aviation composite regulations and light sport aircraft regulations, some of the boundary condition is connect with these regulations, for intense, the payload is use the light sport aircraft regulations. Verify the reliable of the dynamic simulation observe the change between dynamic energy and internal energy, hourglass energy and sliding energy. Then increase the glide slope angle for 3°and 5°, observe the difference between aluminum and composite material main landing gear stress, strain and energy change, the static result shows that composite material stress decrease 5%, strain decease 30%, weight decrease 8%, and establish the reliable simulation platform. Provide the data for light sport aircraft design and analysis.

碩士
國立成功大學
航空太空工程學系碩士在職專班
107
The purpose of this thesis is to research and investigate main landing gear door malfunctions that frequently occur in T-34C aircraft. Aircraft airflow changes continuously in the air. In order to find the reason for landing gear malfunctions, I proposed a hypothesis with fixed characters and values in a real situation. I collected the frequency of discrepancies in T-34C aircraft in 2014. According to the technical order and operating principles of the T-34C landing gear system, I posited that there is a pressure difference between the inside and outside of the landing gear cabin when the aircraft are in the air. I calculated the force of the T-34C airfoil (NACA23016) in CFDRC when aircraft fly at 90, 100, 110, 120 knots per hour at an altitude of 10,000 ft. The results of experiments indicate the following: 1.Technicians need to adjust the landing gear tension (54-67 pounds). 2. The pilot should put the landing gear up when flying at speeds over 100 knots per hour.

Thesis (M.S.)--University of Tennessee, Knoxville, 2004.
Title from title page screen (viewed Sep. 20, 2004). Thesis advisor: George W. Garrison. Document formatted into pages (x, 89 p. : ill. (some col.)). Vita. Includes bibliographical references (p. 39-40).