This master’ thesis deals with the design of the front landing gear for Zlín 40 aircrafts. The main emphasis in the research part of the work is placed on the selection of a new nose landing gear and the subsequent design of the structure. For the structural design was prepared a new mass analysis and load cases. The load-bearing capacity of the structure is verified using analytical and numerical methods of FEM. An important step of the work is the design concept of structure. The aim of the work is to point out the new possibilities of the nose landing gear structure and verify its feasibility for the case of future implementation.

This diploma thesis deals with the flow analysis around the landing gear nacelle of L 410 and with its following aerodynamical optimalization. In the first part the calibration is performed on the known geometry which was tested in wind tunnel. The following parts contain own design of the optimal geometry, design of the computional mesh with its numerical solution and results evaluation.

Les avions légers sont conçus pour être utilisés dans les zones reculées d'un pays, où les infrastructures de transport sont inadéquates ou inexistantes. Ils peuvent atterrir sur différents types de piste (glace, gravier, sable, gros cailloux...). Le problème principal de ces avions est le défaut d’absorption d’énergie cinétique à l’atterrissage, bien qu'une partie des énergies de choc soit absorbée par les pneumatiques sous-gonflés. Des chocs et des rebonds peuvent se produire mettant en péril la sécurité de l’avion et des passagers. Le but de ce travail est de développer un outil numérique qui permet de modéliser les trains d'atterrissage, de prévoir leur réponse dynamique dans des conditions extrêmes, et de comparer leur capacité à dissiper l’énergie à la rencontre des obstacles. Étant donné son rôle primordial dans l'absorption des chocs, une étude expérimentale est dédiée à la caractérisation du pneumatique de brousse. Cette étude permet de construire un modèle éléments finis détaillé du pneumatique en prenant en compte la géométrie et la structure matérielle complexe. Une deuxième partie est consacrée à la modélisation numérique de quatre systèmes de trains d'atterrissage (existants ou proposés). De nombreuses simulations de roulement sont réalisées afin d'étudier, d'une part l'influence des conditions de roulement et l'influence de la taille et de la forme de l'obstacle d'autre part. L'analyse des amplitudes des efforts et des rebonds transmis à l'avion au cours du roulement permet d'évaluer les réponses dynamiques des différents trains et de comparer leur efficacité de dissipation / Light aircraft, such as bush planes, are designed for use in undeveloped areas of a country where transport infrastructure is inadequate or non-existent. They can land on different types of runways (ice, gravel, sand, big stones ...). The main problem with these aircraft is the lack of kinetic energy absorption at landing, although some of the shock energy is absorbed by the underinflated tires. Hard landing conditions such as shocks and rebounds may occur and endanger the safety of the aircraft and passengers. The aim of this work is to develop an efficient numerical tool for studying landing gear systems, predict their dynamic response in extreme conditions, and compare their energy dissipation. Given its primary role in shock absorption, an experimental study is dedicated to the characterization of the bush tire. Then, a detailed finite element model of the tire is developed, taking into account real geometry and material specificities. A second part is devoted to the numerical modeling of the different systems of landing gears (existing and proposed). Combined finite elements with structural elements are used. Thus, stress, deformation and energy within landing gears components could be obtained. Multiple dynamic rolling simulations are carried out in order to study, not only the influence of the rolling conditions (such as rolling velocity, tires inflation pressure, etc.), but also the influence of the size and the shape of obstacles. Systems' transient responses while rolling over ramp are evaluated, as well as the efforts and rebound displacements transmitted to the aircraft. A dissipation efficiency comparative study between the landing gears is conducted

The design of the landing gear is one of the more fundamental aspects of aircraft design. The design and integration process encompasses numerous engineering disciplines, e.g., structure, weights, runway design, and economics, and has become extremely sophisticated in the last few decades. Although the design process is well-documented, no attempt has been made until now in the development of a design methodology that can be used within an automated environment. As a result, the process remains to be a key responsibility for the configuration designer and is largely experience-based and graphically-oriented. However, as industry and government try to incorporate multidisciplinary design optimization (MDO) methods in the conceptual design phase, the need for a more systematic procedure has become apparent. The development of an MDO-capable design methodology as described in this work is focused on providing conceptual designer with tools to help automate the disciplinary analyses, i.e., geometry, kinematics, flotation, and weight. Documented design procedures and analyses were examined to determine their applicability, and to ensure compliance with current practices and regulations. Using the latest information as obtained from industry during initial industry survey, the analyses were in terms modified and expanded to accommodate the design criteria associated with the advanced large subsonic transports. Algorithms were then developed based on the updated analysis procedures to be incorporated into existing MDO codes. / Master of Science

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

A novel concept in noise control devices for landing gears is presented. These devices consist of elastic membranes creating a fairing around the major noise sources. The purpose of these devices is to reduce wake interactions and to hide components from the flow, thus, reducing the noise emission. The design of these fairings was focused on the major noise sources identified in a 777 main landing gear. To find the major noise sources, an extensive noise source identification process was performed using phased arrays. To this end, phased array technologies were developed and a 26%-scale 777 main landing gear model was tested at the Virginia Tech Stability Wind Tunnel. Since phased array technologies present some issues leading to misinterpretation of results and inaccuracy in determining actual levels, a new approach to the deconvolution of acoustic sources has been developed. The goal of this post-processing is to "simplify" the beamforming output by suppressing the sidelobes and reducing the sources mainlobe to a small number of points that accurately identify the noise sources position and their actual levels. To this end, the beamforming output is modeled as a superposition of "complex" point spread functions and a nonlinear system of equations is posted. Such system is solved using a new 2-step procedure. In the first step an approximated linear problem is solved, while in the second step an optimization is performed over the nonzero values obtained in the previous step. The solution to this system of equations renders the sources position and amplitude. The technique is called: noise source Localization and Optimization of Array Results (LORE). Numerical simulations as well as sample experimental results are shown for the proposed post-processing. / Ph. D.

The diploma thesis deals with the design of the replacement the Z 143 LSi landing gear with the new VUT 100 type landing gear in a retractable system. The first part of this thesis is devoted to the description of the Z 143 LSi aircraft and its landing gear and the description of the retractable landing gear type VUT 100. The next part describes the possible variants of the installation the VUT 100 landing gear, which are critically evaluated. Then there is selected the final variant for the installation, which is designed in Catia V5 software. The final design includes remotorization with Lycoming IO-390 and new design of engine bed. For the proposed solution, a new mass analysis with the calculation of centrations, new cases of ground load, a new flight envelope of load and additional cases of load of a new engine bed are prepared. The proposed engine bed is analyzed by the finite element calculation method in the MS Patran software. Finally, a possible scheme of the chassis retraction system is proposed.

This master thesis deals with the modernization of the main landing gear of the Z 143 LSi aircraft. The main emphasis is placed on optimizing of the landing gear shape and its deformation characteristics. Along with this change, variants made of different materials are examined. The landing load is calculated analytically and the load-bearing capacity of the structure is verified using the numerical FEM method. This work brings a possible replacement of the current chassis, which is production-intensive not only in time and money, but also in terms of cooperation with external companies. The objective is to design a new landing gear and verify the feasibility for the case of future implementation.

Modification of TST-14 MC glider, calculation of flight envelope, distribution of lift on the wing, calculation of loading cases of the wing, strength check of choosen construction nodes, design of the landing gear retraction mechanism, setting up loading of landing gear according to ULKM, strength check of landing gear

An aeroacoustic study was conducted on a 26%-scale Boeing 777 main landing gear in the Virginia Tech (VT) Anechoic Stability Wind Tunnel. The VT Anechoic Stability Wind Tunnel allowed noise measurements to be carried out using both a 63-elements microphone phased array and a linear array of 15 microphones. The noise sources were identified from the flyover view under various flow speeds and the phased array positioned in both the near and far-field. The directivity pattern of the landing gear was determined using the linear array of microphones. The effectiveness of 4 passive noise control devices was evaluated. The 26%-scale model tested was a faithful reproduction of the full-scale landing gear and included most of the full-scale details with accuracy down to 3 mm. The same landing gear model was previously tested in the original hard-walled configuration of the VT tunnel with the same phased array mounted on the wall of the test section, i.e. near-field position. Thus, the new anechoic configuration of the VT wind tunnel offered a unique opportunity to directly compare, using the same gear model and phased array instrumentation, data collected in hard-walled and semi-anechoic test sections. The main objectives of the present work were (i) to evaluate the validity of conducting aeroacoustic studies in non-acoustically treated, hard-walled wind tunnels, (ii) to test the effectiveness of various streamlining devices (passive noise control) at different flyover locations, and (iii) to assess if phased array measurements can be used to estimate noise reduction. As expected, the results from this work show that a reduction of the background noise (e.g. anechoic configuration) leads to significantly cleaner beamforming maps and allows one to locate noise sources that would not be identified otherwise. By using the integrated spectra for the baseline landing gear, it was found that in the hard-walled test section the levels of the landing gear noise were overestimated. Phased array measurements in the near and far-field positions were also compared in the anechoic configuration. The results showed that straight under the gear, near-field measurements located only the lower-truck noise sources, i.e. noise components located behind the truck were shielded. It was thus demonstrated that near-field, phased-array measurements of the landing gear noise straight under the gear are not suitable. The array was also placed in the far-field, on the rear-arc of the landing gear. From this position, other noise sources such as the strut could be identified. This result demonstrated that noise from the landing gear on the flyover path cannot be characterized by only taking phased array measurement right under the gear. The noise reduction potential of various streamlining devices was estimated from phased array measurements (by integrating the beamforming maps) and using the linear array of individually calibrated microphones. Comparison of the two approaches showed that the reductions estimated from the phased array and a single microphone were in good agreement in the far-field. However, it was found that in the near-field, straight under the gear, phased array measurements greatly overestimate the attenuation. / Master of Science