No description available.

No description available.

No description available.

Within the overarching area of airplane noise, landing gear noise has been proven to be a major contributor to airframe noise. Despite a large focus given to it by past research work, landing gear noise investigations have continuously failed to include landing lights, completely disregarding their potential for seriously altering the landing gear wake structure and overall noise signature. This thesis is one of the first studies to focus on the effect of landing light orientation on landing gear wake and landing gear noise. Pressure fluctuations in the wake of a simplified single light landing gear model are investigated experimentally for several freestream velocities and at various elevations of measurement plane. The effect of the distance between the light and the landing gear strut is also investigated. Three-dimensional flow is found in the wake at the center, or zero elevation, plane. This three-dimensionality is found to be much weaker at the highest elevation from the light, where the wake is found to be primarily two-dimensional. The nature of the transition region between the three-dimensional flow and two-dimensional flow is not investigated, but it is acknowledged that a transition region exists. Complex flow behaviour leading to a wake width larger than twice the size of the light-strut assembly width is found to be present at the zero elevation, and phase-locked PIV imaging is unable to capture any periodic motion within the wake at this elevation. In contrast, the wake at the highest elevation is found to resemble the flow in the wake of circular cylinders, and phase-locked PIV imaging at this elevation clearly captures an alternate vortex shedding scheme. Due to this difference in wake structures, the periodicity at the highest elevation is found to be stronger than that observed at the zero elevation. Changes in light-strut spacing are found to inversely affect the strength of the periodicity in the wake, as larger spacing is linked to greater influence of three-dimensionality, and therefore a weaker periodicity. Changes in light-strut spacing are also found to be inversely related to the oscillation frequency of the periodicity, with the cause for this relationship possibly explained by the wider wake at increased spacing. It is found that the oscillation frequency of periodicity in the single light landing gear wake is consistently in the Strouhal number range of St=0.16-0.18 for all light-strut spacing distances, freestream velocities, and elevations. The flow around the light-strut assembly is therefore characterized as modulated flow around a cylindrical strut because alternate vortex shedding is dominant except for a slight region where the light acts to generate three-dimensionality, and because the oscillation frequency is near that of vortex shedding from a circular cylinder, St=0.19. The wakes of the single light landing gear and two-light landing gear models are compared, but neither design can be supported as quieter than the other at this time due to the unknown amount of vertical radiation from the landing gear wakes. / Thesis / Master of Applied Science (MASc)

ABSTRACT NON-LINEAR MATHEMATICAL MODELING OF GEAR-ROTOR-BEARING SYSTEMS INCLUDING BEARING CLEARANCE G&Uuml / RKAN, Niyazi Ersan M.S. Department of Mechanical Engineering Supervisor: Prof. Dr. H. Nevzat &Ouml / ZG&Uuml / VEN November 2005, 130 pages In this study, a non-linear mathematical model of gear-rotor systems which consists of elastic shafts on elastic bearings with clearance and coupled by a non-linear gear mesh interface is developed. The mathematical model and the software (NLGRD 2.0) developed in a previous study is extended to include the non-linear effects due to bearing clearances by using non-linear bearing models. The model developed combines the versatility of using finite element method and the rigorous treatment of non-linear effect of backlash and bearing clearances on the dynamics of the system. The software uses the output of Load Distribution Program (LDP), which computes loaded static transmission error and mesh compliance for the contact points of a typical mesh cycle, as input. Although non-varying mesh compliance is assumed in the model, the excitation effect of time varying mesh stiffness is indirectly included through the loaded static transmission error, which is taken as a displacement input into the system. Previous computer program which was written in Fortran 77 is rewritten by using MatLAB 7.0 and named as NLGRD (Non-Linear Geared Rotor Dynamics) Version 3.0. The program is highly flexible and open to further developments. The program calculates dynamic to static load ratio, dynamic transmission error, forces and displacements at bearings. The mathematical model suggested and the code (NLGRD version 3.0) are validated by comparing the numerical results obtained from the model suggested with experimental data available in literature. The results are also compared with those of previously developed non-linear models. The effects of different system parameters such as bearing stiffness, bearing clearance and backlash on the gears are investigated. The emphasis is placed on the interaction of clearances in bearings with other system parameters.

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.

This diploma thesis deals with design of retractable landing gear for Rapid 600 aircraft. The main purpose of this thesis is to analyze different retraction options for front and main landing gear and resulting selection of suitable variants. The thesis is consequently concerned with design of selected options including proposal of automatic landing gear control system and specifying the features and characteristics of this system. In the thesis there is also included the analysis of critical flight conditions which could be detected by this system.

No description available.

No description available.

The general trend in gear industry is an increased focus on gear transmission efficiency. This thesis focuses on the understanding of how different gear manufacturing methods – particularly the contribution of the running-in process – affect the surface characteristics and friction response, with the purpose of increasing gearbox efficiency. The thesis consists of a summary and five appended papers. The research hypothesis in paper A and paper B was that the dry elastic contact area ratio is a descriptive parameter for the contact condition. Paper A deals with the influence of manufacturing method on the initial contact conditions. The emphasis in paper B is the changes that occur during running-in and correlating these changes to design requirements. Paper C examines the influence of manganese phosphate coating and lubricants, with respect to friction and the risk of scuffing at the initial contact. Paper D examines the effect of running-in load on the friction response for different surfaces. In paper E, the question of whether the load during running-in influences the gear mesh efficiency is further expounded. The main conclusions of this thesis are that the running-in influences the gear mesh efficiency; a high running-in load enhances the gear mesh efficiency. The difference in mesh efficiency is in the range of one tenth of a per cent. Thus, the influence of running-in cannot be neglected because it is in the same order of magnitude as reported for other gear efficiency enhancements. Furthermore, the dry elastic contact area ratio presents a descriptive measure of how surface topography influences the contact, at both a global (form deviation) and local (roughness) level. The surface topography caused by the manufacturing method has a significant influence on the contact area ratio. Shaving was found to have the highest contact area ratio, and would therefore be the best choice if deviations from case hardening could be minimised. It was also confirmed that surfaces coated with manganese phosphate raise the limiting load for scuffing failure up to 13 times compared to the uncoated ground equivalent. / <p>QC 20141002</p>