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In aircraft, the main landing gear wheels skid on the runway at the moment of touchdown because of high slip. A slipping tyre generates enough heat to melt its rubber. Melted rubber is easily eroded by the friction force between the tyre and runway; and part of eroded rubber stays on the runway, and other is burnt off as smoke. Since the early days of airplane use, a number of ideas have been patented to improve tyre safety and decrease the substantial wear and smoke during every landing by spinning the gear wheels before touchdown. In this thesis, there are three parts of research work. First part is to find the effectiveness of the technique of pre-spinning the wheel to reduce the tyre tread heat and wear, and then choosing the initial wheel rotation speed that prevent the tread rubber from melting temperature. For achieving this, a coupled structural – thermal transient analysis in ANSYS has been used to model a single wheel main landing gear as a mass-spring system. This model has been chosen to analyze the wheel's dynamic behaviour and tyre tread temperature and wear during the short period from static to a matching free-rolling velocity in which the wheel is forced to accelerate by the friction between the tyre and ground. The tyre contact surface temperature and wear have been calculated for both the initially static and pre-spun wheels in order to compare the temperature and wear levels for different initial rotation speeds. In the second part, the required torque to spin the aircraft wheel to the required angular speed at approach speed has been calculated using ANSYS CFX, which is used to determine the wheel aerodynamic forces developed by simulation of fluid flows in a virtual environment. In the last part, several types of wind turbines have been simulated.

The research reported in this thesis has examined means of enhancing the performance of the Optimal Trade-off Maximum Average Correlation Height (OT-MACH) filter for target detection in Forward Looking Infra-Red (FLIR) imagery acquired from a helicopter and border security FLIR camera in northern Kuwait. The data acquired with these FLIR sensors allows real-world evaluation of the comparative performance of the various filters that have been developed in the thesis. The results obtained have been quantified using well known performance measures such as Peak to Side-lobe Ratio (PSR) and Total Detection Error (TDE). The initial focus was to study the effect of modifying the OT-MACH parameters on the correlation metrics. A new optimisation technique has been presented, which computes statistically the filter alpha parameter associated with controlling the response of the filter to clutter noise. A further modification of the OT-MACH filter performance using the Difference of Gaussian bandpass filter (named the D-MACH filter) as a pre-processing stage has been described. The D-MACH has been applied to several test images containing single and multiple targets in the scene. Enhanced performance of the modified filter is demonstrated with improved metrics being obtained with less false side peaks in the correlation plane, especially when multiple targets are present in the test images. A further pre-processing technique was investigated using the Rayleigh distribution as a pre-processing filter (named the R-MACH filter). The R-MACH filter has been applied to multiple target types with tests conducted across various image data sets. The filter demonstrated an improvement over the Difference of Gaussian filter in terms of 6 reducing the number of parameters needing to be tuned whilst producing further enhanced correlation plane metrics. Finally, recommendations for future work has been made to improve the use of the OT-MACH filter in target detection and identification. A novel training image representation is proposed for further investigation, which will minimise the computational intensity of using the MACH filter for unconstrained object recognition.

This thesis focuses on the design, development and testing of a two dimensional particle in cell (PIC) code (PICSIE) written in Matlab. The code is applied to the specific problem of modelling the performance of dual stage ion thrusters. The code simulates one full aperture within dual stage ion thruster systems, focusing on the flow of ions through the aperture. Only the ions have been included in the simulation in order to minimize running time. The results produced by the simulation code are compared with results obtained from the vacuum chamber testing of the DS4G prototype, along with results from other simulation codes and research papers in order to verify the performance of the simulation code. The Dual-Stage 4-Grid (DS4G) and Dual-Stage 3-Grid (DS3G) thrusters are both sim- ulated in order to compare the performance of the two thrusters and assess the benefits and disadvantages of including the fourth grid in a dual stage thruster system. Different grid configurations are simulated in order to find the most efficient configuration of the ion optics and accelerating voltages for each thruster, with the aim being to find the con- figurations that produce the maximum particle momentum, thrust and specific impulse while minimizing the rate of erosion of the ion optics and maximising the efficiency of the thruster. These simulations are applied to the problem of deciding if the advantages provided in using a 4th grid outweigh the disadvantages compared to the 3 grid design. The results show that if erosion due to backstreaming ions is disregarded, including the fourth grid in the thruster design results in no apparent advantages in terms of the perfor- mance parameters studied in this work. The only noticeable difference between the three and four grid cases is a significant increase in the change in ion momentum observed when the fourth grid is not included in the design. The conclusion of the work is that the fourth grid should not be included in the dual stage design unless a very long lifetime is required and it is thought that erosion due to backstreaming will prevent the three grid thruster from fulfilling this criteria. The concept of propagating waves through the plasma within the ion thruster discharge chamber is investigated, with the aim of discovering any benefits and improvements in performance that may arise and forming a conclusion on whether further study on the topic of waves within the discharge chamber may be beneficial. No improvements in per- formance parameters were observed in this work, although further study in the area may show benefits to introducing waves into the plasma.

Physics of laminar-to-turbulent transition in a separated-reattached flow subjected to two free-stream turbulence levels have been explored using Large-Eddy Simulation (LES). Separation of the laminar boundary layer occurs at a curvature change over a flat plate with a semi-circular leading edge. A numerical trip has been used to generate the targeted free-stream turbulence levels. A dynamic Sub-grid-scale (SGS) model has been employed and excellent agreement has been achieved between the LES results and the experimental data. Detailed investigation of the LES data has been carried out to explore the primary instability mechanism at low (< 0.2%) and high free-stream turbulence (5.6%). The flow visualisations and spectral analysis of the separated shear layer reveal that the two-dimensional Kelvin-Helmholtz instability mode, well known to occur at low free-stream turbulence levels, is bypassed at a higher level leading to earlier breakdown to turbulence. The whole transition process leading to breakdown to turbulence has been revealed clearly by the flow visualisations and the differences between the low and high free-stream turbulence cases are clearly evident. Coherent structures are also visualised using iso-surfaces of the Q-criterion and for the high free-stream turbulence case the spanwise oriented two-dimensional rolls, which are clearly apparent in the low free-stream turbulence case, are not visible anymore. Detailed quantitative comparisons between the present LES results against experimental data and the previous LES results at low free-stream turbulence using a staggered grid have been done and a good agreement has been obtained, indicating that the current LES using a co-located grid with pressure smoothing can predict transitional flows accurately. Comprehensive spectral analysis of the separated shear layer at two free-stream turbulence levels has been performed. Under very low free-stream turbulence condition, a distinct regular vortex shedding and trace of the low-frequency flapping phenomena were detected. Under the higher free-stream turbulence however, a mild high-frequency activity was observed. No low frequency oscillations could be detected.

This report describes a thesis project in aeronautical engineering carried out during April and May 2011 at ST Aerospace Solutions, Arlanda. The company is one of Europe’s leading aviation component maintenance companies. The task for this thesis project has been to develop a baseline overhaul work package for the thrust reverser system of the Rolls-Royce Trent 700 jet engine. An overhaul work package is a collection of maintenance work sheets (MWS) used by the maintenance organization to confirm that a specific maintenance procedure has been carried out correctly. Documenting the maintenance work performed on a component is required in order to comply with the regulations of the European Aviation Safety Agency (EASA). To be able to solve the task, the authors had to study maintenance manuals, learn the functions of the thrust reverser and get an overview of how the maintenance organization works. Much of the work has been conducted in consultation with the company’s engineering department. The result is an overhaul package consisting of approximately 40 MWS’s. These have been designed to promote traceability of actions and to be easily revisable. / Denna rapport är resultatet av ett examensarbete i flygteknik som genomförts under våren 2011. Arbetet utfördes hos ST Aerospace Solutions, ett av Europas ledande företag för komponentunderhåll inom flygindustrin. Uppgiften har varit att utveckla ett översynspaket för reverseringssystemet på Rolls-Royce jetmotor Trent 700. Ett översynspaket består av en uppsättning dokument, så kallade ”maintenance work sheets” (MWS), som används för att säkerställa att underhållsorganisationen har utfört det underhåll som krävs. Detta är ett krav enligt den Europeiska luftfartsmyndigheten EASA:s Part 145. Metodiken har främst bestått i att sätta sig in i relaterad dokumentation och underhållsmanualer, samt att skapa sig en förståelse för hur reverseringssystemet och underhållsorganisationen är uppbyggda. Större delen av arbetet har utförts på plats för att kunna samarbeta och diskutera med företagets ingenjörs- och verkstadsavdelningar. Slutresultatet är ett översynspaket som innehåller ca 40 MWS:er, vilka behandlar hela underhållsprocessen. Paketet har utformats med god spårbarhet och reviderbarhet i åtanke.

Starting in the 1990s, the aerospace industry was challenged to produce products and systems Better, faster, Cheaper. In this paper, we examine some of the underlying reasons for BFC and offer some thoughts to help frame the thinking and action of aerospace industry professionals in this new era. / Lean Aerospace Initiative

Thesis (M.Sc.Eng.) / Guided airdrop systems lacking propulsion may be adversely affected by high winds. Strong winds encountered during Draper Laboratory flight testing prevented lightweight parafoil systems from landing accurately. This thesis introduces and compares multiple guidance strategies designed to address high wind scenarios in cases of differing wind knowledge fidelity. The algorithms presented significantly improve performance in high tailwind and shifting wind scenarios without compromising miss accuracy in standard wind conditions. This adds additional capability to parafoil guidance by substantially increasing the conditions under which accurate landings are possible.

In this study, loss and loading characteristics of compressor tandem blades are evaluated. Whole study was focused on change of the total camber so called turning angle. Effects of camber change were investigated in terms of loss and loading characteristics. Methodology was increasing overall camber first by aligning angular positions of blades and second, if required, using more cambered airfoils. 2-dimensional cascade flow CFD analyses were performed to obtain loss-loading information of different tandem blade combinations. Acquired results were compared with the classical axial compressor blades&rsquo / loading and loss characteristics which were obtained from literature. Results showed that most of the time tandem blade configuration performed better than the single blade counterpart in 2-dimensional cascade flow. Lastly, to clarify the benefit of the study and present the gained performance in numbers, only one cascade flow CFD analysis was performed for a classical single compressor blade. Loss and loading results were compared with the tandem blade counterpart where single and tandem configurations both having the same degree of camber. It was clearly seen that tandem blade performed better again.

The anti-torque mechanism of a NOTAR helicopter is a complex system including vertical tail and pressurized tail boom which provides air ejection used for both circulation control around the boom and creating directed jet air at the end of the boom. This thesis targets the modeling of this mechanism and integrating it to a helicopter simulation model. Flight tests are performed on the MD 600N helicopter to verify the results. Finally, the simulation is compared with flight test data.