Unmasking Aircraft and Rotorcraft Pilot Couplings (A/RPC) prior to vehicle entry into service has been a long standing challenge in the Aerospace Industry. A/RPCs, often only exposed through unpredictable or very specifc circumstances have arisen throughout the history of manned powered ight, and have required short-term 'fixes' to ensure system safety. One of the reasons for this occurrence is th lack of detailed practice regarding the prediction and detection of RPCs prior to full-scale testing. Often in simulation, A/RPCs are only investigated once problems have been experienced during other aircraft qualifcation activities. This is a particular issue for the rotorcraft community, where system sophistication is 'catching-up' with their fixed-wing counterparts. This research helps to extend the state-of-art knowledge surrounding the exposure of RPCs prior to any catastrophic occurrences, through the introduction of novel tools for use both in the rotorcraft design process and beyond. Using key definitions and findings from previous research efforts, objective and subjective measures have been developed for use in both real-time piloted flight and for pre- or post-flight analysis. These tools have been designed to compliment one another, in a process that should reduce the susceptibility to RPC in future rotorcraft. Novel tools developed have been tested through real-time piloted simulation, with results allowing RPC susceptibility boundaries and regions to be identified. Application of all tools developed, both subjective and objective, have been validated through comparison with existing methods. This work provides novel methods to quantify both the propensity of pilot-vehicle systems to RPCs, and the severity of these interactions. Methods have been designed with simplicity of use in mind, whereby they can be applied to vehicles of different configuration, are applicable to a wide range of RPCs, and are easily understandable for prospective users. It is believed that research contained within can contribute to the realisation of European Commission 2020 objectives, by helping to reduce the average accident rate of global aircraft operators.

Theoretical and experimental investigations of the static and dynamic behaviour of thin-walled structures are carried out with the ultimate aim of improving prediction procedures for various aeroelastic phenomena. The dynamic stiffness matrix approach is used for structural idealization, while strip theory and Theodorsen's function C(k) are used for the aerodynamic idealization. The dynamic composite beam with with an axial load centroid, has been carried out using Special cases, that been identified and stiffness matrix for a thin-walled geometric and material coupling together (compressive or tensile) applied at the developed. An exact analysis was then the derived dynamic stiffness matrix. are derivatives of the general case have discussed. A three stage program was developed to compute various static and dynamic properties of thin-walled closed or open section composite beams. In the first stage, equivalent elastic constants (overall laminate moduli) were evaluated for a given stacking sequence and material properties. In the second stage, various sectional properties were computed. When the outputs from these two stages were combined, valuable data on sectional rigidities, mass per unit length, polar mass moment of inertia, and shear centre location from the centroid were obtained. In the third stage of the program, all these properties were used to compute the natural frequencies and normal mode shapes of thin-walled composite structures. These programs can be used individually as well as in a combined manner. An experimental investigation of composite thin plates with varying degrees of bending-torsion coupling was conducted. Flexural and torsional rigidities, natural frequencies, normal mode shapes and flutter speed and frequency were experimentally determined. The results obtained were in close agreement with the theoretical predictions. Various open composite sections were experimentally studied for their static and dynamic properties. The results demanded a more refined investigation of the theory. In addition to the experimental study of composite open sections, a parametric study of uncoupled and coupled frequencies of such sections with common boundary conditions was also conducted. Thin-walled closed aerofoil shaped cantilevered structures were tested to establish flexural and torsional rigidities, shear centre, and the polar-mass-moment of inertia. Natural frequencies and normal mode shapes were also determined. The aeroelastic behaviour of these sections was investigated to establish divergence and flutter characteristics. Comparisons of the experimental results with theoretical predictions of flutter speed and frequency were in general satisfactory and the results provided an insight into the aeroelastic behaviour of thin-walled composite beams. The results are discussed and commented on.

This research work presents a series of investigations into the structural, dynamic and aeroelastic behaviour of composite wings. The study begins with a literature review where the development of aeroelastic tailoring and specific applications of the technology are discussed in detail. A critique of methods for the determination of cross-sectional rigidity properties follows for beams constructed of laminated and thin-walled materials. Chordwise stiffness is shown to be an important parameter that must be considered as it has a significant effect on the amount of bending-torsion coupling present in a beam and, as a consequence, on the value of torsional rigidity. The free vibration characteristics of such beams are then examined using the dynamic stiffness matrix method. Natural frequencies and mode shapes of various beams are studied using the fibre angle, β, and the bending-torsion coupling which is measured (in this study) by the non-dimensional parameter ψ, as design variables. The results show that ψ has only a marginal effect on the natural frequencies of composite beams (wings) but can significantly modify the mode shapes of such beams. It can be used to decouple modes which are geometrically (inertially) coupled in the same way as mass balancing but without a weight penalty. It can also be used to abate the unfavourable coupling introduced by sweep angle. Classical flutter and divergence of swept and unswept uniform cantilever wings are investigated using laminated flat beams (plates) and thin-walled beams of rectangular and biconvex cross-sections. Various parameters, such as, the fibre angle, β, the coupling parameter, ψ, the angle of sweep, Λ, the static unbalance, Xα, and the non-dimensional ratio of the fundamental (uncoupled) bending to fundamental torsional frequency, ωh/ωα, are varied and their subsequent effects on aeroelastic stability are investigated. The importance of torsional rigidity GJ on the flutter of composite wings is shown to be substantial in contrast with ψ, which is generally the most important parameter to be considered when the objective is that of increasing the divergence speed. Modal interchanges in the free vibration and flutter of laminated composite wings are shown to be primarily responsible for behaviour not experienced with metallic wings, in particular the effect of wash-in and wash-out on flutter. The most intriguing features of these investigations, however, are those which show that models adequate for the analysis of composite wings may be based on two parameters, the frequency ratio ωh/ωα and the coupling parameter ψ. Some results are confirmed by independent optimisation studies. Finally, a preliminary investigation is carried out into the flutter suppression and gust alleviation of a laminated composite wing by the use of active controls. The results show that by using an active control in an optimum trailing edge position the gust response of a wing can be significantly alleviated without compromising the already optimised flutter speed by the use of aeroelastic tailoring.

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In this thesis, a methodology is proposed for the conceptual design and optimisation of twin-turboprop Commuter & Regional aircraft suitable for operation over a specific short-haul route. Using this methodology, the optimum configuration and flight profiles of such aircraft for operation over various stage-lengths can be obtained. By significantly modifying an existing computer code for synthesis and trajectory optimisation of commuter aircraft (CASTOR), a new code (CRAGER) has been developed to estimate the generalised cost of travel incurred by a passenger for air-travel between two cities. A new sub-module has been developed for the geometric sizing of a suitable airport as per ICAO/FAA recommendations, and estimation of the airport cost, i.e. the cost associated with setting-up and operating this airport at one of the two cities. This module is incorporated into CRAGER. Generalised cost is assumed to consist of the access cost, flight cost, time cost and the airport cost, and is proposed as a new objective function to be minimised. In an exploratory case study, the efficacy of two stochastic optimisation methods viz. Genetic Algorithms (GA) and Simulated Annealing (SA) was demonstrated for handling complicated objective functions related to aircraft conceptual design. In particular, the SIMANN SA code was found to be quite robust and easy to implement, and came up with better solutions compared to conventional gradient based optimisers for multi-modal objective functions. As an example of the application of the proposed methodology, several case studies were carried out for business travel in India, using both CASTOR & CRAGER. Based on a survey of existing regional airports in India, the airports were classified under three levels, enabling estimation of airport cost associated with operating a specific aircraft. A model was developed for predicting the demand for business travel in India between a metropolitan city (hub) and another city located near-by (spoke). The case studies revealed the non-linear nature of the airport sub-module, due to the airport classification system followed by ICAO & FAA. It was seen that when the annual travel demand is low, the generalised cost is dominated by the airport cost and the time cost. With increase in annual travel demand, however, the flight costs dominate the generalised cost, hence larger aircraft have lower generalised costs. High-capacity aircraft were seen to have a low flight cost, but this advantage was more than overcome by the excessively high airport and time costs associated with them. Compared to pressurised aircraft, the un-pressurised commuter aircraft suffer from severe penalties due to limitations imposed on their cruising altitude and descent profile. Finally, the optimum 50 seater aircraft obtained by CRAGER had better or marginally lower DOC and generalised cost compared to existing aircraft.

This study outlines the requirement for a company to be able to manage its intellectual capital. On the basis of this requirement this study presents a new design methodology based around the requirements of the military aircraft industry. It tackles the difficult management problem of capturing, storing and re-using valuable company product knowledge. The detailed research documented in this thesis focuses on the conceptual design area of this methodology. Work in this area has resulted in the development of a further methodology for the conceptual design arena. This methodology is called the intelligent conceptual engineering system (ICES). The ICES methodology embraces the artificial intelligence disciplines of knowledge-based systems and case-based reasoning. Through the evolutionary development of the ICES methodology a significant contribution to knowledge has been made in three areas. Firstly, this study introduces a new method of assigning justifiable numerical weights to design drivers acting on the design process. Secondly, the work introduces the novel concept of using secondary rules in the knowledge-based system so a 'best structure' can be derived from the manufacturing and structures perspectives. Finally, this work adds a new concept to case-based reasoning called the 'jury technique'. These concepts, developed to support the ICES methodology have been placed in a prototype design decision support tool.

A major characteristic of aircraft evolution is the rapid growth in the electrical and electronic content of each subsequenat ircraft generation.T he dominant technology used in an aircraft electrical power distribution network to switch power and to protect the aircraft wiring from hazardous electrical faults is the electro-mechanical relay switch and the electro-thermal circuit breaker. Despite the maturity of these devices they do however suffer from a number of problems relating to reliability, accuracy, and limited operational lifetime. The design, fabrication and testing of a novel Solid State Power Controller (SSPC) is described. The design uses power MOSFET's to provide both the power switching operation of a relay, and the power interruption capability of a circuit breaker. The majority of the control functions required by this device are performed digitally by virtue of a real time program executed on an embedded microcontroller. A number of methods are derived for characterising existing I2t wire protection trip response curves. Reproduction of a true 1 2t trip response in real time using iterative computational methods is described. An examination of the semiconductor thermal characteristics was undertaken. The methods adopted for extracting the power semiconductor thermal response involved direct measurement using infrared thermal imaging techniques and simulation using a computer based modelling tool. Knowledge of the semiconductor die temperature is of vital importance in the context of the overall protection strategy. A finite difference calculation performed in real time has been demonstrated as a viable method to predict the operational temperature of the MOSFET power switching devices used in the design

In this study the dynamic induced velocity field of a model helicopter rotor - excited in collective and cyclic pitch at frequencies extending to 1.5 times the nominal shaft speed - is investigated using mainly hot-wire and laser Doppler anemometry. The dynamic induced velocities are found to vary significantly with radial station and frequency. For cyclic excitations, azimuthal variations are also observed. The results point to the dynamic induced flow being influenced by the distribution of shed vorticity in the wake and cannot be explained using simple momentum theory. Vertical variations of the measured inflow response are also observed, with phase changes possibly partly due to transmission type delays. At frequencies above shaft speed a change in character of the induced flow is seen and around shaft speed an increase in the general level of turbulence is found. The available data on the dynamic induced velocity field of a rotor under controlled excitation, are substantially extended. The measured induced flow response was compared to that predicted using the Pitt and Peters dynamic inflow model. In the 'collective' case good agreement was found, suggesting that the primary inflow model parameters such as the inflow gain and apparent mass are correct with some evidence that a higher order inflow representation might be desirable. A novel method is used to infer the aerodynamic hub loading, which could not be directly measured, from the blade flapping data. This is used to isolate the inflow response using the Pitt and Peters dynamic inflow model and the results are compared with experimental measurements. The method shows the Pitt and Peters dynamic inflow representation to be adequate in the 'collective' case. In the 'cyclic' case, the inferred hub loads were very sensitive to the blade model and hence conclusions for this case are limited. A literature survey and review of the Pitt and Peters dynamic inflow model are also given

In traditional aircraft wing structural design, the emphasis has been on pursuing the minimum weight or improved performance. The manufacturing complexity or cost assessments are rarely considered because it is usually assumed that the minimum weight design is also the minimum cost design. However, experience from industry has shown that this is not necessarily the case. It has been realised that in the cases where no manufacturing constraints are imposed, the extra machining cost can erode the advantages of the reduced weight. As manufacturing cost includes material cost and machining cost, whilst reducing weight can reduce the material cost, if the manufacturing complexity increases greatly as a result the overall cost may not go down. Indeed, if the manufacturing complexity is not checked, the machining cost could increase by more than the amount by which the material cost reduces. To enable the structural manufacturing complexity to be controlled, manufacturing constraints are established in this thesis and integrated into the optimisation of the aircraft wing structural design. As far as the manufacturing complexity is concerned, attention has been paid to both 3-axis and 5-axis machining. The final designs of optimisations with manufacturing constraints prove the efficiency of these constraints in guiding the design in the manufacturing-feasible direction.