A compound helicopter is a hybrid vehicle, fundamentally a helicopter. It uses an auxiliary lift and propulsion device(s) in order to eliminate the lifting rotor high speed limitation of retreating blade stall effects, thus allowing flight characteristics comparable in many respects to those of fixed-wing aircraft. The primary objective of this thesis was to perform a design study investigating the validity of the concept of compounding, then selecting and designing a shaft-driven single compound helicopter intended for use as a ground support and anti-tank VTOL aircraft. The selection included a complete parametric and sizing analysis which were based on three defined maj or mission requirements: a maximum forward speed of 250 knots; payload of 1500 lb and cruising endurance of 3 hours at 225 knots. Of the many configurations studied, a single-rotor compound helicopter featured with convertible tail prop/rotor was found to be the most suitable for the intended application. Stability/control characteristics and performance capability of the designed aircraft were found to meet or exceed military specifications and flying quality requirements. structure, dynamics and cost analysis were considered to be beyond the scope of the design study.

A Jeffcott rotor consists of a disc at the centre of an axle supported at its end by bearings. A bolted Jeffcott rotor is formed by two discs, each with a shaft on one side. The discs are held together by spring loaded bolts near the outer edge. When the rotor turns there is tendency for the discs to separate on one side. This effect is more marked if the rotor is unbalanced, especially at resonance speeds. The equations of motion of the system have been developed with four degrees of freedom to include the rotor and bearing movements in the respective axes. These equations which include non-linear terms caused by the rotor opening, are subjected to external force such from rotor imbalance. A simulation model based on these equations was created using SIMULINK. An experimental test rig was used to characterise the dynamic features. Rotor discs open at a lateral displacement of the rotor of 0.8 mm. This is the threshold value used to show the change of stiffness from high stiffness to low stiffness. The experimental results, which measure the vibration amplitude of the rotor, show the dynamic behaviour of the bolted rotor due to imbalance. Close agreement of the experimental and theoretical results from time histories, waterfall plots, pseudo-phase plots and rotor orbit plot, indicated the validity of the model and existence of the non-linear jump phenomenon.

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As a consequence of metal fatigue, cracks can develop and grow in operational aircraft. Periodic inspections must be made in order to detect and repair them before they reach a dangerous length. Cracks which grow from holes are a significant problem for aircraft since the wings and fuselage can contain many thousands of fasteners, or rivets. Since it is impractical to remove them all, inspection must be made with them installed. Research into the application of eddy currents to this problem has led to the development of a scanning procedure in which a small coil is moved around the circumference of the fastener while its impedance is repeatedly measured at different positions. This set of data constitutes an image which can be analvsed using pattern recognition techniques to identify the presence of a crack. A self-contained automated instrument has been built on these principles. It incorporates a microprocessor which controls all aspects of the systems operation, including analysis and display of results. Tests show that it can detect the presence of simulated radial cracks as small as 0.2 mm long beneath the heads of fasteners. The natural extension of these ideas leads to the concept of eddy-current imaging in which a 3D picture of a defect is reconstructed from measurements of the surface magnetic field. The feasibility of implementing this, using techniques such as tomography, is discussed.

This thesis presents the development of a computerized design synthesis for canard-delta combat aircraft. This is complementary to, and follows the philosophy of, an existing RAE system for conventional combat aircraft with swept wings (Ref. 1). The background to the work and the Research Programme objectives and limitations are initially examined. The design of a baseline canard-delta combat aircraft is then described together with all the assumptions and decisions which led to its final configuration. The philosophy behind the progressive evolution of the aircraft geometry and packaging modules from the baseline configuration is explained in detail. The development of detailed modules for the estimation of the aircraft aerodynamics and performance is then presented. A full description of the investigations into the effects of canard-delta interference on the aircraft aerodynamics is also included. The mathematical content of the aircraft geometry, packaging, aerodynamics and performance modules is presented separately in the appendices in greater detail. The development and architecture of the design synthesis and graphics programs are finally presented and the program operation is described with the aid of flow-charts. A comprehensive user's manual and a design example are also provided.

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