This paper analyses a new approach utilising potential functions to autonomously control constrained attitude slew manoeuvres using gas jet thrusters. The method hinges on defining a potential function from the geometric configuration of the satellite's current attitude, the final target attitude and any pointing constraint which may be present. It will be demonstrated that complex path shaping and planning can be achieved using little computational effort. The method is mathematically validated using Lyapunov's theorem, and so can be considered for safety critical applications.

The aerodynamic effectiveness of a cylinder-flare body at zero incidence under laminar and turbulent boundary-layer conditions has been studied experimentally. Two nose geometries, namely a 10° half-angle sharp cone and a hemisphere, were used. The study has been carried out in a hypersonic gun tunnel at a Mach number of 8·2 and a Reynolds number of 158,100, based on the cylinder diameter, at flare angles 0°, 10°, 20°, 30° and 45°. The surface flow was studied using oil-dot and liquid crystal techniques. Some information regarding the shock layer was obtained from schlieren pictures. The effects of entropy layer and boundary-layer state on flare effectiveness were deduced from pressure measurements over the cylinder and the flare.

Airspace is identified through well defined volumes of the Earth's atmosphere. Airspace control is defined to consist of rules and procedures by which aircraft conduct their flight and by which aircraft approach and cross volume boundaries. Airspace control should optimise the flow of traffic under the constraint that no collision occurs. To date, the design of airspace control has been largely heuristic. Two fundamentally opposed philosophies and designs have evolved over the last fifty years. There has been little, if any, formal comparison of the relative performance of these designs.

A new conceptual conflict-avoidance model is presented showing the need to maintain situational awareness for all conflicts. It reveals the essential requirement for communication channels in the conflict avoidance function. Human perceptual performance is related the required system response to conflict. These human factors can be mathematically related to physical parameters embodied in airspace rules and procedures. The impact of changes in airspace performance due to variations in physical parameters derived from models of the communication channels can now be measured. Use of the conflict-avoidance model presented in this paper identifies serious deficiencies in present designs and postulates that fundamental architectural changes are required to reduce safety hazards and produce designs of sufficient reliability, particularly for uncontrolled airspace. Designs based on stable and adequate communications are shown to be required and are now technologically feasible.

An experimental investigation was carried out of the incompressible boundary layer flow along a flat plate, in the presence of an adverse pressure gradient that corresponds to a linear retardation of the free stream velocity. The turbulence level in the free-stream was 0·12% and transition occurred with the laminar boundary layer being close to separation. For three values of the Reynolds number (2·56, 3·11 and 4·09 million based on the reference length that is defined as the reciprocal of the nondimensional-velocity gradient) the laminar, transitional and turbulent regions were studied by single (normal) hot-wire surveys at several streamwise positions. This allows the fluctuations of the streamwise velocity component to be followed from the amplification of laminar instability waves, through breakdown in the intermittency region, and the subsequent development towards a more or less developed turbulence structure. The study reveals that within the transition region fluctuation levels are reached throughout a large part of the boundary layer that are significantly higher than those in fully developed turbulent flow, which is partly a direct consequence of the intermittent character of the flow. For the highest Reynolds number additional cross-wire surveys were carried out in the turbulent region to observe the development of the turbulent stresses following transition. The data are interpreted in terms of structural coefficients, eddy viscosity and mixing length. Also, these results indicate that the transition process can be associated with turbulence levels well in excess of those occurring in fully developed turbulence, and reveal the relaxation of the outer region turbulence structure.

A study was conducted to identify possible improvements to the current certification and operational procedures for turboprop powered aircraft operating in icing conditions. Information was gathered through a series of interviews with airframe and engine manufacturers and also, operators and aircrews in Europe and Canada. The significant issues raised during the interviews are discussed, and a number of recommendations are made for future research and development activities in die area of aircraft icing. These recommendations identify the need for improved ice protection methods, enhanced thermodynamic models in ice prediction computer codes, and development of an ice prediction probe to warn aircrew that they will soon be entering icing conditions. Recommendations also include improvements to pilot training, and the need to make weather forecasts of icing more accurate and specific.

A future advanced supersonic transport aircraft (AST) has fundamental characteristics and problems inherent to supersonic cruise aircraft with corresponding unique control and handling characteristics.

In order to optimise the aerodynamic performance across the full flight envelope a fully integrated flight and propulsion control system will be required. However, this will need to be designed from the outset within clearly defined flight control and performance guidelines.

Relevant existing and AST specific handling qualities criteria will need to be developed if a successful commercial transport aircraft is to be produced.

This paper begins by presenting an overview of existing supersonic transport (SST) aircraft operations and current second generation SST research activities and design considerations. This is followed by an analysis of the principal aerodynamic, dynamic and control characteristics of SST and AST aircraft and their effect on the aircraft’s handling qualities. Finally, some possible solutions to the control and handling issues are investigated, assessed and presented.

An Euler method for computing compressible hovering rotor flows is described. The equations are solved using an upwind finite-volume method in a blade-fixed rotating co-ordinate system, so that hover is a steady problem. Transfinite interpolation, along with a periodic transformation, is used to generate grids for the periodic domain. Computation of these flows to an acceptable accuracy requires fine grids, and a long integration time for the wake to develop, resulting in excessive run times on a single processor. Hence, the method is developed as a multiblock code in a parallel environment, and various aspects of data passing and communication between processors have been considered. It is shown that a considerable increase in performance is available from the use of non-blocking and asynchronous communication. It is also demonstrated that increased performance may be available by balancing the residual levels rather than the number of cells on each processor.

This paper reviews some current problems in unsteady aerodynamics and discusses some future challenges. The emphasis is on problems associated with separated flows, such as buffeting and limit cycle oscillations. Suggestions are made to indicate how experimental facilities (such as cryogenic windtunnels) and computational fluid dynamics might be exploited to address these questions.

A three-dimensional unsteady Navier-Stokes solver has been used to simulate stall inception in a single row ten passage segment of a transonic fan, the NASA rotor-67. At subsonic flow conditions, the 3D results illustrate a rotating stall inception with short scale part-span cells rotating at around 80% rotor speed, similar to that observed in some low speed experiments. However, at a supersonic relative inflow condition, the results show that an isolated blade row tends to stall in a one-dimensional breakdown pattern without first experiencing rotating stall. At near-stall conditions, significant self-excited unsteadiness is generated by the interaction between the tip-leakage vortex and the passage shock wave. Further computations for two-dimensional configurations indicate that it is possible to have a rotating pattern of instability in transonic blade rows associated with circumferential synchronised shock oscillation.

This paper examines the dynamic stalling of a finite wing of aspect ratio 3·0 when subject to constant pitch motions up to and beyond stall. In particular, unsteady surface pressure data were obtained at 192 locations on the wing surface and these were then analysed to provide information on the nature and phasing of dynamic stall events in both the chordwise and spanwise directions. It was also possible to obtain sectional force and moment coefficients by integration of the pressures measured on specific chordal arrays. This provided valuable insight into the load distribution on the wing throughout the range of motion. On this basis, it was established that the wing loading distribution was consistent with conventional understanding of steady wing loading up to the incidence at which the dynamic stall vortex was initiated. Beyond this point, the formation and subsequent convection of the vortex structure was found to be strongly three-dimensional but, nevertheless, exhibited many of the features of two-dimensional dynamic stall.

I was born on 6 June 1902, in Handsworth, a borough in Staffordshire, which in 1911 became part of Greater Birmingham. Handsworth, in those Edwardian days, could be described as a dormitory suburb of Birmingham. Its character is now vastly changed and today it houses large numbers of our immigrant population.

My father, William John Roxbee Cox, is described on his marriage certificate as a master jeweller and indeed was, at the time of his wedding, working with his father, Samuel James Cox, a reasonably prosperous manufacturing jeweller in Birmingham. Samuel had married an American lady, Emily Power Jones, who was, I believe, distantly related to him, and my father was their only child.

My mother was Amelia Stern, the third child of Henry Stern, a Pole who became a naturalised Englishman. My memory of him is vague but pleasant. I think he must have been a nice man. He was an engraver on glass. He died of pneumonia in 1904 at the age of 54. His brother Louis became a Church of England parson, but did not achieve major preferment.

Non-destructive evaluation (NDE) technologies are a critical component of a collaborative engineering environment. The role of NDE simulations in component design, manufacturing, certification, integrity and repair are identified and discussed in the context of a futuristic intelligent synthesis environment (ISE) that facilitates collaborative engineering. Each of these critical areas needs to be simulated in a virtual reality environment and is expected to have a large effect on the cost, life, safety, and risk of aerospace products. In a collaborative engineering environment, NDE simulations will provide ‘real-time’ feedback to component designers and systems engineers. This feedback is necessary to achieve optimum overall system-level benefits.

The degree of complexity and randomness of aircraft tracking which can be safely managed is a fundamental question for a given airspace design. To answer this question and to provide optimum conflict resolution strategies, the nature of conflict needs to be thoroughly understood. This paper reviews traditional conflict models showing how these models may be integrated into a more unified model based on computational geometry. This mathematical approach is being investigated for the specification and management of future airspace, achieving a more solid architectural basis for airspace design. This approach has the potential to significantly reduce the subjectivity when attempting to model controller and pilot workload, an important requirement in future designs.

This paper is meant primarily for non-specialist readers who may not be familiar with aeroelasticity. The main objective is to direct the reader to some important texts and papers that have been published in the areas which embrace aeroelasticity, from which the reader may gain sufficient knowledge about the subject. Since aeroelasticity is a large field which requires considerable knowledge in several related areas newcomers can often be daunted by the subject. This is further compounded by the great amount of published material available. This paper will assist the reader to locate key publications and help identify major works which have been useful in studying the subject. A comprehensive list of references is included which will help to identify key subject areas, researchers, research establishments and publications for further study.

Shockwaves are present in a flow as soon as the Mach number becomes supersonic. Being viscous phenomena, Shockwaves are a source of drag which can be predominant when the Mach number is significantly higher than one. In supersonic air intakes, the production of entropy by shocks is felt as a loss in efficiency. At high Mach numbers, Shockwaves produce a considerable temperature rise leading to severe heating problems, complicated by real gas effects. The intersection - or interference - of two shocks gives rise to complex wave patterns containing slip-lines and associated shear layers whose impingement on a nearby surface can cause detrimental pressure and heat transfer loads. The impact of a Shockwave on a boundary layer is the origin of strong viscous interactions which remain a limiting factor in the design of transonic wings, supersonic air intakes, propulsive nozzles and compressor cascades. More effort is needed to improve prediction of these interactions and to devise new techniques to control such phenomena.

The performance and robustness of a classical multivariable controller and one H∞ compensator are assessed on a model rotor rig. Both control schemes are subjected to sinusoidal and step input tests in the pitch and roll axes under a range of operating conditions and configurations. A brief description of the characteristics of the rotor mathematical model is provided, followed by a summary of the design assessment criteria. Following a description of the two control law design techniques, the performance of each controller is verified on the mathematical model prior to evaluation on the rotor rig. In absolute terms, there is a poor correlation between the simulated and experimental values of the design assessment criteria for both controllers. However, in relative terms, the H∞ control law achieves higher levels of damping and lower cross-couplings than the classical scheme although the measured improvements are not as substantial as predicted. In experimental frequency response tests at increasing advance ratios and various rotorspeeds, the H∞ scheme again consistently achieves the lowest levels of cross-coupling. In summary, the results show that although there are practical performance and robustness benefits to be gained by employing more complex control algorithms, model uncertainty will substantially reduce the predicted benefits.

A simple but effective method is presented to analyse the effects of asymmetric external stores on flutter of an aircraft in this paper. The method is a kind of ‘direction derivative’ technique, and can be easily applied to predict whether the asymmetric external stores increase or decrease the flutter speed. By using the present technique the varying tendency of flutter speed can be determined preliminarily. This can be very useful and valuable to the designers at the beginning stage of flutter analysis. The effectiveness of the proposed method is proved analytically.