In recent years, interest has grown in the use of small satellites for a variety of applications. In certain missions, where propulsion systems are necessary, electric propulsion technology can offer advantages. Small satellite technology and applications are reviewed and some of the features of various types of electric propulsion are discussed: missions where small satellites might use electric propulsion are described.

Data mining is a process of finding correlations and collecting and analysing a huge amount of data in a database to discover patterns or relationships. Flight delay creates significant problems in the present aviation system. Data mining techniques are desired for analysing the performance in which micro-level causes propagate to make system-level patterns of delay. Analysing flight delays is very difficult – both when looking from a historical view as well as when estimating delays with forecast demand. This paper proposes using Decision Tree (DT), Support Vector Machine (SVM), Naive Bayesian (NB), K-nearest neighbour (KNN) and Artificial Neural Network (ANN) to study and analyse delays among aircrafts. The performance of different data mining methods is found in the different regions of the updated datasets on these classifiers. Finally, the result shows a significant variation in the performance of different data mining methods and feature selection for this problem. This paper aims to deal with how data mining techniques can be used to understand difficult aircraft system delays in aviation. Our aim is to develop a classification model for studying and reducing delay using different data mining methods and, in this manner, to show that DT has a greater classification accuracy. The different feature selectors are used in this study in order to reduce the number of initial attributes. Our results clearly demonstrate the value of DT for analysing and visualising how system-level effects happen from subsystem-level causes.

It has long been realised that there is a precise analogy between the properties of vibrating mechanical systems and those of alternating current electric circuits. It was from this analogy that the concept of “ mechanical impedance ” (more appropriately termed “ dynamic stiffness ”) was derived, thus enabling the theory of certain types of mechanical vibration, notably torsional motion, to be put on a more rational basis.

By means of analogous elements it is possible to represent a mechanical vibrating system, provided it includes no bending elements, by an equivalent electric circuit. The author has been unable to discover any full description of the process, and the object of the present paper is to set out the principles underlying the procedure and to illustrate them briefly by examples.

The current interest in supersonic transport aircraft makes it appropriate to consider the problems of propulsion nozzle systems for high speed flight. The discussion will be confined mainly to this field of activity.

In the absence of external drag and weight factors, the ideal configuration to maintain optimum thrust at all flight speeds would employ a mechanically variable area ratio nozzle. By such means the jet flow could be fully and properly expanded at all times.

A practical design to accommodate such variations is inherently complex, and so an alternative solution using aerodynamic techniques has been sought. It is necessary to remember that the success of whatever method is eventually chosen must rest on its ability to combine a high performance at cruise with very small loss during other critical phases of the flight plan.

This paper describes some of the results of a nozzle research programme aimed primarily at solving the above problem, with an attempt to explain the philosophy behind the aerodynamic techniques tried. Some discussion is given of the experimental difficulties in establishing a sufficiently accurate standard of measurement for design point performance. In a few chosen configurations experimental results have been extensively backed by theoretical studies.

The need to demonstrate off-design behaviour in the presence of an external flow field is stressed, with special reference to the misleading results often obtained from static tests.

Finally, some attention is given to the question of base bleed, with its repercussions on the installation of the propulsion nozzle in an aircraft.

Coatings of chiral-nematic liquid crystals are known to change colour under different levels of surface shear stress. In this study, the liquid crystal coating was used to provide information about flow separation and reattachment on a backward facing step and a delta wing respectively. The tests were carried out at a free-stream velocity of 25ms-1. The Reynolds number based on the step height of the backward facing step is 16,000 and based on the chord length of the delta wing is 270,000. The study revealed that the locations of boundary-layer separation and reattachment can be identified from spatial variations in the surface colour. Agreement was obtained between the results acquired from liquid crystal and surface oil flow technique. The variation in hue was used to improve the determination on the location of flow characteristics. This study showed that the liquid crystal coating is an effective method for the qualitative study of separated flow characteristics.

Much of the data published on the subject of cost prediction for aircraft has dealt with empirical methods of estimating the total engineering hours of design and development. Less seems to have been written by or for the practising estimator, concerned not only with the total estimate at the initial stages of the project but also with its continuous refinement to full go-ahead, on to certification and later still to variants. In this paper the authors describe some of the methods they use, the historical background against which the methods have evolved and discuss some of the problems which are met.

The results obtained from exact numerical solutions to the laminar boundary layer equations are compared with those given by the approximate method of Luxton and Young and the comparison shows that the latter method may be used for cases involving non-constant wall temperatures. This satisfactory result arises essentially from the fact demonstrated by the calculations that the skin friction is relatively insensitive to wall temperature gradients. It is also shown from these results that there is a lag in the propagation of wall temperature changes through the boundary layer. In consequence the Stanton number is a heat transfer parameter of doubtful value in cases of non-uniform wall temperature.

This paper deals with the problem of radar target tracking in cluttered environment from plane position indicator (PPI) radar images collected by low-cost incoherent radar. For this purpose a new five-step technique is proposed, including background subtraction, clutter suppression, measurements extraction, tracking and data fusion; the tracking step uses a particle filtering based data association method. Radar measurements, including target information and clutter interference, are checked whether it belongs to tracking target by data association with Kalman predicted state. If the measurement is generated by target, target state is updated by Kalman filter, and vice versa the predicted state keeps invariant. Moreover, smoothed tracks are given by Kalman smoothing of filtering results. The performance of the tracking algorithm is deeply investigated against Monte Carlo simulations. Finally, the overall multi-frame-based technique is applied to two sets of live PPI radar images, and the results show the effectiveness of the proposed approach.

Every control system employs some computing elements and it is customary to designate systems after the type of computing predominantly used in them. Thus, we have hydromechanical systems, pneumatic systems, fluidic systems, analogue electric systems, and so on. Traditionally, as described by Watson, the aircraft gas turbine has used hydromechanical control (see Fig. 1). The diagram does not depict any particular engine component but illustrates some of the principles used in a variety of present-day systems. A mixture of bellows, springs, cams, orifices, etc, compute according to their particular arrangement; frequently the fuel itself is used as the computing medium. Essentially such systems compute continuously using physical representations of the measured parameters. They are, therefore, of analogue form.

An overview of some of the problems, which have to be overcome in the design of hypersonic missiles or projectiles, is given. In the main, these are connected with the high levels of heat transfer rate suffered by such vehicles, particularly those induced by aerodynamic control surfaces. Some of the aspects of heat transfer, induced by, and suffered by such controls are presented. Data are presented and discussed, regarding the effects of flow separation due to flaps or flares, the effects of sharp and bluff fins (both swept and unswept). Finally, the aerodynamic interactions and heat transfer rates induced by reaction control jets are presented.

An experimental study of bow-wave trajectories for a sphere in CO2 has been made in a shock tube, using a drum-camera-schlieren technique, for incident shock Mach numbers of 2·4, 2·8 and 4·0. Results show that vibrational relaxation has only a slight effect on the bow-wave formation time but significantly affects the stand-off distance in steady flow.

The work to be described forms part of an experimental study into the overall influence that the end region of a flap has on the flow of a high lift wing system. Here, our attention will be restricted mainly, but not entirely, to the tip flow of the flap itself.

The study has been a collaborative venture over the past three years between British Aerospace-Civil Aircraft Division and the Aerospace Engineering Department of Bristol University, the latter funded by an SER.C research grant. BAe's major contribution was the undertaking of the main test programme, with University participation, using a large swept wing, high lift half model in the Filton low speed wind tunnel. The model was loaned by RAE for the study.

The classic problem of stability and transition to turbulence of an incompressible flow over a flat plate subjected to uniform suction through the surface is considered. This is an important “model” problem for laminar flow control and the results have direct application to the design of low drag aerofoils. Detailed mean boundary layer calculations are presented and the flow stability is determined by obtaining numerical solutions of the Orr-Somerfield equation. Transition conditions are estimated by using the semi-empirical en method. Accurate values have been obtained for the levels of suction necessary to delay instability and transition indefinitely. Consideration has also been given to the effect of surface suction upon the plate drag.

The analysis of Freeman is extended to the hypersonic flow of an inviscid, vibrationally relaxing gas past a bluff body. Expressions for the shock shape, streamline shapes and stand-off distance are derived; these expressions have been evaluated for a sphere for various values of an appropriate non-equilibrium parameter Λ.

A semi-empirical analysis of unstable crack propagation in thin sheets is given. An effective value of the crack tip strain concentration factor is used as the criterion for instability. Good correlation is achieved with experimental results from unreinforced sheets of aluminium and titanium alloys and high-strength steels. The interdependence of geometry and stressstrain curve properties in determining the unstable crack propagation characteristics of sheet materials is illustrated in an appendix.

The Ninth Lanchester Memorial Lecture was given by Professor W. A. Mair, MA, FRAeS, on “STOL—Some Possibilities and Limitations” in the Society's Lecture Theatre on 12th May 1966. The Chair was taken by the President, Mr. A. D. Baxter, MEng, CEng, FRAeS. Before the lecture he presented the Society's Gold Medal for 1965 to Professor M. J. Lighthill, DSc, FRS, FRAeS, for “his outstanding original work in many fields of Aeronautics”, explaining that Professor Lighthill had been unable to be present at the Wilbur and Orville Wright Memorial Lecture in December 1965 when the Society's main awards for the year were presented.

The President then said that this was the first meeting of the Society since his installation as President and it was a very pleasant way to start his year in office with first, the presentation of the Gold Medal to one distinguished scientist and second, the introduction of another as the Lanchester Memorial Lecturer.

There would be many members of the Society who would remember Dr. Lanchester, his attendance at lectures and his contributions to the discussions. It was true, however, that the real stature of such men was rarely recognised at close quarters and often only in the light of later developments was the importance of their work realised. It was 20 years since Dr. Lanchester's death and their Memorial Lecture was in its ninth year. Each year, each President had added a tribute to this great man. He was a man of many parts—a scientist, musician, poet and engineer and aeronautics owed much to him. It was fitting that the Lecture had established a tradition of surveying some field of research associated with aerodynamics, in which Lanchester was so eminent. He thought that Lanchester would approve of both the subjects discussed and the distinguished men who had honoured his memory by presenting them. Before introducing Professor Mair he wished to welcome Mrs. Lanchester and Mr. George Lanchester and his wife, and Mrs. Mair.

Professor Mair must be well known to most of them. After graduating in Mechanical Sciences at Cambridge in 1939 he had joined the Royal Aircraft Establishment at Farnborough, where he scent some six years in the Aerodynamics Department doing research on high subsonic speed, both in the wind tunnels and in full-scale flight. In 1946 he had gone to the University of Manchester as Director of the Fluid Motion Laboratory and since 1952 he had held the Francis Mond Chair of Aeronautical Engineering at Cambridge. His chief interest there had been mainly in low speed aerodynamics and his authority in that field was widely recognised. In 1963 he had been appointed Chairman of the Powered Lift Committee of the Aeronautical Research Council.

Luminescent paints allow non-intrusive measurement of pressure and temperature at high spatial resolution without prior knowledge of the flow-field. Experiments have demonstrated that a ‘standard’ luminescent paint technique, developed by BAE Systems, can simultaneously measure steady pressure and temperature. This is achieved through knowledge of the paint phosphorescence lifetime rather than the absolute intensity, which increases the measurement accuracy. In addition, a new ‘fast’ paint has been calibrated at the University of Bath for the measurement of unsteady pressure using a variable frequency pulsing air jet. Pressure measurements were made with both paints in the wake of various excrescences, sized to produce vortex shedding in the frequency range 500–4,200Hz, in a transonic tunnel. The extent of the wakes was determined from a flow visualisation technique. Time-averaged measurements, using both luminescent paints, and transient measurements of the unsteady pressure field, made with the fast paint, were compared with transducer data. For all cases the luminescent paint data compared well with the conventional measurements and the Strouhal number agreed well with data from the literature. The use of luminescent paint for the simultaneous measurement of pressure and temperature over a NACA 0012 aerofoil, as well as the quantification of convective heat transfer is examined in Part 2.

It is a pleasure and indeed an honour to be invited to contribute this paper to the 70th Birthday Tribute to Professor A. D. Young, in recognition of his longstanding friendship and as a colleague of the author for many years.

It was Professor A. D. Young, at the College of Aeronautics in 1949, who gave the necessary guidance and encouragement to the author in starting research into aerodynamics noise, which was possibly one of the first attempts made in making a quantitative assessment of the noise from a turbulent air jet.

The paper discusses the early experimental work and its conclusions, and how it led to attempts to reduce jet noise through the use of vortex generators and the corrugated nozzle. The comparison between theory and experiment is commented on with reference to the early work on acoustic sources and the questions this comparison raised. A final section is included which attempts to close the gap in our understanding of jet noise generation.

The assessment of damage due to impacts in composite sandwich panels and the component life reductions associated with such damage is becoming increasingly important within the aerospace industry. This study analyses minimum gauge, non-metallic honeycomb wing panels subject to impact damage. In all instances the damage is caused by ‘soft body’ impactors travelling at elevated velocities to simulate bird strike and other soft debris. The damage formed during these impacts is shown to be large in plan area but shallow and primarily causes crushing of the core in a thin layer. Loading of the panels after impact has been performed to determine the reduction in load carrying capacity and associated failure mechanisms. Damage due to soft body impact is shown to be very different to the classical rigid body impact upon which current repair schemes are based. As a result in many applications the use of current repair schemes may be inappropriate. The viability of new repair techniques is discussed with particular attention to the prevention of failure mechanisms due to loading after impact.

The object of this paper is to present an analytical method of investigating the flexure of a non-uniform beam under transverse loading. A method due to Strandhagen for a uniform beam is extended to the case of a non-uniform beam, the deflection appearing in the form of a Fourier series, the coefficients of which are functions of the loading, the end-conditions, and parameters which define the non-uniform flexural rigidity of the beam.