As one of the first speakers at this Symposium, with no particular axe to grind and no panacea to offer, I think my most useful contribution will be to provide some sort of backcloth for later contributors. I therefore propose to discuss the relative effects of some of the factors affecting the design efficiency and operating costs of short-range aircraft so as to try to arrive at some impression of what are the more important things to concentrate on. This has been done before at various times, but I think it is worth doing again as a starting point for this discussion. The views expressed are my own and not necessarily those of RAE or MoA.

I shall be talking mainly in terms of generalised long-term effects, and the factors and exchange rates quoted will be the overall effects on an aircraft still in the design stage, assuming that it is re-optimised if necessary as each factor is varied. Without implying any preference one way or the other, I will assume a conventional wing-plus-body design with jet or fan engines; other contributors will be dealing with the possibilities of all-wing layouts and with the question of propellers versus jets for short ranges. I assume that we are thinking in terms of stage lengths of the order of 250-500 miles, and the costs and exchange rates will be quoted for this sort of range; so far as relative sensitivities are concerned the precise value is not very important once one is in this bracket (as compared with 1000-1500 miles, for instance).

The use of unmanned aerial vehicles (UAVs) in various military and civil applications is the subject of much current attention. With recent developments in personal computer technology, and the availability at affordable cost of peripherals, and electronic and optical sensors, UAVs for long endurance missions, with flight autonomy beyond the visual range, have become an attractive challenge for study in universities and research institutes. This paper describes the development of a target-lock-on optical remote sensing system to be used as a payload in a university-class UAV. To accomplish autonomous way-point navigation for the conduct of optical sensing surveillance, a gimbaled-platform with servo control and an Attitude and Heading Reference System (AHRS) navigation system for UAV position and attitude measurements have been developed. The UAV also utilises a Global Position System (GPS) receiver, a pressure altimeter, gyroscopes and an electric compass. A novel mathematical model is proposed to calculate the optimal parameters for orientating the CCD camera line of sight with a ground target, designated in real time from a ground control station. Both ground and flight test results have demonstrated the feasibility of the navigation control scheme and the UAV’s ability to conduct ground target acquisition and image transmission.

It is Sometimes required to find the maximum amplitudes of vibration attained and the speeds at which they occur when a machine is run through its critical speed with different accelerations. The solution of this problem for single degree of freedom systems has been obtained by Lewis and by Ellington and McCallion for mechanical vibrations and by Hok for the equivalent electrical case. These solutions require higher mathematics (contour integration, Fresnel's integrals or series solutions leading to Bessel functions). The purpose of this note is to show how, by using simple integration only, an alternative method of solution can be obtained for both zero and small values of damping.

In the spring of 1914, in view of the tenth anniversary of the Aerodynamic Institute at Koutchino, near Moscow, I published a booklet in which I gave a survey of the Institute's activities since its foundation and concluded it as follows: “The problem of aerodynamical flying is solved, but, after the conquest of air space, another conquest, more difficult and of higher import, is offered to the ambition of man— the conquest of interplanetary spaces. “The brilliant progress of science gives hope that, in a more or less distant future, this problem will be solved in its turn through the patient and co-ordinated efforts of searchers impassioned by the greatness of this idea.

“The brilliant progress of science gives hope that, in a more or less distant future, this problem will be solved in its turn through the patient and co-ordinated efforts of searchers impassioned by the greatness of this idea.

A numerical method, based on the panel technique, has been developed for calculating the time-averaged separated flow about a wedge. The mathematical model, with constant vorticity in the wake, gives an infinite extension of the wake and constant base pressure while incorporation of the dispersion of vorticity in the wake into the mathematical model leads to its finiteness and non-uniform under-pressure. Experimental tests have been conducted in a low speed wind tunnel on models haying different wedge angles. The theoretical and experimental results agree closely for different configurations and specific values of dispersion factors. However, the agreement for base pressure is poor.

Automatic navigation systems for aircraft often use gyroscopes to measure the changes in the direction of motion of the aircraft they are controlling. These measurements are fed back to the mechanisms moving the control surfaces of the aircraft.

Such a system is usually designed, in the first instance, assuming the aircraft structure to be rigid and such that the system is then stable.

Now suppose the aircraft structure, considered elastic, is disturbed in flight by, say, a gust. Normal modes of vibration of the structure will be excited, the resulting oscillations will be detected by the gyroscope and fed as error signals to the control surface actuators. If the actuators are capable of following these error signals, the control surfaces will also oscillate, exciting the structure further and so completing the cycle. This cycle may be unstable.

In shock wave turbulent boundary layer interaction, upstream influence is defined as the distance from the inviscid shock wave to where the incoming boundary layer is first disturbed. The latter position is generally taken as being where the mean wall pressure first increases above the undisturbed value. Wall pressure fluctuation measurements in two Mach 3, high Reynolds number interactions have shown that unsteadiness of the separation shock wave structure results in the instantaneous upstream influence varying over a range of values. Upstream influence as defined above is actually the maximum of this range and, at this distance upstream of the shock wave, the probability of finding the flow disturbed is correspondingly low. The minimum value of the range is the distance from the inviscid shock wave to where the incoming flow is always disturbed. In all of the cases studied the latter station was found to be just upstream of the separation point.

A technique for the prediction of buffeting response in flight from wind-tunnel tests on models of conventional construction is described and assessed. Results are presented from tests on models of a Gnat T Mk 2 trainer aircraft, and predictions are compared with flight measurements of buffeting made during high incidence manoeuvres. Flight/tunnel comparisons of buffeting response measurements on the TACT F-111 and SAAB 105 aircraft are also discussed. In general, good agreement is demonstrated between measured and predicted responses. Some remarks are also made on the determination of damping ratios from accelerometer or strain gauge readings recorded under buffeting conditions.

Military aircrafts are often subjected to severe flight maneuvers with high Angles-of -Attack (AOA) and Angles of Sideslip (AOSS). These flight attitudes induce non-uniform in flow conditions to their gas turbine engines which may include distortion of inlet total pressure and total temperature at the Aerodynamic Interface Plane (AIP). Operation of the downstream compression system with distorted inflow typically results in reduced aerodynamic performance, reduced stall margin, and increased blade stress levels. In the present study the steady state total pressure distortion induced to the Aerodynamic Interface Plane due to the aircraft’s flight attitude have been estimated in terms of distortion descriptors. The distorted conditions at the interface between the intake and the engine have been predicted by using Computational Fluid Dynamics (CFD), where 33 different aircraft flight attitudes have been tested. Based on the obtained results the effect of Angle-of-Attack (AOA) and Angle of Side Slip (AOSS) on the distortion descriptors have been studied. The results showed that the distortion effect becomes more pronounced whenever this specific airframe configuration is exposed to incoming flow with an AOSS. Among the tested cases, the greatest total pressure defect at the AIP in terms of difference from the average value and of circumferential extent was calculated for the flight attitudes of 0·35M flight with 0° AOA and 8° AOSS and 0·35M fight with 16° AOA and 16° AOSS.

This paper presents the development and implementation of a user-defined material (UMAT) model for NiTi Shape-Memory Alloy (SMA) wires for use in LS-DYNA commercial explicit finite-element analysis software. The UMAT focusses on the Shape-Memory Effect (SME), which could be used for actuation of aerostructural components. The actuation of a fundamental structure consisting of an SMA wire connected in series with a linear spring was studied first. The SMA thermomechanical behaviour obtained from the finite-element simulation was compared with that obtained from the analytical solution in MATLAB. A further comparison is presented for an SMA-actuated cantilever beam, showing excellent agreement in terms of the SMA stress and strain as well as the tip deflection of the cantilever beam. A mesh sensitivity study on the SMA wire indicated that one beam element was adequate to accurately predict the SMA thermomechanical behaviour. An analysis of several key parameters showed that, to achieve a high recovery strain, the stiffness of the actuated structure should be minimised while the cross-sectional area of the SMA wire should be maximised. The actuation of an SMA wire under a constant stress/load was also analysed. The SMA material model was finally applied to the design of morphing aluminium and composite aerofoils consisting of corrugated sections, resulting in the prediction of reasonably large trailing-edge deflections (7.8–65.9 mm).

Aerodynamic designers of transport aircraft have been dreaming for decades of being able to use, for high speed design problems, some of the advanced computational tools that they now have available to them such as the three-dimensional transonic flow methods and three-dimensional finite-difference boundary-layer methods. It is anticipated by the designer and his management that the appropriate use of these new advanced computational methods on the wing design of the next subsonic transport aircraft configuration will typically result in an improved aerodynamic technology level, an improved aerodynamic efficiency for a given level of aerodynamic technology, and reduced design costs through a reduction in the amount of wind tunnel testing required and the resulting shortened time period required to define the final lines.

This paper provides an overview of techniques developed for the application of support vector regression in the domain of simulation and system identification of helicopter dynamics. A generic high fidelity FLIGHTLAB helicopter model is used to train and validate a number of pitch response SVR models. These models are then trained using flight data from a Sikorsky Seahawk helicopter. The SVR simulation results show significant promise in the ability to represent aspects of a helicopter’s dynamics at a high fidelity. To achieve this, it is important to provide the SVR kernel with knowledge of past inputs that encompass the delay characteristics of the helicopter dynamic system. In this case, the use of nonlinear auto regressive eXogenous input network architecture achieves this goal. Good performance was achieved using input data that encompassed between 300 to 500ms worth of historic response.

A method for accommodating engine deterioration via a scheduled linear parameter varying quadratic Lyapunov function (LPVQLF)-based controller is presented. The LPVQLF design methodology provides a means for developing unconditionally stable, robust control of linear parameter varying (LPV) systems. The controller is scheduled on the engine deterioration index, a function of estimated parameters that relate to engine health, and is computed using a multilayer feedforward neural network. Acceptable thrust response and tight control of exhaust gas temperature (EGT) is accomplished by adjusting the performance weighting on these parameters for different levels of engine degradation. Nonlinear simulations demonstrate that the controller achieves specified performance objectives while being robust to engine deterioration as well as engine-to-engine variations.

This paper examines the changing role aerodynamic technology plays in the design and development of modern combat aircraft. It reviews several aspects of aerodynamics which contribute to aircraft performance and handling characteristics. It considers the importance of a range of technologies, the contribution each makes to the final integrated solution and comments on the compromises necessary through the design cycle to optimise the overall weapon system, sometimes to the cost of one of the component technologies. The technologies discussed are in no way exhaustive but attempt to encapsulate the breadth of the subject, to illustrate its diversity and to point the way for the future development if aerodynamic technology is to continue to make an important contribution to the design of combat aircraft.

Each of the component technologies are discussed in terms of the contribution it makes, the tools and techniques used to predict, analyse and interpret the technology contribution, and the requirements for the direction of the development of the technology for the future.

Before considering the technologies themselves it is important to understand the environment in which they will be used, which increasingly conditions the manner in which they are employed and suggests the direction for their development.

This paper begins, therefore, by briefly reviewing the changes to the environment in which the fighter pilot operates and the manner by which his requirements, and therefore the specification of the aircraft, are defined before going on to look at the overall contribution each technology makes in the design process.

In the modified free-streamline theory for the separated flow past bluff bodies due to Roshko, the velocity on the separated free streamlines is expressed as

Uv=kU0,

where U0 is the velocity of the undisturbed stream and k is a constant. If it is assumed that the pressure on the base of the body is uniform and equal to the pressure on the free streamline, then application of Bernoulli's equation leads to;

k =(1-Cpb)½,… (1)

where Cpb is the base pressure coefficient.

The design and analysis of axial turbomachine blade profiles has usually been done assuming the flow to be two-dimensional, that is assuming the blade-to-blade stream surfaces are parallel planes. Similarly, most of the detailed experimental studies of blade profiles have been done in nominally two-dimensional cascades or using wall boundary layer suction to achieve (on average) two-dimensional conditions. In an actual compressor or turbine, however, this condition rarely obtains.

In 1929 when I was a young schoolboy in York, I was fortunate to become one of a small band of nomadic gliding enthusiasts centred around a most enterprising chap called Percy Watson, who had built himself a German Zoegling training glider above his chemist's shop in Micklegate. Each weekend we flew this machine — on which one sat in the open with an awe-inspiring view of the ground—from a wide variety of hills and precipices in the country to the east of York in the direction of Scarborough and Whitby.

In 1936, as a result of this exciting and sometimes quite terrifying activity, I joined Slingsby Sailplanes at Kirbymoorside, where I became happily involved in the design and development of Kirby Cadets and Tutors and the like. It was a most satisfactory occupation for a young chap dedicated to gliding and in consequence I developed a love of the wolds and moors of East Yorkshire from Sutton Bank to the sea, which continues to this day.

Future developments and trends in the data processing industry will have an earlier and stronger impact on aerospace than upon any other segment of industry. The use of data processing by aerospace in scientific, administrative and automation applications typically precedes and anticipates that of society and industry at large. My discussion, therefore, will focus on the total use of data processing and its technologies in our industrial-based societies. First, I will present an overview of data processing in terms of usage and dollars, then look at the world of computers a decade hence from a user's and administrator's point of view. Then I will offer a view of that world of computers from a technologist's point of view, and finally, discuss the impact of such a scenario on our society.

The term data processing industry, as I will use it, includes all those who are involved in providing data processing capabilities: equipment and software manufacturers, programming and operations staffs of user installations, professional data processing organisations, and university and research computer science groups. In short, those who design and produce our computer-based systems and services.