As the first international project of this kind, the German-Dutch Wind tunnel (DNW) is under construction in the Noordoostpolder, The Netherlands. The DNW will be among the largest and most extensive complete low speed wind tunnels in Europe. This project is based on previous specifications and design work for two former national projects (now abandoned) which were similar in size and performance and mutually complementary in view of the tasks. The DNW will contribute to filling the gap still existing in the field of aeronautical test facilities in Europe for effective aircraft development work.

The DNW will consist of a closed circuit tunnel (total length of centre line: 318 m) with three interchangeable atmospheric test sections with cross-sectional sizes of 9.5m x 9.5 m, 8 m x 6m and 6 m x 6 m; the maximum speed is about 60, 110 and 145 m/s respec-tively. In addition, an open jet configuration will be available with special features for aero-acoustic tests. The single-stage speed-controlled fan of 12 m diameter has a nominal drive power of 12.7 MW. The standard equipment will include an air exchange system and a heat exchanger in the circuit, a model sting support, a six-component balance, and a distributed computer system for data acquisition/reduction and control purposes.

In the period since the inception of civil jet transport, during which a dramatic increase in travel and commerce by air has taken place, the research and development directed towards the containment and reduction of aircraft noise has spread across a steadily broadening front. The noise of the simple jet engines which propelled the first civil transport aircraft was almost entirely due to the high exhaust jet velocities that were used to obtain thrust from comparatively small mass flows. This is illustrated in Fig. 1(a), where it is seen that noise from other sources, such as the compressor and turbine, is comparatively insignificant. Thus aero engine noise research in the late fifties and early sixties was concentrated mainly on the prediction of jet noise and the development of noise-reducing propelling nozzles. It was not until bypass engines began to appear, with higher propulsive efficiencies resulting from lower exhaust jet velocities and higher mass flows, that the noise of their larger compressors drew attention to the turbomachinery as an additional source requiring investigation.

This paper deals with the problem of determining an optimal controller which minimises the norm of a given aircraft while guaranteeing that an upper limit of its norm is not exceeded. The problem is tackled by means of a linear matrix inequality formulation, which allows one to constrain the eigenvalues of the model to within a fixed region of the complex plane. Key features of the method are the possibility of simultaneously

• 1. keeping the maximum value of the input demand under control

• 2. taking flying quality requirements into account

• 3. assuring a minimum level of system robustness against uncertainties of the model.

The approach is simple to handle and is well suited to the design of aircraft stability augmentation systems. A discussion of two case studies demonstrates the effectiveness of the procedure.

Approximate solutions for the critical load of an axially loaded strut, and for the deflection produced in an eccentrically loaded strut, are obtained by the Energy Method. For most practical purposes these solutions compare favourably with solutions based on successive approximation, since for the same accuracy the time required for a solution by successive approximation is much greater.

The heading aerodynamic noise includes all cases where sound is generated by fluid flows. It includes aeolian harps, edge tones and related phenomena as well as vortex, boundary layer, wake and jet noise. In the strict sense it does not include propeller noise and the direct noise generated by; bodies in motion. However, in view of their importance as sources of aircraft noise some of their more important aspects will be discussed briefly and compared with the similar properties of pure aerodynamic noise.

In general it is audible aerodynamic noise which is of major interest at present, but it would be unwise to neglect entirely the ultrasonic aspects. These have received little attention as yet.

The title of this paper could cover a number of interesting problems ranging from the ultrasonic scream from compressors and its (alleged) effect in producing “jet sickness,” to the noise from supersonic propellers but, since it is “in particular Jet Noise” which is under discussion, this paper deals entirely with that subject. Some new facts are presented, mostly obtained at my own firm, with the active encouragement of the Ministry of Supply, and some of their implications are discussed.

Today the aerospace industry is ranked in the top three industrial sectors in the UK. With air traffic expected to more than double by 2015, there are tremendous wealth creation opportunities for those who satisfy their customer's needs. Innovation — the successful exploitation of new ideas — is a key ingredient in achieving this. It is an engine of growth because it delights the customer — and that delight is the basis for long-lasting customer loyalty. Henry Royce recognised the importance of exceeding the customer's expectations and laid the foundations for Rolls-Royce's long tradition of innovation. With historical illustrations, from the Silver Ghost motor car to today's flagship — the Trent aero engine — this paper highlights the key elements which are necessary to promote innovation and have led to many Rolls-Royce “firsts”. A review of today's state-of-the-art aero engines details current innovations, and their associated customer benefits, while a view of future markets reveals an insight into future aero engine developments and technical challenges. The solution to some of these challenges will require the application of advanced technologies. In anticipation of the customer's requirements, the development of these advanced technologies is discussed together with their potential customer benefits.

The 909th Lecture to be given before the Society and the 16th Main Lecture at a Branch, was held under the auspices of the Chester Branch of the Society on 8th April 1954. Mr. K. G. Hancock, Chairman of the Chester Branch, expressed the pleasure of the Branch at having a Main Meeting of the Society at Chester and welcomed the visitors, particularly the officers of the Main Society. He then asked the President, Sir William Farren, to preside for the rest of the Meeting.

The first research carried out in France relating to air cushions was effected in 1957 by the Bertin Company. The phenomenon was first observed during thrust measurements on inward directed annular jet silencers (Fig. 1), in which the effects of air inlets were being studied. Thrust was measured by the weighing of a plate located in front of the nozzle; when the secondary air inlets were closed, the scheme was in fact the one of the peripheral jet air cushion and the thrust read on the dynamometer was found to be much greater than the theoretical jet thrust (Fig. 2).

It should be noted that this work was an extension of research carried out by SNECMA concerning striction, that is to say the control of the exit area of the engine nozzle by means of an inward directed peripheral fluid curtain the purpose of which was to increase the pressure inside the exhaust pipe which is the characteristic of annular jet air cushions (Fig. 3).

Project reviews are carried out to enable the right decisions to be taken to achieve project objectives. However, these decisions are often taken on incomplete, optimistic, inaccurate, misleading or simply wrong information. Whilst incompleteness is inevitable with the complex and rapidly changing nature of high technology engineering projects, it is important that the project manager has a good appreciation of the extent to which these other factors may affect the progress information upon which judgements are made. This paper explores a few of the traps the author has come across, and suggests possible approaches to avoid some of them.

A systems perspective is recommended, with a focus on risk management, resolving ambiguity, rapid response, trend analysis, earned value principles and taking account of the effects of organisational changes.

The problems involving vibration which affect helicopters can be divided into two major categories:

• (a)Forced vibration effects

• (b)Aeroelastic and aeromechanical instabilities.

Forced vibration effects are subdivided into two categories.

• (i)Effects due primarily to aerodynamic forcing; and

• (ii)Effects due primarily to mechanical forcing.

Forced vibration effects have important repercussions in the area of:

• (i)Crew comfort and efficiency

• (ii)Fatigue strength of dynamic components and the airframe

• (iii)Reliability of electronic equipment.

The most important forcing effect is aerodynamic in origin, and this will be considered first.

It has long been known that compressibility affects the maximum lift coefficient at Mach numbers as low as 0·15. A schematic flight envelope (Fig. 1) shows that there are two main phenomena to be considered; the effects of compressibility on the low speed stall, and on the high subsonic speed stall.

In the low speed stall regime there is, in general, a decrease of the maximum lift coefficient with increasing Mach number which is appreciable even at typical aircraft landing speeds. A knowledge of the lift boundary throughout the envelope is necessary if allowances are to be made for gusts and if a safe rough-air performance is to be determined.

This subject, even as it applies to those areas which are the direct or partial responsibility of the test pilot, is a comprehensive one, and it is not intended to embrace it completely. Specifically this paper will touch only on the area in which the pilot is principally involved. Further, it is not the intention to catalogue the tests required for certification or to describe all of them in detail, but rather to discuss the whole certification process in more general terms.

The purpose of Certification is to establish a minimum safety standard, but when forming that standard, sight cannot be lost of the feasibility of achieving it, both practically and commercially. Inevitably, therefore, the discussions or arguments that arise over establishing the standards against which aircraft are going to be assessed must centre around the problem of where the balance between safety and cost should be struck. As previously implied, absolute safety is not only probably impossible to achieve, but quite clearly commercially impractical. The constructor's task must be, therefore, a process of resolving the often conflicting ideas of the various bodies and agencies that attempt to define the “balance” and within that definition offer a commercially attractive aircraft. If he strays widely from the prevailing definition, even in the interests of increased safety, he is in danger of pricing himself out of business. This fact is rather obvious, but no excuse is given for stating it since it is thought to be so fundamental to the subject under discussion, and one that is often overlooked, particularly perhaps by those who are not so involved with the day-to-day operation of aircraft.

Presentation of the Daniel and Florence Guggenheim International Memorial Lecture is both a high honour and a challenge. The challenge is implicit in the final two words—to present to you both a lecture and a fitting memorial to the remarkable Guggenheim family. I believe that the subject which I have chosen is particularly appropriate for this task. As many of you know, Daniel Guggenheim, in the years from 1925 to his death in 1930, sponsored and endowed the now famous Guggenheim Aeronautical Laboratories in major universities across the USA. It is clear from his writing that these were not simply gifts to the universities—conventional endowments—but that they reflected Daniel Guggenheim's vision of a future in which the aircraft would link cities and countries in a safe, efficient civil transport system surpassing all other modes of travel.

Spinning/Rolling Airframe Missiles (RAM) mostly use an analog (ON-OFF type) control approach that deflects control surfaces (fins) at minimum and maximum positions continuously, and control is achieved by applying phase shift between the minimum and maximum deflections during a complete roll cycle. Therefore, the control signal shape changes continuously during the roll cycle. In this study, a novel single channel digital controller is designed and tested for a high spinning rate (10–20 Hz) RAM. The digital controller adjusts the amplitude of fin deflections instead of applying a phase shift. In this way, control signal shapes are predetermined in design to completely decouple yaw and pitch dynamics. At the beginning of each roll cycle, the algorithm decides on the control signal shape and amplitude to apply throughout the cycle. Delays on the actuator system and sensor measurements which might lead to instability at high spinning rates are handled effectively thanks to the predetermined control signal shapes that are changing with 90-degree intervals. Detailed geometry of a surface-to-air spinning missile is used to obtain aerodynamic coefficients for the entire flight regime (i.e. from launch to terminal phase) via Missile DATCOM. The 6-DOF flight dynamics model and the controller algorithms are built in MATLAB/Simulink environment. The proposed digital controller is tested systematically for various scenarios and the performance is compared with the conventional analog control approach. The digital controller gives better performance compared to the analog approach under the influence of servo delays and sensor noise.

The ability to perform air-to-air refuelling (AAR) can dramatically extend the utility of helicopters, through effectively providing unlimited range. For helicopters, AAR is typically performed utilising the probe-and-drogue aerial refuelling method. This is a complex manoeuver, where normally both the helicopter and tanker aircraft are operating at the limits of their flight envelopes. In addition, the wake flow from the tanker aircraft can cause a significant disturbance on the refuelling helicopter. This paper presents the initial evaluation of an AAR scenario constructed within DLR’s flight simulator, the Air Vehicle Simulator (AVES), based on current procedures and pilot interviews. A mission task was defined to assess the scenario in AVES and results are subsequently discussed. For pilots unfamiliar to formation flight or HAAR, the results show the difficulty of the flying task itself at the given cueing. Measures for improvement in future investigations are suggested.

Numerical methods have been developed for the prediction of aerodynamic characteristics of canard wing configurations by considering both attached and separated flow over the canard surface; the flow over the main wing surface is always assumed to be attached. Experimental tests have been conducted in a low speed wind tunnel to compare the theoretical results predicted by the numerical methods. The comparison shows good agreement up to approximately 16° incidence.

In this paper, a novel thrusting manoeuvre control scheme is proposed for a small spacecraft which is based only on the gimbaled thrust vector control (TVC) system. The spacecraft structure is composed of a body and a gimbaled thruster where common attitude control systems such as reaction control system (RCS) and spin stabilisation are not employed. A nonlinear two-body model is considered for the characterisation of the gimbaled-nozzle spacecraft where the gimbal actuator provides the only active control input. The spacecraft attitude is affected by a large exogenous disturbance torque which is generated by a thrust vector misalignment from the centre of mass (CM). To achieve some performance goals in the both transient and steady-state modes, a new control scheme is derived based on the combination of two linear and nonlinear controllers. The proposed method ensures the attitude and thrust vector stability during an impulsive orbital manoeuvre while eliminating and rejecting an exogenous disturbance torque. The numerical simulations illustrate the applicability of this method for using in a small spacecraft and its efficiency in sustained operation.

Throughout the course of a flight mission, a range of aerodynamic conditions, including design-point conditions and off-design conditions, are encountered. As the bypass ratio increases and the fan-pressure ratio decreases to reduce the engine’s specific fuel consumption, the engine diameters increase, which results in an increase in the nacelle weight and overall drag. To reduce its weight and drag, a shorter nacelle with a length-to-diameter ratio $L/D = 0.35$ is investigated. In this study, an adaptive cokriging-based multi-objective optimisation method is applied to the design of a short aero-engine nacelle. Two nacelle performance metrics were employed as the objective functions for the optimisation routine. The cruise drag coefficient is evaluated under cruise conditions, whereas the intake pressure recovery is evaluated under takeoff conditions. The cokriging metamodel are refined using an effective infilling strategy, where high-fidelity samples are infilled via the modified Pareto fitness, and low-fidelity samples are infilled via the Pareto front. By combining parameterised geometry generation, automated mesh generation, numerical simulations, surrogate model construction, Pareto front exploration based on the non-dominated sorting genetic algorithm-II and sample infilling, an integrated multi-objective optimisation framework for short aero-engine nacelles is developed. Two-objective and three-objective test functions are used to validate the effectiveness of the proposed framework. After the optimisation process, a set of non-dominated nacelle designs is obtained with better aerodynamic performance than the original design, demonstrating the effectiveness of the optimisation framework. Compared with the kriging-based optimisation framework, the cokriging-based optimisation framework outperforms the single-fidelity method with a higher hypervolume value at the same number of iteration loops.

This paper concentrates on the trajectory tracking problem for a stratospheric airship subject to underactuated dynamics, unmeasured velocities, modeling inaccuracies and environmental disturbances. First, a coordinate transformation is performed to solve the underactuated issue, which simultaneously permits a priori assignment of the tracking accuracy. Second, a finite-time observer is integrated into the control structure to offer the exact information of unmeasured velocities and uncertainties in an integral manner. Then, by combining the backstepping technique with the method of adding a power integrator, a new output-feedback control strategy is derived with several salient contributions: (1) the airship’s position errors fall into a predetermined residual region near zero within a finite settling time and stay there, while all the closed-loop signals maintain bounded during operation; and (2) no artificial neural networks and filters are adopted, resulting in a low-complexity control property. Furthermore, the presented method can be extended readily to a broad range of second-order mechanical systems as its design builds upon a transformed system model. Rigorous mathematical analysis and simulations demonstrate the above theoretical findings.