The unsteady load response in the frequency domain for a general two-dimensional body has been determined. Systems with one degree of freedom have been considered. The theory is based on the potential incompressible flow, and resolves around a mathematical treatment that starts from the theory of Drischler and Diederich. Admittance for the lift force and pitching moment (or side force and yawing moment for non lifting systems) has been calculated in closed form or numerically for aerofoils, swept back and swept forward wings, delta wings, and some ground vehicles (various car shapes) using sinusoidal and square gusts. Simulations have been performed for a wide range of gust speed ratios. The general features of the admittance function are discussed. It is proved that for some geometries there is an large number of frequencies that yield critical damping. These frequencies are generally very high. Comparisons with existing experimental data are good in the whole range of practical frequencies.

Despite the common title of this series of papers, the specific area into which we now move originated on a more global scale than the title suggests. Thus in the spirit of the plan set down at the outset for this review, viz that major ideas from abroad must be included, contributions from such countries as France, Germany and the United States here warrant greater prominence.

In Part 3 of this review we surveyed the development within Britain of the stress-skinned streamlined monoplane. Since the 1920s increasing numbers within Britain’s government research establishments, the universities and industry had been actively promoting this advance. Nonetheless, the practical hardware’s eventual emergence by the mid-1930s was largely driven by industry’s need for greater aerodynamic efficiency and a desire to excel. Thus record-breaking attempts, events such as the Schneider Trophy and MacRobertson races, all provided the impetus for this. So, too, did the commercial pressure of a new generation of American airliners and, for those astute enough to interpret them as such, the alarum calls of an impending Second World War. As a result of the appreciable decrease in drag coefficient achieved, coupled to a massive improvement in piston engine power, military aircraft, in particular, proved capable of flying not only further and higher but also dramatically faster. A further consequence, however, was that certain wartime high-speed fighter aircraft began to encounter serious, even fatal, compressibility effects as their enhanced speeds in dives reached subsonic critical Mach number conditions.

Seaplanes were an important feature of aviation during its first four decades, both for long range transport and high airspeeds. Research, and the testing of new designs, was carried out at the Marine Aircraft Experimental Establishment at Felixstowe until 1958. However, the record of this scientific work at MAEE has never been fully reported until this paper. The main scientific topics described are, stability during take-off and landing, hydrodynamic resistance, landing impact, spray formation and its control. Armament research and testing receive special attention. A large fleet of prototype seaplanes was type tested; results from these type tests are summarised to show the wide range of designs needing to be assessed. In a final section the authors consider how seaplanes may return to the main stream in the 21st century.The two authors were respectively Head of the Scientific and Technical offices at MAEE in the 1940s.

A few of us, like Tennyson, have the gift of foreseeing the future. (see Fig. I). Another few, like Juan de la Cierva have the gift of delivering the future. They are the innovators.

Those who know Tennyson's verse will recall that his vision was of transportation by air of people and freight and also sadly of weapons. These were the tasks for which aircraft have primarily been developed – that is until recently.

Let us move back a few years from Cierva's day to view the work of another innovator – Von Karman. His machine was a harbinger of the future in that it was not designed for a transport task but for a surveillance task (Fig. 2). It did not survive for long since Von Karman lacked the light-weight, compact, electro-optical sensors available today and he was forced to carry aloft two mk 1 eyeballs attached to a heavy and bulky man.

A project was recently completed that investigated the ability to predict the onset of flutter using tools like the flutterometer. This project used an experiment called the aerostructures test wing that was flown while mounted to the flight test fixture on an F-15. Several flight tests were conducted to expand the envelope and determine the aeroelastic dynamics of the experiment. The final flight ended with destruction of the experiment due to the onset of flutter. The flutterometer attempted to predict this onset by analysing the flight data. The results indicate the flutterometer is able to generate a conservative estimate of the flight conditions associated with flutter. This paper details the flight tests of the experiment and the resulting predictions from the flutterometer.

This work deals with tailoring of adaptive material included at the roots of hingeless helicopter rotor blades to be used in individual blade control (IBC) strategies.

Usually, IBC strategies involving the use of adaptive materials either consider adaptive material embedded in the blade structure for inducing strain deformations, or apply adaptive actuators for controlling segments of the blade (e.g. for moving trailing-edge flaps).

Here, the adaptive material is used to provide augmentation of modal damping in a passive control approach, that can be conveniently tuned so as to make it the most suitable for the actual rotor configuration under examination. The presentation of a procedure for tailoring this ‘smart spring’ is the aim of the paper.

The aeroelastic blade model considered consists of a cantilever slender beam undergoing flap, lead-lag and torsional motion, coupled with a strip theory approach for the prediction of the aerodynamic loads, based on the very low frequency approximation of the pulsating-free-stream Greenberg’s theory.

Starting from this model and applying the Galërkin method, generalised mass, damping and stiffness matrices of the basic blade, as well as the incremental generalised mass, damping and stiffness matrices due to the ‘smart spring’ have been determined, the latter depending on the ‘smart spring’ inertial and elastic characteristics.

It will be shown that the application of an optimal control criterion, followed by a low frequency-approximation observer, yields the identification of the most suitable ‘smart spring’ characteristics for augmentation of rotor blade aeroelastic stability. The validity of this procedure will be demonstrated by numerical results concerning the stability analysis of two hovering blade configurations.

The challenges of helicopter simulation are being tackled across a broad front as technology is developed to meet the needs of Industry. Traditionally, the strongest impetus has come from the training community and this is likely to continue for some time as simulation technology advances at increasing pace, raising fidelity standards. The development of PC-based simulation technologies is providing a significant spur in this development and lowering the cost, making complete simulation systems of reasonably high fidelity available to smaller organisations. This paper describes the first year of operation with such a system at the University of Liverpool – HELIFLIGHT. With its full motion, wide field-of-view visuals, programmable force-feel system and the comprehensive FLIGHTLAB modelling environment, we describe the HELIFLIGHT system as high fidelity and the first year of utilisation saw extensive use in a variety of handling qualities and pilot-vehicle technology research and teaching. Some of these are described in the paper and from a year of many highlights, the EU-funded programme to develop handling qualities for a civil tilt rotor aircraft is selected to demonstrate the versatility of the HELIFLIGHT system.

In the autumn of 1902 the Wright brothers spent just over eight weeks at their test site in the Kill Devil Hills near Kitty Hawk, North Carolina, testing their third Glider design. During the trial period they implemented an inter-linked roll-yaw control system. Together with the forward canard surface, this gave them control over vertical and horizontal components of the flight path. They were also able to hone and perfect their piloting skills. In just two days in the final week, they made about 250 glides. The success of the trials instilled the confidence in the Wright brothers to proceed rapidly to the construction of a powered aircraft. Within a month of returning to Dayton, they were writing to engine manufacturers with their specification – an engine that would develop eight to nine brake horse power, weigh no more than 180lb and be free from vibration; they would not find a suitable powerplant and had to design and build their own. The invention of the powered aeroplane in 1903 somewhat overshadows the earlier critical flight control developments, but the birth of flight control in 1902 opened the way for aviation to flourish. With the aid of modern flight science techniques – wind-tunnel testing, computational flight dynamics and piloted simulation, this paper examines the technology of the Wrights' 1902 glider. The research forms a part of the Liverpool Wright Project, aiming to bring to life the Wright brothers' achievements in this centenary period. Wilbur and Orville Wright are recognised by many as the first aeronautical engineers and test pilots. In so many ways they set standards that today's engineers and organisations benefit from. Their work in the period 1901 to 1902 reflects their genius and the paper reviews this work in detail, examining the design, aerodynamic characteristics and flying qualities of the aircraft that first featured a practical three-axis control system.

The intrinsic dependence on the necessary minimum structural performance of inflatable aircraft evacuation slides and slide-rafts in the event of and emergency or precautionary aircraft evacuation is described in the context of the certification of both new (or modified) aircraft and slide designs. The concepts of the pneumatic structure with analytical and numerical methodologies are briefly reviewed. Fundamental principles of inflatable evacuation slide performance and assessment are presented, while the characteristics of typical structural responses are identified for single deck aircraft. The implications of evacuation from an upper deck of a VLTA are identified in the interpretation of two new commercial inflatable evacuation slide designs. Alternative meso and macro pneumatic structural forms are proposed as evolutions of the conventional inflated tube. Outline details of a simple mixed finite element and vector-based simulation algorithm for the analysis of pneumatic structures precede examples verifying the numerical formulation and demonstrating the potential of multi-cell beam (meso) and “semi-pneumatic shell membrane” (macro) pneumatic concepts. Recommendations for future research conclude the paper.

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.

This paper reviews the research on Gurney flaps and related high lift trailing edge devices. It investigates aerofoil performances at Reynolds numbers Re ≅ 105 and below, both with the clean configuration and various Gurney flap sizes. The device height is optimised, and a semi-empirical formula linking flap height to free stream speed and aerofoil chord is proposed. The analysis shows that the optimal size of the device is always below the boundary-layer thickness at the trailing edge. Discussion of results includes analysis of hysteresis loops occurring in the L/D performances. These are mostly due to large changes in drag and small changes in lift, which occur when the aerofoil is restored to the reference angle of attack.

Modern fighter aircraft have been associated with lateral self-excited limit cycle oscillation known as ‘wing rock’. Simulations of wing rock have been encouraged to develop a complete understanding of the fluid mechanism that triggers and drives the oscillation, as well as for prediction purposes. Previous simulations of wing rock in wind/water tunnels were almost exclusively limited to a single degree-of-freedom in roll, due to the difficulty encountered in mounting the model to freely oscillate in more than one degree-of-freedom. Numerical simulations, utilising computational fluid dynamics, were also limited to roll-only degree-of-freedom. The loss of simulation accuracy due to the reduction of the actual wing rock degrees-of-freedom to roll-only has not as yet been fully investigated. In this study wing rock is numerically simulated in three degrees-of-freedom: roll, sideslip, and vertical motion for a generic fighter model. The unsteady Euler equations are coupled with the rigid-body dynamic equations through an innovative sub-iteration algorithm to simultaneously solve the coupled equations. The effect of including the sideslip and vertical degrees-of-freedom was found to delay the onset angle-of-attack of wing rock by 5° and reduce the limit cycle amplitude by about 50% with the frequency remained almost unchanged.

Experimental work has been carried out to study the unsteady flow-field characteristics related to shock-wave/boundary-layer interaction. Tests were carried out on an axisymmetric configuration that has a semi-cone angle of 35° and a flare angle of 20°. Further influence of low γ gases (C02 and CF4) on the overall interaction process is also investigated. Both surface and off-surface analysis has been carried out. Off-surface study has been made with a laser schlieren system. The purpose of this study was to investigate the source of the unsteadiness related to such interactions. Two types of shock motions, namely, flapping and rippling could be identified for air, the relative importance of each of which is strongly dependent on the location within the interaction and on the type of test gas. Spectral analysis shows the large-scale motion of the separation bubble to be the main source of high amplitude fluctuations. However, the existence of separation bubble itself does not necessarily indicate the prevalence of unsteady flow conditions.

Emergency evacuation of future very large transport aircraft (VLTA) in the event of a survivable crash poses a challenge for aircraft manufacturers and certification authorities. In addition, the increase in passenger capacity and flight duration associated with such airframes requires that some general cabin safety issues be revisited. Information gained from previous accidents and research has been reviewed with particular regard to VLTAs. This has included consideration of the issues associated with the aircraft configuration, the behaviour and training of the cabin crew, passenger behaviour in emergency situations, and issues relevant to future trends within the industry.

Unmanned aerial vehicles (UAV) have seen a rapid growth in utilisation for reconnaissance, mostly using single UAVs. However, future utilisation of UAVs for applications such as bistatic synthetic aperture radar and stereoscopic imaging, will require the use of multiple UAVs acting cooperatively to achieve mission goals. In addition, to de-skill the operation of UAVs for certain applications will require the migration of path-planning functions from the ground to the UAV. This paper details a computationally efficient algorithm to enable path-planning for single UAVs and to form and re-form UAV formations with active collision avoidance. The algorithm presented extends classical potential field methods used in other domains for the UAV path-planning problem. It is demonstrated that a range of tasks can be executed autonomously, allowing high level tasking of single and multiple UAVs in formation, with the formation commanded as a single entity.

The CAA has recognised the need to develop civil standards for unmanned aerial vehicles (UAVs). Accordingly the CAA Directorate of Airspace Policy has published the document ‘CAP 722 –Unmanned Air Vehicle Operation in UK Airspace – Guidance’, (which can be accessed via the CAA website — http://www.caa.co.uk/docs/33/CAP722.pdf). The document itemises the top-level military and civil regulations which impact upon the operation of UAVs in the UK. One of the items listed within the document is ‘Civil Certification’ of UAVs. This particular aspect is the responsibility of the Design and Production Standards Division, (D&PSD), of the CAA Safety Regulation Group. The purpose of this paper is to present and explain the current position of D&PSD regarding the appropriate design standards to be applied for the civil certification of the airworthiness of UAVs.

This paper presents the CAA position that UAVs should be granted permission to fly by qualifying for certificates of airworthiness, by demonstration of compliance with defined airworthiness standards comparable to, and derived from, those applied to manned aircraft. The paper also presents a method for determining, to a first approximation, the level of airworthiness standards which should be applied to any particular design of UAV by reference to the existing codes of airworthiness requirements for manned aircraft.

An experimental investigation has been conducted on the mixing layers produced from the merging of two non-parallel streams. To study the effect of velocity ratio on its development, mixing layers were produced with velocity ratios 0·7, 0·8 and 0·9. The boundary layers were untripped and initially turbulent in all the cases. For each velocity ratio, measurements were made at six streamwise locations. It was found that for velocity ratios 0·7 and 0·8, mixing layers appear to attain self-similarity but failed for 0·9 within the measurement domain. The development distance of the mixing layer flow was increased with increasing velocity ratio and the splitter wake was found to play an important role in its development. The mixing layer growth was found to decrease with increasing velocity ratio though the spread of the layer was larger at the high speed side.

The aim is to explore the philosophy of air traffic management with different strategic visions of the future: to answer the key question: ‘Who is to prevent mid-air collisions and how are they to accomplish this?’ The best strategic vision may just be the one that has the best match with the consensus on the desired strategic direction. Nevertheless, it must satisfy the main safety, financial, human performance etc. constraints. To explore the question, a blend of concepts from a range of disciplines has been used. These include risk analysis, financial decision-making, ‘cognitive engineering’ research and simple cybernetics. ‘full delegation’ – with pilots being responsible for all the tasks related to separation assurance – appears to meet most of the constraints. Some important issues for safety analyses of full delegation are sketched. Research into the nature and rate of future conflicts in a full delegation environment, using models of error processes, is crucial.