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 turn of the century produced the expected crop of articles listing space achievements over the past 30-40 years. Many of them, particularly those connected with the Moon landing, made the front pages of newspapers all over the world, and are still regularly served up in television programmes. Nevertheless, they constitute an inadequate basis on which to make an assessment as to where — if the expression can be permitted — we now stand in space. It is no longer sufficient to look at progress in the individual space segments: satellites, launchers and the often neglected ground segment. The springs of action are now to be found elsewhere: the uptake of space applications by the end-users (most of whom have no knowledge of, or interest in, space); the increasing role of the private sector in financing space systems; the inter-twining of the civilian and defence programmes; political and international trade considerations, etc. This.article is an attempt to review progress against the background of these external factors and to present a balance sheet. In order to leave posterity with further palpable proof of the author's fallability, the article will close with a few thoughts on future trends and technological developments.

Although small in comparison with some other global activites, civil and military space operations account for about $50bn annually. Of this, slightly less than 10% can be identified as European, compared to just over 50% for the United States. This volume has been stable for several years and promises to continue at least for the near future, although the distribution between the various sectors is changing. Space is therefore an activity of considerable importance to public and private sectors alike, even though it has lost its high place on the political agendas of many countries.

This paper reviews some of the options for limiting emissions from aircraft engine exhausts. Its main purpose however, is, to investigate the possibility of a Government-airline partnership and to this end, the issues are reviewed along with a summary of the possible approaches that have been identified to date.

Detailed numerical comparisons of pressure and flow angle measurements made in stage three of a four-stage, large scale, low speed, axial compressor are presented. The measurements are in both the rotating and stationary frame and were obtained as part of a BRITE/EURAM collaborative study of cantilevered and shrouded-stator compressor configurations. The numerical analysis is 3D, considers three blade rows simultaneously and incorporates multiple row effects by use of a conservative mixing-plane model allowing circumferential variation at the mixing plane.

The paper discusses the early results of a study sponsored by Alstom Gas Turbines to examine steady-state, multiple blade-row modelling techniques. Growth in the endwall flow region due to multi-row effects is revealed from both the numerical and experimental results. The numerical simulation is conducted without altering blade gap spacings to assist numerical stability; the axial gap is increasingly being seen as a critical performance parameter for multiple row analysis. The limitations inherent in an approach using mixing-planes are presented and a review of alternative, more rigourous, treatments of these effects is then discussed. These treatments attempt to retain the unsteady flow structure in a steady-state model by the derivation of so-called deterministic stresses.

Reduction of aircraft manufacturing cost benefits aircraft direct operating cost (DOC). The degree of stringency in specifying aircraft smoothness influences cost, i.e. the tighter the tolerance, the higher is the manufacturing cost. Discrete surface roughness arising from manufacturing tolerance at the wetted surface may be seen as an ‘aerodynamic’ defect. Features such as steps, gaps, waviness and fastener flushness (termed excrescence), seen as defects, contribute to aircraft parasitic drag.

The study is conducted on an isolated nacelle which is considered to be representative of an entire aircraft. Eleven key manufacturing features at the wetted surface of a generic long duct nacelle are identified, each associated with surface roughness. The influence of tolerance allocation at each of the key features is investigated to establish a relationship between aircraft aerodynamics and associated costs. The initial results offer considerable insight to a relatively complex problem in a multi-disciplinary environment.

Excrescence drag arising out of these ‘aerodynamic’ defects is assessed by using CFD and semi-empirical methods. Cost versus tolerance relationships are established through in-house methods using industrial data.

The aircraft unit price typically contributes from two to four times more than the fuel burn to aircraft direct operating costs. A trade-off study between manufacturing cost and aircraft drag indicates that, in general, there is scope for some relaxation of present-day tolerance allocation, to reduce aircraft acquisition cost, which would in turn reduce direct operating costs.

The Defense Advanced Research Projects Agency (DARPA) Micro Adaptive Flow Control programme is described using a series of illustrative examples. Adaptive flow control is defined to be the active modification of aerodynamic flows using small, time-dependent actuators in judiciously chosen locations. A diverse set of large-scale applications is described, in which micro adaptive flow control has a substantial overall system benefit.

The Millennium now being upon us, it is perhaps appropriate to pause a while and take stock before leaping into an ever more problematic future. But why pause? Indeed, why bother with the past? Surely our newest, ever more sophisticated computer packages provide all the necessary paths to that next commercial edge, that future, unassailable military superiority? To this the German polymath, Gottfried Wilhelm von Leibniz, provides an apt, timely and, indeed, timeless corrective:

Some aspects of propulsion integration issues for ramjet powered missiles are outlined in this paper. The benefits of ramjet propulsion in the Mach 2-4 range over other types of airbreathing propulsion and rocket propulsion are well known. Compared with solid rocket motors, ramjet engines offer a much higher specific impulse and the capability of thrust management, enabling longer stand-off ranges and more flexible operation.

An overview of the ramjet engine cycle is given, highlighting engine/intake matching issues. This is followed by a performance comparison between a generic ramjet and a solid rocket powered missile (the air-to-air configuration is examined by way of example in this paper). As well as overall performance, intake integration and missile steering issues are considered.

A description of a wind tunnel test model, intake design and tunnel testing is given. The effects of design Mach number and side-wall removal have been investigated for twin ventral rectangular intake configurations. These tests were aimed at optimising performance at different flight conditions and improving tolerance to yawed flight. The impact of the alternative intake designs on missile performance is discussed.

God and Noah were not only the earliest recorded partnership in the history of naval architecture but they were also the most successful. God prepared the requirement and outline specification; Noah responded with a fully engineered design and construction which was not only to survive the worst floods ever seen but was also completed on time. Of course, we know nothing about cost overruns, but I doubt that cost was uppermost in Noah's mind and labour - he used his sons - was in any case cheap!

It has long been a requirement in air transport that no single failure can have a catastrophic effect. As nothing can ever be failure free, fail-safety in design and operation must be provided in all respects.

This paper explores the design background, application and history of the concept of fail-safety in air transport and the vital role it plays in overall safety. It is suggested that fail-safety is the most important discipline of all those involved in safety in design and operations. Without it, the current air transport safety levels, even using the latest technologies, would not be possible.

In the modern air transport system, all accidents are due either to fail-safety implementations breaking down, or not having been adequately provided, or due to extremely remote multiple coincident failures. It can be argued that inadequacies in fail-safety provisions at the very low target failure rates now demanded, is the main reason for the near constancy of the accident rate, and the consequent increase in numbers of accidents as the world fleet grows. In the forefront of fail-safety problems is the inadequacy of its use in the management operations of crew in the modern air transport cockpit.

Recently, grid fins have been receiving increasing attention as a practical and efficient means of controlling missile trajectory. Preliminary studies at IAR have demonstrated that modern CFD methods can be used for computing flows past complex grid fin type configurations, and that these methods are more soundly physically based than the earlier vortex lattice and/or shock expansion methods.

The current paper addresses the issue of the grid fin size, in terms of both the panel thickness and the frontal shape. The study covers three thicknesses for the grid fin panel, with front shapes having a simple blunt square face, as well as a sharp knife-edge shape. In addition, an important aspect of the present investigation is to quantify the aerodynamic effect of the ramp fairing installed immediately upstream of the blunt base upon which the grid fin assembly resides. A comparison of flow field characteristics and aerodynamic coefficients of the grid fin assembly, with and without the fairing ramp, would provide a direct means of evaluating the effect of the ramp. At this stage, the investigations are based on Euler calculations. The present study focuses on a standard grid fin configuration mounted on a generic cylindrical body.

This paper will examine the prospects for propulsion systems for large civil transport aircraft over the next two decades, to the year 2020. This period is likely to see the market drivers for future propulsion system development change from the more traditional ones of fuel consumption and weight, to also include those that affect the impact of civil aviation on the environment, and the continuing pressure to reduce the cost of ownership of civil engines, namely, product unit cost, maintenance costs and reliability. Fifty years of civil aero-engine development are reviewed and trends showing the likely limits to the main engine performance parameters are provided. The paper concludes with consideration of a number of new civil aircraft and engine concepts that may emerge in the next 20 years

Ladies and gentlemen, it is an honour and a great pleasure to present this Lanchester Memorial Lecture. I thank the Royal Aeronautical Society and its Aerodynamic Committee for inviting me. In preparing this lecture I greatly enjoyed the added significance of presenting it in the historical context set by Lanchester. But the real pleasure is to be here among many good friends with whom I worked together for shorter or longer periods.

“A body that in its motion through a fluid does not give rise to a surface of discontinuity.” So Lanchester defined a ‘ streamline body’ in his standard work Aerodynamics. With ‘ discontinuity’ the boundary is meant between the outer flow and the dead water region formed by fluid that departs from the surface as illustrated nicely in Fig. 1 for the flow around a cylinder.

The flow over a yawed circular cylinders is a research area of current interest in aerodynamics due to the inherent similarities with that of the swept wing configuration. These models however, must be carefully mounted in order to suppress a phenomenon known as attachment line contamination. This contamination occurs when models span the entire test section width, exposing the flow to the highly disruptive test section wall turbulent boundary layers. One way of suppressing this phenomenon is to mount the upstream end of the model off the test section wall, whereby eliminating the interaction between the boundary layer and the model. Mounting the model with the upstream end free of the wall however, introduces end effects which are transported inboard from the downwash over the free end.

A study has been carried out of the aerodynamic interference flow arising at the junction of a cambered, swept-forward wing and a flat plate on which a fully-developed turbulent boundary layer approached the junction. CFD predictions of the pressure field in the junction region were carried out. Flow visualisation tests and surface pressure measurements over a wind-tunnel model were conducted at incidences from -3° to +9°. With the wing at zero incidence, a single-tube yawmeter was used to explore the flow around the leading edge of the junction arid an X-wire anemometer to examine the mean velocity and turbulence fields in the streamwise corners and at the trailing edge. The Reynolds number of the tests, based on the streamwise chord and a free-stream velocity of 30ms-1, was 1·03 x 106.

At low incidence, a very weak separation occurred in the plate boundary layer, a very short distance upstream of the junction. However the oncoming stream converges into the junction, appearing to confine any vortical motion at the leading edge to within a very thin layer below the closest point of measurement to the plate. Rudimentary vortical flow developed slightly downstream of the leading edge, but dissipated further downstream. Although weak vortices were measured in the trailing-edge cross-flow plane, these were attributed to separations just upstream. The turbulence activity in the streamwise corners was found to be surprisingly low, especially on the compression side of the junction. Estimates of the skin-friction showed that it was lower over the majority of the trailing-edge crossplane than in the plate boundary layer upstream of the junction. At higher incidences, flow visualisations revealed severe stall in the junction, with large three-dimensional recirculating regions forming.

The Cooper-Harper scale is currently the only well-established scale for assessing aircraft handling qualities. However, as a result of having a unidimensional format the Cooper-Harper scale lacks diagnostic power and has also been criticised for exhibiting poor reliability. The Cranfield Aircraft Handling Qualities, Rating Scale (CAHQRS) is a new, multidimensional rating scale using concepts from two established scales, the NASA-TLX workload scale and the Cooper-Harper scale. This paper provides an overview of the development of the CAHQRS and the results from a series of validation trials in an engineering flight simulator. An in-flight refuelling task and an approach and landing task using a range of control laws were used in these evaluations. The results showed that the CAHQRS had high positive correlations with the Cooper-Harper scale. However, the CAHQRS also demonstrated greater validity, diagnostic power and higher test/re-test reliability than the previous scale.

Although new jet transport aircraft in today’s fleet are considerably quieter than the first jet transports introduced about 40 years ago, airport community noise continues to be an important environmental issue. NASA’s Advanced Subsonic Transport (AST) Noise Reduction programme was begun in 1994 as a seven-year effort to develop technology to reduce jet transport noise 10dB relative to 1992 technology. This programme provides for reductions in engine source noise, improvements in nacelle acoustic treatments, reductions in the noise generated by the airframe, and improvements in the way aircraft are operated in the airport environs. These noise reduction efforts will terminate at the end of 2001 and it appears that the objective will be met. However, because of an anticipated 3-8% growth in passenger and cargo operations well into the 21st century and the slow introduction of the new noise reduction technology into the fleet, world aircraft noise impact will remain essentially constant until about 2020 to 2030 and thereafter begin to rise. Therefore, NASA has begun planning with the FAA, industry, universities and environmental interest groups in the USA for a new noise reduction initiative to provide technology for significant further reductions.

Market research predicts a large growth in numbers of passengers as well as airfreight volume for the aircraft industry. An expected concomitant increase in competition for the European aircraft industry demands that the efficiency of new aircraft has to be drastically improved. One approach to achieve this is the aerodynamic optimisation of the wing. The fixed wing is designed optimally only for one flight condition. This flight condition is described by the parameters altitude, Mach number and aircraft weight which vary continuously during the mission of the aircraft. Therefore, the aircraft is just periodically near the chosen design point. To compensate for this major disadvantage, an adaptive wing for optimal adaptation and variation of the profile geometry to the actual flight conditions is under development. DaimlerChrysler Aerospace Airbus, DaimlerChrysler Research and the German Aerospace Centre (DLR) are working as project partners on concepts for a variable camber and a local spoiler bump. In this paper structural concepts developed by the German Aerospace Centre for both objectives will be presented. The concepts are designed under the aspect of adaptive structural systems and require a high integration of actuators, sensors and controllers in the structure. Special aspects of the design will be discussed and first results, analytical, numerical as well as experimental, will be presented. Part of the concept design is also the development of new actuators optimised for the specific problem. A new actuator concept for the spoiler bump based on a cylindrical tube and activated either by pressure or multifunctional materials (e.g. shape memory alloys) will additionally be shown.