The Global Positioning System (GPS) is already being used for certain aviation applications and some safety critical air traffic services will be based on GPS. These air traffic services must achieve allowable levels of safety before they can be accepted. For this to occur, GPS based navigation systems must achieve a defined level of performance specified in terms of accuracy, integrity, continuity and availability. This must be determined by various analysis techniques including failure mode and effects analysis (FMEA) and integrity assessment. Because of the high percentile requirements placed on integrity (as the parameter most directly related safety), it is unfeasible to measure system performance by demonstration (field trial). Realistic simulation informed by some field experience is usually employed. However, the current simulation-based approaches for receiver autonomous integrity monitoring (RAIM) performance assessment have a number of weaknesses including the use of coarse (large) spatial and temporal sampling intervals, loose definitions of error and geometric correlations, a lack of sampling of all geometries and the inability to account for critical points due to uncorrelated factors.

This paper proposes a dynamic sampling method that takes account of these weaknesses, identifying dynamically only the required points for integrity performance assessment. Comprehensive simulations carried out to test the proposed approach for a single point, an area, and a non-precise approach (NPA) flight path to Gatwick airport in the United Kingdom show that the method can be effective in capturing all the points enabling a robust and reliable assessment of system integrity.

The effects of the flow of exhaust gases intentionally orientated on the rear wing element of a generic Formula One car body have been studied. A qualitative analysis of the effectiveness of a cold nitrogen jet on a NACA 0012 type of aerofoil has been conducted. The Reynolds number of the jet was 13,000, based on the jet velocity and diameter, and of the bodywork was 54,000, based on the free stream velocity and bodywork length. The lift coefficient was measured via a three-component strain-gauge force balance at four different ground-to-aerofoil heights (32, 45, 60 and 90mm) and incidence range –20 to +20 degrees. The surface flow patterns were visualised using the oil flow technique and were compared with numerical simulations. Pressure measurements were conducted using pressure tappings. The CFD solver was FLUENT. The RNG k-ε model was selected to solve the turbulent flow transport equations. The numerical study also comprised the investigation of the aspiration generated by exhaust gases when these are ejected inside a duct of greater diameter. A parametric investigation relating the relative diameter of exhaust pipe and outer duct and the relative overlap between the sides of the duct and the exhaust pipe was performed.

As civil aviation expands, environmental aspects and fuel savings are becoming increasingly important. Amongst technologies proposed for more efficient flight, air-to-air refuelling (AAR), ‘hopping’ and flying in close formation (drag reduction), all have significant possibilities. It will be interesting to know also how these technologies may co-exist e.g. AAR and formation flying.

In military use, AAR is virtually indispensable. Its benefits are real and largely proven in hostile and demanding scenarios. We present a case for applying AAR in a civil context to show that substantial reductions in fuel burn for long-range missions are achievable. Overall savings, including the fuel used during the tanker missions, would be of the order of 30-40% fuel and 35-40% financial. These are very significant in terms of the impact on aviation’s contribution to reducing atmospheric pollution.

AAR allows smaller, efficient (greener) aircraft optimised for about 3,000nm range to fulfil long-range route requirements. This implies greater usage of smaller airports, relieving congestion and ATC demands on Hub airports. Problems due to shed vortices and wakes at airports are reduced. Smaller engines will be needed.

Integrated (accepted) AAR could lead to further benefits. Aircraft could take-off ‘light’, with minimum fuel and reserves and a planned AAR a few minutes into the flight. The ‘light’ aircraft would not require over-rating of the engines during take-off and would therefore be less noisy during take-off and climb-out, permitting more acceptable night operations.

The availability of civil AAR will enable opportunities for hitherto borderline technologies to be utilised in future aircraft. Laminar flow will provide fuel savings and increased efficiency in its own right but could be significantly enhanced within a civil AAR environment. Similarly, supersonic transport may become an acceptable economic option.

AAR affords the possibility of a complete widening of the design space and this should appeal to the imagination of current and future designers.

Currently there is a revival of interest in flying wings for military (and civil) use. The military context has arisen from the future ‘stealthy’ high altitude long endurance (HALE) and unmanned combat air vehicles (UCAV) aircraft. Questions on aerodynamics, control and structural efficiency arise. Compared with conventional wing/tail arrangements, flying wings have a special set of very different constraints. These are mentioned.

Without a trim surface, the constraints on the wing pitching moment dictate the design camber and twist. Control power requirements can be high because of effectively short moment arms. The camber and twist are strongly dependent on trim stability margins. This aspect needs to be understood in detail when comparing different types of planforms.

This paper covers three inter-related aspects – a wing design method, the suitability of solvers used with the method and a comparative study of two, typical UCAV planforms. This is inspired by the need to understand a variety of wings (in the public domain) that are, at first sight, aimed at similar missions. The main emphasis has been on developing and understanding cruise design camber and twist with Cm constraints of stable, neutral and unstable static margins. Spanwise lift and drag loadings have also been presented. Camber design has been via attained thrust methods and a modal approach. It is shown that starting from basic information such as the planform, we are able to predict the anticipated performance with sufficient confidence for comparative assessments of published project data.

Further work is proposed in several areas.

This paper describes the methodology and key results from the first three years of delivery of ‘Flight Handling Qualities’ (FHQ), a problem-based-learning core module for fourth year Master of Engineering (MEng) undergraduates in Aerospace Engineering and optional module for the Systems Engineering MSc Programme, at the University of Liverpool. The module aim is to equip students with the skills and knowledge required to tackle aircraft handling qualities (HQs) and related ‘whole aircraft’ problems. Students are presented with the theory of handling qualities engineering in a series of interactive lectures. The students work in teams of four or five and undertake a number of team-building exercises throughout the first semester. Teams are presented with the idea that the aircraft with its handling qualities is the focus for knowledge acquisition and skills development. Each team is given the task of assessing and quantifying the HQs of a particular aircraft in a particular role, and then developing fixes to any handling deficiencies they identify; the current aircraft include the Wright Flyer, Grob 115, Black Hawk, Bo-105 and XV-15. Teams write an interim report at the end of the first term and a final report at the end of the second term, showing how they have assessed the aircraft, developed solutions to the problems and made recommendations concerning the aircraft’s suitability in the defined role. The reports also address the technical feasibility and economic viability of the proposed upgrades. The teams present their work to mock ‘customers’ (group of staff, another student team, visiting Industrialists) with the objective of demonstrating that the aircraft is now fit for the role. Each individual student maintains a ‘personal learning journal’, in which they document the development of their understanding of handling qualities and, more general, transferable skills. The module is designed to enable students to engage in all elements of the conceive-design-implement-operate (CDIO) cycle.

Effects of boundary conditions on the performance of compact oscillatory momentum and vorticity generators, commonly known as ‘synthetic jet’, ejecting a train of vortex-pairs into still air, were studied experimentally. The different boundary conditions altered the near-device entrainment process of the zero-net-mass-flux actuator. The measurements included hot-wire and Particle Image Velocimetry, cavity pressures and temperatures.

When the actuator operates in still air, a quasi-2D vortex pair is generated due to the extreme shear at the edges of the fluid slug ejected during the blowing stage of each excitation cycle. The vorticity flux exiting the slot determines the resulting vortex-pair circulation. The threshold slot exit velocity, for the current configuration and operating conditions, determines if the vortices will be sucked into the actuator’s cavity or be released. Once released, the vortex convection speed approximately scales with the peak velocity at the slot exit. However, the normalised convection velocity increases with the slot Reynolds number.

When even a very short extension is attached to one ‘lip’ of the actuator exit, the jet is deflected in the direction opposite the extended lip, due to the restriction on the entrainment process. When long, one ‘lip’ extension is attached, such that the vortex pair is ejected parallel to a plate, the coherence of the vortices improve, their phase speed and magnitude decrease.

The effects of high-frequency excitation, ejected perpendicular to a wall into still air, were also investigated. It was found that the presence of the plate does not have a measurable effect on the wall normal excitation, indicating that the majority of the entrainment is taking place from the forward 180° of the actuator exit plane. When the slot is inclined to the surface at a shallow angle of 30 degrees, an unsteady wall jet is formed, transferring momentum along the wall. This is a direct result of the symmetry break, altering the relative magnitudes of the vortex pair.

This paper assesses the financial performance of 35 European airports for the decade 1990 to 2000, comparing those subject to partial or full privatisation with those still in public ownership. In contrast to earlier research, the outcomes of partial factor productivity (PFP), financial ratio (FRA) and data envelopment analysis (DEA) are evaluated, in order to investigate differences attributable to the degree of privatisation. Changes in performance after a change in ownership structure are reviewed. The analysis of sample data reveals economically meaningful and statistically significant differences between publicly owned and privatised airports. The major differences lie in operating efficiency, capital productivity and capital structure. Although partially and fully privatised airports operate more efficiently, this does not translate into significantly higher returns on shareholders’ funds. Due to their at least indirectly government-backed credit standing, publicly owned airport companies can assume more debt relative to their respective equity. This results in considerably higher gearing and financial leverage, which compensates for the comparatively low return rate on assets.

This paper describes the development of a generic aircraft systems dispatch reliability design methodology (ASDRDM) that has been developed for use during early phases of the aircraft systems design process.

The methodology incorporates prediction of both reliability and maintainability through the aircraft design hierarchy, down to component level. It can be applied at the early design stage, but can also be used for advanced design phases and can use generic or actual failure rate and mean time to repair data. It allows designers to modify system architectures and component reliability and maintainability characteristics. The paper shows the validation that has been performed, and its use is demonstrated by a case-study.

In the coming century, the impact of air travel on the environment will become an increasingly powerful influence on aircraft design. Unless the impact per passenger kilometre can be reduced substantially relative to today’s levels, environmental factors will increasingly limit the expansion of air travel and the social benefits that it brings. The three main impacts are noise, air pollution around airports and changes to atmospheric composition and climate as a result of aircraft emissions at altitude. The lecture will review the work done within the Air Travel – greener by Design programme to assess the technological, design and operational possibilities for reducing these impacts. The main aeronautical disciplines all have something to contribute but it is in aerodynamics that the greatest opportunities appear to lie. If these opportunities are pursued, the aircraft in production in 2050 could be very different from those of 2005. It is for the aerodynamicists, supported by the structures and systems engineers and the materials scientists, to make the case for a radical leap.

The development of the non-linear equations of motion for the hang glider from first principles is described, including the complex geometry of control by pilot ‘weight shift’. By making appropriate assumptions the linearised small perturbation equations are derived for the purposes of stability and control analysis. The mathematical development shows that control is effected not by pilot weight shift, but by centre of gravity shift and that lateral-directional control by this means is weak, and is accompanied by significant instantaneous adverse response.

The development of a comprehensive semi-empirical mathematical model of the flexible wing aerodynamics is described. In particular, the modelling attempts to quantify camber and twist dependencies. The performance of the model is shown to compare satisfactorily with measured hang glider wing data obtained in earlier full scale experiments. The mathematical aerodynamic model is then used to estimate the hang glider stability and control derivatives over the speed envelope for substitution into the linearised equations of motion.

Results from numerical simulations of supersonic combustion of H2 are presented. The combustor has a single stage fuel injection parallel to the main flow from the base of a wedge. The simulations have been performed using FLUENT. Realisable k-ε model has been used for modelling turbulence and single step finite rate chemistry has been used for modelling the H2-Air kinetics. All the numerical solutions have been obtained on grids with average value for wall y+ less than 40. Numerically predicted profiles of static pressure, axial velocity, turbulent kinetic energy and static temperature for both non-reacting as well as reacting flows are compared with the experimental data. The RANS calculations are able to predict the mean and fluctuating quantities reasonably well in most regions of the flow field. However, the single step kinetics predicts heat release much more rapid than what was seen in the experiments. Nonetheless, the overall pressure rise in the combustor due to combustion is predicted well. Also, the k-ε model is not able to predict the fluctuating quantities in the base region of the wedge where there is strong anisotropy in the presence of combustion.

Customer requirements and vision in aerospace dictate that the next generation of civil transport aircraft should have a strong emphasis on increased safety, reduced environmental impact and reduced cost without sacrificing performance. In this context, the School of Mechanical and Aerospace Engineering at the Queen’s University of Belfast and Bombardier have, in recent years, been conducting research into some of the key aerodynamic technologies for the next generation of aircraft engine nacelles. Investigations have been performed into anti-icing technology, efficient thrust reversal, engine fire zone safety, life cycle cost and integration of the foregoing with other considerations in engine and aircraft design. A unique correlation for heat transfer in an anti-icing system has been developed. The effect of normal vibration on heat transfer in such systems has been found to be negligible. It has been shown that carefully designed natural blockage thrust reversers without a cascade can reduce aircraft weight with only a small sacrifice in the reversed thrust. A good understanding of the pressure relief doors and techniques to improve the performance of such doors have been developed. Trade off studies between aerodynamics, manufacturing and assembly of engine nacelles have shown the potential for a significant reduction in life cycle cost.

This paper points out the capabilities of fully decoupled fuzzy controller which introduces simple design approach to deal with the coupling effects in controlling two spools, mixed exhausts turbofan engines. The decoupling is performed through proper selection of input parameters to the controller. Digital nonlinear engine/control system simulation is used to construct the fuzzy rules depending on simple logic. The performance of this controller is compared with that of an optimal controller representing efficient classical and conventional techniques. The decoupled fuzzy control system produces favorable transient strategies that other conventional controllers can not attempt due to its inherent proportionality characteristics. It displays improvements in surge margin for both fan and compressor, and temperature margin with almost similar response time during acceleration. Also, the proposed controller has the capabilities to increase the response speed during deceleration independently from acceleration transient.

Unmanned aerial vehicle (UAV) design tends to focus on sensors, payload and navigation systems, as these are the most expensive components. One area that is often overlooked in UAV design is airframe and aerodynamic shape optimisation. As for manned aircraft, optimisation is important in order to extend the operational envelope and efficiency of these vehicles. A traditional approach to optimisation is to use gradient-based techniques. These techniques are effective when applied to specific problems and within a specified range. These methods are efficient for finding optimal global solutions if the objective functions and constraints are differentiable. If a broader application of the optimiser is desired, or when the complexity of the problem arises because it is multi-modal, involves approximation, is non-differentiable, or involves multiple objectives and physics, as it is often the case in aerodynamic optimisation, more robust and alternative numerical tools are required. Emerging techniques such as evolutionary algorithms (EAs) have been shown to be robust as they require no derivatives or gradients of the objective function, have the capability of finding globally optimum solutions among many local optima, are easily executed in parallel, and can be adapted to arbitrary solver codes without major modifications. In this paper, the formulation and application of a evolutionary technique for aerofoil shape optimisation is described.

Initially, the paper presents an introduction to the features of the method and a short discussion on multi-objective optimisation. The method is first illustrated on its application to mathematical test cases. Then it is applied to representative test cases related to aerofoil design. Results indicate the ability of the method for finding optimal solutions and capturing Pareto optimal fronts.

This paper presents a systematic formulation for the simulation of rigid body dynamics, including the short period dynamics, inherent to stage separation and jettisoning parts of a satellite launcher. This also gives a review of various types of separations involved in a launch vehicle. The problem is sufficiently large and complex; the methodology involves iterations at successively lower levels of abstraction. The best choice to tackle such problems is to use state-of-the-art programming technique known as object oriented programming. The necessary classes have been identified to represent various entities in the launch vehicle separation process (e.g., gravity, aerodynamics, propulsion and separation mechanisms etc.). Simple linkages are modelled with suitable objects. This approach helps the designer to simulate a launch vehicle separation dynamics and also to analyse separation system performance. To examine the influence of the design variables on the separating bodies, statistical analyses have been performed on the upper stage separation process and pull out of ongoing stage nozzle from the spent stage of a multistage rocket carrier using retro rockets.

Aerodynamic optimisations of a blended wing-body (BWB) aircraft are presented. A discrete adjoint solver is used to calculate efficiently the gradients, which makes it possible to optimise for a large number of design variables. The optimisations employ either a variable-fidelity method that combines low- and high-fidelity models or a direct sequential quadratic programming (SQP) method. Four Euler optimisations of a BWB aircraft are then presented. The optimisation is allowed to change a series of master sections defining the aircraft geometry as well as the sweep angle on the outer wing for two of the optimisations. Substantial improvements are obtained, not only in the Euler mode but also when the optimised geometries are evaluated using Reynolds-averaged Navier-Stokes solutions. Some interesting features of the optimised wing profiles are discussed.

A ‘two dimensional’ air intake comprising a wedge followed by an isentropic compression has been tested in the Cranfield Gun Tunnel at Mach 8·2. These tests were performed to investigate qualitatively the intake flow starting process. The effects of cowl position, Reynolds number, boundary-layer trip and introduction of a small restriction in the intake duct were investigated. Schlieren pictures of the flow on the compression surface and around the intake entrance were taken. Results showed that the intake would operate over the Reynolds number range tested.

Tests with a laminar boundary layer demonstrated the principal influence of the Reynolds number on the boundary-layer growth and consequently on the flow structure in the intake entrance. In contrast boundary layer tripping produced little variation in flow pattern over the Reynolds number range tested. The cowl lip position appeared to have a strong effect on the intake performance. The only parameter which prevented the intake from starting was the introduction of a restriction in the intake duct.

The experimental data obtained were in good qualitative agreement with the CFD predictions. Finally, these experimental results indicated a good intake flow starting process over multiple changes of parameters.

Flow interaction of three different jet configurations ejecting air from a flat plate into a supersonic cross flow were investigated experimentally and numerically. The test conditions encompassed a jet pressure ratio of Poj, P∞ = 100 at a Mach number of M∞ = 5 and Reynolds number of about Re∞ = 25 × 106 based on the length of the flat plate. The investigated test cases are: a) single jet; b) four jets positioned in-line in main flow direction; c) four jets positioned side-by-side in spanwise direction. The prediction of the overall flow phenomena as occurring within the interaction area was in fair agreement with the experiments, although quantitatively differences occur that will be discussed in the paper.

The results of the comparison are presented and the experimental data are used to validate the applied code.

The development of new methods of producing hypersonic wind-tunnel flows at increasing velocities during the last few decades is reviewed with attention to airbreathing propulsion, hypervelocity aerodynamics and superorbital aerodynamics. The role of chemical reactions in these flows leads to use of a binary scaling simulation parameter, which can be related to the Reynolds number, and which demands that smaller wind tunnels require higher reservoir pressure levels for simulation of flight phenomena. The use of combustion heated vitiated wind tunnels for propulsive research is discussed, as well as the use of reflected shock tunnels for the same purpose. A flight experiment validating shock-tunnel results is described, and relevant developments in shock tunnel instrumentation are outlined. The use of shock tunnels for hypervelocity testing is reviewed, noting the role of driver gas contamination in determining test time, and presenting examples of air dissociation effects on model flows. Extending the hypervelocity testing range into the superorbital regime with useful test times is seen to be possible by use of expansion tube/tunnels with a free piston driver.

A methodology referred to as the continuation design framework is developed for application to nonlinear flight control problems. This forms the basis of a systematic approach to control system design for aircraft operating in highly nonlinear regions of the flight envelope. The essence of the continuation design framework is to combine bifurcation analysis with modern control methods such as eigenstructure assignment. Theoretical and practical issues of the approach are discussed with particular reference to the problems posed by agile fighter aircraft. The proposed methodology is applied to a fifth order hypothetical aircraft model and is shown to provide a visible, flexible and logical approach to nonlinear aircraft control law design.