This contribution presents a novel simulation for a fixed-wing aircraft powered by gas turbine engines and advanced propellers (turboprops). The work is part of a large framework for the simulation of aircraft flight through a multi-disciplinary approach. Novel numerical methods are presented for flight mechanics, turboprop engine simulation (in direct and inverse mode), and propeller dynamics. We present in detail the integration of the propeller with the airframe, aircraft and tonal noise model. At the basic level, we address a shortfall in multi-disciplinary integration in turboprop-powered aircraft, including economical operations and environmental emissions (exhausts and noise). The models introduced are based on first principles, supplied with semi-empirical correlations, if required. Validation strategies are presented for component-level analysis and system integration. Results are presented for aerodynamics, specific air range, optimal cruise conditions, payload-range performance, and propeller noise. Selected results are shown for the ATR 72-500, powered by PW127M turboprop engines and F568-1 propellers.

This paper presents a semi-empirical theoretical model for calculating the effect of nose bluntness on the stability derivatives of oscillating slender cones at hypersonic Mach numbers. It is based on a hybrid blast wave analogy/shock-expansion flow model and is used to obtain closed form analytic expressions for the derivatives for oscillating slender cones. Two models based on zero thickness and finite thickness entropy layers are proposed which are seen to be appropriate to the cases of very small and large nose bluntnesses, respectively. The results are compared with new and existing experimental data and with the predictions of previous theoretical methods.

The introduction of an interference-fit pin in a circular hole in a flat plate is found to result in a reduction in the stress concentration factor at the hole boundary under tension applied to the plate. The S.C.F. decreases rapidly with increase in the ratio of interference stress to applied tension, and decreases also with increase in the ratio of hole diameter to width of plate. Very little difference in the S.C.F. is found for different ratios of Young's modulus of pin and plate.

A series of advanced aerofoil sections suitable for aircraft propellers has been developed. The sections combine advanced supercritical now characteristics with good low-speed performance and are also directly applicable to other rotating aerodynamic machinery, such as low-solidity ducted fans, windmills, etc. The work has focused initially on propeller sections of around 6 per cent thickness/chord ratio, typical of the fundamental blade station where peak loading is usually carried (0.7 × radius). The complete section family covers a wide range of thickness/chord ratios, from 3 per cent to over 20 per cent. The profiles are defined by mathematical formulae and distort with thickness to achieve a shape having optimum performance characteristics at the flow conditions expected for that thickness. A subset of the family is defined for higher Mach number penetration, up to near sonic values. Practical applications of the new sections have shown notable gains.

Viscous/inviscid interaction techniques for calculating the flow about multiple-element aerofoils have been under development in the UK for the last decade producing such programs as MAVIS and HILDA. These methods give reasonable predictions of the lift for viscous attached flow, but fail to give an estimate of the maximum lift and the associated flow separations on the aerofoils. The methods also fail to give adequate predictions of the drag for both attached and separated flow. The disappointing performance of the methods in predicting maximum lift stems primarily from the use of direct methods to solve the first order boundary-layer equations, whilst the poor drag predictions arise from inadequate methods for predicting the development of the flow over the flap. The assumption of incompressible flow could also be a contributory factor in both cases. Methods of overcoming the first restriction are described by using a more appropriate coupling between the inviscid and viscous flows which properly assigns the correct role to each partner in the coupling: this approach is illustrated by ‘semi-inverse’ and ‘quasi-simultaneous’ couplings of a finite-element method for the compressible inviscid flow with an integral method for the boundary layers and wakes. Some methods for calculating the compressible flow about multiple-element aerofoils are also reviewed. However these improvements do not give an adequate estimate of the drag so possible improvements to the calculation of the flow over the flap are discussed.

A knowledge based expert system for the design and analysis of composite laminated struts is described. This system is part of a Composite Design EXpert (CODEX) system that not only performs analysis and design of composite laminated plates and struts, but also incorporates the modelling of uncertainties of information, definition and decision when assessing competing designs. The analysis part of the system is based on a minimum weight optimisation that satisfies the failure criteria of local buckling, overall buckling and maximum strain or maximum stress. Available in the system for analysis and assessment are seven types of strut shapes, six composite materials and aluminium alloy. Examples of strut design are carried out and assessed using this system.

The contemporary approach to helicopter mathematical modelling in simulation for handling qualities applications is to represent each blade individually. This allows incorporation of effects not possible with a multiblade disc representation of the rotor system. This paper addresses the validation of such a model, which is uniquely performed for large amplitude manoeuvres, using a recently-developed approach to inverse simulation. The method is reviewed in the context of model validation, and comparisons between simulation and actual data are presented for a Puma helicopter executing sidestep manoeuvres in low-speed flight. The focus for interpreting the results is in the area of wake modelling. It is concluded that further developments are necessary in this area if helicopter flight mechanics models are to be used in simulation of role-related flight.

Usually a fixed pitch propeller is designed to be optimal at cruise speeds. Thus the efficiency is quite low at takeoff or low speeds, as well as during other flight regimes. The present paper shows that by introducing a flexible element into the blade root, the propeller efficiency can be improved over a wide range of velocities. The flexible element reacts to root flap or torsion moments by changing the blade pitch at the root. The root flexibility and the pitch angles at the root at zero loads are chosen such that efficiency will increase during problematic regimes without decreasing the propeller thrust. In the case of straight blades the torsional moment at the root is too small to be used. In the case of swept blades this moment component is significantly increased and can contribute to the design of an optimal aeroelastically adaptive propeller.

This paper describes a possibility-based multidisciplinary optimisation for electric-powered unmanned aerial vehicles (UAVs) design. An in-house integrated UAV (iUAV) analysis program that uses an electric-powered motor was developed and validated by a Predator A configuration for aerodynamics, weight, and performance parameters. An electric-powered propulsion system was proposed to replace a piston engine and fuel with an electric motor, power controllers, and battery from an eco-system point of view. Moreover, an in-house Possibility-Based Design Optimisation (iPBDO) solver was researched and developed to effectively handle uncertainty variables and parameters and to further shift constraints into a feasible design space. A sensitivity analysis was performed to reduce the dimensions of design variables and the computational load during the iPBDO process. Maximising the electric-powered UAV endurance while solving the iPBDO yields more conservative, but more reliable, optimal UAV configuration results than the traditional deterministic optimisation approach. A high fidelity analysis was used to demonstrate the effectiveness of the process by verifying the accuracy of the optimal electric-powered UAV configuration at two possibility index values and a baseline.

Wing tip sails are small lifting surfaces fitted to the wings in such a way that they use the local air flows about the wing tips, induced by the generation of lift on the wing, to produce a thrust. They act in a manner similar to that of the sail of a yacht when it is sailing close to the wind, hence their name.

Previous work, described in references 1, 2 and 3, has investigated the effects of adding sails to existing wings, extending their span and wetted area. It has long been realised that the correct use of sails is to replace part of the outer wing area with them, in other words to include them in the initial design of the wing. This note describes wind tunnel tests on a simple untapered, unswept wing to examine the benefits from such a design approach and subsequent flight tests on a Cessna Centurion to confirm them.

Natural frequencies of free flexural vibration of rectangular plates may, in many cases, be considerably increased by attaching to the plate one or more elastic stiffening ribs parallel to one edge, or by casting or machining the plate and stiffeners integrally.

Hoppmann has determined by a semi-empirical method the natural frequencies of an integrally stiffened simply-supported square plate, using the concept of a homogeneous orthotropic plate of uniform thickness having elastic compliances which are equivalent to those of the stiffened plate. Filippov has obtained the exact solution for the fundamental frequency of a simply-supported square plate having a number of equally spaced stiffeners and has considered the effect of point loads applied to the stiffeners in a direction perpendicular to the plane of the plate.

A general dynamic model of the hang glider is applied to the analysis of response to control. The transfer functions of the glider to the longitudinal and lateral controls are formulated and some significant results, in terms of frequency response are presented and discussed. The relevant effects of the unsteady aerodynamics on the dynamics of the system are shown and the characteristics of poor lateral control are confirmed as observed in flight.

In this paper, we proposed a simple approach to analyse the efficiency and propulsive characteristics of the high-altitude propeller in accordance to the Vortex Lattice Lifting line Method (VLM) theory, which is commonly used in preliminary design and parametric studies of propeller propulsion. The Computational Fluid Dynamics (CFD) method was used to obtain aerofoil aerodynamic data. The optimal pitch angle and propeller blade chord length (along the radial direction) can be calculated using the information from the database. The propeller wake model sees helical slipstreams applied to both lightly and moderately loaded propellers. The proposed method is capable of identifying the optimal efficiency through varying the number of propeller blades, radius and the rotational speed. The relationship between the optimal efficiency and design parameters is then established. This method was verified using CFD calculations.

The components of an aeroengine gas-turbine combustor have to perform multiple tasks – control of external and internal air distribution, fuel injector feed, fuel/air atomisation, evaporation, and mixing, flame stabilisation, wall cooling, etc. The ‘rich-burn’ concept has achieved great success in optimising combustion efficiency, combustor life, and operational stability over the whole engine cycle. This paper first illustrates the crucial role of aerodynamic processes in achieving these performance goals. Next, the extra aerodynamic challenges of the ‘lean-burn’ injectors required to meet the ever more stringent NOx emissions regulations are introduced, demonstrating that a new multi-disciplinary and ‘whole system’ approach is required. For example, high swirl causes complex unsteady injector aerodynamics; the threat of thermo-acoustic instabilities means both aerodynamic and aeroacoustic characteristics of injectors and other air admission features must be considered; and high injector mass flow means potentially strong compressor/combustor and combustor/turbine coupling. The paper illustrates how research at Loughborough University, based on complementary use of advanced experimental and computational methods, and applied to both isolated sub-components and fully annular combustion systems, has improved understanding and identified novel ideas for combustion system design.

The aerodynamic shape design of a proprotor for a tiltrotor aircraft is a very complex and demanding task because it has to combine good hovering capabilities with high propeller efficiency. The aim of the present work is to describe a two-level procedure and its results for the aerodynamic shape design of a new rotor blade for a high-performance tiltwing tiltrotor aircraft taking into account the most important flight conditions in which the aircraft can operate. Span-wise distributions of twist, chord and aerofoil were chosen making use of a multi-objective genetic optimiser that worked on three objectives simultaneously. A non-linear sweep angle distribution along the blade was designed to reduce the power losses due to compressibility effects during axial flight at high speed. During the optimisation process, the aerodynamic performance of the blade was evaluated with a classical two-dimensional strip theory solver. The optimised blade was than analysed by means of a compressible Navier-Stokes solver and calculations were validated comparing numerical results with experimental data obtained from wind-tunnel tests of a scaled model of the proprotor.

Comparisons are made between some measurements of skin friction and heat transfer over five axisymmetric bodies and the predictions of a simple theory. The development of the theory is outlined and explicit expressions obtained for all the gross turbulent boundary-layer characteristics (δ*,θ,H,Cf and St).

Weight estimation methods are categorised in different classes based on their level of fidelity. The lower class methods are based on statistical data, while higher class methods use physics based calculations. Statistical weight estimation methods are usually utilised in early design stages when the knowledge of designers about the new aircraft is limited. Higher class methods are applied in later design steps when the design is mature enough. Lower class methods are sometimes preferred in later design stages, even though the designers have enough knowledge about the design to use higher class methods. In high level multidisciplinary design optimisation (MDO) fidelity is often sacrificed to obtain models with shorter computation times. There is always a compromise required to select the proper weight estimation method for an MDO project.

An investigation has been performed to study the effect of using different weight estimation methods, with low and medium levels of fidelity, on the results of a wing design using multidisciplinary design optimisation techniques. An MDO problem was formulated to design the wing planform of a typical turboprop and a turbofan passenger aircraft. The aircraft maximum take-off weight was selected as the objective function. A quasi-three-dimensional aerodynamic solver was developed to calculate the wing aerodynamic characteristics. Five various statistical methods and a quasi-analytical method are used to estimate the wing structural weight. These methods are compared to each other by analysing their accuracy and sensitivity to different design variables. The results of the optimisations showed that the optimum wing shape is affected by the method used to estimate the wing weight. Using different weight estimation methods also strongly affects the optimisation convergence history and computational time.

A simple technique is proposed that allows the definition of the geometry and characteristics of an air-jet vortex generator to be defined, using the system requirements in practical design. Typically, the aircraft designer is concerned with the mass flow-rate and air pressure requirements of any pneumatic system for inclusion to an airframe. These parameters are not congruent with those for air-jet vortex generator aerodynamic design, and therefore, some tool is required to bridge the gap.

Such a tool is proposed, based on empirical methods for the prediction of air-jet vortex generator behaviour. The technique allows the comparison of the vortex strength, and the system inputs (the jet mass flow-rate and the air-jet plenum pressure) for the air-jet, for a range of jet nozzle diameters and jet velocity ratios. Through this comparison, the optimum air-jet design can be reached for a given system input.

Recent advances in two lifting surface methods are reported. The present subsonic constant pressure method improves upon the program robustness of the doublet lattice method. The present unified supersonic-hypersonic method extends the range of applicability of lifting surface theory to the Newtonian limit. Based on a uniformly-valid series formulation, the method accurately approximates the non-linear thickness effect, whereas this effect is neglected by the linear theory and overestimated by piston theory. In fact, the present results generally agree well with the trends of several Euler solutions. Among other findings, cases computed by the unified method confirm that the effect of thickness is to reduce the supersonic flutter speed.

Recent work by Tsitas and Kingston(1) has demonstrated that an 8kg 6U CubeSat can be designed to perform Earth observation missions equivalent to those of 50-150kg microsatellites. Their design is reviewed and its commercial potential is compared to the 156kg RapidEye spacecraft. Three other commercial applications of this design are described. These are: a standard spacecraft for space scientists and astronomers; the spacecraft component of an N nation 5 spectral band disaster monitoring constellation and a night imaging satellite. Nanosatellites should now be considered for commercial missions previously thought to require microsatellites.