Runway conflicts pose a significant threat to continued safety in commercial aviation. In recent years, stakeholders have initiated a number of programmes dealing with the issue of runway incursions, with the majority adopting traditional advisory alerting techniques. In contrast, this work proposes the use of directive cockpit alerting, which provides both an alert of the conflict as well as guidance on which manoeuvre to conduct to clear the conflict. This article reports the findings of simulator trials that have been conducted to assess the effectiveness and acceptability of a directive alerting strategy within the context of runway incursions. Statistical analysis performed on the quantitative measures taken from the evaluations have shown that the directive mode of alerting leads to a higher probability of the crew performing the correct action when faced with an alert. This, together with overall participant acceptance of the directive alerting concept, is a strong indicator that the technique has the potential of providing a complete solution to the problem of runway incursions.

In his 1916 book, Aircraft in Warfare, the Dawn of the Fourth Arm, F.W. Lanchester wrote:

The recent successful flight trials of the Taranis low-observable unmanned demonstrator aircraft provide the latest evidence of the UK’s continued capacity for the entire design, development, manufacture, and flight testing of world-leading combat aircraft, particularly with regard to Aerodynamics. Taranis is both the culmination of many years’ research and development in the UK and a starting-point for the next generation of UK combat air systems.

In this lecture, Taranis is reviewed, in such detail as current sensitivities will allow, in the wider context of UK combat aircraft aerodynamic capability, exemplified by the leading roles taken by the UK in the Tornado and Typhoon programmes and the important contribution made to the development of the F-35 Lightning II Joint Strike Fighter.

The immediate technical challenges associated with the aerodynamic design and qualification of a low-observable air vehicle are considerable. In this instance they have been compounded by the balanced view taken within the project of trade-offs against many parameters. However, the UK aerodynamics community faces equally stringent challenges in terms of the identification and delivery of the most appropriate future systems; increasingly complex and demanding operational and functional requirements; and, perhaps most of all, maintaining an affordable and cost-effective capability in the face of strict budgetary pressures and austere economic conditions.

Nevertheless, those challenges are accompanied by a wide range of opportunities, namely for national and international partnership; radically innovative engineering solutions and approaches; new thinking; and the engagement of the best minds and ideas in the UK academic community.

Taranis represented a big integration task, requiring a particular set of skills to pull together the total package, resting on a bedrock of mastery of the technical issues. It has been an inspirational experience for those of us who have worked on it. It has demonstrated that the UK is capable of achieving the most demanding current and anticipated military aerodynamic requirements and has signposted the way to an exciting and nationally important future.

This paper considers four alternative sets of actions that a pilot may use to recover an aeroplane from the stall. These actions: those published by the UK CAA and the US FAA, as well as a power delayed sequence and a pitch delayed sequence, were evaluated on 14 single engine piston aeroplane types. In a limited number of types (five in cruise configuration, two in landing configuration) the pitch delayed recovery gave a safe response and least height loss, but in a greater number of types (six and eight in cruise and landing configurations respectively) it resulted in further post-stall uncommanded motion. The other sets of actions all gave a consistent recovery from the stall, but the least height loss in recovery was also consistently the CAA sequence of simultaneous full power and nose-down pitching input, which normally resulted in approximately two thirds the height loss of the FAA’s pitch first then power method, which in turn resulted in about 90% of the height loss of the trialled power delayed recovery. Additionally the CAA recovery gave the least variation in height loss during stall recovery. It was also found that all of the aeroplane types evaluated except for one microlight aeroplane of unusual design, displayed a pitch-up with increased power in the normal (pre-stall) flight regime. Reducing this to separate components it was therefore shown that pitch control is of primary importance and should be used to provide immediate stall recovery. The thrust control can additionally be used as early as possible to minimise height loss, but if the thrust control is used before the pitch control in the stall or post-stall flight regime, there is some risk of subsequent loss of control. Finally, from the discussion on stall recovery methods, questions for Regulatory Authorities are put forward that should address the current practices.

A numerical investigation of generic open-wheel racing car wing and wheel geometry has been conducted, using original sub-scale experimental data for validation. It was determined that there are three main interactions that may occur, identifiable by the path that the main and secondary wing vortices take around the wheel. Interaction ‘A’ occurs when the main and secondary wing vortices both travel outboard of the wheel; interaction ‘B’ is obtained when only the main wing vortex passes inboard of the wheel; while interaction ‘C’ sees both wing vortices travel inboard of the wheel. The different interactions are achieved when geometric changes to the wing affect the pressure distribution about the endplate, either by altering the magnitude of suction generated by the wing or by changing the locations of peak suction and vortices relative to the wheel’s stagnation regions. As a result, the influence that the wing and wheel have on each other – in comparison to the same bodies in isolation – varies, resulting in significant consequences for downforce and drag.

Steady and unsteady pressure measurements are conducted for a tailless aircraft model. The main aim with the presented experimental work is to investigate the difficulties and possibilities involved in using an available pressure sensing system for accurate unsteady pressure measurement. The experimental procedure which is utilised for unsteady pressure measurements is described in detail. In particular, the importance of synchronised timing is recognised. For a harmonically varying pressure a small time delay in the measurement chain can result in a significant phase shift. Also, difficulties and uncertainties that are still present are pointed out. The results from these experiments are compared to numerical results based on unsteady potential flow theory. In general, the experimental and computational results show similar trends. Especially good agreement is found for the steady pressure measurements. For the unsteady pressure measurements a possible Reynolds number dependency is found for the considered test conditions.

This paper proposes a new wind turbine concept suitable for low-speed winds. The design is studied using a combination of wind-tunnel experimentation and aerodynamic theory. After processing the experimental results, and after comparison with theory, the optimal conditions for the operation of the turbine are identified. Experimental and theoretical results suggest that the design offers a realistic alternative to conventional horizontal axis wind turbines. In addition, the proposed turbine has good power efficiency at low wind speeds, and is suitable for deployment in areas not yet favoured by wind farm developers.

This paper is the first of a two-part review of train aerodynamics. After an initial introduction and broad survey of train aerodynamic issues, and a discussion of measurement, modelling and computational techniques, the nature of the flow around trains is considered – in the open air, with and without crosswinds, and in confined geometrical situations and tunnels. The flow in different regions around the train is described and the main flow features outlined. Part 2 of the paper will then consider a number of issues that are of concern in the design and operation of modern trains based on this description of the overall flow field.

Wing flexibility is well established as providing gust rejection and delayed onset of stall for micro air vehicles. As such, many designs adopt wings of a flexible material mounted onto a skeleton comprised of a stiff leading-edge spar and stiff chordwise strips, called battens. These battens are shown to provide additional strength at localised regions of the wing and thus improve the gust rejection and delay stall; however, their effect on the flight dynamics is less studied. Using a numerical modeling approach, this paper explores a design space of vehicles with a varied number of wing battens mounted onto a baseline vehicle with a flexible wing. The battens are modelled as stepwise changes in torsional stiffness along the wing span. The resulting trim characteristics, static stability metrics and flight dynamics are evaluated. The battens are shown to improve gust rejection but otherwise have a complicated effect across the design space. A reduction in the number of battens improves the longitudinal static stability derivative slightly but lowers the lateral and directional static stability. The damping is decreased for the short period mode and increased for the phugoid and dutch roll modes as the number of battens is reduced.

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.

This paper is the second part of a two-part paper that presents a wide-ranging review of train aerodynamics. Part 1 presented a detailed description of the flow field around the train and identified a number of flow regions. The effect of cross winds and flow confinement was also discussed. Based on this basic understanding, this paper then addresses a number of issues that are of concern in the design and operation of modern trains. These include aerodynamic resistance and energy consumption, aerodynamic loads on trackside structures, the safety of passengers and trackside workers in train slipstreams, the flight of ballast beneath trains, the overturning of trains in high winds and the issues associated with trains passing through tunnels. Brief conclusions are drawn regarding the need to establish a consistent risk based framework for aerodynamic effects.

A new method for wing shape optimisation is presented, in which the wing shape is optimised not only for the best aerodynamic properties but also for minimum structural weight. An advanced structural sizing method for wing structural weight estimation is developed. The method is based on elementary, physics based analyses of simplified structure to determine the amount of required material to resist the applied loads. The sizing loads are determined based on the airworthiness regulations using advanced aerodynamic analysis tools. In this new weight estimation method, the effect of wing outer (aerodynamic) shape on the wing-box structural weight is taken into account. A mathematical equation is derived, which relates the wing-box structural weight to the wing outer shape. The weight estimation method is validated for several existing passenger aircraft. A series of optimisations is performed to optimise the wing shape for a general objective function, which includes both aerodynamic and structural properties of the wing. The aircraft fuel weight is used as the objective function. Different structures are tested both metal and composite ones. The latter includes different composite layups. In order to find the effect of the internal structure on the optimum wing outer shape, the design lift coefficient is assumed to be constant for all the test cases. The results of the optimisations showed that the optimum wing shape is depending on the structural concept (metal alloys versus different composite layups) for different internal structures.

A numerical investigation has been conducted into the influence of flow compressibility effects around an open-wheeled racing car. A geometry was created to comply with 2012 F1 regulations. Incompressible and compressible CFD simulations were compared – firstly with models which maintained Reynolds number as Mach number increased, and secondly allowing Mach number and Reynolds number to increase together as they would on track. Results demonstrated significant changes to predicted aerodynamic performance even below Mach 0·15. While the full car coefficients differed by a few percent, individual components (particularly the rear wheels and the floor/diffuser area) showed discrepancies of over 10% at higher Mach numbers when compressible and incompressible predictions were compared. Components in close ground proximity were most affected due to the ground effect. The additional computational expense required for the more physically-realistic compressible simulations would therefore be an additional consideration when seeking to obtain maximum accuracy even at low freestream Mach numbers.

The mixing promoting capability of right-angled triangular tab with sharp and truncated vertex has been investigated by placing two identical tabs at the exit of a Mach 2 axi-symmetric nozzle. The mixing promoting efficiency of these tabs have been quantified in the presence of adverse and marginally favourable pressure gradients at the nozzle exit. It was found that, at all levels of expansion of the present study though the core length reduction caused by both the tabs are appreciable, but the mixing caused by the truncated tab is superior. The mixing promoting efficiency of the truncated tab is found to increase with increase of nozzle pressure ratio (that is, decrease of adverse pressure gradient). For all the nozzle pressure ratios of the present study, the core length reduction caused by the truncated vertex tab is more than that of sharp vertex tab. As high as 84% reduction in core length is achieved with truncated vertex right-angled triangular tabs at moderately overexpanded level, corresponding to expansion level pe/pa = 0·90. The corresponding core length reduction for right-angled triangular tabs with sharp vertex and rectangular tabs are 65% and 31%, respectively. The present results clearly show that the mixing promoting capability of the triangular tab is best than that of rectangular tabs at identical blockage and flow conditions.

The ‘Ornicopter’ is a single-rotor helicopter without anti-torque rotor developed since 2002 at Delft University of Technology in The Netherlands. The Ornicopter’s principle is similar to the movement of a bird’s wing and is based on actively flapping the blades up and down while rotating them around a shaft to generate both the required lift and the propulsive force. The shaft torque is no longer needed and thus the anti-torque rotor is redundant. The present paper describes the basic principles of the Ornicopter’s forced flapping, discussing the feasibility of the Ornicopter concept with respect to the power required, performance, stability, and vibratory loads. On the one side it is shown that the Ornicopter has a similar power requirement to a conventional helicopter, as well as very similar longitudinal and lateral stability and controllability characteristics to a conventional helicopter. On the other side, the Ornicopter generates higher vibratory loads than in a conventional helicopter, and its performance is strongly limited by the stall effect.

This paper presents an innovative optimisation method for aircraft fuselage structural design. Detailed local finite element analyses of panel buckling are further processed such that they can be applied as failure constraints in the global level optimisation. The high computational costs involved with the finite element analyses are limited by advanced use of surrogate modelling methods. This yields high flexibility and efficiency in the local level optimisation procedure and allows for efficient gradient based search methods as well as more costly direct search optimisations like genetic algorithms (GAs). The method is demonstrated on a composite fuselage barrel design case considering common structural sizing variables like thicknesses and stringer dimensions. Optimised barrel designs are obtained where the constraints that are derived from the panel buckling analyses are active. The total computational cost for the complete local and global level optimisation procedures is in the order of days on common-performance hardware.

A novel formulation of the flight dynamic equations is presented that permits a rapid solution for the design of trajectory following autopilots for nonlinear aircraft dynamic models. A robust autopilot control structure is developed based on the combination of the good features of the nonlinear dynamic inversion (NDI) method, integrator backstepping method, time scale separation and control allocation methods. The aircraft equations of motion are formulated in suitable variables so that the matrices involved in the block backstepping control design method are diagonally dominant. This allows us to use a linear controller structure for a trajectory following autopilot for the nonlinear aircraft model using the well known loop by loop controller design approach. The resulting autopilot for the fixed-wing rigid-body aircraft with a cascaded structure is referred to as the diagonally dominant backstepping (DDBS) controller. The method is illustrated here for an aircraft auto-landing problem under unknown actuator failures and severe winds. The requirement of state and control surface limiting is also addressed in the context of the design of the DDBS controller.

The present work evaluates the performance of different optimisation techniques on a parameter identification problem of aeronautical interest. In particular, the focus is on the classical Least Square (LS) and Maximum Likelihood (ML) methods and on the CMAES (Covariance Matrix Adaptation Evolution Strategy), DE (Differential Evolution), GA (Genetic Algorithm) and PSO (Particle Swarm Optimisation) Meta-Heuristic methods. The test problem is the reconstruction from flight test data of the aerodynamic parameters of an external store jettisoned from a helicopter. Different initial conditions and the presence of measurement noise are considered. This case is representative of a class of problems of difficult solution because of nonlinearity, ill-conditioning, multidimensionality, non separability, and fitness function dispersion. Only reference algorithm implementations found in literature are used. The performance of each algorithm are defined in terms of fitness function value, sum of absolute errors of the estimated coefficients, computational time and number of function evaluations. The results show the efficiency of CMAES in finding the best estimates with the least computational cost. Moreover, tests reveal that traditional methods depend heavily on problem characteristics and loose accuracy at the increase of the number of unknowns.

To improve the crashworthiness of civil aircraft, the design concept of energy absorption structure for civil aircraft is investigated. Two typical different design principles could be identified. The first category includes Helicopter and Light fixed-wing Aircraft (HLA), and Transport, Mid-size and Commuter type Aircraft (TMCA) are classified into the second group. Frame, strut and bottom structure are the three kinds of energy absorption structure for TMCA. The strut layout of conventional civil aircraft is studied and some energy absorption devices are adopted. High efficiency energy absorption structures such as the foam and sine-wave beam are employed as the bottom structure for both of HLA and LMCA. The finite element method is used to analyse and design energy absorption structure in aircraft crashworthiness problem. Results show that the crashworthiness of civil aircraft could be largely improved by using proper strut layout and excellent energy absorption device. The stiffness combination of frame and strut should be considered to get better global aircraft deformation. Supporting platform and failure model are the two core problems of bottom energy absorption structure design. Foam and sine-wave beam under the lifted frame could improve the crashworthiness of civil aircraft.

The current understanding of the aerodynamics of birds in formation flights is mostly based on field observations. The interpretation of these observations is usually made using simplified aerodynamic models. Here, we investigate the aerodynamic aspects of formation flights. We use a potential flow solver based on the unsteady vortex lattice method (UVLM) to simulate the flow over flapping wings flying in grouping arrangements and in proximity of each other. UVLM has the capability to capture unsteady effects associated with the wake. We demonstrate the importance of properly capturing these effects to assess aerodynamic performance of flapping wings in formation flight. Simulations show that flying in line formation at adequate spacing enables significant increase in the lift and thrust and reduces power consumption. This is mainly due to the interaction between the trailing birds and the previously-shed wake vorticity from the leading bird. Moreover, enlarging the group of birds flying in formation further improves the aerodynamic performance for each bird in the flock. Therefore, birds get significant benefit of such organised patterns to minimise power consumption while traveling over long distances without stop and feeding. This justifies formation flight as being beneficial for bird evolution without regard to potential social benefits, such as, visual and communication factors for group protection and predator evasion.