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 HART II test of 2001 provided a significant and comprehensive database of rotor loads, blade motion, blade pressure distribution, acoustic signature and flow field data. A sub-set of these were released for public access worldwide and an International HART II Workshop was established in 2005. This Workshop, open to the international rotorcraft community, has been held since then at both the AHS Annual Forum as well as the European Rotorcraft Forum. Following the requests of participants, the HART II International Workshop database has been undergoing continuous development. This paper describes the current content and status of the data and the documentation material provided within the workshop database.

The “second stage” two-dimensional jet flap experiments are briefly described and some of the results presented with comments. The relative simplicity of these experiments and the measure of their agreement with the theory provides, it is hoped, yet another illustration of the value of comparatively simple experiments in the early stages of work on a novel idea.

The nature of handling criteria and their uses in relation to the prediction of aircraft handling characteristics are discussed. A brief history is given of the development of ideas on handling, and a survey is made of criteria for modern aircraft, looking particularly at the physical factors affecting the pilot, as an indication of the basis of the criteria. The novel handling features arising with new aircraft species like slender wings and VTOL are considered. The scope of flight simulators and variable stability aircraft for systematic study of handling is discussed and the potentialities of theoretical study by means of servo analysis techniques considered. Finally, possible lines of development in relation to the assessment of aircraft handling characteristics are suggested.

This study investigates and proposes a fire detection and suppression system for a smart air cargo container. A series of smoke spread and fire evolution numerical models are executed to assess the performance of container-based fire detection in various fire scenarios. This is to identify the worst case and optimise the location and threshold setting of fire detection sensors, achieving the shortest detection time. It is found that the fire detection threshold (reduction in light transmission = 12%/ft) for a container-based system can be set at three times the standard activation threshold for a cargo-based fire detection system, which can reduce the number of false alarms by three orders of magnitude. Moreover, effectiveness analysis of passive fire protection for the glass fibre-reinforced polymer-made smart container indicates an allowable leakage size of 0.01m2. The risk of internal overpressure has been found to be negligible for the leakage size required by aircraft pressure equalisation.

Operating micro-UAVs autonomously in complex urban areas requires that the guidance algorithms on-board are robust to changes in the operating environment. Limited endurance capability demands an optimal guidance algorithm, which will change as the environment does. All optimal path-planning routines are computationally intensive, with processor load a function of the environmental complexity. This paper presents a new algorithm, the reactive route selection algorithm, for storing a bank of optimal trajectories computed off-line and blending between these optimal trajectories as the operating environment changes. An example is presented using a mixed-integer linear program to generate the optimal trajectories.

The design, manufacture and testing of a 480 cubic metre helium-filled airship, or dirigible balloon, intended for flight above tropical rain forest canopy is outlined. The requirements for the airship and the preliminary sizing method are set-out. Details of the final design and flight test results are included, as well as suggestions concerning future work. Particular attention is paid to the issue of accurate station-keeping and operation close to the canopy with winds present. It is concluded that the development of a truly useful aerial platform for canopy biological studies requires further research in aerodynamics, dynamic simulation and ultra-quiet propulsion systems.

The problem of simulation models capable of predicting the aerodynamic instability of helicopter slung-load cargo containers and bluff bodies is addressed. Instability for these loads is known to depend on unsteady frequency-dependent aerodynamics, but simulation models that include the unsteady aerodynamics do not currently exist. This paper presents a method for generating such models using computational fluid dynamics (CFD) to generate forced-oscillation aerodynamic data and frequency domain system identification techniques to generate a frequency response from the CFD data and to identify a transfer function fit to the frequency response. The method is independent of the responsible flow phenomenon and is expected to apply to bluff-bodies generally. Preliminary results are presented for the case of the 6- by 6- by 8-ft CONEX (container express) cargo container. The present work is based on two-dimensional (2D) aerodynamic data for the CONEX side force and yaw moment generated by a forced oscillation in which frequency is varied smoothly over the range of interest. A first-order rational polynomial transfer function is found adequate to fit the aerodynamics, and this is shown to provide a good match with flight test data for the yawing motion of the CONEX.

The issue of the Royal Aeronautical Society Structures Data Sheets 02.01.28 to 37* prompts the publication of a short survey of the theory on which these sheets are based and of the manner in which they may be applied. To save the need to refer to original sources the theory is developed from first principles; but for brevity the application is illustrated only by one simple example. Other more elaborate applications are illustrated by the example data sheets themselves. A recent paper by Chilver covers the same ground from the mathematical point of view and the purpose of the present paper is to illustrate the practical application of the method to familiar problems in the computation of initial buckling stress for sheet-stiffener combinations.

A Repetitively Enhanced Neural Networks (RENN) method is developed and presented for complex and implicit engineering design problems. The enhanced neural networks module constructs an accurate surrogate model and avoids over-fitting during neural networks training from supervised learning data. The optimiser is executed by the enhanced neural networks models to seek a tentative optimum point. It is repetitively added into the supervised learning data set to refine the surfaces until the RENN tolerance is reached. The RENN method demonstrates the effectiveness and feasibility for a 2D highly non-linear numerical example and the structure design of a two-member frame reaching a convergent solution at 10 and 15 iterations at the maximum error of 1% when compared with the exact solution. Then, the RENN method is applied for a long endurance unmanned aerial vehicle (UAV) aerofoil design optimisation. A Class/Shape function transformation (CST) geometry parameterisation method represents an accurate UAV aerofoil with ten geometry design variables. The high-fidelity analysis solver with structured mesh is used for a UAV aerofoil design problem. Using the RENN method, an optimal UAV aerofoil is obtained using 88 high fidelity evaluations at an error of 1·24%. The process reduces the computational time by 81·2% compared with the full high fidelity model. The optimal aerofoil shows a drag reduction of 10·8% in the cruise condition and an improvement in the maximum lift coefficient and stall angle-of-attack when compared with the baseline AG24 aerofoil.

Structural integrity is a key ingredient of aircraft design. It takes its place alongside flight performance, operational effectiveness, reliability, maintainability and economy in determining, or contributing in very large measure to, the success of a project in service.

What is expected from the contractor for a new project in respect of these qualities is set down by the customer in a specification which includes reference to a set of mandatory design requirements. Thus, flight performance parameters such as speed, range and payload, are defined in the specification : there too is to be found a description of the sorties to be flown, numbers and types of manoeuvres and their severity (conventionally including the levels of normal acceleration) and the regions in which the aircraft is required to operate. Sufficient detail is given to establish, as the process of design evolves, the loading and environmental conditions to which the structure will be subjected.

The vorticity production by a single vortex generator jet in a turbulent boundary layer at high speed and zero pressure gradient was studied by analysing surface-flow patterns. The investigation involved a range of jet mass flow rates and skew angles while the freestream Mach number and jet pitch angle were held constant. A qualitative analysis of the skin friction patterns demonstrated the effective role of the skew angle as a bifurcation parameter. The vortex production is classified into three main regimes as the skew angle increases from zero (fully downstream) to 180° (fully upstream). Better understanding of the physical mechanism behind the transition from the first regime to the second is crucial in the design of the airjet vortex generator.

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 paper presents the aerodynamic characterization of a low-speed unmanned aerial vehicle, with cropped delta planform and rectangular cross section, at and around high angles-of-attack using flight test methods. Since the linear models used for identification from flight data at low and moderate angles of attack become unsuitable for accurate parameter estimation at high angles of attack, a non-linear aerodynamic model has to be considered. Therefore, the Kirchhoff's flow separation model was used to incorporate the non-linearity in the aerodynamic model in terms of flow separation point and stall characteristic parameters. The Maximum Likelihood (ML) and Neural Gauss-Newton (NGN) methods were used to perform the parameter estimation on one set of low angle-of-attack and one set of near-stall flight data. It is evident from the estimates that the NGN method, which does not involve solving equations of motion, performs on a par with the classical ML method. This may be attributed to the reason that NGN method uses a neural network which has been trained by performing point to point mapping of the measured flight data. This feature of NGN method enhances its application over a wider envelope of high angles of attack flight data.

The current understanding of periodic transonic flow is reviewed briefly. The effects of boundary-layer transition, non-adiabatic wall conditions and modifications to the aerofoil surface geometry at the shock interactions on periodic transonic flow are discussed. Through the methods presented, it is proposed that the frequency of periodic motion can be predicted with reasonable accuracy, but there are limitations on the prediction of buffet boundaries associated with periodic transonic flows. Several methods have been proposed by which the periodic motion may be virtually eliminated, most relevantly by altering the position of transition fix, contouring the aerofoils surface or adding a porous surface and a cavity in the region of shock interaction. In addition, it has been shown that heat transfer can have a significant effect on buffet.

The stability and control derivatives are essential parameters in the flight operation of aircraft, and their determination is a routine task using classical parameter estimation methods based on maximum likelihood and least-squares principles. At high angle-of-attack, the unsteady aerodynamics may pose difficulty in aerodynamic structure determination, hence data-driven methods based on artificial neural networks could be an alternative choice for building models to characterise the behaviour of the system based on the measured motion and control variables. This research paper investigates the feasibility of using a recurrent neural model based on an extreme learning machine network in the modelling of the aircraft dynamics in a restricted sense for identification of the aerodynamic parameters. The recurrent extreme learning machine network is combined with the Gauss–Newton method to optimise the unknowns of the postulated aerodynamic model. The efficacy of the proposed estimation algorithm is studied using real flight data from a quasi-steady stall manoeuvre. Furthermore, the estimates are validated against the parameters estimated using the maximum likelihood method. The standard deviations of the estimates demonstrate the effectiveness of the proposed algorithm. Finally, the quantities regenerated using the estimates present good agreement with their corresponding measured values, confirming that a qualitative estimation can be obtained using the proposed estimation algorithm.

We consider the effects of atmospheric disturbances, such as wind, shears, turbulence and wakes, on the aerodynamics of aircraft, in order (§1) to quantify the phenomena in question, and provide a basis for future application to problems of performance and stability. The present method of description of the effects of non-uniformity and unsteadiness of the incident flow on aircraft aerodynamics, is presented in some detail for a head- or tailwind sheared vertically (§2), and its extension to all three components of velocity and six shear derivatives is outlined (§11). The starting point (§3) is the relative life change due to a uniform or sheared wind; in the latter case we introduce (§6) a dimensionless shear number S, which plays with regard to vorticity, a role similar (§6) to the Mach and Reynolds numbers respectively in connection with compressibility and viscosity. The aerodynamics of a body or aerofoil in an incident stream containing vorticity, is specified (§7) by a shear coefficient Cs, playing a role similar to the lift, drag and moment coefficients for aerodynamic forces and torques. The present theory is consistent with the formulas of theoretical aerodynamics, the results of wind tunnel tests and observation of atmospheric disturbances involving shear flows. The use of the concepts of shear number S and shear coefficient Cs allows the calculation (§10) of the uniform wind equivalent to a given shear, ie, the wind velocity which would cause the same lift change as the shear. This equivalent wind may be useful in the calculation of the aerodynamic effects of sheared flows, eg, forebody vortices on a wing, wing in a propeller slipstream, tailplane in a wing’s wake, an aircraft landing, behind another, or flight through storms or microbursts.

This paper presents the results of a research performed at the Research Laboratory in Active Controls, Avionics and Aeroservoelasticty (LARCASE), at ÉTS, concerning optimisation strategies for cruise flight segments with imposed flight time (delimited by waypoints with required time of arrival constraints). Specifically, a new algorithm is presented that identifies the optimal vertical navigation profile (flight altitude and speed optimisation) for a cruise segment with imposed lateral navigation profile, bounded by two waypoints with required time of arrival constraints. The set of evaluated vertical navigation profiles are characterised by identical altitudes and speeds at their initial and final waypoints (at the beginning and the end of the cruise segment under optimisation), a maximum of one altitude step (relative to the initial altitude), and are flown at constant speed. This study investigates the flight performance increase (total cost reduction) for a flight along the optimal vertical navigation profile, relative to a flight at the optimal speed and initial cruise altitude. The evaluation was performed using a medium haul transport aircraft flight performance model, for three lateral navigation profiles and three wind profiles. The algorithm is targeted for Flight Management Systems platforms, to provide the optimal flight trajectory for the imposed lateral flight profile and time constraints.

A simple circuit is described which gives a direct meter reading of the intermittency factor in a turbulent flow. The operation and setting-up procedure of the instrument is discussed.

An initial value method is introduced in this paper for the solution of the two-point non-linear ordinary differential equations resulting from an analysis of the MHD boundary-layer flow originally treated by Greenspan and Carrier. By using this method, the iteration process is eliminated. The method is seen to be applicable to the solution of similar two-point boundary value problems where certain physical parameters appear either in the differential equation or in the boundary conditions and solutions for a range of the parameter are sought.