The heading of this lecture is the “Development of Air Transport During the War” but because time is limited I have had to exclude any mention of the ferry organisation which was responsible for the delivery by air of many thousands of aircraft. The work has however been, described in “The Atlantic Bridge.” The period with which I propose to deal is the 21 months ending in September, 1946. In this short period, in response to the demands of war, the Transport services of the Royal Air Force flew rather more passenger miles than did British Civil Aviation in the preceding 21 years up to the same date, and carried in addition great quantities of freight and military stores. This volume of transport flying, packed into a few short months, gave rise to many problems but also afforded unique opportunities for testing out new ideas and new equipment. My purpose tonight is to give a brief account of what was accomplished, and against this background to examine some of the lessons which were learned and the ideas for the future to which they gave rise.

The series of Chadwick Memorial Lectures was started in 1956 by Harold Rogerson who gave a very complete picture of Roy Chadwick's life and experience as an aircraft designer. Since then lectures in this series have mainly concerned problems on future projects, which would certainly have excited his lively interest, rather than nostalgic reviews of the past.

However, when I was honoured by being asked to give the 14th Lecture of the series it occurred to me that nothing would be more appropriate than a paper on the History of the Vulcan, since it was not only a major Avro enterprise in its own right, but it was also the last project with which Roy Chadwick was intimately concerned. It had a peculiar fascination for him, because he had, all the time I knew him, an enthusiasm for the all-wing transport as the ultimate in aerodynamic and structural efficiency

In a recent note Professor Duncan gives a method for finding the reciprocal of a matrix which is triply partitioned both horizontally and vertically. In spite of the apparent complication of the formulae, such a procedure may shorten the calculations in the case when the submatrices involved are especially simple (e.g. null or diagonal), or when their arrangement exhibits some symmetry. In Ref. 1, the submatrices a to j of the desired reciprocal are obtained by a series of operations summarised in equations (3) to (19); these operations consist altogether of 5 inversions of submatrices, 29 matrix multiplications of various orders and 15 matrix additions.

The name of Sir Henry Tizard always induces in me feelings of humility: I have succeeded him in an office to which he lent distinction for ten years, but I can never hope to emulate his drive and efficiency, nor compete with his almost legendary chairmanship. I remember that in 1964, soon after I was appointed to the Chair of the Aeronautical Research Council, Dover Publications decided to reprint Goldstein's “Modern Developments in Fluid Dynamics“, and I was invited to contribute a Preface. I got out my set of the earlier edition, to be reminded that the first Preface bore the signature H. T. Tizard: somehow, it seemed almost indecent that I, or anyone, should have to write a new Preface. Such are my feelings about Tizard's name and fame: I daresay many of my generation feel as I do.

The Two-Sting Rig system provides captive trajectory and grid survey testing in the ARA 2·74 m × 2·44 m transonic wind tunnel, on models of the order of 10% scale. The system has been in productive operation since 1979, having been used primarily in the captive trajectory mode to predict release characteristics for a wide range of stores/aircraft.

The paper describes the improvements to and developments of the system that have arisen from experiences gained during the last two years of its operational use. A brief description only is given of the general arrangement of the rig. Improvements to performance, simulation capabilities and to wind tunnel productivity are described together with current design studies for new applications.

An appraisal of the overall performance of the method against three other ground based techniques is used to illustrate its merits and defects, using results from recent Two-Sting Rig wind tunnel tests and flight.

Low Reynolds number blade profiles of ReC=105–2×105 as based on the chord length and used for small unnamed air vehicles, and near space applications are investigated for single and counter-rotating (co-axial) proprotors, i.e. acting as rotors or propellers. Such profiles are prone for early stall, significantly reducing their maximum lift to drag ratio. Two profiles previously designed by our continuous surface curvature design approach named as CIRCLE are investigated in order to improve the performance of the proprotors. The profiles are redesigns of the common symmetric NACA0012 and asymmetric E387 profiles. Using general arguments based on composite efficiency and rotor’s lift to drag ratio, the performance envelope is noticeably increased when using the redesigned profiles for high angles of attack due to stall delay.

A new approach is derived to account for the distance between the rotors of a co-axial proprotor. It is coupled with a blade element method and is verified against experimental results. Single and co-axial CIRCLE-based proprotors are investigated against the corresponding non-CIRCLE-based proprotors at hover and axial translation. Noticeable improvements are observed in thrust increase and power reduction at high angles of attack of the blade’s profiles, particularly for the co-axial configuration. Plots of thrust, torque, power, composite efficiency and aerodynamic efficiency distributions are given and analysed.

Detached-eddy simulations for the 1303 UCAV geometry are undertaken aiming to investigate the flow physics of the interaction of a store with the flow inside a UCAV weapons bay. Advanced multi-block topologies had to be used to properly represent the planform of the UCAV and all the details of the weapon bay, including doors and hinges, while sliding meshes were needed to insert the store into the UCAV configuration. Results with an empty bay were encouraging for such complex configurations. Flow visualisation revealed the added turbulent content due to the door leading edges and hinges. The addition of a store in between the doors had little effect close to the front wall of the bay. However averaged flow-fields showed that the proximity of the shear layer to the apex of the store deflected it downwards into the bay and restricted its growth.

The aerodynamic performance of conventional aircraft configurations are mainly affected by the wing and horizontal tail. Drag reduction by shape optimisation of the wing, while taking into account the aircraft trimmed constraint, has more benefit than focusing solely on the wing. So in order to evaluate this approach, the following study presents results of a single and multipoint aerodynamic shape optimisation of the wing-body-tail configuration, defined by the Aerodynamic Design Discussion Group (ADODG). Most of the aerodynamic shape optimisation problems published in the last years are focused mainly on the wing as the main driver for performance improvement, with no trim constraint and/or excess drag obtained from the fuselage, fins or other parts. This work partially fills this gap by an investigation of RANS-based aerodynamic optimisation for transonic trimmed flight. Mesh warping and geometry parametrisation is accomplished by fitting the multi-block structured grid to a B-spline volumes and performing the mesh movement by using surface control points embedded within the free-form deformation (FFD) volumes. A gradient-based optimisation algorithm is used with an adjoint method in order to compute the derivatives of the objective and constraint functions with respect to the design variables. In this work the aerodynamic shape optimisation of the CRM wing-body-tail configuration is investigated, including a trim constraint that is satisfied by rotating the horizontal tail. The shape optimisation is driven by 432 design variables that envelope the wing surface, and 120 shape variables for the tail, as well as the angle of attack and tail rotation angles. The constraints are the lift coefficient, wing’s thickness controlled by 1,000 control points, and the wing’s volume. For the untrimmed configuration the drag coefficient is reduced by 5.76%. Optimising the wing with a trim condition by tail rotation results in shock-free design with a considerably improved drag, even better than the untrimmed-optimised case. The second optimisation problem studied is a single and multi-point lift constraint drag minimisation of a gliding configuration wing in transonic viscous flow. The shock is eliminated, reducing the drag of the untrimmed configuration by more than 60%, using 192 design variables. Further robustness is achieved through a multi-point optimisation with more than 45% drag reduction.

The ever expanding range of applications for unmanned air vehicles covers a wide variety of powerplant requirements. While many vehicles are high value assets and demand similar powerplant attributes to a conventional manned aircraft, there is an emerging requirement for powerplants which are designed to a limited life philosophy. This covers a range of applications: at the simplest level there are vehicles where the mission definition dictates that attrition rates will be high, for example low level reconnaissance, targeting or battle damage assessment, and the entire vehicle may only be expected to make a short number of missions. On the other hand there are applications where it may be more cost effective to remove the need for engine maintenance and to treat the powerplant as a disposable limited life unit.

In general, the industry trend is towards the reduction of life cycle costs, and a significant emphasis is placed upon continuing to increase aero-engine component lives though novel design and improved manufacturing techniques. A limited life application calls for a different approach, as it may be that the powerplant has a life requirement of anywhere between 50 and 250 hours. This allows scope to explore areas of design and manufacture which would not be suitable for a ‘conventional’ engine and can lead to large reductions in engine cost.

This paper seeks to identify the primary cost drivers for a small UAV powerplant in the 10kN thrust class, and to establish the relationships between cost, life and performance at both a whole engine and an individual component level. It also explores the feasibility of using new or unconventional designs and manufacturing methods, and presents a selection of examples.

Analytical methodology is presented to conduct dynamical assembly of simple low order nonlinear responses for system synthesis and prediction using Volterra theory. The procedure is set forth generically and then applied to several atmospheric flight examples. A two-term truncated Volterra series, which is enough to capture the quadratic and bilinear nonlinearities, is developed for first and second order generalised nonlinear single degree of freedom systems. The resultant models are given in the form of first and second kernels. A parametric study of the influence of each linear and nonlinear term on kernel structures is investigated. A step input is then employed to quantify and qualify the nonlinear response characteristics. Uniaxial surge and pitch motions are presented as examples of the low order flight dynamic systems. These examples show the ability of the proposed analytical Volterra-based models to predict, understand, and analyse the nonlinear aircraft behaviour beyond that attainable by linear-based models. The proposed analytical Volterra-based model offers an efficient nonlinear preliminary design tool in qualifying the aircraft responses before computer simulation is available or invoked.

The aviation industry is dominated by the domain of heavier-than-air, fixed-wing, subsonic flight, and central to any design in this domain is the wing itself. One of the earliest debates in aviation still centres around the usefulness of the wing volume. On the one hand it is held that the wing, as an inevitable necessity, should provide the volume also for the payload. On the other, it is argued that more efficient wings do not even have sufficient volume for the entire wing structure. This work proposes precise definitions of the Wing Density and the Inflation Factor, two parameters that can quantitatively reflect the economic and technological trends in aviation. The wing volume of a hypothetical Ideal Wing is derived from the Operational Parameters of any given Flight Objective and compared to the volume requirement of that flight objective. We conclude that the dominant aircraft configuration of the future is likely to remain within the same family of the current dominant configuration, in conflict with some older predictions.

In real gas turbines, multiple nozzles are used instead of a single-nozzle; therefore, interactions between flames are inevitable. In this study, the effects of flame-flame interaction on the emission characteristics and lean blowout limit were analysed in a CH4-fueled single- and dual-nozzle combustor. OH* chemiluminescence imaging showed that a flame-interacting region, where the two flames from the nozzles were merged, was present in the dual-nozzle combustor, unlike the single-nozzle combustor. Flow-field measurements using particle image velocimetry confirmed that a faster velocity region was formed at the flame merging region, thereby hindering flame stabilisation. In addition, we compared the emission indices of NOx and CO between the two combustors. The emission indices of CO were not significantly different; however, a distinct effect of flame-flame interaction was indicated in NOx. To understand the effect of flame-flame interaction on NOx emissions, we measured temperature distribution using a multi-point thermocouple. Results showed that a wider high-temperature region was formed in the dual-nozzle combustor compared to the single-nozzle combustor; this was attributable to the high OH* chemiluminescence intensity in the flame-interacting region. Furthermore, it was confirmed that the size of this interacting region caused the deformation of the temperature distribution in the combustor, which can induce a difference in the increase ratio of NOx emission between high and low equivalence ratio ranges. In conclusion, we confirmed that flame-flame interaction significantly affected temperature distribution in the downstream of the flame, and the change in temperature distribution contributed primarily to the varying concentration of the emission gas.