The need to establish reliable methods of predicting the response of aircraft during taxying on rough runways and the associated dynamic loads and fatigue damage has led to numerous theoretical and experimental investigations of this problem. The present paper is a development of the study reported in ref. (1) which considered the random response of a flexible aircraft to forces transmitted through thei main undercarriage. The purpose of this paper is to apply power spectral techniques to the computation of the response of a rigid aircraft in heave and pitch to runway roughness, taking account of non-linearities in damping in the main and nose undercarriage.

This contribution addresses the subject of engine inlet barrier filters (IBF) for rotorcraft. The purpose of an IBF is to mitigate the risk of particle ingestion by the engine, a situation that can cause irrevocable damage to key components. The risk is significantly elevated during a brownout landing, in which the rotor wake of a descending helicopter interacts with loose ground sediment, causing the generation of a dust cloud. In such a condition, an IBF successfully removes particles from the engine-bound air at the expense of a pressure drop, which grows temporally. The increase in pressure drop is caused by but not limited to an increase in incident velocity and a decrease of mean particle size; however the rate may be slowed by operating the filter at a tangential angle to the flow. The current work presents findings of a parametric study into the factors affecting particle accumulation and the consequential loss of inlet total pressure.

Mission simulation is a critical activity in the development and operation of Unmanned Aerial Vehicles (UAVs). It is important to ascertain the feasibility of a trajectory in a mission. In this work, an algorithm has been developed for feasibility study of a trajectory of a UAV using prescribed path optimal control through an inverse simulation method. This has been done under a Differential Algebraic Equations (DAE)/Inequalities (DAI) framework. The UAV model together with constraints is represented as a high index DAE system. The trajectory that UAV shall take is prescribed as one of the constraint equations. The solution for the DAE system is obtained using a variation of the alpha method that is capable of handling both equality and inequality constraints on system dynamics. The algorithm involves direct numerical integration of a DAI formulation in a time-stepping manner using a Sequential Quadratic Programming (SQP) solver that detects and satisfy active path constraints at each time step (mesh point). In this unique approach, the model and the constraints are always solved together. The method ensures stable solution at each time step, local minimum at each iteration of simulation and provides a regularised basis to the solver. A typical UAV trajectory has been simulated and demonstrated in this paper. This new approach can be used for path planning of UAVs before the actual control law is designed for flight control computer. Compared to other existing computationally intensive techniques, this approach is computationally simple, ensures continuous constraint satisfaction and provides a viable option for model predictive control of UAVs.

Two-dimensional Euler equations are solved on unstructured triangular meshes using commonly available minicomputers. The driving algorithm is an upwind biased implicit cell-centred finite volume scheme. The spatial discretisation involves a naturally dissipative flux-split approach that sharply captures Shockwaves. The grid generation method uses a type of advancing front technique which triangulates a given set of points. To demonstrate the application, the steady flow results are presented for single and two component aerofoils. The unsteady results are obtained using a dynamic mesh algorithm for an aerofoil pitching harmonically about the quarter chord. The paper presents a description of the grid generation and movement algorithm and of the Euler solver, along with results and comparison that assess their capabilities.

In this study, a series of numerical experiments are performed on supersonic/hypersonic flows over an adiabatic flat plate with transitionally and fully rough surfaces. The Mach numbers simulated are 4, 5, 6, and 7; the flight heights considered are 20, 24, 28, 32, and 36 km. First, a modified roughness correction is proposed and validated with the measured data for low-speed flat-plate cases. It is verified that for the equivalent sand grain heights in the intermediate and fully rough regimes, there is a good agreement with the semi-empirical formula available in the open literature. Then, this roughness correction is applied to high-speed flow regime to investigate the effects of flight heights and Mach numbers on drag for rough-wall flat-plate cases. It is found that within the roughness measured in real flight, the roughness height change has little effect on drag compared to the variations of both flight heights and Mach numbers. The drag coefficient derivation between rough-wall and smooth-wall conditions, achieves the maximum value of 0.79% for the 60 cases selected.

It is not only a great honour but also a great pleasure to have been asked to deliver this Sixty-Third Wright Brothers Lecture to the Royal Aeronautical Society. My own associations with the Society and its members have almost always been highly edifying, stimulating and productive in both the personal and professional spheres. I believe that the relationships between our two nations which I have had the opportunity to observe from the government, industrial and scientific standpoints have greatly enhanced the qualities of our institutions and the extent of our progress in aeronautics as in many other areas. We have often been competitive, sometimes fiercely so, but almost never in a destructive way. I still remember from my youth the vicarious thrills of the editorial battles of the 1930s between The Aeroplane and Aero Digest over the merits of British and American air transports and the genuine delight I experienced when I actually met C. G. Grey, Editor of The Aeroplane in that era, at a Society garden party years later. The challenge of worthy adversaries, the hard but fair rules of engagement, and the sportsman’s appreciation of the game well played, in victory or defeat, are as potent sources for excellence in science, technology, business and the professions as they are in contests of skill and daring.

The Air Mail route from Cairo to Baghdad is now securely established. Seven years ago the major portion of it, from Transjordan to Iraq, was no more than a project in certain far-seeing minds. The maps of this region between Amman in Transjordan and Ramadi, a little market town on the Euphrates, 65 miles west of Baghdad, were until 1921 painfully reticent. The countries of Egypt, Palestine, and to some extent Transjordan, had been fairly accurately mapped for some time, and were flown over extensively during the war by ourselves and the Germans. The landmarks are generally speaking abundant, and from the navigational point of view they therefore present no outstanding difficulties.

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.

I have been deeply appreciative of the action of the Council in inviting me to deliver this lecture. No one could be otherwise. The Wilbur Wright. Lectureship has been illustrious in the qualifications of the thirty speakers who have been my predecessors on this platform ; but it is illustrious also in itself, in the manner of its founding, and in the manner in which the Royal Aeronautical Society has carried it on in an unbroken series through two wars and the years between.

In the present era of supersonic and hypersonic flight, structural analysts are well aware of the new problems that arise from the exposure of aircraft and missile structures to elevated temperatures. The task of solving these problems is in its early stage of development. Since the problems are diversified in nature, a different method of solution has to be developed in each case. It is probable that in some cases radically new techniques may have to be devised. Until such time, the structural designer is forced to take a realistic view and use satisfactory extensions of existing methods of analysis.

In a recent Technical Note, Bradshaw offered additional thought on an earlier note by Markland and myself. In doing so he wrote of the efficiency of a diffuser which was confused with the pressure recovery coefficient, Cp. In view of the great significance when designing engine intakes, combustion chambers, nuclear reactor plant and even heating and ventilating systems of even minute improvements in duct efficiency, the distinction is further discussed.

An adaptive method for the computation of steady, viscous compressible flows over a wide range of Reynolds and Mach numbers is presented. The method is based on a well-proven scheme for the solution of the compressible Reynolds-averaged Navier-Stokes equations and employs the flexible AMR-grid structure for the adaptation of discretisation to the computed flow. The basic numerical scheme and the grid structure are reviewed and the sensors employed for the detection of the main flow phenomena are presented. Special attention is given to several flows computed with the adaptive method. The numerical results are partially compared to experimental data and generally a good agreement is observed. It is also recognised that, with the present adaptive method, flow features can be computed with high resolution using greatly reduced computing power. At this time, the method is limited to the simulation of two-dimensional flows, with the extension to three space dimensions currently under development.

Prizes were presented and The Thirty-seventh Wilbur Wright Lecture was delivered before The Royal Aeronautical Society at the Royal Institution, 21 Albemarle Street, London, W.l, on Thursday 28th April 1949. Dr. H. Roxbee Cox, B.Sc., D.I.C., F.I.Ae.S., F.R.Ae.S., President, presided at the meeting.

Appreciable forces can be obtained for steering a vehicle by the use of aerofoils whenever the relative air velocity is high and the air density is not too small. In practice this means velocities greater than 100 ft./sec. and altitudes below about 50,000 ft. Even when they are not in use for steering, aerofoils necessarily add to the drag of the vehicle.

Film cooling performance expressed in the terms of film effectiveness, is divided into initial and final regions containing respectively, the potential core and transition lengths and, the main decay region. The theory of Kutateladze and Leont'ev, which is representative of present approaches, is presented and shown not to apply to the film initial region. To resolve the questions, what is the minimum acceptable value of effectiveness in a given situation, and, what proportion of the resulting maximum permissible cooled distance is initial region, the film cooling of a hypothetical turbojet engine to power a Mach 2-2 cruise supersonic air liner is examined. Experimental data from cooling devices representative of current European practice are used in the analysis to give realistic results.

A new approach for low-drag high-lift system design based on the application of viscous flow solvers was developed in the EC research project EPISTLE. Two high-lift systems for a supersonic commercial transport aircraft (SCT) wing were designed, manufactured and wind-tunnel tested. The predicted large drag reductions were fully confirmed by tests at high Reynolds numbers. These drag reductions significantly reduce the low-speed noise of future SCT configurations. This was estimated by preliminary aircraft design tools. Low-speed noise reduction by aerodynamic means is obtained, as effective high-lift systems enable these aircraft to climb faster.

This paper describes the incompressible flow through contracting ducts as used in windtunnel circuits. The value of the velocity gradients that are critically adverse to the boundary layer development are specified and the contraction profile is derived for two-dimensional flow. Solutions to the flow through three-dimensional contractions of circular, square, and square to rectangle shape are obtained. These lead to simple rules for scaling the profile of two-dimensional flow to provide three-dimensional shapes having short lengths with the required velocity distributions. The development of both laminar and turbulent boundary layers is calculated to provide criteria for the avoidance of separation.

It is an honour and a privilege to commemorate the memory of Sir Charles Kingsford-Smith. It is 41 years since he linked by air the United States and Australian nations. Those 41 years have been years of phenomenal progress and growth from the infant industry of that time to the monumental industry of today.

Forty-one years ago the flying time from San Francisco to Australia was 83½ hours and the elapsed time was 10 days.