The safety of civil aircraft is regulated through a process of airworthiness certification and the application of operational regulations. The main elements of airworthiness are:

• (i) certification of the design,

• (ii) compliance with airworthiness requirements,

• (iii) maintenance and reaction to service problems -continued airworthiness.

The airworthiness requirements are developed through a process of discussion and consultation with all interested parties. Whilst the result is largely a consensus view, the ultimate authority rests with the airworthiness authority. In recent years there have been increased efforts to reduce national differences with the aim of producing a single international code. At present there are two, with European and US international pressures tending to work against ‘improving’ requirements unless there is a clearly recognised need.

The aerodynamic energy method provides a means of flutter-suppression control-law design based wholly on oscillatory aerodynamic forces on a notional structure with notional normal vibration modes. The method has been proposed as a means of flutter suppression regardless of structural considerations, other than those mentioned. As originally conceived, the method is based upon the assumption of totally irreversible active controls. In this paper, the effects of finite impedance of actuators on the implementation of the method are investigated analytically. The conclusions do not augur well for the method.

Combined effects of geometrical and material non-linearities on a cantilever beam having symmetrical cross-section about its central axis with a rotational distributed loading are studied. It is assumed that the stress-strain relation in compression is identical to that in tension. Due to this, the neutral axis coincides with the central axis of the beam. The problem is formulated by means of an integral equation which is suitably converted to a system of nonlinear ordinary differential equations which are solved using a simple and accurate numerical method. Details of the load deflection characteristics for an I-beam and for a beam of rectangular cross-section are presented.

The aerodynamic characteristics of two-dimensional transient aerofoil motions in low-speed flows in a wind tunnel with either closed wall or open (jet) walls, including the effect of a downstream closed wall diffuser, have been investigated. The mathematical formulation for the aerofoil and its unsteady wake is based on linear theory and is solved by a piecewise linear vorticity method; the wall boundaries are represented by distributions of sources. Numerical calculations have been made for various values of tunnel height to chord ratio.

Interference effects on the rate of build up of lift to a steady state following a step change in incidence can be large, especially for open jet tunnels.

The approach taken by this examination of flight simulation in the RAF in the Second World War reflects the fact that one author is an engineer and the other a psychologist. As a consequence the paper not only attempts to examine the technology that was established to create the training devices but also something of the personalities who created the simulators and the applications to which they were applied.

In the space available it will only be possible to skim the surface of a topic which has been relatively undisturbed for some thirty years. The authors hope is that the paper will stimulate interest and admiration for the dedicated and ingenious innovators who set out to create the devices which enabled the Royal Air Force to learn new skills safely and apply them effectively.

The objective of this paper is to present the principles of a mathematical model of aircraft prescribed motion. Requirements imposed on the aircraft motion are treated as program constraints on the system and both the transient dynamic solution of motion equations and the control ensuring the exact realisation of the prescribed motion are obtained as a result. The approach used is equivalent to the Lagrange multiplier method, generalised for the purpose of this paper. It consists of the solution of the set of differential/algebraic equations of index exceeding three. The presented mathematical model has been applied to the simulation of aircraft prescribed motion in a loop. The flight along an ideal circle and the flight with additionally demanded constant velocity are described. Some results of numerical calculations are demonstrated.

A three-dimensional panel method has been used to calculate edge-suction forces for thin sharp-edged wings in incompressible flow. The suction forces have been used to estimate the vortex lift on the wings by means of the leading-edge suction analogy due to Polhamus.

The results for planar wings are in acceptable agreement with other methods based on the suction analogy. A limited comparison with results from experiments for non-planar wings revealed good prediction of lift and drag increments associated with the deflection of leading and trailing edge flaps for ‘conventional’ wings of high sweep, but only moderate agreement for a grossly non-planar configuration.

It is with great admiration and much humility that I am able to give this talk in front of Sir Frank Whittle, universally recognised as the genuine pioneer of turbojet propulsion in the formula that made a success of aviation.

As a matter of fact, the patent request filed by Sir Frank Whittle in 1930 (Fig. 1) comprised all the components of today’s turbojets: multi-stage axial compressor followed by a centrifugal compressor, combustion chamber, turbine coupled direct to the compressor and propulsion nozzle.

In April 1937, with the assistance of British Thomson Houston, Sir Frank Whittle ran his first turbojet on the bench at a thrust of 200 daN (Fig. 2). The year after saw the beginning of the Whittle Wl turbojet tests at a thrust of 380 daN. This engine was to receive consecration by a first flight in May 1941 in a Gloster E28/39 specially built for the purpose. Subsequently, this aircraft was fitted with a 650 daN version incorporating an air cooled turbine.

Supersonic cavity flows driven by a thick shear layer at Mach 1·5 and 2·5 are studied by solving the two-dimensional unsteady compressible Navier-Stokes equations in terms of mass-averaged variables. The length to depth ratio of the rectangular cavity is three. The numerical scheme used is the finite-difference algorithm by Brailovskaya. A two-layer eddy-viscosity turbulence model is used. The results are compared with experimental data. The computations show the self-sustained oscillations at Mach 1·5 and 2·5. The continuous formation and downstream shedding of leading edge vortices is demonstrated. The oscillatory modes are correctly predicted. The first mode is attributed to a large unsteady trailing edge vortex moving in the transverse direction. Based on the analysis, it is considered that the oscillation in the length to depth ratio three cavity is a longitudinal one and is controlled by a fluid dynamic mechanism rather than a purely acoustic one.

Experiments were conducted to study the types of flow that occur on the lee surface of delta wings at supersonic speeds. Two sets of flat topped delta wings of different thickness (wedges with 10° and 25° normal angle respectively), each with leading edge sweep angles of 45°, 50°, 60° and 70°, were tested. The measurements, carried out at Mach numbers of 1·4, 1·6, 1·8, 2·0, 2·5 and 3·0, included oil flow visualisations (on both sets of wings) and static pressure distributions (on the thicker wing only). In addition, a 60° sweptback delta wing with a normal angle of 40° was also tested. The tests on this wing included both oil flow visualisations and static pressure measurements. From these and other existing measurements, the leeside flows have been classified into nine distinct types, namely (i) leading edge separated flow with secondary separation, (ii) leading edge separated flow with secondary and tertiary separation, (iii) leading edge separated flow with a shock wave beneath the primary vortex, (iv) leading edge separated flow with shock-induced secondary separation, (v) fully attached flow, (vi) flow attached at the leading edge with inboard shock-induced separation, (vii) mixed type of flow, (viii) flow with a leading edge separation bubble and (ix) leading edge separated flow with a shock wave lying on the lee surface in between the leading edge vortices. These types of flow have been displayed in a plane of Mach number and angle of attack normal to the leading edge. The experimental results indicate that increasing wing thickness has no qualitative effect on the types of flow observed but does shift the boundaries between some of the types of flow.

The objective of this paper is a description of animal swimming and flying locomotion in terms of wave theory. In this context various oscillatory organs of locomotion, such as flagella, fins and wings, are interpreted as waveguides capable of transmitting mechanical transverse waves. Furthermore, the Poynting concept is used, according to which every type of wave transports not only energy but also momentum. Even with no detailed knowledge of the hydro- and aerodynamic flow fields it is possible to calculate the wave power, the propulsive force, and the propulsive efficiency with the means and methods of vibrational theory alone.

A three-dimensional integral formulation for the solution of the full potential equation and the associated numerical algorithm, the field-integral method, are presented. The method is a direct extension of a two-dimensional method and in particular retains the simple grid generation requirements noted in that method. Results are presented for the flow over body shapes and a complex winglet configuration, and are compared with existing transonic methods and experiments with good agreement. The further work necessary to provide a fast, robust method for use in design is outlined.

Features of aircraft which influence flow separations, and hence the onset of buffeting, should be always of interest to an aerodynamicist. The present compilation of such features is based on notes made during a visit to the USAF Aircraft Museum in Dayton, Ohio. Although two low-speed aircraft with high aspect ratio wings are considered, the emphasis is primarily on transonic and supersonic military aircraft, with wings of lower aspect ratio.

Some recommendations are made to stimulate research into improved methods to control flow separation, particularly for future transonic and supersonic aircraft.

The concept of air propelled vehicles to travel in deserts is reviewed. An analysis of trafficability problems in Egyptian deserts is presented with emphasis on sand surfaces. Theoretical equations are derived for the prediction of acceleration, resistance to motion and range at constant speed of the Aero-Roue and the hovercraft over sand.

This paper is concerned especially with the reliability of inspection in the nondestructive testing of military aircraft structures. The first part considers design philosophies, examines how the requirements for inspection arise and highlights the difference between the approaches being adopted in the USA and in the UK.

The second part examines what data are already available on the reliability of inspection and discusses the UK programmes that are aimed at gathering more data.