Among my collection of aviation papers and souvenirs, a favourite item is the Art souvenir and programme of the 1909 Blackpool Meeting. There, as a young schoolboy, I saw for the first time an aeroplane flying in a strong, almost gale force, wind. Bleriot's successful Channel crossing and the great Aviation Week held at Rheims had stimulated organisation of the first aviation meetings to be held in England, at Blackpool and Doncaster. It was a great treat, and an exciting experience to be taken to this meeting by my father, to see the new heavier-than-air flying machines. When we arrived at the flying ground, it had turned out a wet morning, with a strong wind.

In the past, the Society did much for Lighter-than-Air, through its lectures, most of which I was able to attend. I well remember that anti-airship man, E. F. Spanner, who used to face a basically hostile audience, and the fighting speeches from that great protagonist for airships, the late Captain Boothby.

The first, I think, to give lectures on airships was the late Colonel Waterlow in 1912 and 1913, but I was at Wellington then, and so was not present. Nobody fought harder than he did for airships, and he was very helpful to me when I used to visit the airship station at Wormwood Scrubbs.

The gustiness of the atmosphere is studied, among other reasons, because of its importance in producing loads on aeroplane structures much larger than the loads occurring in calm air.

Atmospheric turbulence is studied by observing the behaviour of aeroplanes passing through it, by observing the motion of balloons or other articles carried along by the wind itself, or by examining the fluctuations in velocity or direction occurring at a point fixed relative to the earth. The first of these methods is the most flexible and is the most convenient for aeronautical investigators.

From the earliest days of flying, gusts have been a problem for aircraft. In the very early flights aircraft were flown only when it was nearly dead calm and few gusts were met. Later on and, in fact, almost up to the Second World War, flying was greatly restricted by the ground and air conditions at the aerodrome. This meant that there had to be fairly good visibility and that the grass aerodrome must not be unduly softened by water. Since the war, aircraft have been flown with much greater regularity.

Quite often, those whose honour it has been to deliver the Wilbur Wright Memorial Lecture have used the occasion to present a survey of progress along a fairly broad front and thence to predict what the future holds in store.

It may be that the courage, insight in experiment, and skill in craftsmanship, which culminated in that successful demonstration of fifty years ago last December, have excited those whose privilege it has been to commemorate that achievement to undertake flights in the realm of prophesy. A time so near the fiftieth anniversary might be considered unusually appropriate to historical review and philosophic speculation, but since Sir Harry Garner's 1952 Lecture “Prophesy and Achievement in Aviation,” the Royal Aeronautical Society has been busily converting crystal balls into models of the Montgolfiere balloon.

The planar vortex lattice method is extended to the case of wings in small-amplitude oscillations in ideal flow. Vortex rings are used to represent the bound vorticity on the wing and the trailing vorticity in the wake. A modified procedure for solving the unknown vortex strengths gives greater computing efficiency. Comparisons with results reported in the literature show good agreement for the various test cases considered. Convergence with increasing lattice density is uniform.

The serious mathematical complications of the kinetics of the aeroplane spin have given birth to methods of explanation based on assumptions and simplifications, the application of which, not unfrequently, has led to confusion and misunderstanding on the part of the student, let alone error on the part of the initiator of the method.

One of the problems, is the selection of the geometric parameters that have to be introduced as opposed to those which may be left out of the picture. Obviously, in such complex movement as the spin, the most obscure parameters are the angles of the motion. Unfortunately, there is a minimum number of such angles which is necessary and if one, hopefully, begins with a lesser number, one soon finds that the rest have to be put in place, even tardily, if the puzzle is to be completed.

The main contribution of psychology to the design of displays up to the present time has been in advising on detailed points of design. It is suggested that there are three areas in which psychology can make a useful contribution; these are

(a) in stating the basic characteristics of the human operator, particularly the working of the perceptual mechanism,

(b) in stating the effect of environmental conditions on performance, and

(c) in assessing the information required and in advising on man's rôle in the system.

This paper presents a method for assessing two-dimensional aerofoil lift and pitching moment characteristics including trailing edge and gross laminar separation. The model used is a direct viscid-inviscid interaction scheme based on a vortex panel method with boundary-layer corrections and an inviscidly modelled wake. The integral boundary-layer methods adopted behave well in the region of separation and thus, good comparisons with measured separation characteristics are obtained. Generally the predictions of lift and pitching moment may be considered to be within the experimental error, but where this is not the case, the applicability of the modelling technique is discussed.

The rapid progress made in mechanical engineering during the present century has brought many troublesome problems in its wake. One of the most serious of these troubles arises from resonant and such like vibration. It has, therefore, become increasingly necessary for a designer to take account of vibration. A powerful instrument for this purpose was provided by the late Lord Rayleigh, whose method for finding an approximation to the fundamental frequency of vibration of an elastic system is fairly well known. In this paper an attempt is made inter alia to explain Rayleigh's Principle and to clarify, so far as the author is able to do so, the basis of the principle. Other devices for ascertaining approximate frequencies are also given and an appendix has been added on forced vibration experiments.

In this paper an algorithm for the trajectory tracking of a three-dimensional trajectory, assigned as a function of time, is presented. The proposed control system is suitable for application on unmanned aerial vehicles (UAVs) or for aircraft that require accurate path tracking, as in the case of rotorcraft in nap-of-the-earth (NOE) flight conditions. The control system logic features (i) an external loop based on a simple guidance scheme and a two-time-scale inverse simulation algorithm, and (ii) an inner loop, based on a linear-quadratic (LQ) full-state-feedback controller. In this way the control action is split into two contributions, i.e. a feedforward command, in order to follow the trajectory generated by the guidance scheme, and a feedback increment, for compensating external disturbances and model uncertainties. A rotorcraft model is used to demonstrate the algorithm capability in a NOE–like flight task. System robustness is analysed and control system performance are discussed in terms of the error between vehicle state and desired trajectory at a given time. Simulation of a representative manoeuvre shows that the feedforward estimate of the control action is accurate and only minor compensation is required from the LQ tracker. The algorithm is suitable for a number of applications, as (i) no simplifying assumptions are postulated for the model, (ii) there are no restrictions on the flight condition, and (iii) the computational time should allow for real–time implementation.

The problem of symmetrically loaded circular plates of constant thickness is covered adequately in several of the standard textbooks on the strength of materials. Formulae are derived enabling the deflections and stresses to be readily calculated in any portion of the plate. The problem is complicated by the introduction of a variable thickness and by a variation of material properties due to a temperature gradient down the radius of the plate; conditions such as are encountered in gas turbine wheels, bearing support diaphragms and flexible disc couplings. Methods exist whereby the plate can be solved if the thickness is a simple function of the plate radius, but in practice this is not always so, the profile often being complicated by flanges and spigots.

The engine/airframe integration design is one key differentiating factor for making efficient transport aircraft and this topic will become more important for future aircraft as the turbofan engine diameter is increased leading to a stronger engine-airframe interaction. Hopefully, the capabilities of advanced numerical simulations allow the involved complex phenomena to be taken into account and this is illustrated in this paper through several research studies: the use of the Reynolds averaged Navier-Stokes equations together with the drag extraction techniques to predict the drag, the simulation of unsteady complex interaction between the jet and the pylon with the zonal detached eddy simulation method, the pylon and nacelle design through multi disciplinary optimisation and the flow control technologies.

The primary purpose of this note is to draw attention to the powerful influence of Coriolis forces and flapping pin offset on helicopter stability. It is shown that, for a conventional rotor of small offset, the damping in pitch and the flight stability are greatly reduced by the absence of drag hinges, an effect which may explain the use of stabilising bars on the successful helicopters which use this configuration. A “see-saw” rotor without some form of synthetic damping would be very unpleasant to fly by present-day standards.

We have published elsewhere a considerable amount of work on the development of the cathode ray engine indicator and, while most of the pressure elements and circuits which have been developed are perfectly satisfactory on normal petrol and Diesel engines, it has been impossible up to the present time to obtain a really satisfactory pressure-time card on the high duty boosted aircraft engine, the main difficulty being due to the super position of mechanical vibration on the pressure-time diagram. A satisfactory knock indicator has, however, been produced and a few of the results are here discussed, in the hope that they may be of general interest.

In Figs. 1 and 2 are shown two cantilevers, one acted on by a force which maintains its direction as the cantilever deflects, and the other acted on by a follower force which remains tangential to the end of the cantilever. It can be shown, by a simple demonstration, that a follower force is non-conservative (see Bolotin), and therefore has the capability, if it exceeds a certain critical magnitude, of causing oscillatory instability. Thus, the follower force system in Fig. 2 can become unstable in the oscillatory sense while the Euler Strut in Fig. 1, being a conservative system, can become only “statically” unstable, i.e. with the strut diverging monotonically from its equilibrium position. The follower force system can, of course, also become statically unstable. The overall stability of this system has been examined by Bolotin and Beck. Herrmann and Bungay have investigated the stability of a system that combined the main characteristics of the two above in any chosen proportion.