With the death of Albert Peter Thurston we have lost a man about whom it might truly be said that he had a longer connection with aviation than any of his contemporaries. A pioneer of the early days who maintained throughout his life a keen interest in flying, he was deserving of far more credit and renown than has yet been accorded him.

Born on 31st October 1881, he was the son of Peter and Elizabeth Thurston. He graduated at East London College (later Queen Mary College), London University, in 1905, passing the BSc examination with first class honours. In February 1905 he joined the Examining Staff of the Patent Office.

For some considerable time, experience has been accumulated on the retardation of military aircraft on landing by means of a brake parachute. A patent for such a device, for example, was granted to Captain, now Colonel, Prospero Freri, in Italy in 1930. The first useful applications were towards the end of the Second World War on gliders and fighter aircraft, but systematic use of this type of decelerator on American aircraft began just before 1950. The first postwar British service aircraft fitted with a brake parachute was the Vulcan, followed closely by the Lightning and the Victor. These three aircraft use brake parachutes to reduce the landing run and also to reduce wear and tear on the aircraft brakes and tyres. The Lightning in particular has been the subject of extensive application of the brake parachute.

To have been chosen to deliver the 53rd Wilbur Wright Memorial Lecture is an honour of which I am very conscious and deeply appreciative.

Upon such an occasion I think it is appropriate that we pause to consider the truly great contributions made to aviation by Wilbur Wright, his brother Orville and the many pioneers who followed them, and to consider the effects of their contributions upon our lives.

I doubt very much if the Wright brothers in their most optimistic dreams could have imagined the tremendous progress aviation would make following their first powered flight 61 years ago.

A surface hot film was used as a boundary layer transition indicator on wind tunnel models at Ifiach numbers from 1·3 to 4·0. The results illustrate the difficulty of fixing transition with distributed roughness on small models at supersonic speeds.

A test vehicle, in the G.W. sense is a body used in free flight to test components, structures, aerodynamics, servo controls, guidance systems and propulsion. The body may have weapon-like characteristics or may be designed purely to investigate a particular phenomenon or theory which has a bearing on the design of weapons. From the inception of the G.W. Department this work was given an important place in the programme and played a major part in laying the foundation of knowledge and experience on which the G.W. work in this country was built.

Two early test vehicles were CTV.1 and KTV.1. CTV.1 was used for a good deal of aerodynamic investigation, together with the development of free flight instrumentation and measurement techniques, it was our first “beam rider”, and was also used in a command guided role. The beam riding work was done in co-operation with TRE who were responsible for the guidance aspects of CTV.1. RTV.1 was a larger vehicle used mainly on beam riding guidance research. A later version was used in a vertically launched role to study launching and stability problems preparatory to the Black Knight work.

The CTV series culminated in CTV.S which itself took various forms. The CTV.S Series I was designed for aerodynamic measurements on a coasting dart at high incidences and therefore high altitude. CTV.S Series 2 was designed for kinetic heating investigations while CTV.5 Series 3 was an upper atmosphere sounding rocket, later known as Skylark and still providing a valuable service.

RTV.2 was designed for further work on liquid fuel propulsion and semi-active radar guidance research and was developed further to become the better known GPV. An interesting method of recovery from the sea was developed for this vehicle. With the requirement for ballistic missiles and satellite launchers a whole new field of work on missile structures, stability, control and guidance was opened up. This called for the development of the latest and very successful test vehicle, Black Knight.

This paper is concerned with two-dimensional, incompressible fluid motion generated within a square cavity (a) by an outer stream and (b) by the action of a flat surface passing over one of its sides. This type of motion (“cavity flow”) is considered to consist of a boundary layer surrounding an inviscid “core.” A solution of a linearised form of von Mises’ equation is obtained for steady flow in the boundary layer for constant pressure and that of a small periodic variation around the walls of the cavity. From this analysis the vorticity imparted to the core is obtained. The motion in the core is then determined on the basis of the persistence of this value of the vorticity. Experimental results are given for (a) and (b) and compared with the theory. A method of solution of the non-linear boundary layer problem is indicated.

In part 1 of this paper the shape of an axially symmetric ducted body, of given length and fineness ratio, having minimum pressure drag was derived using the Newtonian impact pressure law. It was shown that this shape closely approximated that found by a computer method of Guderley, Armitage and Valentine which employed the general flow equations. Indeed the two curves could be distinguished only for values of the diameter ratio Δ=di/df, of the initial and final diameters, so small as to be outside the range likely to be used for cowl shapes.

In the course of a recent meeting of the Performance Data Sheets Committee of the Royal Aeronautical Society to discuss thrust measurement in flight, it was pointed out that it is easy to apply the equations of motion incorrectly to the case of an aircraft which is losing mass due to fuel consumption. The rate of change of aircraft momentum is obviously affected by the loss of mass and so, at first sight, it may appear that the margin of thrust over drag required to achieve a given acceleration and /or rate of climb at any particular instant would be affected also. In fact this is not the case. To clarify this point, this account of the momentum and energy balances of an aircraft with an air-breathing engine has been prepared at the suggestion of the Performance Committee.

It is shown that, in regions near peak strains, improved accuracy of measurement with a strain gauge or extensometer, can be obtained by taking readings over more than one distance including each point. A better estimate of the true strain can then be derived than will be given by a single reading. Peak errors in the region of 8 to 10 per cent can thus be reduced to 1 or 2 percent.

Two methods are described: one in which measurements are made at equal intervals along a line, keeping the gauge length constant; the other using different gauge lengths centred on the point concerned, the latter being suitable where a grid can be marked on the surface.

When a long unreinforced flat elastic strip with free edges is bent to a uniform curvature about transverse axes in its own plane, anticlastic curvature is produced due to the influence of Poisson's ratio. Provided that the applied curvature is sufficiently small, the anticlastic curvature is constant across the strip and is proportional to the applied curvature. A finite deflection analysis shows, however, that the anticlastic deformation is reduced by the action of middle surface stresses, and the deformed strip approaches asymptotically a cylindrical form as the applied curvature is increased. Nevertheless, in some engineering applications it is necessary to limit the anticlastic deformation when the applied curvature is small, and for this purpose transverse ribs can be attached to the strip. In this note a small deflection analysis is given of the effect of uniformly spaced rigid ribs on the deformation of such a strip.

In the design of cascade blading for compressors and turbines it is often assumed that the maximum efficiency will be attained at the maximum loading that just avoids separation and critical Mach number effects. In a turbine, the overall pressure gradient is favourable so that it should be possible to achieve very high loadings and yet avoid separation. The question then arises as to whether or not such high loadings would produce a high efficiency. The present note suggests that in fact there is an optimum loading, beyond which there would be no improvement in efficiency even though separation and critical Mach number effects were avoided.

Of the Several Methods available for the measurement of boundary shear, the simplest is perhaps the Preston tube. It is a total head tube resting on the boundary for which the difference between the dynamic pressure on the tube and the static pressure on the boundary is correlated with the boundary shear. It was evolved by Preston in 1954 mainly from similarity considerations and the existence of the wall law. In 1955, Hsu obtained Preston's original calibration curve theoretically for the one-seventh power law. In this note, a theoretical calibration curve is developed for the logarithmic law which describes the velocity distribution for larger Reynolds Numbers.

The Familiar process of dimensional analysis for aerodynamics equates a force to a function of several variables liable to affect it, in terms of the dimensions M, L, T, and yields the numbers known as the Reynolds number and the Mach number of the flow. These numbers are generally regarded as useful and sufficient means of denoting the regimes of flow in conventional circumstances, where the force developed on a body results solely from the relative motion between the body and a mass of fluid.

On behalf of my Company, which manufactures the RAE Head-up Display Equipment referred to in K. J. Holden's paper in the December 1964 issue of the Journal (pp 833-6), I would like to correct some misunderstandings which seem to exist and to amplify certain statements in this otherwise interesting and informative contribution to the techniques of instrument displays.

Dr. Holden states: “The essence of the (RAE) display is an attempt to reproduce the appearance of the runway as it would appear to the pilot.” This statement is incorrect as the flight director symbol to which he refers, is made up of a “target spot” (a’) and associated director lines (a) in Fig. 1. This symbol is a pure integrated flight director and is not and never has been intended to represent the runway.