It is a great privilege to have been invited to give the 1963 Trenchard Memorial Lecture, and I welcome the opportunity to pay tribute to the memory of a great soldier and airman. Lord Trenchard's deep understanding of the meaning of air power, his single-minded insistence on its proper use, and his dedicated leadership of the Royal Air Force during its formative years, will continue to inspire successive generations of airmen. It is appropriate that the Royal Aeronautical Society's Trenchard Memorial Lecture should be given here at Henlow before an audience of young airmen; for it will be their responsibility to master the new techniques on which will depend the continued evolution of air power.

It is an honour, a privilege and a pleasure to deliver the Inaugural Lecture of the Test Pilots’ Group. It is encouraging to see such strong support for this function and on looking round it is only too apparent that there are many more able and deserving pilots present to deliver this lecture.

It is perhaps appropriate, first, to say a few words about the Group itself.

On the 28th November 1963 the Council unanimously approved the formation of a Test Pilots’ Group within the Society. The aim of the Group is The general advancement of aeronautical knowledge in the test flying field. It is hoped that through the Group the test pilot will be able to make a worthwhile contribution to the objects and purposes of the Society, at the same time advancing his own professional knowledge and standing.

Starting from the momentum integral equation an analysis is made of fully-developed flow in a straight pipe. This analysis shows the assumptions implicit in the one-dimensional theory of adiabatic constant-area flow with friction. For conditions of practical interest the approximations associated with the use of the one-dimensional flow theory are shown to be small.

Flow with a developing velocity profile and flow in a bend are then analysed. Introducing approximations revealed in the analysis of fully-developed flow, a simple relation is obtained between the variation of mean flow properties along the duct under incompressible and compressible flow conditions. This relation may be written in the same form as the corresponding relation derived using the one-dimensional flow theory. In a similar manner to one-dimensional flow theory, the relation is readily extended to apply over a series of components of constant cross-sectional area.

The results of the analysis are also presented in terms of static and total pressure loss coefficients. This form of presentation demonstrates that there are appreciable effects of Mach number, on the pressure loss coefficients, where they are often assumed to be small.

The analysis does not enable the variation of the mean flow properties to be calculated ab initio. Its application is to be found in problems where a knowledge of the performance of a component, or series of components, is required under compressible flow conditions, the performance under incompressible flow conditions already being available from theoretical or experimental data.

A comparison of predicted and experimental data for flow in bends and flow in combinations of duct components shows good agreement over much of the subsonic speed regime.

The casual reader might think that there is a mistake in the title of this paper, but the first authenticated descent by parachute was made in 1797 by Andre Jacques Garnerin in Paris. Subsequently, M. Garnerin also made the first parachute descent in England, in 1802, and some thirty-five years later Mr. Robert Cocking, then sixty-one years of age, made a descent in a parachute of a very different design. This descent resulted in his losing his life.

In the interim period between the two descents in England, considerable speculation arose about the designs. The authorities in “Aerostation” of the day put forward some remarkable hypotheses about the problems involved and it might perhaps be of interest to the many people who are now familiar with parachutes to read about them. It is no accident, of course, that the parachute first made a positive appearance at this time. Man had just learnt to free himself from the earth by means of hot air and gas balloons and thus the need for a means of escape was born.

It is probably not necessary for an economist to justify his temerity in addressing the Air Law Group of this Society on Licensing since I am here by invitation. But it is worth noting that a great deal of air law is, in fact, concerned with the economic regulation of the industry: the law is endeavouring to give effect to conclusions about how best to arrive at certain economic results.

I shall not discuss any details of the law relating to air transport licensing: I shall concern myself with the broad economic issues which underlie the law. I shall start from first principles and ask “Why should we regulate air transport?” and, if there are good reasons for so doing, “what are the essentials of a regulatory system?”.

This contribution to the proceedings of the Agricultural Section of the Society is intended: —

• (a) To describe a problem in agricultural logistics which when solved should help developing countries in Asia to increase their food production, especially of rice.

• (b) To suggest that the problem could be solved from the air.

• (c) To offer some layman’s suggestions as to methods by which aircraft and associated installations might be designed and organised to meet the special situation to be found in Asia. From professional advice on these suggestions it is hoped that a workable plan may be devised, and the necessary finance provided from Government or commercial sources to carry out the necessary research and development.

• (d) If a workable plan can be devised it is hoped that one or more of the countries which might benefit would wish to accept any assistance offered and to co-operate in the arrangements necessary.

• (e) While the observations in this paper are believed to be generally applicable to the flat rice-growing monsoonal areas of Asia the ideas have been derived from working experience (for three years) in only two of these countries: Burma and E. Pakistan.

In talking about trends in land tenure and ownership, I propose to confine myself, mainly, to agricultural land in England and Wales, as agriculture is by far the biggest single use to which our land is put. Let me say, at once, that there is a marked lack of co-ordinated statistics on many aspects of the subject and I have, therefore, thought it best to round-off the majority of the figures quoted. For the convenience of those who may wish to pursue the matter further, a list of the main sources of information has been included in the references.

In projecting future turboshaft engines for helicopter appUcations the engine designer is faced with the problem of selecting the size of engine to meet the likely size, configuration, performance and economic requirements of future helicopters. It is also desirable to meet as many different helicopter applications as possible with the same basic engine design. The helicopter designer is, likewise, faced with the problem of which engines could be available for the future and how they could best be tailored to his requirements. This is the perennial problem of the “chicken and the egg.”

This paper summarises the results of a preliminary study of the problem, based on some assumed airworthiness requirements and simple engine assumptions and, while it makes no claim to be a method in itself of assessing the problem, it does show the sort of trend which could be expected.

Blue Steel is an air-surface missile carrying a thermonuclear warhead and intended to enable the V bombers to operate without going into areas in which they would be exposed to concentrated guided weapon attack. It has a canard configuration with small delta-shaped foreplanes for pitch control, a rear-mounted wing with inboard ailerons and a pair of fins of which the upper carries a yaw damper; the lower fin folds sideways to give sufficient ground clearance when the missile is installed on the aircraft (Fig. 1). Its exact performance cannot yet be stated but it is the largest of the British Missiles to get into Service.

Recently, the effect of sweepback on the boundaries of supersonic panel flutter was studied in Ref. (1), (2) and (3), all of them dealing with rectangular plates.

The present note considers the problem of panel flutter boundary of plates in the shape of a parallelogram with all edges clamped.

It is assumed that Ackeret's theory of linearised two-dimensional supersonic aerodynamic loading gives an adequate approximation to the air forces for high Mach numbers.

The criterion of instability is the coalescence of frequencies.

A four-mode solution was obtained by means of Galerkin's method using first two streamwise and spanwise deflection modes. The results are represented in the form of diagrams for different aspect ratios (a/b) and sweep angles(ϕ).

Measurements of profile drag, base pressure, wake turbulence and vortex shedding frequency have been made on a 9 per cent thick aerofoil in the presence of a secondary air flow, ejected from the blunt trailing edge. It is shown that the decrease in profile drag caused by the base bleed is associated with a decrease in the strength of the vortex street. The initial formation of the vortices occurs further downstream as the bleed quantity is increased. As a result, a greater proportion of the shed vorticity is diffused before the street is formed.

We are living at a time of transition in civil aviation, between subsonic and supersonic flight. Subsonic flight has no connection with ground transport and supersonic flight, as now envisaged has no connection either. It is thus rather necessary to explain the title of this paper which would otherwise be irrelevant.

Measurements of oscillatory derivatives made in various tunnels at the NPL over the past few years have indicated that slotted walls, as used in high-speed tunnels, may give rise to large interference effects on damping derivatives. Other workers in this field, notably in America, have also observed interference effects both with solid and with slotted walls. This paper presents the available evidence, so that those making similar measurements may be aware of the effects.

The problem of combustion pressure oscillation in liquid-fuel rocket motor operation has long been the subject of theoretical and experimental investigations.

The low frequency (less than 200 cps) type of oscillation, known as “chugging”, has been thoroughly analysed and the problem solved (see Crocco, 5th Combustion Symposium, p. 164).

This Note is concerned with the more complex (and more destructive) high frequency oscillations, covering a range from about 1000 to 6000 cps. Such oscillations can resonate with the acoustical modes of the combustion chamber. Longitudinal, tangential and radial oscillating modes have been observed.

The separation or breakaway of over-expanded gas from a nozzle wall plays an important role in the estimation of the thrust from a rocket engine when run at altitudes considerably less than the design. A number of reports have been written on the subject but the agreement of test results has not appeared to be good.

In an effort to clarify the position, the Rocket Department of Bristol Siddeley Engines Ltd. has carried out tests on experimental combustion chambers having static pressure tappings in the nozzle divergent section. These tests have shown that, contrary to some previous suggestions, the pressure at which the gas separates is neither constant nor independent of the nozzle length. The paper, which includes results from other workers, divides the field into separation adjacent to the nozzle exit and also at positions where the area ratio is less than 80 per cent of the exit area ratio.

For the most part, consideration is given to conical nozzles having divergence half angles of 15° to 17°, but comment is made on the effects of divergence and other variables. A tentative suggestion as to the mechanism of separation is also made.

Finally, the effect of separation on the sea-level thrust of a nozzle designed for high altitude Is shown.

Blue Streak is to be the first stage booster of a three stage satellite and space probe launcher being developed in Europe. The main contractor for the Blue Streak rocket vehicle is Hawker Siddeley Dynamics Ltd. with the propulsion system the responsibility of Rolls-Royce Ltd. The work reported in this paper was carried out under Ministry of Aviation contract and forms part of the United Kingdom participation in the initial programme of the European Launcher Development Organisation (E.L.D.O.).

The static or “tethered” firing of liquid-propelled rocket vehicles is an essential process in the establishment of operational reliability before attempting launchings.

A type of structure for which no general method of analysis appears to be available is that of a curved beam of low torsional strength and stiffness supported by a torque box. This note outlines ways of analysing two simple cases.

Tests have been made to examine the dynamic response of representative heliport structures to helicopter landing loads. The loads applied by an S.5S helicopter were measured by British European Airways and the corresponding strains, reactions and deflections occurring in the instrumented test platform were recorded by the Building Research Station.

This paper describes the specially designed recording equipment fitted to the helicopter and discusses the data obtained from over 400 heavy landings. It is concluded that:—

• (a)The tyre deflection method used to measure applied load was better than the others considered.

• (b) Overall accuracy achieved was in the order of ± 10 to 15 percent.

• (c) Accuracy could have been improved if more time had been available to eliminate the effects of follower bounce and to establish the exact degree of sideloading present on the mainwheels.

• (d) There was inconsistency in oleo performance which had a marked effect on the time-history of load application.

• (e) The time-history of load application also depended on whether or not the rotor was running and providing lift.

• (f) In very few of the landings from a low hover and in none of the 30 or so run-on landings did all four wheels touch together; this is the most critical loading of the structure.

• (g) Despite the large number of heavy landings earlier in the trial the undercarriage finally failed at 19 fps which was considerably in excess of its design velocity.

The initial buckling stresses of rectangular panels under applied axial loads are in general increased both by circumferential tensile stresses and by the curvature of the panel. The present Note gives theory to estimate these stresses for panels forming part of an unstiffened cylindrical shell. All edges are free to rotate. This condition is often closer to the actual rotational edge restraint of curved panels in conventional stressed-skin construction than the clamped condition, especially in the case of lightly-reinforced shells. The axial generators in the mid-plane of the panels are held straight at the longitudinal edges. All other axial generators are also assumed to remain straight before buckling (no “mattress effect”). The middle surface is restrained at the curved edges of the panel against radial deformation during and after buckling.

Design curves are presented for several values of the parameter (ab/Rt), followed by a typical example.

The recent analytical studies of rocket engine combustion based on propellant vaporisation as the rate controlling parameter, especially those by Spalding, and Priem and Heidmann, have contributed greatly to our appreciation of the mechanism of stable combustion. Critical combustion experiments on a small scale engine have shown fair agreement with vaporisation predictions, but have also revealed the need to understand and improve the mixing process.

In parallel with performance measurements in a combustion system, detailed measurements of the atomisation process including the break-up mechanism and drop-size distribution have been made. However, there are many gaps in our knowledge of the subject and further work remains to be done.

It is thought that the high-speed photographic and gas sampling techniques developed for these investigations provide useful research tools for more detailed studies of the problems.