There are many problems in practice, particularly in the fields of buckling and vibration, where the required end result is a curve showing the relation between the eigenvalue and one or more of the basic parameters of the physical system. For example, the curve relating the buckling stress and side ratio of a rectangular plate, with some specified set of edge conditions, under uni-axial compression may be required. Or the problem may be the buckling of a rectangular plate of given proportions, under combined compression and shear, and the determination of the relation between the two types of load at buckling. Alternatively, the effect on the frequency of vibration of varying a concentrated mass, or the stiffness of an elastic constraint at a given point in an elastic system may be required.

In September 1957 the first small satellite was placed into orbit around the earth by the U.S.S.R. Since that time a very competitive situation has developed between the U.S.S.R. and the U.S.A. Each side has presumably used its military ballistic missiles, together with hurriedly-developed second and third stages. We are now reaching a situation in the West where more carefully prepared and optimised rocket stages are being used, with the basic I.C.B.M. and I.R.B.M. first stages. The result of this is to put larger payloads into orbit for a given launch weight. Recently, cost figures for the past^ present and future satellite launchers have been quoted.

In the first Cierva Memorial Lecture, Professor Bennett dealt with the life and work of Juan de la Cierva. He was priviledged to know Cierva personally and to work with him. He described in vivid detail the qualities of Cierva as a man and the many aspects of his work which contributed to the successful evolution of rotating-wing aircraft. The lecture was aptly titled “The Era of the Autogiro.” At the time of Cierva's death in 1936, the autogyro had been well established and the helicopter, which was to supersede the autogyro, was only beginning to show promise as a satisfactory flight vehicle. By the time I first became directly associated with rotating-wing aircraft, some eight years later, Cierva had already become one of the legendary figures of aeronautics.

Although in recent years aircraft structures have tended to become rather complex, it is still possible in many cases to approximate the structure to a single cell tube with four corner booms during the initial design stages. Since extreme accuracy in computation is neither possible nor desirable in the early stages of design, the analysis has been restricted to structures with bulkheads which may be considered to be rigid in their own plane, although the effect of bulkhead flexibility can readily be included if thought to be of importance.

This note is concerned with the solution of the warping constraint problem for such structures without the necessity of solving a large number of linear simultaneous equations. The method is very similar to the Moment Distribution Method for continuous beams.

This paper is intended as an introduction to the theory of ablative processes in a hypersonic environment. The various types of ablation are discussed and the general heat transfer equation for an ablating body is given. The effects of radiation are introduced and the physical significance of the gasification ratio is explained. Throughout the paper the effects of a chemically reacting boundary layer are ignored.

Figure 1 illustrates a load diffusion problem which occurs in ship structural design, and which may also be relevant to aircraft structures. A load applied to one end of a stringer is diffused into the attached sheet and eventually reacted by shearing forces at the longitudinal edges. The transverse edges of the sheet and the other end of the stringer are not loaded.

Various methods, which differ in their assumptions regarding stresses and displacements in the sheet, are available for tackling this problem. For calculating the distribution of load or stress in the stringer it makes little difference which method is used. The “finite stringer” method of reference (1) is the simplest and should be sufficiently accurate for most cases.

The shear stiffness of a beam in bending is commonly determined by measuring the central deflection δ in a three-point loading test for a range of values of the span L under a constant central load. The value of bending stiffness, EI, and shear stiffness, GA, can then be obtained by plotting δ/L against L2 and drawing the best straight line through the points so obtained. The slope of this line for unit central load is then 1/48EI and its intercept on the δ/L axis is 1/4GA on the simple “Engineer's” theory.

The determination of the critical axial load of a strut having one or more intermediate supports and varying stiffness is made difficult by the highly transcendental nature of the simultaneous equations involved. It is therefore usual to make a test of the stability of the strut at some arbitrarily chosen load, as for example when applying the convergence technique. The behaviour of the strut then indicates whether the chosen load is too high or too low, and another load is selected and another test made. Although the true critical load is eventually reached, it is clear that if its value can be fairly closely approximated at the outset, then the labour of calculation will be greatly reduced.

A recent paper(1) gives details of an investigation on the low endurance fatigue behaviour of an aluminium-zinc-magnesium alloy (D.T.D. 683). It becomes apparent in subsequent discussion that information on another aluminium alloy to B.S. L65C would satisfy a wider practical interest than the former. Although the equipment used for the earlier work was engaged on another project, it was decided that the latter should be halted for a period to enable a brief programme on low endurance fatigue to be conducted on B.S. L65C material which had previously been kindly provided by the Aluminium Development Association.

Land development through pasture improvement has made great strides in recent years in many parts of the world. This has been made possible by a better understanding of the principles of pasture production following the pioneering work of the late Sir George Stapledon and his school of grassland enthusiasts. Improved strains of pasture plants, the use of lime and fertilisers, the development of mechanical aids and a better understanding of the animal in grazing management have all been involved in the development.

The equations showing how to correct for the effect of non-uniformity of the Atmosphere when computing the angle-of-climb (or descent) are well known and can be found in Refs. 1 and 2.

From Ref. 1, a climb at constant Mach number M implies a factor F on the Aircraft Weight to give the true angle-of-climbs (in our units for R) given by the expression

The future helicopter brings to mind a vast multi-engined aircraft capable of speed in excess of 150 knots, and of payloads of 8,000 lb. or more. This is not the aircraft for agriculture.

Experience has shown that once the all-up weight of the helicopter gets beyond 3,000, 4,000 lb., its manoeuvrability is reduced to such an extent that the characteristics which make it the most ideal vehicle for aerial agriculture are lost.