To be asked to give the Lanchester Lecture, on the topic of helicopters, is a great honour and just now a wonderful chance. We all know of Lanchester's basic contributions to our knowledge of the way in which lift is generated by the creation of a vortex system. For fixed wings the flow patterns are now known and the theories are in the third stage of refinement. But on helicopters, although it has been the topic of intensive research for fifteen years or more, the subject is much farther back. The results obtained are fascinating technically and pictorially and I would cheerfully discuss them for hours. But our understanding is far from complete and I have regretfully decided to throw away a wonderful chance and leave the topic to a less formal occasion.

To be invited to give the British Commonwealth lecture was an honour which I was proud to accept. As one whose professional life has been concerned mainly with airworthiness of civil aircraft, the choice of the title of the lecture was simple.

But I found some difficulty in choosing a theme. The invitation to give this lecture coincided with the issue of the White Paper Civil Aviation Policy. This White Paper placed a large question-mark against the pattern of airworthiness control in future. It seemed to suggest considerable changes to the form in which the Air Registration Board had existed for 33 years, but what the future form would be was obscure.

The recording of aircraft operational data in service has long been considered to be a desirable addition to the data available to an airline. A limited amount of this information has always been provided by the pilot's log, but the capability of recording this data automatically has been delayed until recent years by the lack of recording systems which were both reliable and yet not too costly to the airline's overheads. The availability of possible systems in the immediate post-war years led to attempts to introduce governmental regulations covering the provision of such systems, but it was not until 1958 that the design of reliable airborne systems led to the introduction by the CAB of the first American regulations for this type of equipment. These American regulations were followed by other countries, notably France, Australia and the UK. The mandatory use of aircraft flight recorders derived from government requirements to record a limited number of flight parameters to assist in the evaluation of aircraft accidents.

The side force produced by gas injection through a single port into the supersonic regime of a rocket nozzle is composed of the natural reaction of the fluid leaving the port and the force due to pressure fields set up within the nozzle by the interaction of the secondary and primary flows. The obstruction presented to the main flow by the entering secondary fluid produces a shock system originating from the vicinity of the injection port. The pitch and yaw of a rocket can be controlled by simultaneous secondary gas injection from two ports mutually at right angles. With two ports operating, the respective shock wave systems produced can interact and hence cause an alteration of the side forces which would be produced if the ports were operating independently.

In a recent paper, Portnoy discussed the properties of a slender-wing with a slender half-body of revolution mounted beneath it. Another configuration of the same type has a fuselage of rectangular cross-section underneath the wing. The present note gives results for the lift on this class of configurations in attached flow and compares it with that for other wing-body combinations.

Ward's slender-body theory describes the flows about appropriately slender configurations where viscous effects are negligible (i.e. the boundary-layer thickness is small in comparison with the transverse dimensions of the body and no separation occurs upstream of the station under consideration). A restriction of the simplified version used in this note is that no element of a load-bearing surface may be upstream of that station. This implies that the wing span must not decrease in a spanwise direction. Another assumption we make is that no leading-edge separation occurs.

The calculation of the inviscid, incompressible flow past non-lifting three-dimensional bodies has been greatly facilitated by A. M. O. Smith and his collaborators, using distributions of elementary singularities over the surface of the body. There is considerable current interest in the extension of this work to lifting bodies, involving the representation of the real viscous wake by a vortex sheet of zero thickness in the inviscid model of the flow. In view of this interest, it is appropriate to consider the way in which such a vortex sheet behaves at the trailing edge of a wing with non-zero trailing-edge angle. Is the sheet tangential to the upper surface of the wing, to the lower surface, or to neither?

The note is concerned with four points in the analysis of laminar shock-induced boundary-layers in undissociated gases. The first point concerns the restrictions imposed by the requirement that similar solutions be obtained. The second point concerns the properties of two simple solutions which can be obtained when the Prandtl number is unity. The third point concerns the accurate prediction of surface heat transfer rate in terms of surface shear stress. Here, an extension and correction to a method employed by Spence is presented. The fourth point concerns the accurate prediction of surface shear stress, a slight modification to an existing mean enthalpy method being suggested in an attempt to correlate most of the available data.

In Part I the analysis was given of a circular hole (radius a) reinforced by a compact ring symmetrically placed either side of the shell skin which was assumed to be attached to the ring at its shear centre and centroid. The shell radius/thickness ratio (R/t) was assumed not to be large enough for non-linear effects to be significant.

Space Technology, internationally, is now in its second decade and already in this comparatively short time new skills and disciplines have emerged and are still emerging. In other papers you will have read of new developments and improvements in electrical power supplies, ion propulsion systems, attitude control and telecommand and data handling. But in the midst of this brave new technical world there is the still small voice of the structures engineer who it is commonly thought only has to offer his 18 gauge sheet suitably bent, honeycomb panels, rivets, brackets, and a simple practical outlook. Perhaps due to the elementary and familiar nature of his materials, the structures engineer tends to be taken for granted when compared with his colleagues working in the more exotic technical fields. The usual procedure followed when a new satellite design is being undertaken and the part played by the structures engineer and analyst is described. Examples are given and views expressed on design philosophy and its implementation.