The instrument described here is designed to measure mean flow directions and velocities in the three-dimensional boundary layer. Its particular advantage is the small amount of interference it introduces, while allowing measurements to be made close to the surface and providing an acceptably large traverse distance normal to it. In its present form it is restricted, however, to flat surfaces where space beneath the surface is not at a premium.

The pure torsional vibration of uniform thin-walled beams of open section, which is governed by the differential equation

has been extensively analysed by Gere He derived the exact frequency equations for beams with a variety of end conditions. However, these equations are, in most cases, highly transcendental.

This note uses an energy approach to obtain approximate frequency equations for the fixed-fixed and the fixed-simply-supported beams. A fixed end is one which allows no twist and no warping and a simply-supported end allows no twist but permits warping to take place freely. The approximating functions used are those corresponding to the exact solution of the problem if the torsional resistance caused by the St Venant system of shear stresses is zero. These functions are similar to the characteristic functions of simple beams in flexure.

The term “All-Weather Systems for Helicopters” is capable of many different interpretations dependent upon operational requirements. Certainly there are no hard and fast rules laid down defining the equipment required to enable a helicopter to operate under adverse weather conditions. The accuracy to which the aircraft has to be flown under instrument conditions and the ability of the pilot to complete a given mission safely without undue fatigue are the prime considerations which need to be considered in determining the facilities and degree of sophistication necessary for a flight control system.

The organisations involved in health facilitation are 3 international ones, 1 national one and 1 local one.

The three international ones are:

(a) The World Health Organisation, an offshoot of the United Nations and before that the League of Nations. This body has headquarters at Geneva and disseminates on a daily basis, world-wide information on epidemic diseases, thus keeping countries fully informed of the current disease position in other countries.

(b) The International Civil Aviation Organisation, which is a consortium of Government Agencies which draws up statutory regulations for the international control of air travel including, among others, personnel and medical problems. Its objective is to implement the Chicago Convention which, in turn, was the successor to the Paris Convention. It is obviously desirable that recommended practices of medical standards for pilots should be uniform throughout the world. Sir Frederick Tymms was at one time the UK representative.

(c) The International Air Transport Association, a voluntary organisation of air operators which endeavours to regulate conditions among commercially competing airlines. The medical committee, like other committees, makes an annual report to the Executive. Sir Wjlliam Hildred was its distinguished chairman for many years.

The application of the matrix displacement method to large displacements and strains, as formulated in refs. 1, 2, 3, is based on the idea of natural modes. This method was significantly generalised to triangular and tetrahedronal curvilinear elements in TNs 17 and 18 (ref. 4), where the important new concept of the local sub-element was first presented. A further obvious extension of the approach should cover curved beams in space, and, what is much more important, shells. However, the realisation of a theory which includes such elements is not straightforward and requires some subtle considerations on the natural modes of a local sub-beam. In order to give a clear presentation of the underlying physical assumptions, we first discuss in this note the natural mode technique on a generalised basis and apply it then to a curved beam in space. The idea of the local sub-element emerges thereby in all its significance. The examples investigated here cover an arbitrary curved beam in space with initial curvature and twist and the special case of a circular arch. To limit the length of the note we have to exclude the effects of shear deformability in bending, and warping in torsion. Moreover, to simplify the formulae we assume that bend ing is defined about the principal axes. The beams in question may be classified as slender and are part of the ASKA library (CUBA for curved beam in space and CIRCA for circular aroh). Part II of the note will include the effect of large displacements and show how the ideas of ref. 4 may be adapted to curved beams and similar structural elements.

An aircraft designer, working on one type of aircraft from inception to first flight, can now expect to be involved with only five different types in the whole course of his professional life. This is about 8 years per aircraft and explains why it is now timely and even popular to be airing views on the shape, manufacture, characteristics and operating requirements of the late 1970 civil air liners.

Circumstances can arise in which a rectangular panel, forming part of a structure, is subject to non-uniform in-plane compression, and in which it is important that instability of the panel should not occur. Problems of this nature occur, for example, in the structure of modern highspeed aircraft subject to the transient thermal stresses that can arise from rapid changes of speed or altitude.

The development of carbon fibres which exhibit high strength and stiffness raises many problems in the design of such fibre reinforced structures. One such problem concerns the optimum arrangement of fibres to support a given load system or load envelope, and this has been treated by Harris for planar load envelopes bounded by given values of applied stresses σX, σY and τXY. Here we consider a problem of optimum fibre arrangement to transfer a torque T across an annulus bounded by inner and outer radii r0 and kr0, respectively. This problem is much simpler than Harris', insofar as only one load system is considered, but it differs insofar as the stress pattern is not isotropic.

When a hovercraft travels at forward speed, the change in ambient pressure due to the airflow around the vehicle affects the forces experienced by the air cushion and hence, the static and dynamic stability of the vehicle. Such changes are likely to be especially important for a tracked hovercraft entering, or operating within, a tunnel. Knowledge of their magnitude is important in determining the smallest, and hence cheapest, acceptable tunnel.

The lecture I am going to give attempts to cover, in forty-five minutes a subject that really merits a series of lectures. This, of course, displays a fitting disregard for minor difficulties, of which, I am sure, the dauntless spirit of Sir George Cayley would have approved.

The broad title permits consideration of all methods of intelligence gathering from the air, including the more widely known optical photographic systems, and has been deliberately selected for this purpose. To avoid clumsy and longwinded definitions I will frequently have recourse to the the use of “in” terms such as Sensor, Multi-Sensor, Exploitation, Environment and many others.

It is clearly unnecessary, before an audience with such experience of aeronautical matters, to explain why scientific, technical and technological research is a fundamental requisite for the growth of the aerospace industry, or why the growth of that industry is one of the factors vital to economic expansion. Nevertheless, I feel it would not be amiss to remind you of the great spur which the particularly advanced nature of the techniques involved in aeronautics provides for all the other industries (air and sea transport, communications, etc), which can often apply to problems closely affecting the general public, solutions which have been initially developed to meet the exacting requirements of aeronautical engineering.

The direct use of satellites is already beginning to have enormous influence on the development of civilisation in our world. An initial study of the benefits to be obtained for mankind by the use of satellites to survey the natural and man-made resources of the earth leads to the inescapable conclusion that this will undoubtedly be one of the major applications of satellite technology that will evolve in the next few years. It is only very few years ago that the real impact of this use of space became evident, but already in that period of time an extremely wide range of types of measurements and different use of such data has been examined and a considerable amount of experimental work been carried out both in earth terrestrial laboratory conditions and also using equipment orbiting in space. There is now a wealth of data on what is possible already and might be possible in this new field of endeavour. I shall attempt in this paper to summarise the main potentialities of different types of systems and try and relate some of the key elements of the satellites to the natural resources being observed.

To describe steady, two-dimensional, constant-density flow in a laminar boundary layer on a curved surface, a single equation may be derived from the complete Navier-Stokes equations, with no approximations being necessary. The conditions under which similar solutions are attainable are discussed, and the validity of some previous calculations is upheld.

During his presentation Air Cdre. Tyndall told you that the foundations of the procedures recommended by the Downey Committee were laid down in the late 1950's and early 1960's. May I remind you of the Internal Directive of March 1960 he mentioned which stated that cost control must be accorded equal importance with technical control. All of us have been developing our techniques of programming and monitoring technical achievements over the years, but at the time the investigations of current practice were being made for the Downey Committee in 1964-65 it was found that in twelve projects investigated only one contractor had procedures for monitoring and controlling cost progress adequately integrated with those for monitoring and control of technical achievement.

Current ICAO standards covering the design of airports arise, in many cases, from the problems of flight operations and it would be a waste of time to repeat these. What this paper is intended to do is to discuss, briefly, some aspects which may be new or seen to deserve special emphasis.

The theory of modal control is concerned with the design of control loops for systems with governing equations which can be adequately approximated by linear vector-matrix equations of the form

where x is the system state vector, y is the control vector, A is the matrix of the uncontrolled system, and B is the control matrix.

The review of the literature suggests that the planar motion of a rigid satellite in a gravity gradient field has been the subject of considerable investigation during the past ten years. In contrast the dynamic study of a satellite executing librational motion out of the orbital plane has received comparatively little attention. Such an investigation is important because as pointed out by Kane, for large amplitudes the transverse motion is strongly coupled with that in the plane.

The lack of information may be due to the complex nature of the problem. The non-linear, non-autonomous, coupled equations of motion involving a large number of parameters are not amenable to simple, concise analysis. Some simplification may be achieved by restricting the satellite motion to a circular orbit. For this case, as indicated by Auelmann, closed zero-velocity curves exist under certain conditions which limit the amplitude of motion.