In the usual Berry (I) expression of the generalised theorem of three moments (i.e., generalised in the sense that end load deflection effects are taken into account) the lateral loading on a continuous beam is regarded as uniformly distributed over each bay into which the beam length may be divided (either naturally by supports or artificially for convenience of analysis). In this paper the lateral loading is taken as distributed parabolically so that the resulting equations may be used as a sort of Simpson's rule for dealing with any arbitrary loading. By taking into account the “ sinking “ of supports any particular beam can be divided up into a convenient number of bays over each of which the lateral loading may be assumed to be parabolic. We may thus obtain reasonably accurate solutions for the bending moments, etc., in a continuous beam under almost any type of lateral loading.

The problems which occur in defining the thrust of a jet engine and the internal drag of a ducted body are considered, and formal definitions and names are given for the concepts considered to be of importance.

Whilst carrying out various tests on radiators and airscrews in Iraq, it was necessary to take the air temperatures up to 10,000 feet, and the results of twenty-six flights are given in these notes as it is thought they may be of interest to aircraft designers requiring data to predict the performance of their aircraft in a tropical climate.

A method is described for determining the inlet and exhaust valve area requirements of a two-stroke cycle engine. It is shown that the valve timings are interdependent and that the final choice is a compromise with a number of other factors.

Flying, in common with all means of transport, is affected by adverse weather conditions, but the necessity of aeroplanes to maintain flying speed introduces a major difficulty of its own. The older forms of transport are able, in the last resort, to evade their difficulties by coming to a dead stop. An aeroplane must, literally, fly in the face of its difficulties. It must fly blind in clouds and perhaps land in fog. Over and above this, flight under certain meteorological conditions introduces a danger unique to aircraft. Ice may deposit at all leading edges and grow to windward, at critical regions of the relative airflow, in shapes which increase drag and seriously decrease lift. The accumulated ice adds to the weight. Unsymmetrical ice deposits on the airscrew blades cause dangerous engine vibrations which can only be kept in check, if at all, by throttling back at the expense of thrust. Venturis and pressure head orifices become blocked with ice, rendering the instruments they serve useless. External controls may become jammed. In short, many adverse factors to prevent flight may be brought into play simultaneously by the mere fact that particular meteorological conditions have been encountered.

The purpose of this paper is to indicate in a simple but quantitative form the primary aerodynamic factors governing the performance of a hovering helicopter (since the ability to hover is its prime virtue) and to show how the necessity to operate at a reasonable forward speed restricts that hovering performance. The paper is mainly of interest to potential users of helicopters and to others not actively engaged on helicopter design.

The standard power relationships for hovering flight, as developed by Glauert and Squire, are interpreted in graphical form, and the effect of forward flight in limiting the choice of aerodynamic and operational parameters, due to the onset of blade stalling and compressibility, is illustrated by means of boundaries on these graphs. The power requirements in forward flight are not considered.

The Wilbur Wright Lectures not only commemorate that pioneer flight on which the art of practical aviation was founded but also offer homage to the brilliant research and invention which made that flight possible. It is, therefore, natural and fitting that such a large proportion of the preceding 25 lectures have dealt specifically with the application of research to matters aeronautical. The materials of aeronautical construction can also justly be classed as the outcome of much research into many fields of pure and applied science, with practical results that have made some contribution towards the advancement of aviation and, hence, fittingly form the subject of a Wilbur Wright Lecture. Accordingly, when the Council of the Royal Aeronautical Society honoured me with the invitation to deliver the 1938 lecture on this subject, I naturally read up the preceding lectures and was somewhat surprised to find that materials, as such, had not previously been dealt with in this connection. The task of making the first survey of a field of such alarming scope, in a necessarily limited space and time, involved some anxious reflection regarding a suitable method of treatment; it appeared that a detailed discussion of personal research, or even of a selected group of materials, must have such a limited scope as to be incompatible with what is implied in the allotted title. To the casual observer, the really wide range of the more familiar materials of construction that have been available for some years, allied to the normal steady improvements that have been effected and those that may be expected, may appear to offer all that is required for the aeronautical requirements of the next decade or so, so that reviews of the materials of, say, 1924, 1931, 1938 and 1945 would mainly represent a story of development rather than change ; actually, this is not the position. A relatively few years has seen the relinquishment, temporary or permanent, of the position held by steel as a structural material; the use of light alloys has become very general, an improved form of wood is definitely in the field while it may be that the entire structure of moulded plastics will become a practical proposition in the fairly near future. Then, the accomplishment of the aims of the engine builder with regard to units of much greater powers are retarded to a certain extent by the fact that a number of materials appear to have reached the visible peak of their development; new materials are urgently required. Again, who would care to prophesy that the airscrew of the future 2,000-4,000 h.p. engine will even be made of any kind of metal, although the present aluminium alloy propellers give such good performance.