Since the advent of the aircraft gas turbine engine, various ways have been employed for feeding the fuel into the combustion chambers in the most advantageous manner. Perhaps the most commonly employed method has been the use of swirl atomising nozzles, and in this group is the spill type which has been used successfully for many years in industrial oil burning furnace equipment.

Arising from the general review of burner nozzles made for the aircraft gas turbine engine in its early days, spill burners were used experimentally on the W2/700 engine. Among the problems encountered was that of achieving suitable flow matching characteristics between the several burners of a set and also, that of arranging a satisfactory control system. The knowledge gained by this early work has been made available and has proved helpful to those who chose to carry on with this particular type of fuel nozzle.

Recent interest has been shown in stability problems in which the parameters in the relevant characteristic equations are not constant. For instance, the coefficients in the characteristic equation for the stability of flutter of an aeroplane's wings are functions of the speed of the aircraft. When the aircraft is accelerating or decelerating it is therefore necessary to consider whether the resulting variation of the coefficients is sufficiently rapid to invalidate a calculation of stability which is based on the assumption that the coefficients are constant. Similar stability problems arise in connection with guided missiles.

In Part I. of this paper the theoretical stress analysis was given for a hexagonal braced tubular structure, supported at one end and subjected at the other to a system of longitudinal forces, giving no resultant load and no resultant couple. This tube had no bracing members in the planes of the bulkheads.

This Note describes the design and construction of a “ Tilting Test Bed ” for helicopter engines for Alvis Ltd., for which some onerous requirements were laid down (Fig. 1). The most important of these were that:—

1. (i) Readings of engine torque and b.h.p. must be given by a dynamometer, so as to provide accurate data.

2. (ii) The engine, and therefore the complete test plant, must be capable of being tilted, while running, through 120°—from the horizontal to the vertical and 30° beyond.

3. (iii) During the tilting process the engine throttle setting must remain unaffected and the readings of torque, b.h.p., fuel consumption, and so on, continue with unaltered accuracy.

4. (iv) A powerful fan must be incorporated, for cooling certain types of engine not provided with selfcontained fan, and the air-blast must continue unchanged during tilting.

The Eighth British Commonwealth and Empire Lecture was given by Mr. R. E. Hardingham, O.B.E., F.R.Ae.S., M.S.L.A.E., before the Royal Aeronautical Society on 2nd October 1952 at the Institution of Mechanical Engineers, Storeys Gate, S.W.I. The audience included a number of distinguished guests, among them visitors from overseas and representatives of the Divisions of the Society.

Mr. G. H. Dowty, F.R.Ae.S., President of the Society, at whose suggestion the British Commonwealth and Empire Lectures were started in 1945, presided over the meeting. After welcoming the guests Mr. Dowty introduced Mr. Hardingham, outlining his career briefly. Mr. Hardingham was one of the original apprentices at the Royal Aircraft Establishment and in 1921 joined the de Havilland Aircraft Co. Ltd. Later he served for three years with the Air Ministry during which period he was associated with the Aeronautical Inspection Directorate and the Directorate of Technical Development. He joined the Air Registration Board on its formation in 1937, becoming Principal Surveyor in 1945. In 1947 he was appointed Secretary and Chief Executive and that same year became an Officer of the Order of the British Empire. Mr. Hardingham has represented the United Kingdom at a number of International Conferences.

The supersonic and subsonic jets are both considered by the method used by Miles for an oscillating aerofoil between wind tunnel walls.

The present problem and that of Miles are special cases of the flow past an oscillating aerofoil between porous walls, and provide a useful check for results in the porous wall problem. It may be assumed that the ratio of the change in pressure across a porous wall to the normal velocity at the wall defines a quantity called the porosity parameter, which is a constant at any particular point on the wall. For the special cases of the porosity parameter being everywhere infinite and zero, the porous wall corresponds to the solid wall and the free jet boundary respectively.