Earlier sections have dealt with engines which have been developed almost entirely with the object of war and destruction. The fighter engine has been pushed all the time harder and harder to obtain greater output, with increased rate of supercharge, higher critical altitude, and more power to manœuvre under all possible conditions and attitudes of the aircraft. Performance has been achieved at almost any expense, provided reliability was ensured for a given period; such items as the time between overhaul and fuel consumption have been secondary considerations. In a similar way bomber engines have been continually stepped up in power to give maximum output at rich mixture for takeoff, so as to project the greatest possible load of bombs into the air, and every attention has also been given to providing the highest weak mixture cruising power at altitude, in order to allow for the necessary power to maintain flight at a reasonable altitude during the early part of the mission, when the machine is fully loaded.

The A.G.P. is required to produce 20 kw. A.C. and 3 kw. D.C. continuous normal full load, at 3,750 r.p.m. The load is required for operating the electrical services on a large aircraft and must be maintained both when it is stationary and when it is in flight up to an altitude of 11,000 feet.

The A.G.P. must run cool in the standard English summer atmosphere (23°C. at ground level) and draw the necessary air from ports cut in one side of the aircraft. These ports must be formed from a 1ft. diameter hole divided on its diameter. The cooling air is to be drawn in through the forward semi-circular hole and, after passing through the installation, expelled through the rear semi-circular hole.

For the problem of bombing from a distance we may use either ordinary wingbombs or wing-bombs acting by propulsion (e.g., rocket propulsion). The uses of such bombs have been thoroughly discussed by Rougeron in his well-known book “L’Aviation de Bombardement.” (I).

Tanks in the form of a surface of revolution are sometimes employed for carrying fuel. The purpose of this paper is to show how the stresses, due to the internal hydrostatic pressure, in a shell of this kind can be calculated when the equation of the generating curve is given. The acceleration imposed on the shell and its contents will be assumed to be at right angles to the axis of revolution, hence shear as well as direct stresses are set up. It will be supposed that no longitudinal bulkheads are fitted, and the shell will be taken as very thin so that the bending stresses in it are negligible. No attempt will be made to examine the stress distribution in the neighbourhood of a relatively rigid supporting ring; as shown by Timoshenko these ‘ end effects ’ are appreciable only in the immediate vicinity of the support. Nor will the stability be considered of those portions of the shell which are subjected to compression. Thus attention will be confined to what are commonly described as the membrane stresses.

The speed of flight of an aircraft at high altitudes is still usually determined by the indirect method of measuring the dynamic pressure in flight. The acknowledged defects of this method—the effect of interference by near parts of the aircraft on the static pressure at the tapping point, the necessity of calibration of the pressure readings by tedious quadrilateral flights over measured ground distances or a suspended static head, the indeterminate effect of the Mach number at high speeds, inaccuracy of the ‘air temperature measurements owing to stagnation of the flow at the instrument, errors of the elastic pressure capsule owing to hysteresis and temperature variations, and the inaccuracy of the mean values obtained by averaging the measured dynamic pressures—have all contributed to raise a demand for a simpler and more accurate method of airspeed measurement.

Initially, supercharging of aero-engines was introduced with a view to restoring the pressure in the induction manifold at altitude to that corresponding to sea level. During recent years this has been changed, and supercharging is now employed not just to maintain sea level pressure in the induction manifold, but to boost engines at altitude, in order to develop high B.M.E.P.s and thereby obtain high power outputs at high power to weight ratios.

The author has described elsewhere (reference 1) the general principles of the dynamic stiffness method of analysing torsional vibration problems. Amongst the systems treated were those involving simple spur or helical gear-steps. The method can also be applied, however, to deal with epicyclic gearing, making proper allowance for the effect of flexibility in the gear-housing. The present paper outlines this extension.

A similar method may be used to allow for housing flexibility in normal spur gearing.

This note is intended to cover the more interesting items of progress made since 1930 by the Fairey Aviation Company, Limited, in methods for ascertaining the relief centrifugal bending moments due to bending deflection in twisted propeller blades. Ref. 1 describes the only reliable method known to the writer in use at the commencement of this period. The first substantial change was made in 1932, when the time required to obtain a solution was reduced from over a week to about half a day without any considerable sacrifice in accuracy. Owing to independent research and the usual circulation of junior staff the 1932 method is now fairly widely known under various names, but this note would be incomplete without its inclusion as it forms the basis of subsequent methods. The convergence by this method is not very rapid as it only halves the error at each successive approximation. An alternative method reducing the error to about one-tenth at each step is also given.

The experiments were carried out in the high speed wind tunnel at Guidonia on three brass spheres of 40, 60 and 80 mm. diameter, supported on rear spindles and on two steel cylinders of 15 and 30 mm. diameter respectively, which passed through the air jet.

Both the total drag and pressure difference between the front stagnation point and a variable point at the rear were measured.

The pressure distribution on similar models which could be rotated and which were provided with pressure holes was also determined.