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.

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.