It is only within recent years that the helicopter has emerged from the experimental aircraft category to a position in which it can be considered as an effective operational and commercial means of aerial transport. The development of the helicopter to its present stage is due to extensive work in many countries, particularly in America, and it is unfortunate, but unavoidable, that Britain was unable to take a larger share in this work.

This paper discusses the elementary use of non-dimensional parameters for analysing the performance of a simple jet turbine engine. The coniponents of the engine—intake, compressor, combustion chamber, turbine and final nozzle—are linked together by means of the component characteristics. The possible running points are such that the characteristics are satisfied simultaneously when the whole of the engine is in equilibrium.

The components of the engine in general can be matched only at one point, called the design point. Performance af equilibrium points away from the design point may be predicted by the methods described, before the engine is built.

The paper also shows how the essential parameters governing the behaviour of the jet turbine engine are linked with the aircraft parameters.

A Study of the evolution of the flight I faculty—and in particular its effects in I the realm of Nature and in human affairs—reveals analogies which are, perhaps, of more ithan technical interest. When due proportions have been established, it will be seen that the current period in the development of human locomotion is comparable to that very remote epoch during which Nature, having herself solved the problem of flight, exercised the faculty in accord with some inscrutable law. The analogy gains strength from the fact that changes of a profound kind in the conditions of life on this planet followed the evolution of flight in Nature; and that changes no less profound in character have taken, and are now taking, place as the result of man’s so-called ‘conquest of the air’ brought about by technological advancement.