This paper has been prepared as a continuation to the very interesting general airship paper read before the Royal Aëronautical Society by Wing-Commander T. R. Cave-Brown-Cave. An attempt has been made not so much to describe in detail the various parts of a rigid airship as to discuss along broad lines the underlying requirements and problems and the difficulties facing future development. It is hoped that this paper will also serve as an introduction to further papers dealing with specialised parts of the general subject “ Rigid Airships,” such as mooring, fabric, machinery installations, etc.

When considering problems connected with future technical development, it is in the first instance necessary to realise clearly the scope and functions of the operational requirements, and thus to provide a sound basis from which to start. The first problem to consider in this connection is the difference between military and commercial requirements.

The advent of the use of aircraft for purposes other than warfare will involve the appearance of several additional aspects into the already numerous considerations which have to be applied during the evolution of the design of an aircraft.

During the recent war, designers were called upon to produce designs in which performance and manœuvrability were the foremost considerations, and sacrifices of other factors, including safety and stability, had to be made in order to attain supremacy in these directions. It is true that during the latter stages of the war matters concerning ease of production, the use of alternative materials and accessories, and facilities for maintenance did receive a certain amount of attention; but in view of the speed at which designs and production had necessarily to mature, the amount of thought which could be given towards such considerations was very limited.

The decision as to what strength shall be given to the structure of an aeroplane is made as a result of previous experience. It is well known that it is quite impossible so to design the structure as to render it unbreakable under any condition of flight without increasing the weight to such an extent that the aeroplane is useless as a flying proposition.

The result has been that load factors have been specified for different types of aeroplanes such as experience has shown will render the structure safe for any reasonable treatment in the air.

The principal factor to be fixed is that for the case when the centre of pressure is in its most forward position. Once this is determined the remainder of the structure can be designed consistently with it.