For the purpose of one brief lecture, it is necessary to set close boundaries. In expansive mood one might, with your permission, discuss the aim in general of aeronautical research, the bending of this Force of Nature to the Use and Convenience of Man; a subject so wide and so difficult, especially our critics would say in respect of Convenience, as to call for a series of lectures rather than this single one. The immediate aims can be dealt with more briefly, and it is that which T propose to attempt. They are, in the first place, safety im flight, and, in the second, increase in what is termed performance. No other aim 6f aeronautical research compares in importance with these.

The paper by Dr. A. H. Chilver (October 1955 Journal) purposed “ to present alternative theoretical approaches to the problem of local instability of a simple type of panel with unflanged stiffeners.”

Examination of these alternative approaches reveals that they are in fact identical and are based on the same approximate representation of the buckled form of the plate by sinusoidally varying lengthwise and transverse deflection, and of the stiffener by sinusoidally varying twist. The difference in the results obtained by Dr. Chilver is explained by the fact that whereas in the first analysis he uses plate theory correctly to express the strain energy in the stiffener, in his second analysis he omits entirely the torsion-bending energy.

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.

In preparing this lecture I found it necessary, when considering recent changes in aircraft design, constantly to ask myself the question “Is this particular change due to airworthiness requirements or does it arise from reasons other than airworthiness?” In fact, one must consider whether requirements have any influence at all on the development of trends in design. Should design be likened to a runaway horse with requirements following some way behind, or are requirements a strict rein by which the pace and direction of design is controlled?

My own answer to these questions is that the pace at which development takes place is not influenced at all by airworthiness requirements, but that requirements help to prevent design from running off the path of safety. To carry the analogy a little farther, the faster the development is, the more difficult it is to keep it running on the path of safety.

Four essential features are generally required of any form of transportation : Speed, safety, comfort and economy. The airplane must compete with other forms of transportation and with other airplanes. The greater speed of aircraft travel justifies a certain increase in cost. The newer transport airplanes are comparable with, if not superior to, other means of transportation. Safety is of special importance, and improvement in this direction demands the airplane designer's best efforts.