In the Journal for October, 1923, I gave the following formulæ for the frequencies in torsional vibration of the crankshaft system (see Fig. 1) of a direct drive engine having equal throws and equal journals, viz.:—

1

and

2

where

3

c=torsional stiffness (the CI/L) of an “equivalent journal”;

p=polar moment of inertia of the “equivalent pulley” of a throw;

r=ratio of the torsional stiffness of the shaft between the airscrew and the first “ equivalent pulley,” to that of an “ equivalent journal “;

n=number of throws.

During the last few years there has been a vast improvement in the manufacture and the manipulation of stainless steel tubes for both commercial and aircraft purposes.

It is my privilege to speak to you to-night on some aspect of the work of testing experimental aircraft, and in order to present my subject to you in as lucid a manner as possible, I am going to ask you to consider that we actually have a machine before us waiting for its first test.

The application of scientific principles to the design of aircraft and aircraft equipment during the post–war years has yielded results which are becoming increasingly apparent. The time interval which elapses between the conception of an idea and its application to production aircraft is necessarily long, but it would seem that we are just commencing to reap the reward of much patient study.

An attempt will be made to present a picture of the progress which has recently been made and to indicate the lines along which further research would appear most profitable. In making this review it is inevitable that attention should be paid particularly to Service aircraft. The more difficult the problem the greater is the ingenuity required to solve it, and the ever increasing demands made upon the designers of Service aircraft have stimulated research to perhaps a greater extent than is the case with civil aircraft, the requirements for which are less complex.

In the development of Italian aeronautics four periods can be distinguished :

A first period, covering the 15th, 16th and 17th centuries, in which the first idea of the technical possibility of human flight, both on the heavier and on lighter than air principles, was conceived in Italy and the physico–mechanical conditions of animal flight explained. In thfs period are to be met the names of Leonardo da Vinci, Francesco Lana and Alfonso Borelli working on independent lines.

A second period, in which Italy produced a number of distinguished aeronauts, among whom Vincenzo Lunardi and Francesco Zambeccari became well known in England for having carried out in London the first balloon ascents in 1784-85. In this period, which, starting with the discovery of the brothers Montgolfier, does not go farther than the first decades of the 19th century, Italy did not combine with an interest in practical air navigation any actual scientific contribution to its development.

To understand aviation in Holland well, it is necessary to draw special attention to two points. The first is that Holland is a small country with a small military force and industry; both are also relatively small. The second point is that Holland has always occupied a central position in traffic lines. These two leading factors also rule things in aviation. They explain the following:

The industry exists without any financial aid from the Government and only a small number of military machines are required annually. The air–traffic company (K.L.M.—Royal Dutch Air Lines) has a small amount of Government subsidy, but has, however, the advantage that the interest of our bankers and shipping concerns, in a quite natural way, is directed towards traffic in general and this interest could be won for air traffic in particular. The Government is fully alive to the importance of this new branch of transport.

When we now turn to history the following can be seen.