Aeronautics has advanced a long way since that December day in 1903 when Wilbur and Orville Wright successfully completed the first flight test ever to be made on a powered aircraft. Since then much has been learnt about the science of aeronautics and great developments have taken place in the methods and techniques of aeronautical research. Wind tunnels have been built capable of testing models at very high speeds and at high Reynolds numbers, and many other powerful research techniques have been developed to assist in the design of aircraft. The behaviour of the aircraft itself in flight remains the final test, however, and there are still many problems which can be investigated adequately only in flight with a piloted aircraft.

In this lecture it is proposed to illustrate the contribution which flight research can make towards the advancement of knowledge of aeronautics by discussing some of the more important aspects of this work.

The purpose of this paper is to explain the principles governing the behaviour of structures under transient dynamic loads, such as those encountered by aircraft structures during landing or flying in gusty weather. The paper is intended mainly for the young aeronautical engineer who may not be particularly well versed in this aspect of stress work.

The rate of ice accretion on an aircraft depends upon meteorological factors and aircraft characteristics. There are on the one hand atmospheric pressure and temperature; water content; droplet size; electrostatic conditions. On the other hand, there is the collection efficiency made up of aircraft component design characteristics such as size; shape; material; surface finish. Finally, there are aircraft flight variables such as speed; attitude; skin temperature; vibratory state.

Meteorologists are able to define potential icing intensity if they can forecast the ambient factors mentioned. The intensity may be defined as light, moderate, or severe, or by some such broad adjective, with reference to a hypothetical collector. Similarly, the air-worthiness authority, e.g. the Air Registration Board, must be satisfied that an aircraft can be operated safely in the appropriate meteorological conditions. Therefore the probable association of each meteorological factor with the others needs to be known.