In preparing this lecture I was conscious of the fact that there were many phases of the development of a modern fighter which I had not covered, and which would possibly be of greater interest to the specialists on that particular subject than those that I did include. To them I offer my apologies, however, this lecture is not intended to be a handbook or reference on the design of all-weather fighter aircraft, but was prepared more or less as a chronicle of the main events leading up to the current development flying of Canada's newest defence weapon system, the supersonic all-weather CF-105, or Avro Arrow, and its associated equipment and environment (Fig. 1).

Two simple examples of aeroelastic effect are given in which chordwise distortion is important. The first relates to static distortion of a solid wing at high temperature using non-linear relations derived by Mansfield. It is shown that the chordwise distortion is stabilising as regards divergence, but leads to considerable loss of lift. The second example shows that chordwise distortion can reduce the flutter speed of a flat plate.

Results of an experimental investigation of the distribution of skin friction along the wall of a plane turbulent wall jet are presented. The measurements show that it is possible to describe the variation of skin friction coefficient by a formula similar to the Blasius formula which is based on experimental results of turbulent pipe flow. This is simply achieved by considering the inner layer of fluid between the wall and the position where the velocity is a maximum as a boundary layer with an outer uniform free stream of velocity equal to the local maximum velocity.

Other measurements of velocity distribution indicate that within the experimental range and accuracy, the velocity profiles in the jet are similar and that the rate of change of velocity and width of the jet can be expressed by simple power laws. These results are then partially compared with theory.

The science of aeronautics has developed rapidly in a very short space of time, when one reflects on the remarkable achievements which have been made since the advent of powered flight just over fifty years ago. This rapid advance has made the aircraft designer more keenly aware of any new design techniques which would assist him in his further understanding of the problems involved. In the pioneering days of aircraft development the aerodynamic characteristics were obtained largely at the flight test stage of a design. Through time, however, the designer learned that quite a lot of useful information could be obtained from ground tests in wind tunnels, and he therefore made use of an aerodynamic simulation in its broadest terms, in the form of a wind tunnel model. This was an important advance in design technique in that the concept was established of evaluating performance by means of a “model,” in the initial stages of a project design. A much later generation of aircraft resulted in the need for automatic and power control aids to flight. Further advances have resulted in completely pilotless and automatic flight.

The use of models in the determination of aircraft behaviour is as old as flying itself, and wind tunnel models in particular have played a very important part. Now that supersonic flight of aircraft and missiles is a matter of common experience, it seems appropriate to look at some of the difficulties involved in the supersonic tunnel testing of models of such machines.

A Method is presented for determining approximately the effects of small changes in the characteristics of a dynamical system on its free motion. Successive factorisations of the determinantal equation, as the system is altered, are avoided at the expense of accuracy, but the influence of the small changes on, for example, the stability of the system, are quite easily determined.

Crabtree (July Journal, page 525) has suggested a simple method for estimating the transition position on an aerofoil, based on the use of a single curve of momentum thickness Reynolds number (Rδ2) against a pressure gradient parameter at transition, mr. This curve makes some allowance for the effects of pressure gradient and laminar separation on the transition “point”, neglecting the effects of roughness, free-stream turbulence, and so on, but is considered “adequate for most practical purposes”. However, transition is a complex phenomenon, sensitive to a great variety of factors, so that Crabtree's method should be accepted with some reservations.