Many may expect the major emphasis to be given to problems of design of manned aircraft for supersonic flight. Of these, there will be some more qualified to speak on supersonic aircraft matters than I am, for my own experience in supersonic aerodynamics has been predominantly in the guided weapon field. Perhaps this is no disadvantage, for I believe that the aircraft designer has much that he can learn from the guided weapon designer.

Aircraft and missiles have much in common; for both are, or are intended to be, vehicles for conveying efficiently a payload through the air from one point to another. The fact that, in military applications at least, “efficiently” often means “as quickly as possible,” gives rise to a requirement for supersonic speeds in both aircraft and missiles.

Few aeronautical engineers would disagree that the development of new propulsive systems has been the main influence responsible for the achievement of supersonic flight. This is not the same thing as claiming that sustained flight at these speeds, over fairly long ranges and with reasonable economy, would ever be possible without correspondingly large contributions from the aerodynamicist, the structural engineer, and the designers of various equipment. However, if we had been limited for all time to the piston engine/ propeller power plant almost universally employed juring the first 40 years of heavier-than-air flight, it is unlikely that we should ever have exceeded a Mach number of one.

The main factors determining the shape of a supersonic aeroplane or missile are aerodynamic in origin. However, as always, a compromise with structural considerations must be achieved, zero wing thickness for supersonic aircraft being just as unattainable as infinite aspect ratio for subsonic ones.

This compromise is more far-reaching in the supersonic aircraft because of the much greater importance of aeroelasticity.

In addition, there are entirely new problems which arise from the high structural temperatures attained in supersonic flight.

At this stage in the Symposium three papers have been presented on the subject of Supersonic Flight. They will have left untouched a field which is much too wide and extensive to cover in a single paper. In fact, any attempt to cover the major problems remaining would result in a superficial and valueless effort. However, the general problem of control, particularly that resulting from the elimination of the pilot, is clearly the next major consideration and this is basically the theme of this paper.

Other major problems may be described as those associated with Electrical and Mechanical Engineering; they include power supplies, services and, in particular, refrigeration. If one looks back some twenty years these problems were not considered of any great importance, although at some stage every designer must have decried their reliability. In fact “ electrics again ” seems to have been heard far too frequently when trouble occurred.

In Switzerland aircraft often have to take off and land in narrow mountain valleys where a strong, irregular wind is blowing. In these circumstances one faulty casting may cause failure of a control; or a small part, if insufficiently heat-treated, may fracture and result in the loss of the aircraft. For this reason, thorough inspection during production and careful maintenance of the aircraft are of prime importance. Control within the aircraft factory consists of inspection of the raw materials, such as bars, sheet metal, tubes, castings, forgings and so on; testing of the most important parts during manufacture to detect cracks and to control the heat treatment; and the final control of all parts, of components and of the whole aircraft. Maintenance inspection reveals cracks, corrosion and other defects of the most important parts of the aircraft.

The possibility of control of circulation around aircraft wings and gas turbine blades by ejection of air from the aerofoil into the main stream has drawn attention to the manifold problem. Discharge velocity distributions along the length of the wing or blade must be uniform, and it is important that the detailed nature of the flow in the supply manifolds should be understood. The distributions of velocity in manifolds supplying multicylinder internal combustion engines, in gas burners and in manifolds supplying canal locks are other allied problems.

The theory of thin aerofoils at small incidence and flap deflection is very well established. For certain purposes it is desirable to know how an aerofoil will behave in potential flow when the flap is deflected through large angles.

To this end, an attempt has been made to develop a theory of thin aerofoils in which the flap deflection angle may be large.

The results obtained are compared with those derived by an alternative method of direct conformal transformation by F. Keune.