It has almost become a tradition in recent years to begin a paper on boundary layer by paying a tribute to the great Prandtl and his famous paper in which he introduced the conception of boundary layer into Fluid Dynamics.

The year 1954 is, however, not only memorable to mark the passing of fifty years since Prandtl's classical demonstration of the effect of boundary layer suction on the flow pattern around a cylinder; it is also memorable because in 1954 most convincing demonstrations of practical applications of boundary layer control for aircraft have taken place. I am referring, in particular, to the demonstrations with the Attinello flap in the United States which mark the introduction of one form of boundary layer control as an engineering and practical reality.

The problem of analysing the behaviour of a structure as a combination of members joined together, may be stated in the form of a question—What system of loads must be applied to a single member of the combination so that its behaviour as an isolated member is identical to its behaviour as an integral part of the structure? The question becomes clearer upon defining some of the terms used in stating the question.

Progressively less information becomes available from the Soviet Union about the development of its aircraft industry. In examining the material that has been released during the past five decades, much confusion arises in the initial attempts to piece this material together chronologically and to show realistically the development of the aircraft industry in the Union of Soviet Socialist Republics. It seems that much time would be spent before a somewhat realistic picture might be obtained. Therefore, it appears appropriate that a definitive analysis be presented at this time.

The industrial development under the Communists in the Soviet Union is, and has been, a direct result of a bureaucratic state-planned economy. Voznesensky points out that the balance of the national economy, which lies in the hands of the State, includes the production and allocation of the social product, the production and allocation of fixed capital, the balance and distribution of man-power, the production and allocation of national income, the balance of money incomes and outlays of the population, and the balance and allocation of material resources.

The first idea about unsteady motion in the atmosphere seems to have been the vague notion of “ Air Pockets”—areas or gaps, wherein the air just does not generate lift, and an aeroplane falls in consequence. It is astonishing how widely this view is still held.

Those engaged in aviation soon learned that unsteady flight was due to turbulence and two sorts, friction and orographical, were quickly recognised. Friction turbulence, which affects only the lower layers of the atmosphere, can best be observed by watching a soaring sea-bird in a breeze. The friction of the water surface creates a velocity gradient or variation of windspeed with altitude, and the bird will probably be diving down-wind, and climbing into wind, with no effort— from the bird's point of view a fair approach to perpetual motion. However, the air is really a mass of tiny eddies where friction is at work and close observation of the bird's wings and feathers will show them to be constantly in motion as they yield to each puff.

The problems discussed here are those of a uniformly inclined and skew loadings on a finite rectangular plate such as would be obtained by the action of wind or rain on a large door of an aircraft hangar or other such building. Such a force may be considered constant in magnitude over the area of the plate but non-normal in its direction with the plate.