In this paper a simple approximation method is presented for rapidly computing the lift distributions of arbitrary aerofoils. The numerical results are compared with those obtained by an exact method and for many purposes show a satisfactory degree of accuracy. The latter, for all practically occurring cases, can be estimated at the start of the computation work with the aid of the comparison examples given.

I want this evening to present some reasons for believing- that we can build successful aeroplanes of enormous size, and, what is more important, that they will not be merely monuments to a desire for the gigantic.

In the past, bold computers have defined upper limits to the size of aeroplanes. Their prophecies have varied, and most of them have been belied by practical achievement. Their arguments were usually based on what has been called the “ Cube Law ” or the “ Square-Cube Rule.” This rule, though it has apparently proved misleading, is indeed correct when properly applied, and it forms a convenient point from which to begin an enquiry into the feasibility of the giant aeroplane.

Assuming the formation of plastic hinges at the quarter points of a ring subject to a diametral compressive force, a comparison is made between experimental collapse loads and those predicted by use of a simple expression based on the use of plastic rectangular stress blocks, for some common materials; good correlation is obtained with aluminium.

A member may be said to fail when it yields completely at several positions and so allows collapse as a mechanism to occur. The smallest load at which this happens marks the end of useful life of the member. In the case of very thin rings loaded at the ends of a diameter in compression, as shown in Fig. 1, it is obvious that the sections of greatest bending moment are at A, B, C and D. These moments will continue to increase with increasing diametral load.

The following paper does not pretend to be a complete and exhaustive survey of all the theoretical and experimental work which has been done up to the present on the subject of control beyond the stall.

It is confined to main questions and to a report of the practical research work upon which my colleagues and I have been engaged during the last two years.

In doing so I am well aware of the incompleteness of our research work and its methods, which aimed more at finding ad hoc than general solutions. The outlook of the engineer is different from that of the learned scientist. Not for him is the tranquil and contemplative atmosphere that surrounds purely scientific research work. If he breaks new ground he has neither time nor means to strive for a thorough, complete and general treatment of the particular problem he encounters. His work is limited by financial considerations; hampered by a rigid system of Works Orders; and by the lesser interest in so-called “unproductive” work which characterises industrial institutions. In short, from his point of view, the solution is infinitely more important than the theory or the methods by which it is obtained. A practical solution often presents itself automatically if the physical conditions of a particular problem are properly recognised, even if the degree of accuracy does not satisfy the rigid requirements of pure scientific research.

How much is known about high altitude clear air turbulence? Sufficient to show that aircraft may, with little or no warning, experience bumpiness which the pilot would describe as “ moderate ” or, on occasions, “ severe,” at altitudes up to at least 40,000 feet, thus including altitude bands where commercial jet aircraft will be flying during the next few years. The phenomenon, therefore, is of significance to airline operators and the requirement is for the aircraft commander to be supplied with sufficient information to enable him to avoid such turbulence, or to provide him with adequate warning so that crew and passengers can be properly prepared for it. This does not imply that there is evidence to suppose that clear air turbulence may be of such severity as to affect the safety of a flight. It is important, however, to take good care of the passengers and their comfort is an essential consideration.

A new proof is given of a method whereby records of the transient vibrations of linear systems can be analysed to give the damping factor and frequency of each mode of vibration associated with the motion. The method is applicable to acceleration, velocity or displacement records, and as the amplitude of each mode can be found, by using a suitable number of pickups, the normal modes of continuous systems may also be determined. Obvious applications lie in the analysis of flight flutter test data, and of the transient responses of servomechanisms.