For many years there have been used in aircraft construction aluminium alloys to a steadily increasing extent, and particularly alloys of Al.-Cu.-, Mg. and Al.-Cu. capable of being improved by heat treatment. Among the different methods known for permanent connection of structural parts, the rivet is still to-day the most reliable and safest connecting element. According to the special quality of this light metal group, due to their natural material characteristics and owing to the fact that in most cases the connections of aircraft structural parts are very complicated and highly stressed, the rivets are always driven cold. Due to these conditions, the tools, machines and working methods for strengthening of riveting diverge essentially from the commonly known riveting methods of general machine construction. In the course of my lecture I shall give further details regarding these questions.

The recently issued Report of the Aeronautical Research Committee draws attention to the fact that much work, apparently of academic interest only, is now of direct practical utility. In particular, the theories of the boundary layer and of turbulence, though admittedly very incomplete and uncertain and lacking a secure scientific foundation, have been developed to the stage in which they can be applied to explain and predict the behaviour of aircraft, and to show how aircraft may be improved. The physical structure of the boundary layer will be described, and the methods by which the problems have been attacked mathematically to get useful results and to check the theories.

In conclusion, the theory of the boundary layer will be applied to the calculation of the drag of an airship or aeroplane fuselage under full-scale conditions, and to an explanation of the behaviour and performance of different types of aerofoils.

This paper deals with the problem of operating a large fleet of transport aircraft and managing the problems that arise from mechanical and avionic defects in the machines.

We, in BEA, for a long time made the common mistake of treating this mainly as a technical problem, requiring for its solution a thorough analysis of defect sources followed by engineering modification action. After pursuing this course for a number of years it became apparent that, although results were achieved, more important influences were nullifying the benefits. A wider analysis of the problem was, therefore, undertaken which made it clear that the primary problem was the management of ground operations at the London hub of BEA's system. At this point the effort of the three operating departments (Flight Operations, Engineering and Traffic) converged and had to be effectively integrated.

Minimum drag shapes of given length and base area are investigated for hypersonic flow using both Newtonian impact theory and free molecular flow theory. The drag of Newton’s minimum drag body, which has previously been evaluated by numerical means, is derived as an analytic expression. The analytical results are applicable to a range of local pressure laws allowing minimum drag shapes obtained using impact theory to be directly compared with low density flow equivalents using free molecular flow. The low density shapes are found to have larger blunt regions at the nose and significantly larger drag coefficients. For free molecular flow the drag varies with the surface reflection characteristics. As the fraction of diffuse reflection at the surface increases, the drag increases and the sensitivity of the drag to changes in the minimum drag shape is reduced.

At the first meeting of the Aeronautical Society of Great Britain in June, 1866, the author read a paper “On Aerial Locomotion and the Laws by which Heavy Bodies impelled through Air are Sustained.” Since that date, the writer has only occasionally reverted to the subject, but has never been convinced that flight is impossible for man, considering the apparent ease with which large birds traverse the air.

The power required to maintain the flight of the screw vanes mentioned in the paper (now extensively used for flying-shot practice), was estimated at the rate of three-horse power for each hundred pounds raised. This is widely in excess of the reality, because when the first force that causes ascension is exhausted, the instrument in its subsequent descent, acts as a mere dirigible parachute. This is a most extravagant means of absorbing power. For example, a man weighing 150 lbs. attached to a parachute having this number of square feet, descending 1,300 feet per minute, will be expending six-horse power on the yielding air.

Navigation has been defined as “the business of conducting a craft as it moves about its ways“. This broad definition of navigation encompasses the whole process of handling, steering, control, guidance and operation of the craft in a safe and economic manner. Navigation has a much longer history than aeronautics. As man first began to explore the world and to develop trade, the need for safe and predictable operation of the craft was a spur to the application of the most advanced science and technology of the day.

There is an old saying in the aircraft industry that you can make a brick fly, if you give it enough power. How true this is I would not care to say, but it is certainly true that the worries of the designer are lessened if he knows that he can always give the throttle a little extra push, if all else fails.

This is not to say that the design of a conventional, high powered, aircraft is a simple, hit or miss affair, that would be ridiculous, but it does serve to show the special difficulties faced by the builders of a man-propelled aircraft who have less power available to them than is used by a small electric fire.

First, it is necessary to define productivity and the way it is measured. Productivity is a ratio of an output to an input; it is, therefore, somewhat analogous to the engineering concept of efficiency but unfortunately without the accompanying rigour of definition of input and output in energy terms. In productivity measurement, the output can be in value terms, in weight or volume or number, while the input can be numbers of men, man hours, wages or capital or some combination of these. These points are illustrated in Fig. 1, but in this paper I will be concentrating mainly on value outputs and manpower and labour cost inputs. A fuller account of the subject is contained in Ref. 1.

It is suggested that those wishing to familiarise themselves with the general history of Pitcher's work consult “Aviation” by C. H. Gibbs-Smith, HMSO, 1970, pages 85-90, and items 1 and 2 in the references at the end of this paper, although it should be remembered that this paper amends some of the information contained in these sources.

When dealing with famous men in history, perhaps one of the most persistent and difficult questions is that of their relative importance. It is very easy, in a bout of enthusiasm or contempt, to over- or underestimate the influence that a person may have had upon his contemporaries. This applies no less in aeronautics than elsewhere. The example of Percy Sinclair Pilcher (Fig. 1), the British gliding pioneer, is a case in point.

The role of meteorology in air operations is becoming increasingly important and an understanding of meteorology is desirable in the consideration of a number of the problems to be faced. The forecasting of winds en route and the use of these forecasts is one such problem, which has been brought into greater prominence by the advent of fast, high-flying aircraft. A great deal of work is being done on upper air winds and it is already clear that curious and significant phenomena sometimes occur. Thus very high winds are sometimes found in belts of limited lateral extent—the so-called “jet stream.” Not only high winds, but high rates of change of wind occur in such regions and they are clearly a potential source of difficulty to the navigator. Apart from the jet stream —a meteorological highlight of recent development—airline operators are also concerned with the problem of route planning.

The reinforcement for holes in tensile stress fields sometimes takes the form of an extensive thin plate attached to the sheet, especially if the reinforced region is of integrally machined or bonded construction. Such reinforcements are often placed eccentrically, that is on one side of the sheet only. It has been shown both experimentally and analytically that such an eccentrically placed reinforcement can promote considerable bending stresses.

Wittrick gives curves showing the effect of eccentricity in the case of the circular hole with an eccentrically located annular plate reinforcement in a plane, axially symmetric stress field. High, but only local, bending stresses exist which simple theory will not predict. The stresses are markedly higher than those given with the corresponding symmetric reinforcement. For example, under axisymmetric loading it is possible to design an optimum plate-reinforced neutral hole (i.e. the stress concentration factor is 1·0 in both sheet and reinforcement) if the reinforcement is deposed symmetrically about the plane of the sheet. If however it is placed totally eccentrically then for realistic sheet stresses bending raises the sheet concentration factor 2·0.

The dynamic stall characteristics of a NACA 0015 performing ramp-up motions are considered. Pressure data show the development and convection of structures at the leading and trailing edges, which indicate differing degrees of what are described as leading edge and trailing edge stall mechanisms. When a transition strip is placed at the leading edge, the characteristics of leading edge stall predominate, and the growth of the structure at the trailing edge is suppressed. In addition the stall vortex convection speed is observed to alter significantly, which is interpreted as a change in the vortex origin, size, strength and trajectory.

In view of the strong claims for offset flapping and drag hinges made by Mr. Payne in his Technical Note (September 1955) I would like to make the following comments.

Many of his conclusions depend on the assertion that there is a steady inertia force on the rotor hub when the rotor tilts. This force is simply the reaction on the hub due to the sideways thrust component and should not be included with the external forces on the helicopter.

This paper attempts a view of the development of civil aviation in a rather broad and fundamental way, deliberately avoiding any detailed discussion of the many technical aspects of this large and complex industry.

Anyone who is associated in any way with the design and production of aircraft and with the administration and operation of airlines and airports will be only too well aware of the immensity of the technological and organisational effort involved. And looking back over the past 50 years, the development of civil aviation into a major world industry can be viewed, rightly, as a major technological achievement. However, any technological development and the successful evolution of any transport system or industry must be initiated and sustained by some form of social demand. Frequently the demand is difficult or impossible to identify, indeed the idea of a demand may be less useful than the idea of a welcoming response to supply: technical advance frequentiy seems to generate a new market rather than to satisfy an existing one. Nevertheless aviation has during its development passed through a number of phases and been subject to shifts of objective, sometimes gradual, sometimes very rapid, reflecting changes in the response of individuals, companies, nations, and now perhaps even of the world community at large. These changes in demand may be expressed as changes in priorities and we have tried, in Fig. 1, to give some indication of how the balance of demand appears to have shifted as aviation (in this case, both civil and military aviation) jhas progressed from its early status as a sporting pastime to its present position as a world-wide transport system.

It is indeed a privilege to be asked to deliver this, the Second Lecture inaugurated by the Royal Aeronautical Society as “ The British Commonwealth and Empire Lecture.” I feel particularly gratified at being asked to follow in the wake of so distinguished a pioneer in Commonwealth Civil Aviation as Mr. Hudson Fysh, who delivered the Lecture last year. I am, however, at the same time distressed by the sequence, because after reading the outline of experience and achievement which was presented in such graphic form by Mr. Hudson Fysh, I realise acutely that I cannot offer you anything comparable. There can be from myself no first-hand account of pioneering or achievement, neither am I a competent spokesman for any of the organisations which have played so great a part in building up the British contribution to world aviation.

The internal motjon of a fluid assumes one or other of two distinct forms; either the elements follow one another in a direct and simple manner, or else they wander about in erratic paths as they progress downstream. In the first kind of motion, called “ regular ” or “ streamline,” the components of the velocity at any selected point are either constant, or vary in a definite manner directly related to the boundary motions. In the second, known as “ turbulent,” these components continually change in an irregular way, which cannot apparently be connected with the regular boundary motions.

In previous notes approximate values of the elastic critical loads of continuous and composite struts were obtained. In the case of continuous struts a semi-graphical technique was employed, while for composite struts values were derived from approximate solutions of the transcendental equations governing the behaviour of the struts. In the present note, the approximate elastic critical loads of coupled struts are investigated by a third method, using approximate expressions for the stiffness and carry-over factors entering into the equations expressing the critical conditions of the struts.