Beryllium, though of increasing application in the metallurgical and electrical industries, must still be classed as a relatively uncommon element. This would appear to be chiefly because no large scale application of the metal has yet been made; most commercial applications involve the addition of small amounts of beryllium to other metals, notably copper.

If a large scale use for beryllium were to be discovered, there would be little difficulty in the production of sufficient metal to fulfil a reasonable .demand. Its ores are widespread, but unfortunately are seldom found in heavy local concentrations. The processing of these ores is somewhat difficult on a commercial scale, but not prohibitively so. Extensive researches have been made on these problems, because of the incentive given by the exceptional “lightness” of beryllium, its high melting point and particularly, by its high modulus of elasticity.

When accepting the invitation to present the Seventh Louis Blèriot Memorial lecture, the author was deeply conscious not only of the honour which was bestowed upon him by this invitation but, in an equal measure, of the responsibility which attached to it.

For the first time one of the eminent memorial lectures is devoted to the rotating wing; the helicopter has been raised to the level of discussion of the great aeronautical papers.

The natural impulse of the gentler sex when faced with a great occasion is invariably: “how shall one dress?” To the author, a somewhat similar problem became manifest: how can the helicopter, this new-comer, best be “ dressed?” How should it be presented, so as to make not only a good impression but also a full and, above all, a true impression?

From time to time w.e hear of mysterious engine failures, sometimes resulting in forced landings, in which the engine is reported to have gradually lost power until it was ticking over or had cut out completely. This may have been accompanied by sticking of the throttle, so that the pilot was unable to control his engine, and by rough running. Full power is usually recovered at lower altitudes or after landing, and when the engine is run up no defects can be discovered. At certain times of the year similar symptoms have been observed in the case of engines running on the test bed.

Experience has shown how dependent is the airship upon weather conditions —more particularly for a safe ascent and descent. The numerous experiments with windscreens, tractors, mooring posts and landing gear emphasise the difficulty of handling an airship on the ground and of manoeuvring it in and out of its shed.

It is in the endeavour to minimise these risks that this study has been undertaken. In the discussion as to the most advisable course for an airship to adopt for its own safety when surprised by unfavourable weather, it should be remembered that in all the examples which follow, it is a case of “making the best of a bad job”; and that no pilot would wittingly leave his base with the knowledge of such bad weather impending except under pressure of war time necessity. It is hoped to demonstrate that in some cases it might be possible by skilful navigation, aided by the frequent communication of isobaric charts by wireless telegraphy and by accurate positions given frequently by the same means, for a pilot to keep in the air during the passage of bad weather and thus avoid the risk of wreck by attempting a premature landing.

In the recent paper by Warren a summary was made of current data on two-dimensional bow shock wave detachment distances. It was shown that the experimental results of Griffith and Alperin, as well as the detachment distances computed by Vincenti and Wagoner, could be collapsed into a single curve by using Spreiter's Transonic Similarity Parameter. This has been confirmed by the present authors who have found that the experimental results for wedges obtained by Bryson also correlate favourably with the curve given by Warren (Fig. 3 of Ref. 4).

The results of the foregoing workers have been for steady flow conditions. However, it has been noted by Lilley et alia that a steady shock wave pattern can be established in free flight only after steady motion has been maintained for a considerable (infinite) time. In general, the locus of detached bow shock waves depends on the time history of the motion whenever a body is accelerated from subsonic speed.

Throughout the animal kingdom powered flight is a surprisingly common attribute and whenever it occurs both the sustenation and the propulsion are provided by the same structural and aerodynamic mechanism. There is, in fact, but a single aerodynamic reaction which is divided, for convenience, into thrust and lift. In earlier times this convention was presumably not recognised, for the ornithopter appears to have formed for some centuries the principal technical basis of man's aspiration to heavier-than-air flight. Of the exceptions, Leonardo da Vinci's helicopter is now, of course, an accepted vehicle, but this lecture is concerned mainly with fixed-wing aircraft for which it is significant that success came only with the aeroplane, or, as Lachmann has recently put it, with the powered glider.

I wish to support S. W. Greenwood's plea (December 1953 Journal) for defining “specific impulse” as Thrust/Mass flow of propellants.

Apparently some engineers are now using Thrust/weight flow of propellants as the definition of specific impulse, but it would appear that this innovation is merely due to inability to distinguish between mass and weight. The system used at the Royal Naval College, Greenwich, of using the capital letter to denote weight or force (e.g. Lb.) and the lower case to represent mass (e.g. lb.) is a very convenient way of distinguishing between the two.

A general approach and tentative solution has been indicated to the problem of estimating wing skin thickness from preliminary design data. The solution is presented in a form that permits calculations to be made quickly and with a minimum of effort.

In deriving the empirical formula relating perimeter and area of the aerofoil section, only symmetrical sections were considered. The amount of camber normally employed, however, should not alter the results appreciably.

While the problem has been dealt with only partially and as yet only tentative empirical coefficients have been suggested, it is hoped that the author’s considerations of the problem will be of some interest and use at this stage.