Many types of detonation may be distinguished, and the causes are to be found in the engines as well as in the fuels. Obviously one single cause would not be expected to be found, but, on the contrary, quite a number of properties which will be more or less of influence under different engine conditions. These may differ widely, yet there is more unity in the multitude of causes of detonation than might be expected, and this the authors will endeavour to illustrate. They must apologise for mentioning many well-known, in addition to new, views, but it is necessary to do this for the general exposition of the material.

Two principal types of engines should be considered to-day :–

1. (1) That in which the fuel is added to the air at the end of compression (in air compressing or Diesel engines), and

2. (2) That in which the fuel is added to the air before compression (mixture compressing, e.g., petrol engines).

Most methods of increasing the output of petrol engines seem to attract the “ demon of knocking ” ; the reverse is true for Diesel engines, which is hopeful for their future development.

1. (1) Survey of the present methods of carrying out air transport service when visibility is bad.

2. (2) What is essentially required of technical aids for landing under bad weather conditions.

3. (3) Short survey of current German methods for solving the problem of landing in fog.

The necessity for being able to carry out air transport unhindered by weather conditions is inseparably associated with the idea of commercial air service. This great problem of “ flight in any weather ” has confronted us since the inception of regular services between places having corresponding traffic needs, that is to say, since the very birth of air transport.

No one denies that speed is an essential to air travel. It seemed curious to me that air liners were operating at speeds varying from 100 to 150 miles an hour, and some months ago I set out to find a logical basis for determining the most economical speed of flight. I did not expect to arrive at an exact solution; but, rather to my surprise, I satisfied myself that I could give a general answer to most of the problems that interested me. I ventured to submit my calculations in a short memorandum to the Aeronautical Research Committee, and I had the privilege of meeting a sub-committee with whom I discussed my ideas. It was suggested that some further calculations on the same lines would be of interest, and it was proposed by Mr. Tizard, the Chairman of the main committee, that I should send a communication on the subject to the Aeronautical Society. The paper that I am reading to-night is the result of this suggestion.

The Townend Ring has been the subject of a large amount of experimental research and its general characteristics are now well understood. The following paper is the first theoretical treatment of the ring which has appeared. It was originally presented as a thesis to the University of Delft by Capt. G. Otten and published in Holland in November, 1932. The author has made the following abbreviated translation of it into English in collaboration with Dr. H. C. H. Townend, who also suggested a few modifications.

This paper is an endeavour to present, to the members of this Society and others, as complete information as possible on the subject of a much discussed anti-knock material and to try and dispel any misconceptions which some may still have regarding the use and behaviour of ethyl.

The development of the modern aviation engine has made rapid strides during the last two or three years. The very rapidity of this development, however, has brought an exceedingly important fact home to the engine manufacturers; this is, the influence of the fuel in governing engine performance and reliability.

In the earliest stages of the development of the aeroplane the speed range obtainable was small, flight occurred only at fairly high lift coefficients, and induced drag was the predominant component of total resistance, hence successful flight depended on the achievement rather of minimum weight, minimum wing loading and maximum engine power than on the achievement of minimum possible parasite resistance.

The subject defined by the title of this paper is one which cannot be covered completely in the time at my disposal. I propose therefore to confine my remarks to-night almost entirely to the aerodynamic aspects of the problem and to put before you some possible advantages that may be gained by substituting a variable pitch airscrew for the normal fixed pitch airscrew, and in certain cases to compare the results with those given by the introduction of a variable gear airscrew. The mechanical side of the problem is a subject complete in itself and will not be dealt with here.

To deal effectively in the course of a single lecture with the subject of light alloys for aircraft is, to-day, practically an impossibility. Actually, the various alloys of aluminium that are put forward for consideration by the aeronautical engineer do not vary amongst themselves to such an enormous extent as to make one or other of over-riding interest, and much the same might be said of the alloys of magnesium. Despite this position, so much of interest is occurring in both fields, and so many alloys are being put forward having some characteristic or another of real interest, that the aircraft engineer, and in fact any other engineer, could readily be excused if he felt somewhat nonplussed when he surveyed the multitude of materials that are offered for his employment. I am relieved, therefore, that your Council decided that this lecture should give special prominence to the alloys of magnesium. I am assuming that by this they mean those alloys which consist of magnesium in a great preponderating proportion, but I feel that the time is appropriate also to make some reference to those alloys which consist principally of aluminium, but which possess definitely useful properties in consequence of the presence in them of certain relatively small proportions of magnesium. I propose, however, first to consider the alloys rich in magnesium, and will endeavour to provide some data of a rather fundamental type which may be of definite service to the aeronautical engineer when he is engaged in comparing the relative importance and value of the magnesium alloys made available to him in commerce.

The title chosen for this paper is a somewhat ambitious one, as prophecies in any sphere of engineering are always dangerous. Especially is this so in such a young and progressive branch as aeronautics, where changes are rapid, and developments considered modern and up-to-date to-day, may, in a few years, be thrown aside as being obsolete. However, when I received the honour of an invitation to read a paper before the Royal Aeronautical Society, I chose this title with “malice aforethought,” if only with the idea of inviting criticism and discussion.

In this paper I propose not only to comment on the lessons learned in the flight over Everest and Kangchenjunga, but also to indicate approximately what is involved in the initiation and organisation of such an expedition. It can only be on the rarest of occasions that a scheme emerges full-fledged from the nests of the mind and this expedition was no exception.

The subject of tail buffeting first came into prominence in this country early in 1931 when the Accidents Investigation Sub-Committee of the Aeronautical Research Committee issued their report on the accident to a Junkers monoplane at Meopham, Kent. The Sub-Committee gave it as their opinion that tail buffeting was the probable primary cause of this accident, and recommended that the phenomenon should be investigated. At this time tail buffeting (Leitwerkschutteln) was quite well known in Germany, where the low-wing monoplane, which is peculiarly susceptible to this trouble, was a popular type of aircraft; and some full-scale experiments on the subject had already been made by the Deutsche Versuchsanstalt fiir Luftfahrt. The findings of the Accidents Investigation Sub-Committee caused an intensive study of buffeting to be undertaken both in Germany and in this country, and the enquiry was also taken up in the United States at a later date. As a result of these studies tail buffeting is now quite well understood, and methods for its avoidance have been established.

Major Green in his paper has given prominence to a subject which is now becoming of wide interest and great commercial importance. A method of assessing the economic value of speed is very desirable and Major Green has attempted to do this by means of an index figure.

I would like to put forward a method which, whilst it does not provide a datum or index figure, offers a ready method of comparing two or more machines, taking into account those features of the aircraft which are of economic importance. It must be accepted that the geographical and political features of different routes, time-tables, and other such extra-to-aircraft items could be included in any method of comparison without the use of an empiric formula, the relative importance of whose terms would be largely a matter of opinion. Further, this method is based not on subsidy earning but profit earning capacity.

The petrol engine has become so firmly established as the motive power for aircraft, automobiles and small vessels that a short while ago it would have seemed almost impossible that its supremacy could be challenged. It is no exaggeration to say that it was the petrol engine which made aircraft possible, while on the road, despite the fact that the steam engine is fundamentally more suited for traction work, the petrol engine has practically ousted its rival from the field. Even for the heaviest vehicle, where, owing to cheap coal, the lower running cost at one time gave the steam vehicle an advantage, the petrol engine is nearly universal, while at sea, for launches and small craft, the steam engine has practically disappeared.

The chemist regards magnesium as a highly reactive metal for such reasons as the inflammability of its powder or foil in air, its active displacement of hydrogen gas from many aqueous chloride solutions and its position near the reactive end of the electrode-potential series. All these suggest that the metal would be unsuitable for constructional engineering. Yet engineers use alloys, rich in magnesium, up to 98 per cent. of the metal, for an increasing number of services, although the alloying elements do not, as a rule, greatly cut down, and may even increase, the corrosion rate. Their industrial use is possible because the liability to corrode, reckoned over a reasonably prolonged period, is not a definite property of a metal such as conductivity which is subject only to relatively small changes with alteration of environment, but is highly specific to metal-liquid and metal-gas systems. Moreover, these systems may undergo important changes with time owing to the intervention of films of corrosion products, and the rate of attack may be governed by the physical characteristics of these films which will vary with the adjacent liquid and gases. Thus in stagnant caustic alkalies magnesium may be reckoned as almost incorrodible because of the intervention of a film of hydroxide of the self-healing type which, in these conditions, is highly impervious to magnesium ions; but in the presence of alkali chlorides the corrosion product is physically different and rapid corrosion occurs. Many dilute acids attack magnesium rapidly but hydrofluoric acid scarcely at all, no doubt owing to the formation of a protective film of fluoride.

This paper presents the results of co-ordinated research by The Pratt and Whitney Aircraft Co. (engines), the Chance Vought Corp. (airplanes), and the U.A.T. Research Division, all subsidiaries of the United Aircraft and Transport Corp. These studies were directed toward improving the performance of airplanes through reducing the drag of radial air-cooled powerplant installations as nearly as possible to the minimum necessary for adequate cooling.

It is possible to trace, in the flying equipment of birds, feathered versions of many of the refinements that render the modern aeroplane more efficient than its predecessors. It would, therefore, be a mistake to ignore birds as a guide to possible future developments. One of the most interesting groups of birds is that which includes all the owls, for there is a possible connection between the manner in which their strikingly silent flight is achieved and the increasingly pressing problem of silencing airscrews.