1. (a)Introductory.—The paper deals with experiments carried out in the engineering laboratories of the University of Manchester on a Crossley solid-injection oil engine in which small quantities of hydrogen or coal gas were introduced along with the air supply to the engine.

2. (b)Range of Investigation.—Three series of trials were run with hydrogen, each at a different load, namely, 53·4, 39·4, and; 24·4 b.h.p. The maximum amount of hydrogen used was slightly more than 3 per cent. by volume of the air supply, corresponding, at the lightest load, to some 14 per cent, by weight of the oil fuel supply.

   Three corresponding series of trials were run using coal gas in place of hydrogen, the maximum volume of gas employed being 5 per cent. of the air supply. At the lightest load this corresponds to approximately 2·4 times the weight of fuel oil used.

3. (c)Conclusions.—Such quantities of hydrogen or coal gas can be used satisfactorily in the type of engine considered. No trouble was experienced due to pre-ignition or other causes, and the engine appeared to run more sweetly when gas was being used.

   When running at constant load and speed, the admission of small quantities of gas appears to cause combustion to take place at a slower rate, giving a lower maximum pressure and more burning down the expansion stroke. The thermal efficiency is in consequence slightly reduced, while the heat-losses to exhaust are increased.

In introducing the subject of valve steels to this Society I do so, not because of any special knowledge which I possess, but on account of the general interest which is being taken in the subject at the present time. It is quite evident that the valve steels which have been regularly used are not satisfactorily meeting all the present conditions, and therefore advances will have to be made, especially as much greater engine efficiencies are being demanded. Presumably the valve has to withstand much severer conditions than formerly. In many cases the result, as far as the valve is concerned, means a higher working temperature, which in turn affects many other properties of the steel such as scaling, the tendency to air-harden, etc.

In endeavouring to present a paper on the relative problems of supercharging aircraft and motor-car power units, the author wishes to convey at the outset that no attempt is being made to give a scientific investigation of air compression, but rather to review the present stage of supercharger development, the difficulties which have to be met by the engine designer in applying such a device to a high-speed petrol engine, and with the hope of stimulating from this review a discussion on the possible advantages to be obtained thereby.

For the purpose of this paper, supercharging an internal combustion engine may be defined as :–The filling of the cylinder during each cycle by mechanical means in the form of a pump, with a greater amount of charge than would be possible with natural aspiration.

Valuable lives and thousands of pounds worth of equipment are lost in collisions each year.

The graphs of civil aviation traffic show that an accident in May of 1922 was followed in June by a drop in the average monthly passenger traffic of 325 passengers. A more serious accident in May, 1923, was followed by a drop in traffic during May and June of 750 passengers.

There is thus every incentive to minimise the risk of collision as far as possible, if only from an economical standpoint, as apart from the humanitarian.

Under the existing regulations there is danger of collision not only from all points of the compass in a horizontal plane—and, even at sea, with rules based on a thousand years’ experience, collisions are all too frequent—but from every conceivable direction of which the pilot is the unfortunate centre.

Rule of the Air No. 29 is perhaps the best exposition of the present state of affairs in air navigation.

In addressing you, I wish to express, first of all, my sincerest thanks for the honour you have bestowed upon me to speak before the Royal Aeronautical Society of London about the “ Development of the Commercial Air Traffic in Germany.” It is with great pleasure I take the opportunity of giving you information about our ideas and intentions, and I hope that my explanations will assist in improving the understanding of our mutual needs in the service of the world's commercial air traffic. The Chairman of the Royal Aeronautical Society sent me a number of particular questions, and my speech, for this reason, goes in some instances very much into details which otherwise I would not have mentioned.

If I now ask you for your attention to tell you something about the air traffic in Germany, I may mention that I have been with the management of German air traffic companies since 1919.

Major Carter has dealt with this question in his paper. He has originated a method and invented an expression. With his “resonance factor” as weapon he has started a crusade against the enemy and sees prospects of converting him into a friend.

The first point to consider is whether the design should take the form of a monoplane or a biplane. For a reasonably low wing loading and high aspect ratio one immediately finds that the structural weight of the wings alone comes-out rather heavy for a monoplane. If to this be added the necessarily relatively high structure weight of the hull and floats, one is led to the conclusion that to keep the weight down so that the machine may come under the term “ light,” a biplane seems preferable to a monoplane. There is also the point that it is desirable to keep the ailerons well clear of the water. This is easily arranged in the case of a biplane by having the ailerons on the top wing only.

One next considers whether it would be preferable to have a twin-float seaplane or a flying boat design. The flying boat can be moored out in all weathers short of a gale. This is a great advantage from the ordinary user's point of view. The twin-float seaplane does not possess, in one's opinion, this advantage to the same degree.

Since the vaiious nations definitely set out upon the course of aeronautical armaments, the problem of the organisation of this new service has arisen, and appears to present serious difficulties if it should be necessary to effect periodical changes and modifications or at least substitutions in personnel.

This uncertainty is due partly to the fact that quite new questions are being dealt with; partly to the erroneous process of enforcing upon the new fighting service the rules of the older ones—the army and navy; and in a larger measure to the practical difficulties which have to be faced at every turn in passing from the theoretical field to the actual.

In the following pages an attempt is made to present the chief problems which arise in the aeronautical field, so as to form an idea for their solution, adducing opinions frequently diverse and antagonistic which the experts maintain in their respective arguments.

It is with considerable diffidence that I find myself about to address you to-night upon the subject of the Paper, which is “The Training of Aircraft Apprentices.” I say with considerable diffidence, firstly; because I realise how very important to the future of aeronautical practice is this question of the preliminary training of mechanics, and secondly, because my own practical experience of this subject is limited to a few years.

I hope that some of those who will take part in the discussion, after the reading of the Paper, will correct any mis-statements I may make in connection with civilian apprentices and will be able to put before you such problems as, are peculiar to that side.

In the tragedy of R38 it is the structural failure which happens to have attracted most attention. The tragic consequences which resulted from the structural failure were fatal almost solely because of fire.

The nature and causes of the structural failure are now well known, and in the science and art of hull design sufficient progress has been made to render future structural failure as improbable in an airship as in a ship at sea. It is fitting, therefore, that a large proportion of the essays submitted for the R38 Prize should describe work which has been done to eliminate the initial cause of failure.

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.

One of the latest branches of scientific research in which aircraft have been employed is that of polar survey and exploration. It is well known how much time can be saved, and how much labour avoided by using aircraft for surveying large areas of difficult country. There is probably no part of the world more difficult of access than the regions surrounding the two Poles, and there is certainly no part of the earth where exploration and survey is harder to carry out.