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Aviation History
1926
1926 - 0686.PDF
to encourage, as far as possible, structural as well as aerodynamic efficiency, which this basis definitely does do. Unfortunately, as has been pointed out in these columns repeatedly, extreme efficiency and cost of production are antagonistic one to the other, and the more refined a structure the more expensive it is. Thus in the end we are brought back to the subject of cost, which is, in our view at least, the factor that will mainly govern the future of popular flying. To us it appears that logically the next step must be a competition in which the rules are designed with the subject of cost as a primary consideration, and that either it must be an engine competition in which competing engines will be required to develop a certain specified power at certain specified propeller speeds (so as not to preclude the geared engine), or a competition for machines in which cost is the first consideration, but which have to attain a specified performance. As we enlarged considerably upon this subject last week, we may leave it at that. Lest it should be thought that we consider this year's competition entirely wasted, we would point out that this is by no means the case. To our way of thinking, it can justly be claimed that, if the competition has done nothing else, it has at least produced one remarkable aeroplane and one very promising engine. The Avro " Avian," with a ratio of total loaded weight to empty weight of 2-3, must be said to mark a very distinct forward step, the more so as the machine combines with this extra- ordinary ratio a very high top speed, pointing to clean aerodynamic design. Thus in the Grosvenor Cup race the " Avian " averaged, we believe, 97-5 m.p.h., carrying its full competition load. It is probable that actually the machine was faster with this load than it would have been with a smaller load. Certainly it would be likely to be more comfortable to fly, since with a lighter load it would have had to fly at a smaller angle of incidence—in other words, would have had to be " held down " a 1 the time. As, for practical purposes, the machine will not be required to carry a useful load of 828 lbs., it would seem that the next step in the conversion of what is admittedly a competition design into a practical aeroplane will be the fitting of slightly smaller wings, when the machine should do at least 105 m.p.h. with a useful load, including pilot, passenger and luggage, of somewhere in the neighbourhood of 400 to 500 lbs. This figure would also allow for strengthening up certain parts which prolonged experience might show to be on the light side for a machine intended for fairly rough usage, as distinct from competition work in the hands of a highly skilled pilot. Although the Armstrong-Siddeley " Genet " engine did not shine in the competition, it would be a very great mistake to suppose that the engine is not a promising one. Let us examine very briefly the facts concerning it. To begin with, the engine was pro- duced in what must be pretty well record time for a new design. It had to be kept down to a certain specified weight, and in their desire to obtain the maximum power the designers " cut it fine," and it SEPTEMBER 23, 1926 was found that dual ignition could not be fitted, as the second magneto would have brought the engine to more than the permissible weight by a few pounds only. Obviously, for practical purposes, it matters not in the least whether the engine weighs 169 lbs. or 180 lbs. In the competition, however, it did matter, and there can be little doubt that if dual ignition had been provided neither Broad nor Hinkler would have had their forced landings. The substitu- tion of a steel spindle for the duralumin spindle used for the magneto drive is a very minor matter, and will further increase the reliability of the engine. At the moment pilots report the engine to have a " rough " period at round about 1,500 r.p.m., but this, again, is a matter which can, and doubtless will, easily be put right, so that there is, in spite of the results obtained in the competition, no reason to doubt that the " Genet " will prove a very useful engine. Concerning the winning machines and engines, the Hawker " Cygnets " and the Bristol " Cherubs," the former are twro years old, and already in 1924 were realised to be extremely efficient machines, structurally as well as aerodynamically. The ratio of total loaded weight to empty weight of the Hawker " Cygnet " in the competition was approximately 2 • 1, or nearly as good as that of the " Avian," while this machine is, of course, at " the other end of the scale " in that it is very small and a light 'plane in the original sense of the term, which the " Avian " cannot be said to be. Up to the present the H. G. Hawker Engineering Company has not, as far as we know, contemplated entering the light 'plane market, but it is to be hoped that the recent success at Lympne may result in a reconsideration, and that the " Cygnet " will have successors. For the Bristol " Cherub " the competition has been an unqualified success. Not only was it the only engine to complete the competition, but, so far as we have been able to ascertain, neither of the four Cherubs " fitted in the " Brownie," the two " Cygnets " and the " Pixie," gave the slightest trouble throughout the competition. Thus it can justly be claimed that the " Cherub " is now to be regarded as an absolutely trustworthy engine, and at least, as reliable as engines of ten times its power. The position with regard to the " Cherub " is really rather pathetic. Here we have an engine which has now reached a stage of perfection that gives cause for the greatest satisfaction. And yet the trend of modern ideas on the subject of light 'planes is such that it seems almost to have become accepted a> a truism that engines of 60 to 70 h.p. are wanted. If that is really the case, it will mean that the " Cherub " is de trop. We personally hesitate to adhere uncon- ditionally to that view, and even if the 34 h.p. two- seater is not found to be the right type, surely single seaters with this power should serve a useful purpose at the clubs, etc., for further practice by those who have already obtained their " ticket," not to mention the possibility of using such low-power single-seaters in the R.A.F. as messengers, for practising and training at low cost, etc. The Bristol " Cherub " in Germany MR. EBERHARD VON CONTA, of Bambery, Germany, who is an owner of a Messerschmitt monoplane fitted with a Bristol " Cherub" Series III engine, has written tn the Bristol Aeroplane Co., Ltd., stating that he recently made an altitude flight on this machine and attained an altitude of 5,000 m. (16,400 ft.)—which includes the height of the aerodrome above sea level, 247 m. (810 ft.). As this was the limit of his recording barograph he did not attempt to fly higher. So far the " Cherub " in this machine has completed 65 hours, and the only adjustment made was the changing of one sparking plug- Within the next week or two Mr. Conta proposes to undertake a flight over the Alps, from Munich to Verona, with a passenger. 610
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