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Aviation History
1932
1932 - 1024.PDF
FLIGHT, OCTOBER 13, 1932 Gloster " Gannet " biplane, the Parnall " Pixie," the Vicker's " Viget " and several others. From a competition point of view, the " Wren " and the '' Anec'' were the most successful types, tying for the first prize for low fuel consumption. Both did the rather amazing mileage of 87-5 miles per gallon of petrol. The " Anec " also got first prize for ceiling, with 14,400 ft. to its credit, while the Avro monoplane completed 80 laps of the 12-5 miles circuit, or a total of 1,000 miles during the week. It will, we think, be agreed that these were extra ordinary performances. Yet the only machine which was used really extensively later was the little D.H. 53, which did nothing much in the competition but which afterwards, when fitted with the Bristol Cherub engine, did quite a lot of useful flying. If one asks oneself why those little machines never " caught on," the answer can be expressed in one word: " Engines." It was not, in our opinion, the small power of the engines (the " Wren " had but 10 b.h.p. maximum at its disposal) which proved the obstacle. Nor was it altogether the qualities of the aeroplanes, which on the whole were very effi cient, and although light were not as flimsy as might be expected. But the engines exhibited a uniformly high standard of unreliability! Speeds of nearly 60 m.p.h. were recorded for several machines, and the little " Pixie," with small wings, even put up 76 m.p.h. The " Wren," in spite of its 10 h.p., did more than 50 m.p.h. There is little doubt that, had the engines been reliable, the machines would have been the forerunners of cheap aerial runabouts. The one objection that could be raised, apart from engine unreliability, was that all machines were neces sarily (in view of the low engine powers) single- seaters. In the following year another competition was held at Lympne. This time competing aircraft had to be of the two-seater type, and the engine capacity was limited to 1,100 c.c. Again quite a large number of types was produced, but none which survived as a quantity-production model. The two-seaters were, on the whole, better aircraft than had been the single-seaters of the previous year, but engine un reliability was again rampant. In fact, the younger generation, private-ownerly speaking, who has ex perience of the modern light-plane engine only, with its wonderful reliability, can hardly be expected to realise how thoroughly unreliable an engine can be. The sum total was that, as we have said, none of the types went into quantity production afterwards. What happened, and it may be of interest to recall a fact which in these days is likely to be overlooked, was that the Air Ministry decided to subsidise a number of flying clubs, provided these used light aeroplanes. The view was generally held that an engine capacity of 1,100 c.c. was insufficient, and that the unreliability of the Lympne engines in the 1924 competition was due to running the engines too hard. In the meantime, the A.D.C. company had produced the Cirrus engine of 4,500 c.c., while concurrently the De Havilland Aircraft Co. had produced the Moth. The rest of the history of the " light " aeroplane as we know it to-day will be familiar to all our readers. At the present time there is an obvious tendency towards reverting to light machines fitted with engines of lower power than those to which we have now become accustomed. This is so not only in this country but also in Germany. When it is remem bered that, for years after we abandoned the 1,100-c.c. ideal, German designers continued to turn out machines of approximately that class (only in the end to abandon it and make a desperate effort to catch up with Great Britain in the race towards first 100, then 120, and finally 150 or so h.p.), the return to the earlier modest ideal is rather interesting. What the upshot will be no man may say. That we shall ever go back to the 400-, 600- or 750-c.c. engines of the 1923 light aeroplanes seems unlikely. That we shall see single-seaters with engines develop ing some 30 h.p. and two-seaters with 40-50 h.p. engines, seems likely. But before that can come about, engines of around these powers, and of as good reliability as our present larger engines, are the first consideration. In other words, it is up to the engine designers. The Air Ministry can help greatly. It can even help enormously by not placing quite so many obstacles in the way of early development. There is no terrible crime in letting an enthusiastic experimenter go into the air over an aerodrome with an engine which is unblessed by Farnborough. Air craft design has progressed somewhat since 1923. What is wanted is an engine of approximately the power we have outlined, but it must be smooth and it must be reliable. An engine which is ever on the point of shaking itself out of the machine is no manner of use. Nor is one which stops every two or three hours. The second direction in which history is promising to repeat itself is in the matter of '' pusher '' arrange ments of the engine. Some of the earliest machines were of the " pusher " type. The Wrights in America, the Voisins and Farmans in France and the Howard Wrights and Bristols in England. Then A. V. Roe introduced the tractor in England, Bleriot in France, and soon the poor old " pusher " dis appeared. If one looks for the reason it is to be found mainly in the high drag of the open tail-girder systems used, in the high " stilty " undercarriage which the low placing of the old pusher engines required, and possibly to a slight extent to the diffi culty of cooling air-cooled engines of other than the rotary type. The net result was a marked inferiority in performance for a given engine power. With modern methods of construction and modern knowledge of aerodynamics, it should not be impos sible to overcome most, if not all, of these drawbacks. The " pusher " should be capable of coming some where near the ubiquitous tractor in aerodynamic efficiency. But, the tractor advocates will say, why do we want " pushers " ? There are several advantages in this arrangement. Far and away the most important is that of view. No matter how carefully designed, the tractor aeroplane, even with the inverted engine, gives a very considerable ' blind " cone. The pusher, on the other hand, gives to all intents and purposes unobstructed vision in the most important directions. A second advantage of the engine-behind arrange ment is that the occupants are out of the pulsating slipstream. Effective windscreens can be made to give in an open machine as good protection from draught as gives the cabin of an enclosed tractor aeroplane. Oil and exhaust fumes from the engine do not reach the occupants, so that the " pusher " is cleaner altogether. And, finally, the noise from an engine behind seems to be much less than from an engine in front. It may be a little difficult to pro duce theoretical reason for this, but it seems to be the unanimous opinion of all who have flown, in " pushers." So let the good work proceed.
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