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Aviation History
1938
1938 - 1152.PDF
398 FLIGHT. APRIL 28, 1938. in spark-ignition engines, using the high-octane fuels, have caused the diesel to lag behind on account of its greatei specific weight. For long-range machines, however, it does seem that the future has a part for the diesel engine to play, and the development of a suitable power unit should be of national concern. Present indications seem to be that commercial air- craft will fall into four categories: (a) A small twin-engine machine of 10,000 lb. all-up weight. (b) Medium-size airliners of 25,000 1b. employing two 01 tour engines. (c) The "mainliner" of 55,000 to 65,000 lb. using.four engines. (d) A transatlantic airliner which may take the form of a flying boat or landplane of 100,000 to 150,000 lb. with six engines or more. In the first three categories there will naturally be variants to meet big-load short-haul purposes and long- haul medium-load purposes. With the bigger craft the tendency will be to place more and more of the equipment, fuel and load into the wing structure, thereby reducing wing-bending moments, and so avoiding the cube-square law, which militates against big aircraft schemes. ; The catapult and arrester gears which, until now, have generally received only military support, apart from the German exceptions, are likely to be considered more seriously in the future, together with the alternative methods of the Mayo Composite and refuelling in the air. From figures published, it is shown that the distance required to clear a 50ft. obstacle by an aircraft having a wing loading of 35 lb. and a power loading of io£ lb. /h.p. is slightly over 2,200ft. if a constant-speed airscrew is used. By using flaps and a horizontal accelerating force of ^ G the distance could be reduced to 1,200ft. A rela- tively simple scheme for producing this acceleration, of American origin, is to build up momentum in a fairly heavy flywheel driven by a suitable motor. This stored- up energy is then utilised for providing the necessary accelerating force. The same aircraft on landing would require, with flaps down, a landing run of approximately 2,000ft. from a height of 50ft. The adoption of a suitable arrester gear would make such wing loadings more practicable for com- mercial airliners. The commercial aeroplane of the Mr. H. P. Folland i;ear future will, without much doubt, have a three-wheel under- carriage. The ob- vious advantages of this scheme, name- ly, ease of ap- proach, improved view for the pilot on landing, and safety from ground looping and ill- effects of c r os s winds, all make the slight increase in tare weight well worth while. From investigations made of layouts em- bodying the tricycle undercarriage, and high, -mid and low positions for the wings, it seems likely that the modern airliner will be of the mid-wing variety. The low wing n-a:s held the field until now, but there are certain advantages, particularly aerodynamic, which the mid-wing can claim. Whilst the high-wing undoubtedly holds out attractions from an aerodynamic standpoint, the loss of payload and the increased risks of mechanical trouble likely to arise in the retraction of the undercarriage make the scheme as a whole far less attractive than the mid-wing layout. There is no doubt that at some future date a form of flying wing will come into its own, in which the whole of the passengers will be housed,' with the necessary amount of room for promenading. The fuselage, if found neces- ary, would be utilised for luggage, mails, engineers, crew, etc. New materials will find their application, and chief amongst the materials of the future will be the. plastics in their many and varied forms. Shot welding and machine riveting will play an important part in the fabrication of the modern airliner. • With regard to the developments for additional safety, the =diesel"engine "will increase the payload over long range, reduce the running cost and minimise the fire risk. High Loadings —And Assisted Take-offs, says Mr. Arthur Davenport, F.R.AcS., of Wesflands 1 THINK the commercial aircraft of the near future will A develop along different lines to suit various require- ments. For instance, goods and passenger transport must require aircraft entirely different from those necessary for private flying or training; and 1 think for the former we shall see the catapult type of assisted take-off exploited more and more, with extreme accelerations for the goods aircraft and a moderate acceleration for the passenger* types. High loadings incorporating high-lift devices will prob- ably be developed more and more and we may suddenly find ourselves obtaining marvellous results from boundary- layer control or the like. The large flying boat I consider to have an immense future, with its ability to fly from port to port. A Detailed Review By Mr. A. Hessell Tiltman, B.Sc, F.R.Ae.S., of Airspeed 1 CONSIDER that the development of flaps in the lastfew years has to some very large extent revolutioniseddesign. They have permitted higher wing loadings to be used, thus making aircraft very much more prac- ticable. For the same all-up weight the machine is con- siderably smaller and more robust. Heavier scantlings and skin thicknesses are employed, which make the air- frame much more of an engineering job. One of the most important aspects of future design is the question of safety. Development has been concerned too much with performance rather than with eliminating a number of the hazards which unfortunately are still with; us. The fire risk alone is, I consider, much too big a one, and a lot of thought should be given to this question. Landing speeds, which have gone up in sympathy with wing loading, are inclined to be rather on the high side. There seems to be no doubt that the multi-engined machine has come to stay and that the four-engined machine represents a definite improvement. I think fha in the immediate future advantage will be taken, when four engines are installed, of using the Goodman-Croucn- Bolas effect. It may be possible in this way to »lcreaS* the loading still further, but the hazards mentioned above must be carefully watched. (This is a slipstream effect, oD- tained by tilting the airscrew shaft and "bowing air across the wino.—Ed.)
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