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Aviation History
1946
1946 - 2228.PDF
"SPEARHEAD" AIRLINER Futurist Transport with Four Turbines Driving Contra'rotating Pusher Airscrews INDICATIONS are not lacking that aircraft with s\*pt-back wings will be afeature of design as speeds approach the supersonic barrier. Straws showwhich way the wind is blowing. Already a number of futurist designs of small single-seat aircraft have been evolved, and examples have been flown successfully in this country, in Germany and in America. German technicians early recognized the importance of swept-back (or swept-forward) wings to delay and reduce compressibility effects, and were carrying out a comprehensive pro- gramme of wind-tunnel experiments. In some cases the smaller aircraft with pronounced sweep-back have been announced as forerunners or prototypes of larger craft in view. An impression of a " tailless " design of air liner of 120 to 150ft span with large sweep-back to the wings and propelled by four gas-turbine units, each of some 3,000 h.p., submerged in the wings, is the subject of the accompanying drawing. Air is induced via the span-wise slots arranged at the point of maximum thick- ness of the wing to effect control of the boundary layer. The conception is offered in response to the requests of many readers who have invited drawings of possible types of large-scale liners of the future and embodies features now being actively examined and studied by aircraft project engineers. The possible future types of aircraft are of great interest to flying enthusiasts. The adoption of swept-back wings on a project not intended for sonic—or even near-sonic—speeds may cause some surprise.. It has already been ex- plained, however, that shock waves may be formed on structures travelling at less than the speed of sound, provided the local speed on some part of the body exceeds that of sound. In Germany a number of designs existed of swept- back and swept-forward wing aircraft which had an ultimate speed of some 500 to 550 m.p.h. Teutonic engineers had proved that very great advances in critical Mach number are possible for wings having large degrees of sweep-back. On the other hand, low-speed problems become difficult with an aircraft having wings with an angle of sweep-back of the order of 65 deg or 70 deg, nor are the constructional problems involved in the wing attachment easy of solution^^ Nevertheless, in the absence of practical designs, and as a foretaste m<Sht shape of transport aircraft to come, the projected design is proffered for study and comment. Pending the perfection of large pressurized cabins of proved reliability (and that in itself is a bigger problem than is generally realized) the operational range and altitude of commercial aircraft will, almost certainly, be snorter and lower than recent prognostications would suggest. For that reason the turbine-airscrew combination is expected to enjoy a useful life during an intermediate period, which will eventually lead to pure jet propulsion and the flying wing. In the suggested design illustrated (the drawing was executed by H. Redmill from rough sketches prepared by Flight) which, it will be observed, has contra- rotating pusher-type airscrews to each turbine, the sweep-back is of the order of 45 degrees. The effectiveness of ailerons and flaps decreases rapidly with increased sweep- back, and directional stability being affected, considerably more fin area is necessary than in the case of a straight-wing design. G. S.
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