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Aviation History
1955
1955 - 1658.PDF
18 November 1955 779 The Italian Bossi-Bonomi, designed for the German contest tor man-powered aircraft. Neither it nor the Haessler - Villinger achieved sustained flight by manpower alone. if in training. If suction was assumed to require 0.1 h.p. the propulsive efficiency could be as low as 60 per cent. What might such a two-seater look like? The illustration (right) showed what might be done if Dr. Raspet were in league with Mr. Haessler and Mr. Villinger. The propeller was not only to drive the aircraft, but through its hollow blades it was to pump out air from the wings to provide the laminar boundary-layer. Launching would bt by towing or catapult. The third problem was that of the means of propulsion, which had had far too little attention paid to it in the past. The idea of attaching small motor-cycle engines with propellers had been carried out but with very little success because of the excessive drag of the unit. In most cases where these small engines had been applied, the aircraft itself had not been very efficient aero- dynamically or structurally. While there seemed to be no reason why even auxiliary pedal-cycle engines should not be used to drive an aircraft, the obvious thing was to use the payload, i.e., "to use the power of the man, rather than let him sit mere eating his head off or biting his nails." But if we did not want to use him, we could add an engine, which could be as small as 3 h.p. to fly one man at 50 m.p.h. There were three possibilities: jet propulsion, propeller pro- pulsion and flapping-wing propulsion. The speed of a low-powered aircraft was so slow that a jet would be highly inefficient and so the propeller, in one form or another, must be considered. In the aircraft under consideration, the aerodynamics were sensitive to disturbance and therefore it would be most unwise to use tractor airscrews, and hence the use of a pusher must be assumed. Although most inefficient, we must begin with a pedal shaft lying in the spanwise direction. The propeller inevitably had a shaft which was at right-angles to that, and at a different level and some distance from the initial drive-shaft. One could use chains, belts, gear and connecting rods, and all of these had dis- advantages. Chains and gears were heavy; belts produced high bearing loads and therefore heavy mechanisms; and connecting rods having shafts at right angles were mechanically impossible, although in practice they could be used. The flapping wing could be considered as a propeller that did not go all the way round and there was no reason to suppose that it was any more efficient than a properly designed propeller, except for its effective saving of the profile drag of the propellers. It had one virtue, however, which was shared by no other means of propulsion for, if properly designed, it need have no parasitic drag when not in use, and was therefore the obvious means of propelling an aircraft which was intended to soar part of the time, i.e., when used as an auxiliary source of power. For the man who wanted an efficient sailplane which he could handle all by himself, there existed the modern hang-type of glider such as the recent Horton X tailless design. For such an aircraft there might be a case for an auxiliary drive to extend the glide. Here was one application for the flapping wing if so designed that when not in use it had no extra drag. All or part of the wing might flap, and it was a design problem to discover in a given case Hypothetical two-seat man-powered aircraft, having 60ft span, 214 sfl ft wing area, 485 Ib gross weight, and 35 m.p.h. cruising speed. whether it was easier to flap a small pan of the wing quickly or more of it slowly. The use of auxiliary manpower in a normal sailplane was not worth much because they required so much power. A Minimoa, for instance, needed almost 3 h.p. to fly level. "In 1955," the lecturer concluded, "the development position regarding manpowered flight is like that of powered flight in 1900. A few people then knew that flight was possible but there were gaps in the knowledge such as on wing section data, on light powerplants, on control and stability. Today we can see that if we stretch our knowledge and assurance very little, manpowered flight is possible. We need not be discouraged because this is apparently only possible at very low altitudes, at low speeds and at the expense of some complication and great physical effort. If we did not have to stretch ourselves to do this, it would long since have been done." Points raised during the discussion following Mr. Shenstone's paper included the need to develop more efficient methods of obtaining thrust from muscle power; the possibility of boundary- layer suction by hollow-channel wing construction (i.e. without expending power); and the desirability of flexible wings. Such boundary-layer suction methods, the lecturer commented, indi- cated the type of improvement which could make the task of achieving manpowered flight even easier than his paper had stated. Bird-type flight using flexible wings would be an original contri- bution to knowledge whereas, in his own lecture, he had used only existing facts. Other papers presented during the L.S.A.R.A. Conference were The Use of Dynamically Similar Models for Research, by T. Kerr; The Aerodynamics of Zanonia Macrocarpa, by Prof. A. Raspet (read by Dr. Whitehead of Oxford University); Model Glide Testing, by M. Hacklinger; and Three Lecturettes: Two-speed Rubber Drive, Conditions for a Neutral-aileron Turn and The Payload Competition Problem, by R. H. W. Annenberg. The chair- man of the meeting was Mr. J. L. Nayler, M.A. BRITAIN'S AIRCRAFT—A PRONOUNCEMENT (continued from P. 776) One could not expect operators to buy so large and expensive a machine unless it was used by B.O.A.C., and the Corporation were already committed to the purchase of £85m worth of new equipment, which, Sir Miles Thomas has said, will fill their requirements into the 1960s. This momentous decision drew forth (not unnaturally) a state- ment from Mr. George Edwards, managing director of Vickers- Armstrongs (Aircraft). He said "The decision . . . means we have abandoned to the Americans, without a struggle, this highly important market [for large jet transports]. How important this market is can be seen from the fact that the orders so far placed by a few American operators for big jets total over £200m. The future size of the market could be of the order of £ 1,000m. I think the decision to cancel Britain's only contender in this market is a national decision we shall regret for many years to come." On the other hand the importance of the Rolls-Royce Conway is in no way affected by this decision; on the contrary, every means is to be sought to find applications for it, and it is contemplated that Conways should be installed in one type of V-bomber. Mean- while, the prototype V.1000 will probably be completed next year, and it may find employment as a test vehicle. The new order for Britannias comprises six Britannia 250 LR aircraft to be built at Belfast by Short and Harland. This order is additional to the three similar aircraft ordered by the M.o.S. from Shorts for the use of independent trooping operators. A considerable amount of thought had also been given to the question of replacing the Vickers-Armstrongs Valetta as the standard short-range Service transport. The problem was particularly difficult, and no decision had yet been taken. It was emphasized that, whatever cuts in expenditure might be made—and there were certain to be several—research would be left alone as far as possible. In the past, this country had been badly short of high-speed tunnels (although the position here was easing) and other equipment. Apart from the Fairey Delta 2, there were many types of advanced research aircraft in prospect; and, although we could not buy as many as were used in the U.S.A., it was considered that the types involved were just as ambitious as American research machines being built to a similar time-scale. This involved aircraft designed both for very high Mach-numbers and extreme altitudes. Regarding guided-weapon developments, little more could at present be said. But it was thought that the American lead in this important sphere had not grown during the past year, and in some respects it had even been narrowed. Nevertheless, it was difficult to stretch a limited budget to cover development and production of two or more generations of weapons at once.
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