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Aviation History
1952
1952 - 0152.PDF
66 FLIGHT, 18 January 1952 HELICOPTER HISTORY Patents Reviewed in Lecture to Helicopter Association: Early Work on Jet Drives IIKE so many other things, helicopters appear to have . originated in China. Air. Hayward's paper begins by ' mentioning that the Chinese had probably been making toy helicopters many centuries ago; these were usually a pair of feathers joined by a boss, which was then rotated upwards off a threaded stick (similar toys are sold today). The Chinese, however, did not leave any definite records of their experiments; the first person to do so was Leonardo da Vinci (1452-1519), the Italian scientist, artist and engineer. His illustrated reports showed that his basic theory was on the right lines, and all due credit should be accorded him as the inventor of the helicopter. Had some mechanical driving means existed, his helicopter might well have been capable of flight. It was not until 250 years after da Vinci's death that anyone left record of having sought to improve upon his work. From 1768 onwards, however, helicopter designs appeared frequently, for man was now exercising his ingenuity to find a machine capable of flight. Very few of the models and machines that were built ever achieved flight, for in most cases no suitable power unit existed; many relied upon the physical exertions of the operator. Mr. Hayward's paper deals with a great many such projects, most of* them of French origin; Fig. 1 is an i860 example. The next step brought us to England. Sir George Cayley (1773-1857), "the father of British aeronautics," experimented with airships, gliders and ornithopters and was universally accredited with the honour of having been the first person to design a full-size helicopter. He constructed many models, usually driven by clock springs or whalebone, and then proceeded to design a full- size machine which was to have been driven by steam power. A model of this design (Fig. 2) was built in 1843. The hull-shaped fuselage, designed to be amphibious, housed a small steam-engine which drove the two superimposed rotors by chains; the rotors revolved in opposite directions to balance-out torque, while for forward flight two small four-bladed pusher propellers were provided. Air. Hayward's paper then goes on to consider a number of other nineteenth-century helicopter projects, again mostly of French origin, although British experiments were beginning to become numerous. Rotors actuated by turbines were specified in an 1889 patent by J. Craig (Fig. 3): a steel tubular framework supported a basketwork car, and two tandem rotors, revolving in opposite directions, were shown connected to turbines operated by naphtha vapour generated in a large heated cylinder. Two following patents (also British), embodied, in the first case (C. J. Walker, 1892) a built-in parachute to be opened "in the case of a very rapid descent," and in the second (Los Olivos, !895) provision for a balloon to "assist in lifting the machine, if necessary." Such extracts indicate that the early experimenters often visualized disaster. The lecturer, however, in concluding his first section, observes that these efforts, although probably causing amusement and speculation to the present-day student and designer, were to a high degree responsible for enabling the modern designer to produce a safe and efficient helicopter. Air. Hayward points out that the multiplicity of patents con- TONIGHTJanuary 18th, Mr. L. H. Hayward, patents engineer to the Fairey Aviation Co., Ltd., is to present to the Helicopter Association of Great Britain a paper entitled "A Review of Helicopter Patents." The lecturer will review a number of his torical experiments up to about the beginning of the century; thereafter, because helicopter patents are so numerous, he will confine his review to jet drive developments. By the courtesy of the author and his employers, we are permitted to publish this first instalment of the paoer—taking the story up to the early years of the Second World War—in advance of its delivery. cerning helicopters in general makes it impracticable to review each one, and the main body of his paper is therefore confined to a survey of patents involving jet-driven rotor blades. Among the early designs of this type, the author mentions an especially ingenious project by the Frenchman Heroult, granted a U.S. Patent in 1909. In this design, fuel supplied under pressure to a hollow rotor shaft was led through pipes within hollow blades to propulsive ducts at the tips. Air entered through intakes in each blade and was mixed with the fuel in the first part of the combus tion chamber. The fuel-air mixture then passed along the chamber, expelling the burnt gases from the previous explosion, until it was itself exploded by an igniter. The exhaust gases then escaped from a flared nozzle at the tip of the blade. An oblique flap-valve automatically regulated rotational speed; the greater the centrifugal Fig. 3. The turbine-driven helicopter patented by J. Craig in 1889. force, the more the valve tended to assume a radial position and thus hinder the escape of the propulsive gas. This arrangement was intended to balance the increase in combustion pressure caused by the increased centrifugal force at higher speed. The grotesque machine illustrated in Fig. 4 was due to the Frenchmen Papin and Rouilly, who took out a number of patents for it in 1912. It was described as "an amphibious helicopter having a single balanced rotor, or a rotor made up from 2, 3 or 4 blades." In the single-bladed case, the engine was installed in a stub blade as a counterweight, but in other cases it was as near as possible to the machine's centre of gravity. Fuel and oil supply to the engine, being governed by centrifugal force, was propor tional to the rotor speed. Papin stated that the engine, which could be either a turbine or of reciprocating type, drove a suction fan delivering air along the rotor blades to orifices at the tips. Engine exhaust was admitted to the fan casing and also passed along the blades. The apparatus was stated to have been steered by cyclic pitch-change, rudder surfaces being provided if desired; this equipment was not shown in detail in the patent. There was also provision for autorotation. A captive type of helicopter was the subject of a United States /. A sketch by an unknown inventor of I860. Fig. 2. Sir George Cayley's steam-driven helicopter of 1843.
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