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Aviation History
1951
1951 - 0023.PDF
FLIGHT, 4 January 1951 17 Part t. first Principles and a Brief History : Rotating Systems and Their Controls By Capt. K. 1M. UPTROT, C.B.€., B.A. "'*' * .;..TH E HELICOPTER Presented here is the first of a sequence of specially commis- sioned articles from the pen of an internationally recognized authority on rotary-wing aircraft. It is our belief that these contributions will go far towards clarifying many obscurities surrounding die topic, especially as the author displays the rare ability to interpret complexities in simple bnt precise terms. Captain Liptrot was formerly the Deputy Director responsible for Helicopter Research and Development, Ministry of Supply. AS this series of articles is intended as an introductionto the subject, and primarily for the not-so-well in-formed, it is perhaps as well to open with the question "What is a helicopter? " It is one of a family of neavier- than-air craft known as "direct-lift" aircraft, which are characterized by being able to lift themselves vertically off the ground in still air, which can hover motionless over a given spot and descend vertically under their own power, and which, in particular, can make a safe descent into a relatively small space in the event of power-unit failure. In addition, to be of any practical use, they must be able to move hori- zontally at the will of the pilot at a satisfactory speed, and they must be stable and controllable under all flight conditions. It will be appreciated that in order to obtain aerodynamic lift we must have suitably shaped surfaces moving at an appropriate speed relative to, the surrounding air. In the conventional fixed-wing aircraft the whole vehicle must move at the necessary speed; in direct-lift aircraft, however, the supporting aerodynamic surfaces have this relative velocity quite independently of the motion of the aircraft as a whole, and we have three main classes: — (1) The Ornithopter, in which the surfaces flap or oscil- late. Mechanically it is difficult to achieve the correct wing The 1907 briguet—first helicopter to lift itself and pilot. movement; there are obvious difficulties in control, and the type can be ignored as being unlikely to result in practical aircraft. (2) The paddle wheel or cyclogiro, in which the surfaces are mounted like the blades of a paddle wheel. Schemes which would appear to be satisfactory have been proposed, and at least two tested full-scale. They did not fulfil their original promise and were abandoned. (3) The helicopter, in which the surfaces are mounted like the blades of an airscrew rotating about a substantially ver- tical axis. This type has always had more adherents than the others, and is the one which has now given us an entirely practical aircraft which can be put into the hands of opera- tors, both civil and military. It is to this type that these articles are confined. Since it is only in the last few years that the helicopter has become news there is a widespread belief that it is a new development. This is far from the truth, and indeed, direct- lift aircraft, including the helicopter, wer suggested long before the fixed-wing type. The story of man's desire to fly, The Pescara helicopter, flown in France during 1923.
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