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Published online by Cambridge University Press: 14 September 2016
The fundamentals of the blade-screw theory have been lately the subject of numerous discussions. Most of these discussions are the result of misunderstandings arising from the fact that the fundamental conceptions and quantities involved in the subject are left without sufficient definitions. The blade-screw problem is very complex. Its study requires the use of many new conceptions and physical laws in generalised form. For the last reason, special attention must be paid to their exact statements. The following remarks are intended to bring attention to some of the fundamentals of the subject which seem to be the main source of the misunderstandings which are the most widespread at the present time. All the considerations that follow are quite general; they take place for any blade-screw, but it is the propulsive blade-screw or propeller that we will chiefly have in view here.
Note on Page 597 * “ General Theory of Blade-Screws,” by Dr. George de Bothezat, published, in the Fourthr Annual Report of the National Advisory Committee for Aeronautics, Washington, D.C., 1918.
Note on Page 598 * Let us imagine that a fan, having only a single blade (the other blades may be supposed to have been broken off) is held in one's hand. If such fan will be brought into rotation it will produce a blowing action, experimentally easy to observe (and only accompanied by a disagreeable inertia effect resulting from the asymmetry of the rotating body). If now we will start to move this fan in the direction of its axis it is clear that its blowing action will not disappear, but will only be modified. We will just find ourselves in the conditions of the Drzewieoki experiment. With increasing translational velocity, the blowing action of the fan will decrease and for a certain value of this velocity the blowing action will disappear. Only at this moment will the thrust disappear. It is thus easy to understand that so far as our fan will give a thrust it will blow—this independently of its number of blades—and thus an inflow will exist.
Note on Page 600 * Several private translations of which were used in London, since 1918.