Military aeroplanes, simplified, enlarged; an explanatory consideration of their characteristics, performances, construction, maintenance, and operation, specifically arranged for the use of aviators and students . erial necessaryfor proper strength to resist enormous centrifugal and bendingstresses set up by the rapidly turning blades. It is in the regionof the tips that most of the work is done. The propeller blade has a cross section, not unlike that of a camberedwing. The blade itself has a certain surface area, and it attacks therelative air with a certain angle of incidence, just like an
Military aeroplanes, simplified, enlarged; an explanatory consideration of their characteristics, performances, construction, maintenance, and operation, specifically arranged for the use of aviators and students . erial necessaryfor proper strength to resist enormous centrifugal and bendingstresses set up by the rapidly turning blades. It is in the regionof the tips that most of the work is done. The propeller blade has a cross section, not unlike that of a camberedwing. The blade itself has a certain surface area, and it attacks therelative air with a certain angle of incidence, just like an aeroplanewing. In addition to that, the aspect ratio of the blades is importantjust as if it were a wing. Since the blade as an elementary wing is traveling in a spiral, theangle of the blade with relation to the axis must increase as the hubis approached, in order, in one revolution, for the relative travel of anyblade portion through the air to be the same. This travel of the blade through the air would of course be the sameas the pitch travel of a screw, if the air were solid. And in fact theangle of the blade to the plane swept by the propeller is called thepitch angle. g5St»^y!SSS^^:f:^ygg O/n ^^A. THE TOTAL PRESSURE ON THE PROPELLER, P, MAY BE DIVIDED INTO L AND D,AS DONE ON AN AEROFOIL, BUT WITH THE DIFFERENCE THAT THE ACTIVE FORCE LIS REALLY THE THRUST FORWARD AND THE DRAG D, IS THE TORQUE, WHICH IS OVER-COME BY THE MOTOR. Any point on the blade actually travels through the air a distanceequal to its circumference. But being set at an angle, it moves forwardat the same time. So the combination results in a spiral path, and theactual distance between the beginning and end of this spiral dependson the angle of the blade. 92 Now the horizontal distance, parallel to the propeller axis, to whichthis spiral is stretched, is the distance that the propeller would havepulled the aeroplane in one revolution, if the air had resisted like asolid. This distance is called the pi
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectairplanes, bookyear19
