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Show WHY THE AEROPLANE FLIES E Air Pressure Bereath It and Its Mo- lion Keep the Flying Machine f frem Falling. . Ask a scientist, "What Is an aero- " plane?" and be will reply. "Any flat 1 or slightly curved surface propelled n horizontally through the air." That, t being merely a definition or a thing, li and not an explanation of flight, tells little of what Is moat wonderful about a flying machine. Time aud time , again we have all asked ourselves: Why Is it that this combination of c planes, propellers, motors, and rud- " ders does not fall? Why Is It that 1 a machine many times heavier than l the air stays aloft? t It Is the air pressure beneath It, t and Its motion, that keeps up a plr."a. I If It Is to remain In the air, an aero- n plane must constantly move like a . skater on thin Ice. The skster must move fast enough to reach a new section sec-tion of Ice before be falls; the aeroplane aero-plane must move fast enough to reach 1 a new section of air before It falls. 11 Roth are constantly struggling with e gravitation. t The simplest and moat familiar ex- g ample of an aeroplane Is the kite of i our boyhood days. Ily holding It r agslnst the wind, or by running with . it, if there happens to be ouly a gentle gen-tle breexe, this oldest of flying irv chines Is kept aloft. IdvhiiI a sub. u- 1 tute for the string, some device, in v other words, which will enable you lo a bold the kite In the proper directly.;, t and you have Invented a flying ma- t chine. The pull or the thrust of an engine-driven propeller is that substl-tute. substl-tute. Harper's Magazlue. b |
