Testing Airplanes in a Man-Made Storm 



At the Washington Navy Yard a seventy-five-miles-an hour wind is 

 shot against warships and airplanes to determine their air resistance 



Because the tunnel is so large the models are made big enough to represent the actual machines 

 faithfully in every particular. The wind attains a velocity of seventy-five-miles an hour 



WHAT the model basin for towing 

 small models of ships is to the 

 naval architect, the windtunnel 

 is to the aeronautica 1 engineer. In the 

 past, ships developed good shapes through 

 centuries of service only. A faulty design 

 might prove slow, but rarely unsafe. On 

 the other hand, faulty airplanes are death- 

 traps, incapable of that continuous service 

 from which experience grows. 



The invention of the airplane is due to 

 the windtunnel. Models of wings were 

 exposed to an artificial current of air and 

 the force and direction of its pressure 

 weighed. When the Wright Brothers found 

 that they could not rely oh previous ex- 

 periments made on the airpressure of wings 

 (the German pioneer, Lilienthal, had ex- 

 posed them only to the irregular natural 

 wind), they resorted to a primitive wind- 

 tunnel. All early windtunnels were too 

 small.. They could .not produce air currents 

 fast enough; they were merely ventilating 

 fans that forced fresh air continuously 

 into a small passage. Nevertheless, we 

 owe to them, such as they were, the modern 



fast and stable airplanes and the racing 

 Zeppelin. 



Nothing has so retarded aeronautic 

 progress in America as the fact that work 

 with Professor Zahm's pioneer windtunnel 

 of 1903, at the Catholic University, Wash- 

 ington, D. C, was discontinued. For a 

 decade, while Europe was waking up to the 

 full importance of the subject, our country 

 lacked this most necessary instrument. 



The new windtunnel of the United States 

 Navy is a model for the world. It is end- 

 less, forming a complete circle, or rather a 

 circuit flattened into the shape of a chain- 

 link. As there is no resistance against the 

 motion of the air contained within a closed 

 circuit, except its friction against the walls, 

 and as the blower does not overcome the 

 inertia of continuously renewed quantities 

 of air, this arrangement gives the artificial 

 wind a cross-section of eight feet and a ve- 

 locity of seventy-five miles an hour. 

 The artificial storm is produced by a 

 blower of five hundred horsepower. 



Because the tunnel is so large the models 

 are made big enough to reproduce the actual 



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