Wind, Weather and the Airman 



The Invisible Perils of the Whirlpools, Gusts, 

 and Eddies of the Ocean in which Men Fly 



AIR navigation, in its relation to 

 AA weather, is repeating the history 

 of marine navigation. The slow 

 sailing-ships of early days were the sport 

 of wind and waves; the great ocean liner 

 of today pursues the even tenor of its way 

 regardless of the elements. Under the 

 urge of necessity the military aviator now 

 flies in all kinds of weather, and his high- 

 powered machine negotiates atmospheric 

 difficulties that would have been insupera- 

 ble a few years ago. 

 Nevertheless, even 

 the biggest oceanlin- 

 ers sometimes come 

 to grief, and the day 

 is still distant when 

 the aviator will not 

 need to keep his 

 weather-eye wide 

 open. 



Airships and air- 

 planes are the sub- 

 marines of the at- 

 mosphere, but the 

 element in which 

 they ply is far more 

 fickle than the 

 ocean. The cur- 

 rents of the latter 

 are comparatively 

 feeble and regular; 

 those of the former 

 are often immense- 

 ly powerful and 

 capricious. 



Flow of Air Over a Ridge 



Notice that the crest of the air wave lies a little 

 beyond the crest of the ridge. This does not apply 

 to isolated hills, which the air easily passes around 



Flow of Air Over Two Ridges 



Notice the eddy in the valley to the leeward of the 

 first ridge. In this case the crest of the air wave 

 still lies beyond the crest of the ridge, as seen above 



There Are Winds 

 and Winds 



An aviator study- 

 ing the atmosphere 

 learns much of inter- 

 eat. The structure 

 of the atmosphere 

 with respect to 

 wind is a subject 

 concerning which a 

 great fund of 

 knowledge has re- 

 cently been acquir- 

 ed through the 



A 'Sheltered" Landing-Place May Be Dangerous 



A landing-place surrounded by trees is dangerous in 

 windy weather on account of the air waves between 

 the moving air above and the calm air below 



h^rV^Hrl t^^j^, / ^ 



Waves and Gusts in the Air 



The iihutratinn shows how these an- niadt 

 by smoke. The reader will bo able to 



this phenomenon for himself almost any windy day 



722 



practical experience of aeronauts on the 

 one hand, and the scientific investigations 

 of meteorologists on the other. The 

 mariner dreads a strong wind; the aero- 

 naut an unsteady one. Mere strength of 

 wind is harmless to the aviator, except in 

 starting and landing, and, indirectly, 

 owing to its ability to drive the airplane 

 far out of its intended course. If the 

 stronge3t hurricane that ever blew were 

 perfectly steady, the airman might well 

 be as indifferent to 

 its speed as the 

 average mortal is to 

 the speed with 

 which our terrestri- 

 al globe rotates on 

 its axis. But un- 

 fortunately the 

 wind is hardly ever 

 steady, either in 

 force or direction. 

 It is full of gusts 

 and eddies, up-cur- 

 rents and down- 

 currents, and it is 

 these eccentricities 

 which gradually de- 

 velop in the aviator 

 a sort of sixth sense, 

 a "feel" for atmos- 

 pheric fluctuations, 

 that enables him to 

 adjust his machine 

 instinctively to the 

 forces tending to 

 disturb its equi- 

 librium. He also 

 learns by experi- 

 ence the conditions 

 under which irregu- 

 larities of a pro- 

 nounced character 

 may be expected. 

 He becomes well 

 acquainted with the 

 great mound of air 

 that drives the air- 

 plane upward in 

 passing over a hill 

 or mountain; with 



visible 

 observe 



