Committee on Public Information 



TRUING the airplane, one op the vital initial steps in the construction 



.op America's sky fleet 



A manufacturer who wanted to build flying machines for the government, but whose bid 

 was rejected because his plant was inadequate, was very wroth and declared scornfully that 

 he could whittle an airplane out of a tree in a few weeks' time, at a cost of a few hundred 

 dollars. The illustration shows one of the necessary operations which the whittler would 

 have overlooked — the establishment of an exact level for the key part of the fuselage, or 

 body. The man to the left is watching the bubble in the spirit-level, while the other mechanic 

 is adjusting the supports to the required tautness. 



of the machine must attain the very acme 

 of lightness. 



That very lightness, however, entails 

 enormous strength and perfect adjust- 

 ment. Think of the strain which is ex- 

 erted on every wire and nut, every inch of 

 linen, and every bit of wood as this 300- 

 horsepower mechanism rushes through 

 the air at 150 miles an hour. Cyclones 

 often do not go as fast, and we can easily 

 picture Avhat happens to a strongly built 

 house when the air strikes it at that 

 speed. 



TREMENDOUS PRESSURES MUST BE 

 WITHSTOOD 



But if the strain is great simply be- 

 cause of high speed, what must it be 

 when a plane suddenly careens down- 

 ward, taking a tremendous pressure off 

 one part and hurling it upon another. 



It is that kind of sharp, sudden, unevenly 

 distributed shock which allows the slight- 

 est tap of a knife to crack an egg or 

 the explosion of a depth bomb to crush 

 in the unprepared side of a submarine. 

 Obviously a plane must be built so skill- 

 fully and of such perfect material as to 

 withstand not only the pressure of its 

 cyclone speed, but also the added shocks 

 of its sudden evolutions. 



The one material which gives this 

 double characteristic of strength with 

 lightness is spruce ; not the ordinary 

 spruce, but a super-selected spruce from 

 the giant trees of the Pacific coast. Few 

 would believe that this would present 

 much of a problem with America's vast 

 resources ; but when one considers that 

 only a small fraction of the very best 

 spruce is usable at all, and that the war 

 has vastly increased the demand for that, 



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