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## SECTION V. Control. Paragraph 

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## VI. Aerodynamic stress. 

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## SE<:mON I <JENERAL 

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1. Definition of aerodynamics.-Aerodynamics is that branch of dynamics which treats of the motion of air and other gaseous fluids, and of the forces on solids in motion relative to such fluids. 

2. Purpose and scope.- This manual is designed as a text for the• instruction of airship student pilots and as a reference text for th~ rated pilot. Accordingly the subject has been so approached as to • give the knowledge of aerodynamics essential to the operation of air› ships. Intricate formulas involving higher mathematics, although valuable to the designer, are of secondary importance to the pilot. Such formulas therefore have been omitted and the entire subject so treated as to bring. out basic principles and their application to lighter than air aircraft operation. 

