176 SYMPOSIUM ON AERONAUTICS. 



advance there will be, and widi it the designer of such structures 

 must be quick to seize such advantage as he may. 



Regarding a better disposition of the materials we now have, it 

 may be assumed that there is a more promising field. It is pecu- 

 liarly a field which must be worked in an experimental way, and 

 while much has already been accomplished there is still room for 

 further saving in weight through a better disposition of the elements 

 of structure employed. 



The problem is broadly ; given an aeroplane structure exposed to 

 the hazards of flight and involving baffling head winds, gusts, forced 

 severe banking, diving, quick turning about various axes of motion 

 and all in various combination, required a structure which shall 

 present a substantially uniform factor of safety relative to the 

 extreme stress, in any and all directions, to which it may be sub- 

 jected. 



This is obviously not a problem to be solved by theoretical 

 methods or over the drawing board alone or even chiefly. It is 

 distinctively a problem to be worked out primarily by experience 

 supplemented by experiment, which is, after all, only experience 

 realized under control conditions. 



One of the future developments which should not be lost sight 

 of lies this way and should comprise comprehensive studies of the 

 combinations of structural elements available, always with the view 

 of realizing more efficient results ; that is, a more equable distribu- 

 tion of the strength realized with a corresponding saving in weight. 



The problem of weight economy is vital in the science and art 

 of aeronautics, and the possibilities of advance through a well- 

 ordered program of experimental investigation on full sized forms 

 should not be lost sight of. 



Power Plant. 



We pass next to the subject of the aeroplane power plant. We 

 here meet the following principal problems. 



1. The problem of fuel. 



2. The problem of carburetion or preparation for combustion. 



3. The thermodynamic problem of the transformation of the heat 



energy into mechanical work. 



