AEROPLANE PERFORMANCE CALCULATIONS 



None of these processes is really satisfactory, but they are 

 the best we can do. 



Large Bodies. First obtain the maximum cross-sectional 

 area of each such body in square feet, from the front-view general 

 arrangement drawing, for instance, and note all such features as 

 cockpits, windscreens, or projecting engine cylinder heads and (in 

 the case of seaplane floats and flying boat hulls) steps : these 

 items are to be dealt with later on in the list : at the moment 

 they are to be neglected. 



Let a be the maximum cross-sectional area in square feet : then 

 the values of r for large bodies of different types are given in the 

 following table : 



Tail Unit. The external structural members, king levers, 

 etc., are to appear in another part of the list under their proper 

 headings of struts, wires, etc. : for the present it is only a question 

 of finding the values of r for the fabric-covered surfaces them- 

 selves. First obtain the area in square feet of the tail plane (in- 

 cluding elevators) and the fin (including rudder), from the plan 

 and side view general arrangement drawings, for instance. 



Then the following table gives the required values of r, a 

 being in each case the appropriate area in square feet : 



Struts. First the various struts used on the machine must 

 be collected into groups, in each of which all members have their 

 cross sections geometrically similar. Then the aggregate frontal 

 area of each group is to be noted, and for this purpose it .is con- 

 venient to use one foot long by one inch wide as the unit of area : 

 tapered struts are accounted for by taking their actual frontal 



