io8 AEROPLANE PERFORMANCE CALCULATIONS 



Next fill up the X column as shown and the L/D column as 

 explained in the definition of L/D given above. Then work out 

 the columns in succession. 



The last two columns then give the values of V and P, which 

 can be used to plot the machine performance curve for standard 

 density air under the assumptions of the First Method. 



Second Method. 



W is the total weight of the machine in pounds. 



S is the total area of the wings in square feet. 



c is the chord of the wing in feet. 



/ is the horizontal distance in feet from the e.g. of the machine 

 to the c.p. of the tail plane.* 



/' is the horizontal distance in feet from the leading edge of 

 the equivalent chord f to the c.p. of the tail plane. 



R is the total body resistance in pounds at 100 miles per 

 hour, and has been found by the method of Chapter VIII., page 

 77. If, however, the work of Chapter VIII. has been done in 

 the form of finding R! and R 2 instead, then R = R x + R 2 . 



k^nax and L/D are corrected values and have already been 

 found by the method of Chapter IX., page 85, where they will 

 be found in the last column of the first table. 



* It is sufficiently accurate for our purpose to assume that the c.p. of the tail 

 plane is at the front tail plane spar. 



tThe leading edge of the equivalent chord is on the line joining the top and 

 bottom leading edges of the biplane, and at a distance above the leading edge of 

 the bottom plane of -55 of the gap. 



