30 AEROPLANE PERFORMANCE CALCULATIONS 



Further, as in the Third Method, these two equations lead 

 L b'c + ad 



V 2 = a 7~ 



X L/D 



b' d 



T x + LVD 



and ^ = j- -j-. 



X " L/D 



NOW put a ~ - ~ = e 



b' d 



X + L/D = ? 



and ad' + b'c = ty 



L ^Ir 



" v^ = ~e 



and yj = 6> . 



L T 



Substitute these values of ^ and r^ in equation (4) and we 



obtain 



W/ 



VV/ <^)// 1 A/rr ^ 



V^ = T" + BL ~ c + 1 



.*. from equation (i) 



3 



. - - - (P) 



Equations (V) and (P), with the aid of equations (0), (0), 

 (#'), ('), (^'), and (aT) are in such a form that a tabular method can 

 be applied to them (see Chapter XL). 



The values of L/D and k^ max used above are of course the 

 corrected values taken from the wing characteristic. 



The above equations having been solved tabularly, we have 

 values of V and P for values of X from 'I to I -o : these values of 

 V and P are the data required for plotting the performance curve 

 for standard density air under the assumptions of the Fourth 



