So AEROPLANE PERFORMANCE CALCULATIONS 



P /V N3 



*.T ( T 



P \V 



Therefore, given the point P, V, we can find the point P T , V T 

 by plotting through the point P, V a curve of the form 



y oc x*. 



Starting, therefore, from the point P, V, we can consider the 



point P T , V T as known, since it is the intersection of the curve 



of the form y oc x* which passes through P, V with the P T curve. 



Therefore, V and V T being known, a l is got from equation 



3} in the form 



ft 1 



Now, by the definition of a l given on page 1 8, we see that 



= * ~ p 



q 



.'. (7 = q<T\ + P ... (0") 



where/ and q have the values given on page 19. 



Equations (<r) and (o^), with the aid of the device of plotting 

 the y oc ;r 3 curve, determine cr, from which the ceiling is found 

 corresponding to the original point P, V with the aid of the curve 

 of page 104. 



The maximum ceiling is found by repeating the work for a 

 few points and finding the maximum in the ordinary way. 



A convenient method of applying the theory will be found 

 an Chapter XII., page 125. 



III. THROTTLED FLIGHT. 



Slowest Flying Speed. The slowest flying speed differs 

 from the landing speed on glide, owing to the influence of the 

 propeller slip stream on the wing lift. 



The slowest flying speed can be read off the machine per- 

 formance curve if this has been calculated by the Third Method 

 or the Fourth Method, or it can be obtained by working the 

 performance calculation by the Third Method for the case of 

 X = I 'O as far as the determination of V. 



Throttling Curves. In calculations connected with thrott- 

 ling it is often necessary to plot a number of curves of the form 

 y oc x* across the machine and propeller performance curves. 

 To avoid the labour of doing this repeatedly it is best to scribe 



