174 AEROPLANE PERFORMANCE CALCULATIONS 



A straight line which approximates well to these on the 

 plotting of C and C' on altitude gives c = 535 and a x = 12,450. 

 Then the time t in minutes to, say, 9000 feet is given by 



2-303 x 12,450 . / 12,450 



/ = J J - Iog 10 ( - ^ - = 29-9 minutes. 



535 M 



The plottings in this and the previous example are not given 

 as they are perfectly simple and ordinary. 



Example (ll). Ceiling. Taking the P and P T curves of 

 page 170 and laying the celluloid throttling curves over them 

 we take four values each of V and V T , using alternate throttling 

 curves so as to cover a wide range. The throttling curves used 

 are indicated in dotted curves on page 170. 



Suppose we are dealing with a stationary engine, then 

 / = -161 and q = -839. 



The plotting of Altitude on V (which there is no need to give 

 :here) gives the maximum ceiling as 16,410 feet at an Air Speed 

 Indicator Reading of 62. 



III. THROTTLED FLIGHT. 



Example (12). Slowest Flying Speed. Consider the machine 

 performance curves plotted on page 157: curve (4) has been 

 obtained by the Fourth Method, and therefore the slowest flying 

 speed can be read off it directly : it is 48 miles per hour. 



Example (13). Consumption and Revolutions when Throttled. 



Take the case of standard density air, and work to the P, P T , 



.and P R curves plotted on page 170. A certain number of 



throttling curves are shown on the plotting : using these we 



proceed, for a stationary engine, for which/ = -161 : 



