5 2 



AEROPLANE PERFORMANCE CALCULATIONS 



P' is the effective horse-power required by the machine for 

 horizontal flight at the altitude in question. 



P T ' is the effective horse-power given by the propeller at full 

 torque for the altitude. 



P R ' is the effective horse-power given by the propeller at full 

 revolutions. 



Now suppose that we have curves of P', P T ', and P R ' plotted 

 on a base of speed, and let us consider three particular points 

 (one on each of the three curves), whose co-ordinates are P', V, 

 P T ', V T ', and P R ', V R ' respectively. Also we will take the follow- 

 ing additional definitions : 



I' is the indicated horse-power. 



F' is the horse-power lost in friction in the engine. 



H' is the brake horse-power. 



Q' is the indicated torque. 



N' is the engine revolutions. 



T is the thrust. 



The above refer to the conditions when the machine is flying 

 horizontally throttled, i.e. they refer to the point P', V. 



Corresponding letters with suffix T refer to the point P T ', V T '. 



Corresponding letters with suffix R refer to the point P R ', V R '. 



Corresponding letters in the italic character refer to the point 

 of intersection of the curves P T ' and P R ', i.e. to the condition when 



