AIR PERFORMANCE 



165 



Example (3). Gliding Angle. Taking the same machine 

 again we have 



R = 5io, 



k^ ax - -590, a - 

 S = 695- 



51 x -590 x 695 



= -02440, 



The value of tan 6 (and also the value of V taken from 

 example (i), Chapter XVI II., page 155) is plotted on X as a 

 base on page 167. 



From this curve we get that the minimum value of tan is 

 1107 and occurs at a speed of about 74 miles per hour. 



Therefore the Air Speed Indicator reading for best glide in 

 still air at any altitude is 74, and the tangent of the best gliding 

 angle in still air at any altitude is -1 107. 



Example (4). Gliding in a Wind. Taking once again the 

 same machine and taking as the wind speeds to consider 



z/! = - 40 miles per hour, 



* - ' - 20, 



V 3 = 20, 



v = 40, 



we have 



W 

 R 

 a 



5700, 



510, 



02440. 



