text: quence of developing lift with a finite wing 
  and is termed INDUCED DRAG, D+ 
  In- 
  duced drag is separate from the drag due to 
  form and friction and is due simply to the de- 
  velopment of lift. 
  
  By inspection of the force diagram of figure 
  1.30, a relationship between induced drag, lift, 
  and induced angle of attack is apparent. The 
  induced drag coeficient, CDi, will vary directly 
  with 
  the wing lift coefficient, C,, and the in- 
  duced angle of attack, as. The effective lift 
  is the vertical component of the actual lift and, 
  if the induced angle of attack is small, will be 
  The 
  essentially the same as the actual lift. 
  J horizontal and vertical component of drag is 
  insignificant under the same conditions. By a 
  detailed study of the factors involved, the fol- 
  lowing relationships can be derived for a wing 
  with an elliptical lift distribution: 
  
  > 
  depends on the lift coefficient and aspect ratio. 
  Flight at high lift conditions such as low speed 
  or maneuvering flight will create high induced 
  angles of attack while high speed, low 
  lift 
  flight will create very small induced angles .of 
  attack. The inference is that high lift coefli- 
  cients require large downwash and result in 
  large ,induced angles of attack. The effect of 
  is significant since a very high 
  aspect ratio 
  aspect ratio would produce a negligible induced 
  angle of attack. 
  If the aspect ratio were in- 
  finite, the induced angle of attack would be 
  zero and the aerodynamic characteristics of the 
  wing would be identical with 
  the airfoil sec- 
  tion properties. On the other hand, if the 
  wing aspect ratio is low, the induced angle of 
  attack will be large and the low aspect ratio 
  airplane must operate at high angles of attack 
  at maximum lift. Essentially, the low aspect 
  ratio wing affects a relatively small mass of 
  air and consequently must provide a large de- 
  flection (downwash) to produce lift. 
  
  (1) The induced drag equation follows the 
  same form as applied to any other aerody- 
  namic force. 