text: =(0.318 $+S 
  ) and drag due to lift (G).  The air- 
  
  F%d” 
  (usually 
  plane efficiency factor is some co&ant 
  less than unity) which includes parasite drag 
  the drag induced by lift. 
  due to 
  lift and represents the 
  C Dpmr” is invariant with 
  parasite drag at zero lift. A typical value of 
  C r,Pmin would be 0.020, of which the wing may 
  account for 50 percent, the fuselage and nacelles 
  40 percent, and the tail 10 percent. The term 
  
  D,= parasite drag 
  
  When expressed in this form the induced drag, 
  Di, includes all drags due to lift and is solely 
  a function of lift. 
  The parasite drag, D,, is 
  the parasite drag and is completely independent 
  of lift-it 
  drag of the airplane. 
  > 
  
  ( 
  drag induced by lift and the extra 
  lift-the 
  parasite drag due to lift. 
  Typical values of 
  the airplane efficiency factor range from 0.6 to 
  0.9 depending on the airplane configuration 
  the term of 
  and its characteristics. While 
  drag due to lift does include some parasite 
  drag, it is still generally referred to as induced 
  drag. 
  
  An alternate expression for the parasite drag 
  
  is: 