text: the wing root boundary layer to be more easily 
  separated in the presence of an adverse pressure 
  gradient. Since the upper wing surface has the 
  more critical pressure gradients, a low wing 
  position on a circular fuselage would create 
  greater interference drag than a high wing 
  position. Adequate filleting and control of 
  local pressure gradients is necessary to mini- 
  mize such additional drag due to interference. 
  The sum of all the drags due to form, fric- 
  tion, leakage and momentum losses, and inter- 
  ference drag is termed “parasite” drag since 
  the develop- 
  it is not directly associated with 
  ment of lift. While this parasite drag is not 
  the production of lift 
  directly associated with 
  The variation of 
  it 
  is a variable with 
  lift coef- 
  parasite drag coefficient, C+, with 
  ficient, C,, is shown for a typical airplane in 
  figure 1.34. The minimum parasite drag co- 
  efficient, CDpmi,, usually occurs at or near zero 
  lift and parasite drag coefficient 
  increases 
  above this point,in a smooth curve. The in- 
  duced drag coefficient is shown on the same 
  graph for purposes of comparison since the 
  total drag of the airplane is a sum of the 
  parasite and induced drag. 