text: where 
  
  Pr,=parasite power required, h.p. 
  D,=paraSite drag, lbs. 
  
  V= true airspeed, knots 
  
  Thus, parasite power required will vary with 
  altitude and equivalent parasite area ( f) in the 
  same manner as ‘the parasite drag. However, 
  the variation with speed will be different. 
  If 
  all other factors are constant, the parasite drag 
  varies as the square of velocity but parasite 
  power varies as the cube of velocity. 
  
  Pb% v*3 
  Ph VI 
  -=(-I 
  
  where 
  Prpl= parasite power required corresponding to 
  
  some original speed, Vi 