text: J.f a wing is producing lift, a pressure differ- 
  ential will exist between the upper and lower 
  surfaces, i.e., for positive lift, 
  the static pres- 
  sure on the upper surface will be less than on 
  the lower surface. At the tips of the wing, 
  the existence of this pressure differential creates 
  the spanwise flow components shown in figure 
  1.29: For the rectangular wing, 
  the lateral 
  flow developed at the tip is quite strong and a 
  strong vortex is created at the tip. The lateral 
  ‘flow-and consequent vortex strength-reduces 
  it is zero at the 
  inboard from the tip until 
  centerline. 
  
  to 
  (6) Considering the wing planform 
  have straight lines for the leading and trail- 
  ing edges, the taper ratio, A (lambda), is the 
  ratio of the tip chord to the root chord. 
  
  (7) The sweep angle, A (cap lambda), is 
  usually measured as the angle between the 
  line of 25 percent chords and a perpendicular 
  to the root chord. The sweep of a wing 
  causes definite changes in compressibility, 
  maximum lift, and stall characteristics. 
  
  The existence of the tip vortex is described 
  
  to produce the resultant 