text: practical application to an airplane which is 
  definitely subsonic in performance. 
  
  (F) Sweepback applied to a wing planform 
  alters the lift distribution similar to decreasing 
  taper ratio. Also, a predominating influence 
  of the swept planform is the tendency for a 
  strong crossflow of the boundary layer at high 
  lift coefficients. Since the outboard sections 
  of the wing trail the inboard sections, the out- 
  the 
  board suction pressures tend to draw 
  boundary layer toward the tip. The result is 
  a thickened low energy boundary layer at the 
  tips which is easily separated. The develop 
  ment of the spanwise flow in the boundary 
  layer is illustrated by the photographs of 
  figure 1.33. Note that the dye streamers on 
  the upper surface of the~swept wing develop a 
  strong spanwise crossflow at high angles of 
  attack. Slots, slats, and flow fences help to 
  allay the strong tendency for spanwise flow. 
  
  When sweepback and taper are combined in 
  a planform, the inherent tip stall tendency is 
  considerable. If tip stall of any significance is 
  allowed to occur on the swept wing, an addi- 
  tional complication results: the forward shift 
  in the wing center of pressure creates an un- 
  stable nose up pitching moment. The stall 
  sequence of a swept, tapered wing is indicated 
  by the tuft-grid photographs of figure 1.33. 