text: The principal effect of the extension of flaps is 
  to increase the C,, 
  and reduce the angle of 
  attack for any given lift coefficient. The in- 
  crease in CL,, afforded by flap deflection re- 
  duces the stall speed in a certain proportion, 
  the effect described by the equation: 
  - 
  z% 
  J Ch, 
  v,=v, 
  
  where 
  
  V,,= stall speed with flaps down 
  
  v,=stall  speed without  flaps 
  
  C,= maximum lift coefficient of 
  
  the clean configuration 
  
  C&,= maximum lift coefficient 
  
  with flaps down 
  
  For example, assume the airplane described by 
  the lift curves of figure 1.15 has a stall speed of 
  100 knots at the landing weight in the clean 
  configuration. 
  the flaps are lowered the 
  If 
  reduced stall speed is reduced to: 