text: Since wing dihedral is so powerful in pro- 
  ducing lateral stability it is taken as a common 
  denominator of the lateral stability contribu- 
  tion of all other components. Generally, the 
  contribution of wing position, 
  flaps, power, 
  etc., is expressed as an equivalent amount of 
  “effective dihedral” or “dihedral effect.” 
  
  there is no wing lift 
  to change. Thus, the 
  dihedral effect due to sweepback is zero at zero 
  lift 
  lift and increases directly with wing 
  coefficient. When the demands of high speed 
  flight require a large amount of sweepback, the 
  resulting configuration may have an excessive- 
  ly high dihedral effect at low speeds (high CL) 
  while the dihedral effect may be satisfactory 
  in normal flight (low or medium C,). 
  
  The vertical tail of modern configurations 
  at times, un- 
  can provide a sign&ant-and, 
  to the effective dihe- 
  desirable-contribution 
  dral. 
  If the vertical tail is large, the side force 
  produced by sideslip may produce a noticeable 
  rolling moment as well as the important yaw- 
  ing moment contribution. 
  Such an effect is 
  usually small for 
  the conventional airplane 
  the modern high speed 
  configuration but 
  airplane configuration induces this effect to a 
  great magnitude. 
  It is difficult then to obtain 
  a large vertical tail contribution to directional 
  stability without 
  incurring an additional con- 
  tribution 