text: Directional divergence is a condition which 
  If the reaction to a small 
  cannot be tolerated. 
  initial sideslip is such as to create moments 
  which tend to increase the sideslip, directional 
  divergence will exist. The sideslip would in- 
  the airplane is broadside to the 
  crease until 
  wind or structural failure occurs. Of course, 
  increasing the static directional stability 
  re- 
  duces the tendency for directional divergence. 
  Spiral divergence will exist when the static 
  is very large when com- 
  directional stability 
  the dihedral effect. The character 
  pared with 
  of spiral divergence is by no means violent, 
  The airplane, when disturbed from the equilib- 
  rium of level flight, begins a slow spiral which 
  gradually increases to a spiral dive. When a 
  small sideslip is introduced, the strong direc- 
  tional stability 
  tends to restore the nose into 
  the wind while the relatively weak dihedral 
  effect lags in restoring the airplane laterally, 
  In the usual case, the rate of divergence in the 