text: Dutch roll is a coupled lateral-directional 
  oscillation which is usually dynamically stable 
  but is objectionable because of the oscillatory 
  nature. The damping of this oscillatory mode 
  may be weak or strong depending on the prop- 
  erties of the airplane. The response of the air- 
  plane to a disturbance from equilibrium 
  is a 
  combined rolling-yawing oscillation in which 
  the rolling motion is phased to precede the 
  yawing motion. Such a motion is quite unde- 
  sirable because of the great havoc it would 
  create with a bomb, rocket, or gun platform. 
  Generally, Dutch roll will occur when the 
  dihedral effect is large when compared to static 
  Unfortunately, Dutch 
  directional stability. 
  roll will exist for relative magnitudes of dihe- 
  dral effect and static directional stability be- 
  tween the limiting conditions for directional 
  divergence and spiral divergence. When the 
  dihedral effect is large in comparison with 
  static directional stability, 
  roll 
  motion has weak damping and is objectionable. 
  When the static directional stability is strong 
  in comparison with 
  the dihedral effect, the 
  Dutch roll motion has such heavy damping 
  that it is not objectionable. However, these 
  qualities tend toward spiral divergence. 