text: DIRECTIONAL  STABILITY  AND CONTiOL 
  
  DIRECTIONAL STABILITY 
  
  The directional stability of an airplane is 
  essentially the “weathercock” 
  stability and 
  involves moments about the vertical axis and 
  their relationship with yaw or sideslip angle. 
  An airplane which has static directional sta- 
  bility would tend to return to an equilibrium 
  when subjected to some disturbance from equi- 
  librium. 
  Evidence of static directional sta- 
  bility would be the development of yawing 
  
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