text: HORIZONTAL TAIL. The horizontal tail 
  usually provides the greatest stabilizing influ- 
  ence of all the components of the airplane. To 
  appreciate the contribution of the horizontal 
  tail to stability, inspect figure 4.9. 
  If the air- 
  plane is given a change in angle of attack, a 
  change in tail 
  lift will occur at the aerody- 
  namic center of the tail. An increase in lift 
  at the horizontal 
  tail produces a negative 
  moment about the airplane c.g. and tends to 
  return 
  the trim condition. 
  While the contribution of the horizontal tail 
  is large, the -magnitude of the 
  to stability 
  contribution is dependent upon the change in 
  tail lift and the lever arm of the surface. It is 
  obvious that the horizontal tail will produce a 
  stabilizing effect only when the surface is aft 
  of the c.g. For this reason it would be inap- 
  propriate to refer to the forward surface of a 
  configuration as a horizontal 
  canard (tail&St) 
  “stabilizer.” 
  In a logical sense, the horizontal 
  “stabilizer” must be aft of the c.g. and- 
  generally speaking-the 
  the contribution to stability. 
  
  farther aft, the greater 