text: type of flight control system is decided by the 
  size and flight speed range of the airplane. 
  
  The conventional control system consists of 
  direct mechanical linkages from the controls 
  to 
  the subsonic 
  airplane, 
  the principal means of producing 
  proper control forces utilize aerodynamic bal- 
  ance and various tab, spring, and bobweight 
  devices. Balance and tab devices are capable 
  of reducing control forces and will allow the 
  use of the conventional control system on large 
  airplanes to relatively high subsonic speeds. 
  the airplane with a conventional 
  control system is operated at transonic speeds, 
  the great changes in 
  the character of flow 
  can produce great aberrations in control sur- 
  face hinge moments and the contribution of 
  formation and 
  tab devices. Shock wave 
  separation of flow at transonic speeds will 
  limit 
  the conventional control 
  system to subsonic speeds. 
  
  The most important item of an artificial feel 
  system is the stick-centering spring or bungee. 
  The bungee develops a stick force in proportion 
  to stick displacement and thus provides feel 
  for airspeed and maneuvers. A bobweight 
  may be included in the feel system to develop 
  a steady positive maneuvering stick 
  force 
  gradient which is independent of airspeed for 
  ordinary maneuvers. 