text: LANDING GEAR CONFIGURATIONS 
  
  There are three general configurations for the 
  aircraft landing gear: the tricycle, bicycle, and 
  tail wheel arrangement. At 
  “conventional” 
  low rolling speeds where the airplane aerody- 
  namic forces are negligible, the “control-fixed” 
  static stability of each of these configurations 
  is determined by the side force characteristics 
  of the tires and is not a significant problem. 
  
  The instability which allows ground loops 
  in an aircraft with a conventional tail wheel 
  landing gear is quite basic and can be appre- 
  ciated from the illustration of figure 4.31. Cen- 
  trifugal 
  force produced by a turn must be 
  balanced and the aircraft placed in equilibrium. 
  The greatest side force is produced at the main 
  the 
  wheels but to achieve equilibrium with  the airplane 
  must have adequate lateral control power to 
  contend with the ordinary conditions of flight. 
  The lateral controls must be capable of achiev- 
  ing required roll helix angles and acceleration 
  through prescribed roll dispIacements. Also, 
  the airplane must be capable of being con- 