text: The appearance of “inertia coupling” prob- 
  lems in modern airplanes was the natural result 
  of the progressive change in aerodynamic and 
  inertia characteristics to meet the demands of 
  high speed flight. 
  Inertia coupling problems 
  were unexpected only when dynamic stability 
  analyses did not adequately account for the 
  rapid changes in aerodynamic and 
  inertia 
  characteristics of airplane configurations. The 
  is somewhat 
  The term of “intertia coupling” 
  misleading because the complete problem is 
  one of aerodynamic as well as inertia coupling. 
  results when some disturbance 
  about one airplane axis causes a disturbance 
  about another axis. An example of uncoupled 
  motion is the disturbance provided an airplane 
  when subjected to an elevator deflection. The 
  to pitching 
  resulting motion 
  motion without disturbance in yaw or roll. 
  An example of, coupled motion could be the 
  disturbance provided an airplane when sub- 
  jected to rudder deflection. The ensuing mo- 
  tion can be some combination of yawing and 
  rolling motion. Hence, the rolling motion is 
  the yawing motion to define the 
  coupled with 
  resulting motion. 
  interaction 
  results from aerodynamic characteristics and is 
  termed “aerodynamic coupling.” 
  
  This sort of 