text: depending on the nature of the dihedral effect 
  of the airplane. 
  
  inclination of 
  the inertia axis above the aerodynamic axis 
  will cause the inertia couple to provide adverse 
  yaw with rolling motion. 
  If the inertia axis 
  inclined below the aerodynamic 
  were initially 
  axis (as may happen at high 4 or negative load 
  factors), the roll induced inertia couple would 
  provide proverse yaw. Thus, roll coupling 
  may present a problem at both positive and 
  negative inclination of the inertia axis depend- 
  ing on the exact aerodynamic and inertia 
  characteristics of the configuration. 
  
  It should be noted that initial 
  
  As a result of the aerodynamic and inertia 
  coupling, rolling motion can induce a great 
  variety of longitudinal, directional, and lateral 
  forces and moments. The actual motion of 
  the airplane is a result of a complex combina- 
  tion of the aerodynamic and inertia coupling. 
  Actually, all airplanes exhibit aerodynamic 
  and inertia coupling but of varying degrees. 
  The roll coupling causes no problem when the 
  moments resulting from the inertia couple are 
  easily counteracted by the aerodynamic re- 
  storing moments. The very short span, high 
  speed modern aircraft has the capability 
  for 
  the high roll rates which cause large magni- 
  tudes of the inertia couple. The low aspect 
  ratio planform and flight at high Mach number 
  allow large inclination of the inertia axis with 
  respect to the aerodynamic axis and also add 
  to the magnitude of the inertia couple. 
  In 
  addition, the aerodynamic restoring moments 
  deteriorate as a result of high Mach number 
  and angle of attack and can create the most 
  serious roll coupling conditions. 