text: retreating blade since the relative wind veloci- 
  ties are greater on the advancing blade. This 
  lateral dissymmetry of lift causes the rotor to 
  tilt back due to the gyroscopic effect of the 
  increasing the rotor angle of 
  rotor, 
  attack. 
  is unstable with 
  the rotor 
  changes in angle of attack at forward flight 
  speeds. Since the magnitude of the unstable 
  the magnitude of 
  moment is affected by 
  tilt of 
  the 
  rotor 
  the 
  thrust as well as 
  force, a greater instability exists 
  the thrust 
  for 
  for 
  decreases in angle of attack. 
  In addition, the 
  is greater for increases in angle of 
  instability 
  attack when the rotor thrust also increases. 
  
  further 
  
  Thus, 
  
  If the rotor angle of attack is held constant 
  and the rotor is given a translational velocity, 
  a dissymmetry of lift results since the velocity 
  of the advancing blade is increased while the 
  velocity of the retreating blade is decreased. 
  This dissymmetry of lift causes the rotor to 
  tilt 
  to oppose the change in 
  velocity due to the gyroscopic effect of the 
  rotor. Hence, the rotor has velocity stability. 