text: NAVWEPS 00-BOT-80 
  STABILITY ,AND CONTROL 
  
  slipstream creates a normal force at the plane 
  of the propeller similar to a wing creating lift 
  by deflecting an airstream. As this normal 
  force will increase with an increase in airplane 
  angle of attack, the effect will be destabilizing 
  when 
  the propeller is ahead of the cg. The 
  magnitude of the unstable contribution de- 
  pends on the distance from the c.g. to the 
  propeller and is largest at high power and low 
  dynamic pressure. The normal force created  thrust line is below the c.g., thrust produces a 
  positive or noseup moment and the effect is de- 
  stabilizing. On the other hand, if the thrust 
  line is ,located above the c.g., a negative 
  moment is created and the effect is stabilizing. 
  A propeller or inlet duct located ahead of 
  the c.g. contributes a destabilizing effect. As 
  shown in figure 4.11, a rotating propeller in- 
  clined to the windstream causes a deflection 
  of the airflow. The momentum change of the 