text: Another aerodynamic reference point is the 
  “aerodynamic center, d.e.” The aerodynamic 
  center is defmed as the point along the chord 
  where all changes in lift effectively take place. 
  To visualize the existence of such a point, 
  notice the change in pressure distribution with 
  the symmetrical airfoil 
  angle of attack 
  the upper 
  of figure 1.21. When at zero lift, 
  and lower surface lifts are equal and located 
  at the same point. With an increase in angle 
  of attack, the upper surface lift increases while 
  the lower surface lift decreases. The change 
  ,of lift has taken place with no change in the 
  center of pressure-a characteristic of sym- 
  metrical airfoils. 
  
  for 
  
  The typical jet aircraft does not experience 
  the 
  induced flow velocities encountered in 
  propeller driven airplanes, thus the only sig- 
  nificant factor is the vertical component of 
  thrust. Since this vertical component con- 
  tributes to supporting the airplane, less aero- 
  is required to hold the airplane 
  dynamic lift 
  If the thrust is small and the thrust 
  in flight. 
  inclination 
  is slight at maximum lift angle, 
  re- 
  only negligible changes in stall speed will 
  sult. On the other hand, if the thrust is very 
  great and is given a large inclination at maxi- 
  mum lift angle, the effect on stall speed can 
  be very large. One important 
  relationship 
  remains-since there is very little induced flow 
  from the jet, the angle of attack at stall is 
  essentially the same power-on or power-off. 