text: warning, and preserves lateral control effec- 
  tiveness at high angles of attack. Also, the 
  airplane must maintain positive static longi- 
  tudinal stability at high lift coe&ients and 
  should demonstrate satisfactory stall recovery 
  characteristics. 
  
  damping in roll 
  “autorotation.” 
  
  is generally referred to as 
  
  In order to visualize the principal effects of 
  an airplane entering a spin, suppose the air- 
  plane is subjected to the rolling and yawing 
  velocities shown in figure 4.32. The yawing 
  velocity to the right tends to produce higher 
  local velocities on the left wing than on the 
  tends to 
  right wing. 
  increase the angle of attack for the downgoing 
  right wing (a,) and. decrease the angle of 
  At 
  attack for the upgoing left wing (al). 
  airplane angles of attack below the stall this 
  relationship produces roll due to yaw, damping 
  in roll, etc., and some related motion of the 
  However, at 
  airplane in unstalled 
  angles of attack above the stall, 
  important 
  changes take place in the aerodynamic char- 
  acteristics. 
  
  The rolling velocity 
  
  the aerodynamic 
  characteristics typical of a conventional air- 
  i.e., moderate or high 
  plane configuration, 
  any-sweepback. 
  aspect ratio and little-if 
  Ifs this airplane is provided a rolling displace- 
  ment when at some angle of attack above 
  the stall, 
  the upgoing wing experiences a 
  decrease in angle of attack with a correspond- 
  ing increase in C, and decrease in C,,. In other 
  words, the upgoing wing becomes less stalled. 
  the downgoing wing experiences 
  Similarly, 
  an increase in angle of attack with a corre- 
  sponding decrease in CL and increase in CD. Es- 
  sentially, the downgoing wing becomes more 
  is aided 
  stalled. Thus, the rolling motion 
  rather than resisted and a yawing moment is 
  produced in the direction of roll. At angles 
  is 
  of attack below stall the rolling motion 
  resisted by damping in roll and adverse yaw 
  is usually present. At angles of attack above 
  the stall, the damping in roll is negative and 
  a rolling motion produces a rolling moment 
  This negative 
  in the direction of the roll. 
  
  Figure 4.32  illustrates 