text: Maximum ratio of 
  
  (Mean blade lift coetIicient)3” 
  Mean blade drag coefficient 
  
  It is this ratio which determines the auto- 
  rate of descent. Figure 6.18 illus- 
  rotation 
  trates the variation of autorotation 
  rate of 
  descent with equivalent airspeed for a typical 
  helicopter. Point A on this curve defines the 
  point which produces autorotation with mini- 
  mum rate of descent. Maximum glide distance 