text: with altitude above the tropopause. This is 
  due in great part to the more rapid decay of 
  engine thrust in the stratosphere. 
  
  During a power off descent the deficiency of 
  thrust and power define the angle of descent 
  and rate of descent. TWO particular points 
  are of interest during a power off descent: 
  minimum angle of descent and minimum rate 
  of descent. The minimum angle of descent 
  would provide maximum glide distance through 
  the air. Since no thrust is available from the 
  power plant, minimum angle of descent would 
  be obtained at (L/D)-. 
  the 
  deficiency of thrust 
  is a minimum and, as 
  shown by figure 2.22, the greatest proportion 
  between velocity and power required is ob- 
  tained. The minimum 
  rate of descent in 
  is obtained at the angle of 
  power off flight 
  attack and airspeed which produce minimum 
  power required. For airplanes of moderate 
  aspect ratio, 
  the speed for minimum rate of 
  descent is approximately 75 percent of the 
  speed for minimum angle of descent 
  
  The general item of range must be clearly 
  distinguished from the item of endurance. The 
  item of range involves consideration of flying 
  distance while endurance involves consideration 
  of flying time. Thus, it is appropriate to define 
  a separate term, “specific endurance.” 