text: The configuration of an airplane has a great 
  ratio. Typical values 
  effect on the lift-drag 
  are listed for various types of 
  of (L/D),.. 
  airplanes. While the high performance sail- 
  plane may have. extremely high 
  lift-drag 
  ratios, such an aircraft has no real economic 
  or tactical purpose. The supersonic fighter 
  ratios in 
  may have seemingly low 
  subsonic flight but the airplane configurations 
  required for supersonic flight (and high [L/D]‘*
  at high Mach numbers) precipitate this situa- 
  tion. 
  
  higher angles of attack the drag coefficient is 
  much greater and small changes in angle of 
  attack cause significant changes in drag. As 
  stall occurs, a large increase in drag takes 
  place. 
  
  in airplane per- 
  formance considerations is the lift-drag ratio, 
  L/D. With the lift and drag data available for 
  the airplane, the proportions of CL and CD can 
  be calculated for each specific angle of attack. 
  The resulting plot of lift-drag ratio with angle 
  of attack shows that L/D 
  increases to some 
  maximum then decreases at the higher 
  lift 
  coefficients and angles of attack. Note that 
  occurs 
  the maximum lift-drag ratio, (L/D),,,, 
  at one specific angle of attack and lift coefIi- 
  If the airplane is operated in steady 
  cient. 
  the total drag is at a mini: 
  flight at (L/D),,,, 
  mum. Any angle of attack lower or higher 
  than 
  reduces the lift-drag 
  ratio and consequently increases -the total 
  drag for a given airpiane iift. 
  
  A factor more important 
  
  Many important items of airplane perform- 
  ance are obtained in flight at (L/D),... 
  Typi- 
  cal performance conditions which occur at 
  (L/D),., are: 
  
  maximum endurance of jet powered air- 
  
  planes 
  
  maximum range of propeller driven air- 
  that for (L/D),,, 
  planes 
  
  maximum climb angle for jet powered air- 