text: is to reduce the engine 
  airflow and power output and supercharging 
  is necessary to maintain high power output 
  at high altitude. Since the basic engine is 
  able to process air only by the basic volume 
  displacement, the function of the supercharger 
  is to compress the inlet air and provide a 
  greater weight of air for the engine to process. 
  Of course, shaft power is necessary to operate 
  the engine driven supercharger and a tempera- 
  ture rise occurs through the supercharger com- 
  pression. The effect of various forms of super- 
  charging on altitude performance is illustrated 
  in figure 2.17. 
  
  The schedule of fuel-air ratios with an auto- 
  matic lean fuel-air ratio will automatically 
  provide maximum usable economy. 
  If manual 
  leaning procedures are applicable a lower fuel- 
  air ratio may be necessary for maximum possi- 
  efficiency. The maximum continuous 
  ble  aspi- 
  rated-engine has no means of providing a 
  
  The unsupercharged-or  naturally 
  
  141 