text: temperatures, compressor 
  
  There are various instruments to relate irnr 
  portant items of turbojet engine performance. 
  Certain combinations of these instruments are 
  capable of 
  the thrust 
  immediately relating 
  output of the powerplant in a qualitative man- 
  It is difficult to provide an instrument or 
  ner. 
  combination of 
  immedi- 
  instruments which 
  ately relate the thrust output in a ~arrantitativ~ 
  manner. As a result, the pilot must rely on 
  a combination of instrument readings and judge 
  the output performance according to standard 
  values particular to the powerplant. Some of 
  the usual engine indicating instruments are as 
  follows : 
  
  (1) The tachometer provides indication of 
  engine speed, N, by percent of the maximum 