text: During deceleration conditions, the mini- 
  mum allowable fuel flow is defined by the lean 
  limit 
  If the fuel flow 
  is reduced below some critical value at each 
  RPM, lean blowout or flameout will occur. 
  is illustrated by curve 3 of 
  This condition 
  figure 2.12 which forms the deceleration fuel 
  flow boundary. The governing apparatus must 
  this 
  regulate the deceleration fuel flow within 
  boundary. 
  
  to support combustion. 
  
  To appreciate the governing requirements 
  during the deceleration process, assume the 
  engine described in figure 2.12 is in stabilized, 
  steady state operation at point C and it 
  is 
  desired to decelerate to idle conditions and 
  stabilize at point E. As the throttle is placed 
  at the position for idle RPM, the fuel control 
  will decrease the fuel flow to point D to provide 
  the deceleration fuel 
  the engine 
  decelerates and decreases RPM, the fuel gov- 
  erning will continue to decrease the fuel flow 
  within the deceleration boundary until the idle 
  fuel flow is reached and RPM is established at 
  is closed 
  point E. Of course, if the throttle 
  very slowly, the deceleration fuel flow is barely 
  below the steady state condition and the engine 
  does not approach the deceleration fuel flow 
  boundary. The fuel control must provide a 
  deceleration flow close to 
  the boundary to 
  provide rapid decrease in thrust and satisfactory 
  flight control. 