Campbell shows the effect of different nozzle areas on the steady-state running line. Automatic control of the area was disabled for this investigation. In service the area is open at idle and progressively closes as the engine accelerates as shown by the area scheduling. An adjustable nozzle is not added for this particular purpose but if an afterburner is fitted then it can be used to reduce idle thrust and quicken acceleration times up to the thrust where the afterburner becomes operational. The ideal fan operating line on an augmented turbofan sets fan pressure ratio as high as possible to optimize fan performance and thrust while keeping adequate fan stall margin. The fan operating line is controlled by varying the nozzle area which acts like a throttling valve. The throttling is a combination of thermal from the burning fuel and geometric from the adjustable nozzle area.