What does an engine's "cut-off" refer to?

The term "cut-off" in the context of a gas turbine engine specifically refers to the moment when fuel flow to the combustor is reduced or completely stopped. This action is crucial for controlling engine performance, particularly for managing the engine’s power output and ensuring efficient operation.

When the fuel flow is cut off, it can signify the end of combustion for various operational scenarios, such as during a descent phase or approach, where a reduction in thrust is required. By reducing or halting fuel flow, the engine can transition to a lower thrust level or even into a fuel-saving phase, allowing for the safe and efficient operation of the aircraft.

Understanding the cut-off phase is essential, as it plays a key role in engine management, safety protocols, and overall efficiency during flight operations.