When should the starter be disengaged during engine operation?

The starter should be disengaged when the engine is at its self-sustained speed because this indicates that the engine has reached a condition where it can continue operating independently of external power. Self-sustained speed refers to the point at which the engine is producing enough combustion power to sustain its operation without assistance from the starter. Engaging the starter beyond this point can lead to unnecessary wear on components and potential damage to the engine.

In turbine engines, this is a crucial moment that ensures a smooth transition from the start phase to normal operation, minimizing risks associated with prolonged starter engagement.