When should the starter be disengaged when starting a turbine engine?

The starter should be disengaged after the engine has reached self-accelerating speed because this is the point at which the turbine engine is capable of continuing to operate on its own without the assistance of the starter. Self-accelerating speed refers to the minimum RPM at which the engine sustains combustion and can generate enough thrust to increase its speed without external assistance.

This is a critical moment in the start sequence, as disengaging the starter at this time ensures that the engine has transitioned to a self-sustaining state, allowing for a smooth and efficient operation. If the starter remains engaged too long, it could lead to unnecessary wear on the starter motor and possibly cause damage to the engine’s starter gear mechanism.

Other options touch upon various stages of the starting procedure, but they do not represent the ideal moment to disengage the starter. For example, reaching idle speed may not guarantee that the engine can operate independently, as idle speed is typically a lower threshold than the self-accelerating speed. Similarly, monitoring exhaust gas temperature or fuel flow stabilization are important factors, but they do not specifically indicate that the engine has achieved sufficient speed to operate autonomously.