When does starter disengagement timing occur in an aircraft engine?

Starter disengagement timing typically occurs after the engine reaches idle speed. This is a crucial phase in the engine's start-up process, as the starter is responsible for bringing the engine up to the point where it can sustain combustion and operate independently. When the engine achieves idle speed, it indicates that the combustion process is stable and the engine can maintain rotation without assistance from the starter.

Once idle speed is reached, the starter can safely disengage to prevent any potential damage that could occur from it remaining engaged when not needed. This timing ensures a smooth transition from starting to normal operational conditions, allowing the engine to function efficiently and reliably.