What is the maximum N2 rotational speed to use the starter?

The maximum N2 rotational speed at which the starter can be used is set at 45% N2. This limitation protects the engine and starter from potential damage that could occur if the starter were engaged when the engine is operating at higher speeds. During the start sequence, engaging the starter beyond this threshold could result in excessive wear or failure due to the increased rotational forces that the starter is not designed to handle.

This limit is established based on the performance characteristics of the starter and the engine's operational safety margins, ensuring that both components function within safe operational parameters. By adhering to this limitation, pilots can ensure that the engine starts smoothly without incurring undue stress on the mechanical systems involved.