Final answer:
The starter should not be used if the N2 RPM exceeds a certain limit for safety reasons, but the exact limit depends on the aircraft's model. Usually, a limit around 50 RPM is reasonable, but without specific details, a definitive answer cannot be advised.
Step-by-step explanation:
The starter on an aircraft should not be used if the indicated N2 RPM exceeds certain limits. These limits are specific to the aircraft's make and model, and are critical for safety during the startup procedure of a turbine engine. In many cases, pilots and maintenance personnel are advised not to engage the starter if the N2 RPM is above 10-20%; however, the options provided suggest a higher threshold.
It's important to reference the specific aircraft's operating handbook or a reliable source for this information, but without precise context, a commonly accepted answer cannot be given. Typically, option 1 (50 RPM) would be a reasonable limit for many turbine engines, but without confirming the exact make and model of the engine, providing a definitive answer would be inappropriate.