What mode ensures that the aircraft operates safely above 50% N2?

The accessory gearbox mode is vital for ensuring that the aircraft operates safely above 50% N2, which refers to the speed of the high-pressure compressor in a gas turbine engine. In this mode, critical components such as fuel pumps, oil pumps, and generators are driven by the engine's accessory gearbox.

When the N2 speed exceeds 50%, certain systems become operational and can maintain necessary functions for safe flight operations. This mode allows for efficient management of power distribution and ensures that essential equipment is available for performance and safety during various phases of flight.

The other modes listed—battery, electrical, and standby modes—play different roles and do not specifically guarantee operational safety regarding N2 speed. They are more focused on power management or redundancy, which might not directly ensure safe operation above that critical N2 threshold. This highlights the importance of the accessory gearbox mode for maintaining operational integrity and safety in aircraft engines at higher speeds.