What external feature does the electrical system include for ground operations?

The electrical system of the Pilatus PC-12 NG is designed to facilitate ground operations efficiently, and an external socket for a GPU, or Ground Power Unit, plays a critical role in this context. When the aircraft is on the ground and engine operations are not taking place, a GPU provides electrical power to the aircraft systems. This is essential for powering avionics, lighting, and other onboard systems without relying on the aircraft's batteries.

Using a GPU is particularly advantageous as it ensures that the aircraft's battery life is preserved for flight operations and reduces wear and tear on the engine during pre-flight procedures. It also enhances safety and operational efficiency by allowing pilots and ground crews to run checks and prepare the aircraft without needing to start the engine.

While other features like external lighting ports, start connections, and battery connections have their specific roles, they do not directly relate to standard ground power requirements in the same way that a GPU connection does. Thus, the inclusion of an external socket for a GPU is a vital feature for managing electrical power during ground operations.