Definition
A ground power unit is a portable or fixed external electrical power source used to supply electrical power to an aircraft while it is on the ground, allowing systems such as avionics, lighting, and engine starters to operate without relying on the aircraft's battery or running engines.
Plain English
A GPU is an outside power source that plugs into the airplane on the ground, so the airplane can run its electrical systems or start its engines without draining its own battery.
Context Anchor
Pilots encounter GPUs on ramps, at gates, and during preflight or maintenance when aircraft electrical systems need power before the engine is running.
Why Pilots Care
Using a GPU prevents draining the aircraft batteries and avoids running the APU, saving fuel and reducing noise at the ramp.
Intuition Check
A GPU is not part of the aircraft’s normal in-flight power system. It is outside power used while the aircraft is on the ground.
Example Sentence 1
The lineman connected a GPU to the aircraft so the pilot could start the engine without straining the battery on the cold morning.
Example Sentence 2
At airports without a hangar power supply, the GPU provides the only reliable source of electricity for preflight avionics checks.