When is external power used on the ground?

When is external power used on the ground?

• A. Only during maintenance hours.
• B. For preflight checks, engine start, or when on-ground power is required and engines are not yet providing electrical power.
• C. Only after engines are running.
• D. To supply pneumatics only.

Answer: (B)

External power on the ground is used to energize the aircraft’s electrical system while the engines are not yet providing power. This allows you to run cockpit instruments, avionics, radios, lighting, and environmental controls, and to perform preflight checks without relying on the engines. It also provides the power needed to start the engines, so you can bring the aircraft online without waiting for the engines to generate electricity first. Pneumatic power, not electrical, is handled separately—air sources for starting or cabin/air conditioning come from bleed air from the engines or the APU, or from a dedicated air cart. So external power is about supplying electrical power, not pneumatics. That’s why it’s used for preflight checks, engine start, or any on-ground situation where electrical power is required but the engines aren’t yet providing it.

External power on the ground is used to energize the aircraft’s electrical system while the engines are not yet providing power. This allows you to run cockpit instruments, avionics, radios, lighting, and environmental controls, and to perform preflight checks without relying on the engines. It also provides the power needed to start the engines, so you can bring the aircraft online without waiting for the engines to generate electricity first.

Pneumatic power, not electrical, is handled separately—air sources for starting or cabin/air conditioning come from bleed air from the engines or the APU, or from a dedicated air cart. So external power is about supplying electrical power, not pneumatics.

That’s why it’s used for preflight checks, engine start, or any on-ground situation where electrical power is required but the engines aren’t yet providing it.