On the ground without external power connected, which source is commonly used to supply electrical power?

On the ground without external power connected, which source is commonly used to supply electrical power?

• A. Engine-driven generator on left engine
• B. External ground power cart
• C. Battery power only
• D. APU generator

Answer: (D)

On the ground, with no external power connected, the usual source of electrical power is the aircraft’s Auxiliary Power Unit (APU) generator. The APU is a self-contained turbine in the tail that can start up independently of the main engines and provide electrical power to the aircraft systems, avionics, lighting, cabin conditioning, and even start power for the engines if needed. Using the APU keeps the airplane self-sufficient without needing to run a main engine just to supply power, and it’s quicker and more flexible than waiting for or relying on external power. Battery power alone can’t sustain all required loads for an extended period, and engine-driven generators would require the engines to be running (which isn’t the case here). External ground power is another option when available, but the scenario specifies that no external power is connected, so the APU generator is the practical choice.

On the ground, with no external power connected, the usual source of electrical power is the aircraft’s Auxiliary Power Unit (APU) generator. The APU is a self-contained turbine in the tail that can start up independently of the main engines and provide electrical power to the aircraft systems, avionics, lighting, cabin conditioning, and even start power for the engines if needed. Using the APU keeps the airplane self-sufficient without needing to run a main engine just to supply power, and it’s quicker and more flexible than waiting for or relying on external power.

Battery power alone can’t sustain all required loads for an extended period, and engine-driven generators would require the engines to be running (which isn’t the case here). External ground power is another option when available, but the scenario specifies that no external power is connected, so the APU generator is the practical choice.