What is the typical role of the APU generator in electrical distribution?

What is the typical role of the APU generator in electrical distribution?

• A. It powers cabin lights only.
• B. It provides an additional AC power source, often powering the essential and/or main AC buses when engines are not driving generators.
• C. It powers the landing gear.
• D. It is used only on the ground and not during flight.

Answer: (B)

The APU generator’s job is to provide an independent source of electrical power for the aircraft’s distribution system. It acts as an extra power source so the essential and sometimes main AC buses can stay energized even when the engines’ generators aren’t driving them—such as during engine start, on the ground with engines off, or as a backup in flight if an engine-driven generator fails. This keeps critical systems like avionics and flight controls powered without relying on the engines. It’s not limited to cabin lights, and it isn’t restricted to ground use only—the APU can supply power in flight if needed, although the exact use depends on the aircraft’s electrical configuration.

The APU generator’s job is to provide an independent source of electrical power for the aircraft’s distribution system. It acts as an extra power source so the essential and sometimes main AC buses can stay energized even when the engines’ generators aren’t driving them—such as during engine start, on the ground with engines off, or as a backup in flight if an engine-driven generator fails. This keeps critical systems like avionics and flight controls powered without relying on the engines. It’s not limited to cabin lights, and it isn’t restricted to ground use only—the APU can supply power in flight if needed, although the exact use depends on the aircraft’s electrical configuration.