What is the primary purpose of the APU's electrical generator within an aircraft system?

• A. To provide electrical power to aircraft buses when main engines are not providing power.
• B. To provide mechanical thrust to the main engines.
• C. To supply hydraulic pressure to landing gear.
• D. To cool the main engine.

Answer: (A)

The main idea is that the APU’s electrical generator provides electrical power to the aircraft’s electrical buses when the main engines aren’t supplying power. This lets cockpit instruments, avionics, lighting, environmental controls, and other essential systems run on the ground or during engine start, and can serve as a backup power source in flight if needed. It’s about supplying electricity, not producing thrust or directly driving hydraulic pressure or cooling. The other options mix up propulsion, hydraulics, and cooling functions, which aren’t the generator’s primary role.