What does the alternator power?

• A. The engine oil system
• B. The aircraft's electrical system and recharges the battery
• C. The fuel pump
• D. The landing gear hydraulics

Answer: (B)

The core function being tested is how the aircraft’s alternator supports power for the airplane’s systems and battery. When the engine runs, the alternator is driven by a belt from the engine and generates electrical energy for the aircraft. That electrical energy powers avionics, lights, radios, instruments, and other electrical loads, while also charging the battery so it’s ready to provide starting power and serve as a backup. If the alternator is producing properly, it keeps the electrical system running and continuously replenishes the battery. If it stops producing, the system relies on the battery alone until it’s depleted or power is restored.

The other systems listed—engine lubrication, fuel pumping, and hydraulic landing gear power—have separate power sources. The oil system is driven by the engine-driven oil pump, the fuel pump has its own drive (engine-driven or electric), and the hydraulics are powered by their own pumps, not the alternator’s primary role.