What is the role of the aircraft alternator during flight?

• A. It provides power only for navigation equipment.
• B. It converts DC to DC at different voltage levels.
• C. It connects the aircraft to the external power grid.
• D. It supplies electrical power to the DC bus and charges the battery via rectification.

Answer: (D)

The essential idea is that the alternator is the aircraft’s main source of electrical power during flight, producing AC that is then rectified to DC to feed the DC bus and charge the battery. The engine drives the alternator, which outputs three-phase AC. A rectifier converts that AC into DC and a regulator keeps the DC bus voltage stable (around 28 volts for many aircraft). This DC power goes to the avionics, lighting, sensors, and other systems, while the battery is kept charged so it’s ready for starts and can smooth any temporary demand or generator loss. So the role is to supply electrical power to the DC system and charge the battery via rectification. It isn’t limited to navigation equipment, it doesn’t convert DC to DC, and it doesn’t connect to an external power grid.