Definition
An aircraft electrical generator that produces alternating current internally through a rotating magnetic field, then rectifies that output to direct current using built-in diodes before delivering it to the aircraft electrical system. Despite producing DC at its terminals, it is called an alternator because the generation process itself is alternating, unlike a traditional DC generator that uses a commutator.
Plain English
A device on the engine that makes electricity for the aircraft. It generates the electricity in an alternating form first, then converts it to the steady direct current the aircraft needs.
Context Anchor
Seen in aircraft electrical system descriptions, alternator checks, charging-system indications, and maintenance discussions.
Derivation
Alternator comes from the Latin alternare, meaning 'to do by turns.' The name refers to how the current inside the unit reverses direction by turns as the rotor spins. The 'DC' label tells you what comes out after the internal rectification, not what is produced inside.
Why Pilots Care
It keeps the battery from discharging and ensures continuous power to radios, lights, and instruments while the engine runs.
Intuition Check
Do not read “DC alternator” as a device that makes direct current from the start. It makes alternating current inside, then converts it to direct current for aircraft use.
Example Sentence 1
After engine start, the pilot checked the ammeter and confirmed the DC alternator was charging the battery.
Example Sentence 2
A failed DC alternator forces the pilot to rely on battery power alone until landing.