Definition
AC generators are engine-driven electrical machines that produce alternating current — current that reverses direction many times per second — to power aircraft electrical systems. In most light aircraft they are called alternators, and their AC output is converted to direct current by a rectifier before being delivered to the aircraft bus and battery.
Plain English
A device turned by the engine that makes electricity for the aircraft. The kind of electricity it makes flows back and forth rapidly, and in small aircraft it is usually changed into the steadier kind before being used.
Context Anchor
Seen in aircraft electrical system descriptions, cockpit electrical indications, and abnormal checklists for generator failure.
Derivation
Generator comes from the Latin generare, meaning 'to produce' or 'to bring forth.' An AC generator is simply a machine that produces alternating current — electricity whose flow alternates direction rather than moving steadily one way.
Why Pilots Care
AC generators supply the steady electrical power needed for avionics, navigation, and communication systems, directly affecting flight safety and system reliability.
Intuition Check
Do not think of an AC generator as a battery. A battery stores electrical power; an AC generator makes electrical power only while it is being driven.
Example Sentence 1
Most modern light aircraft use AC generators, commonly called alternators, instead of the older DC generators.
Example Sentence 2
Larger aircraft often use multiple AC generators to meet the high electrical demands of modern avionics.