Definition
An electric current that flows in one direction only, at a steady voltage, between a positive and negative terminal. In aircraft, DC is the standard form of electrical power supplied by the battery and the alternator/generator system, used to operate most onboard electrical equipment.
Plain English
Electricity that flows steadily in one direction, like the power from a battery. It is the kind of electrical power most aircraft systems run on.
Context Anchor
Seen in aircraft electrical system descriptions, instrument power-source notes, and discussions of battery or standby power.
Derivation
From 'direct,' meaning straight or one-way, and 'current,' the flow of electricity. The name simply describes what it does: electricity that flows in one direct path, as opposed to alternating current (AC), which reverses direction many times per second.
Why Pilots Care
Aircraft batteries and many cockpit instruments run on DC power; loss of DC can disable essential systems in instrument flight.
Analogy
DC is like traffic moving one way down a one-way street. The flow keeps going in the same direction instead of reversing back and forth.
Intuition Check
DC does not mean “battery only.” It describes the one-way direction of the electrical flow; a battery is just a common source of DC power.
Example Sentence 1
The aircraft battery supplies 24-volt DC power to the avionics and lighting circuits.
Example Sentence 2
The alternator converts engine power into DC to keep the battery charged and instruments operating.