Definition
An electrical supply of 28 volts in which current flows in one direction only. It is the standard low-voltage DC bus level used in most turboprop and many transport-category aircraft to power avionics, lighting, instruments, relays, and control circuits.
Plain English
A 28-volt electrical supply where the current always flows the same way, used to run most of the airplane's smaller electrical equipment.
Context Anchor
Seen in turboprop electrical system descriptions, cockpit voltage indications, battery discussions, and equipment power requirements.
Derivation
Direct current' means the electricity moves steadily in one direction, unlike alternating current (AC) which reverses back and forth many times per second. The 28-volt level became the aviation standard because it pairs naturally with a 24-volt battery system: the generator or alternator output sits a few volts above battery voltage so it can charge the battery and carry the load at the same time.
Why Pilots Care
Maintains reliable power to essential flight instruments and systems; pilots verify it during preflight and troubleshooting.
Analogy
Think of it like a car electrical system, but at an aircraft level of about 28 volts instead of a car’s usual 12 volts. The important idea is steady one-way electrical flow.
Intuition Check
“Direct” does not mean fastest or shortest here. It means the electrical current flows in one direction. “Current” does not mean wind or water movement here. It means the flow of electricity.
Example Sentence 1
The avionics, cockpit lighting, and instrument panel are powered by the airplane's 28-volt DC bus.
Example Sentence 2
During the electrical check the pilot confirmed the battery was delivering proper 28-volt direct current.