Which set correctly lists the four common aircraft system voltages?

• A. 12 VDC, 24 VDC, 115 VAC, 230 VAC
• B. 28 VDC, 28 VAC, 120 VAC, 240 VAC
• C. 14 VDC, 28 VDC, 115 VAC, 200 VAC
• D. 15 VDC, 30 VDC, 110 VAC, 190 VAC

Answer: (C)

The four common voltages in aircraft electrical systems span both DC and AC power, reflecting how power is distributed for different loads. Modern aircraft use a main DC bus around 28 V for most electrical equipment, with some smaller or older circuits operating at 14 V DC. For AC power, aircraft typically use 115 V AC, often at 400 Hz, for higher-power loads and certain avionics or systems, and there are configurations where around 200 V AC appears in specific installations. This combination—14 VDC, 28 VDC, 115 VAC, and 200 VAC—covers the common voltage levels encountered across the aircraft’s electrical system, making it the best match. The other options mix voltages that aren’t standard together in typical airframe power distribution, so they don’t align with how aircraft electrical systems are normally defined.