Which statement about 400 Hz power systems in aircraft is true?

• A. They use 60 Hz for primary power distribution.
• B. They allow smaller, lighter transformers and electrical components.
• C. They require more complex rectification than 28 V systems.
• D. They are not used in aviation.

Answer: (B)

Higher frequency in aircraft electrical systems allows smaller, lighter transformers and components. At 400 Hz, the magnetic core and windings needed for a given power rating can be much smaller than at 60 Hz, so the transformers, inductors, and related gear weigh less and take up less space. This weight reduction is crucial in aviation, where every pound matters, and it enables more compact and efficient power distribution without sacrificing performance.

The other statements don’t fit with how 400 Hz systems are used. Aircraft power distribution isn’t based on 60 Hz; 400 Hz is the standard to save weight. While rectification is part of supplying DC loads from the AC system, saying rectification is inherently more complex than a 28 V DC system isn’t accurate, since 28 V systems are already DC and don’t require the same kind of AC-to-DC conversion. And yes, aviation does use 400 Hz power.