What electrical frequency is commonly used for aircraft electrical systems powered by the APU on the ground?

What electrical frequency is commonly used for aircraft electrical systems powered by the APU on the ground?

• A. 400 Hz
• B. 60 Hz
• C. 50 Hz
• D. 1 Hz

Answer: (A)

Aircraft electrical systems are designed around a higher frequency to save weight. Using 400 Hz means that transformers, generators, and motors can be much smaller and lighter than they would be at 50 or 60 Hz, while still delivering the necessary power for avionics, flight controls, and other systems. That weight savings is a big deal in aviation, where every kilogram matters. When the APU is on the ground, it provides 400 Hz AC power to the aircraft’s electrical buses so the systems operate in the same electrical environment as in flight. Using 1 Hz would be impractical, and 50 or 60 Hz would require substantially larger and heavier equipment, offsetting the advantages.

Aircraft electrical systems are designed around a higher frequency to save weight. Using 400 Hz means that transformers, generators, and motors can be much smaller and lighter than they would be at 50 or 60 Hz, while still delivering the necessary power for avionics, flight controls, and other systems. That weight savings is a big deal in aviation, where every kilogram matters.

When the APU is on the ground, it provides 400 Hz AC power to the aircraft’s electrical buses so the systems operate in the same electrical environment as in flight. Using 1 Hz would be impractical, and 50 or 60 Hz would require substantially larger and heavier equipment, offsetting the advantages.