Aircraft power supply 400 Hz refers to the 400 Hz AC power supply used in aircraft. Aircraft use their engines to generate 400 Hz AC, but when the engines are off on the aircraft parking apron at the airport, it is necessary to supply the power from an external source. A 400 Hz AC power supply for aircraft is used for this purpose. 400 Hz AC power is also used in the development, manufacturing and testing of avionics (electronic equipment used in aircraft for flight).

Matsusada Precision's AC power sources can also be used in the development of avionics.