Plain English Meaning

The systems on the aircraft that supply the energy needed to make the instruments and equipment work. Some instruments run on suction from a pump on the engine, and others run on electricity from the engine and battery.

Full Definition

In an aircraft, the systems that drive the flight instruments and other onboard equipment. The main sources are engine-driven vacuum (suction) pumps, engine-driven electrical generators or alternators, and the aircraft battery. Different instruments rely on different sources: traditional gyroscopic instruments such as the attitude indicator and heading indicator are commonly powered by the vacuum system, while the turn coordinator, electronic displays, radios, and lights are powered electrically.