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.
Plain English
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.
Context Anchor
Seen when studying the aircraft electrical system and checking how the airplane is powered before and during flight.
Why Pilots Care
Understanding the sources lets pilots recognize power failures early, select the correct backup, and keep critical instruments running.
Intuition Check
Do not read “power” here as engine thrust or horsepower. In this context, it means electrical energy for the airplane’s systems.
Example Sentence 1
During preflight, the pilot checked both sources of power by confirming the vacuum gauge was in the green and the alternator was charging the battery.
Example Sentence 2
When the alternator failed in flight the pilot relied on the battery as the remaining source of power for the essential instruments.