What is an attitude indicator and how is it powered in most modern aircraft?

• A. Provides artificial horizon; now typically electric or electric-driven AHRS; some older planes used vacuum systems.
• B. Measures altitude and vertical speed.
• C. Controls air conditioning system.
• D. Indicates engine temperature.

Answer: (A)

Attitude indicators show the aircraft’s orientation relative to the horizon by displaying an artificial horizon and a small airplane symbol. The key idea is how that gyro-based reference is powered. In modern aircraft, the attitude information comes from an electric source—often an electric gyro or, more commonly, through an AHRS (Attitude and Heading Reference System) that provides data to the cockpit display. This electric approach is reliable and integrates with other flight computers. In older planes, those gyros were driven by a vacuum system created by the engine, which spun the gyro to keep the horizon stable on the indicator.

So the correct choice points to providing an artificial horizon and being powered by electric-driven systems (with AHRS in many modern airplanes), noting that vacuum systems were used in older aircraft. The other options describe instruments that measure altitude/vertical speed, control environmental systems, or indicate engine temperature, which are unrelated to the attitude indicator.