Installed as a flight instrument on most of today’s aircraft, an attitude indicator is used to display the aircraft’s orientation during flight. Also known as an artificial horizon, this instrument relays two major indications to the pilot: pitch and roll angles. Most attitude indicators include a horizon with two different colors, normally blue and brown, to represent the sky and earth. A miniature airplane in the center of the display shows the aircraft’s orientation relative to the horizon. Degree marks indicating the amount of pitch or bank are often drawn on the instrument to indicate the exact aircraft orientation.
Most attitude indicators found in general aviation aircraft operate on the principal of gyroscopic rigidity. An attitude indicator features a gyroscope that spins at a high speed, powered by vacuum air supplied by the aircraft’s engine-driven vacuum pump or pumps. Spinning gyroscopes will naturally want to remain flat, like the surface of the Earth, while an aircraft maneuvers in flight. The instrument is then able to determine pitch and roll angles using internal sensors. It is important to note that most attitude indicators will fail during excessive maneuvers and will be rendered unusable for a period of time.
The attitude indicator is a required instrument for flight in poor weather, when instrument flight rules (IFR) are in effect for pilots. Flight during periods of clear visibility and high clouds, when visual flight rules (VFR) are in effect, do not require the instrument's use. While it's not required for VFR, it is advisable to have an attitude indicator, because it will greatly enhance a pilot’s situational awareness and aid him should he encounter a loss of flight visibility.
While flying in IFR conditions, pilots heavily rely on their attitude indicator to display the aircraft’s orientation relative to the Earth. This requires advanced training, because pilots are required to go from usually visual cues such as the horizon to using this small instrument on the cockpit’s dashboard. Flight in IFR conditions requires the pilot to receive an instrument rating from a certified flight instructor. Instrument-rated pilots are required to maintain proficiency through routine flights and evaluations.
More sophisticated aircraft feature more sophisticated attitude indicators. Most commercial jets, for example, use attitude heading and reference systems (AHRS). This type of attitude indicator uses more advanced gyroscopes and magnetometers, which can also supply information regarding the aircraft’s heading. Larger aircraft often feature more than one attitude indicator for use by one or more pilots.