An attitude indicator includes a stationary dot and lines that represent the aircraft and wings. Behind this display is a moving field that represents the horizon. By seeing the relationship between the aircraft and the horizon, the pilot can determine the aircraft's orientation.
Mechanical attitude indicators include a gyroscope that is powered either by a vacuum pump or an electrical motor. The gyroscope has two degrees of freedom, allowing it to display both the pitch and bank of the aircraft.
While the aircraft rotates, the gyroscope remains in the same orientation with relationship to the ground. The ground display is linked to the gyroscope by a lever.
Mechanical attitude indicators are only able to display rotation up to a certain extent. Most fail to function when the plane is banked more than 100° or pitched more than 60°.
Some aircraft use electronic attitude indicators, which make use of computer systems to present the same information. Many of these planes have a back up mechanical attitude indicator, should the plane's computer systems fail.
