Attitude indicator

An attitude indicator (AI), also known as gyro horizon or artificial horizon or attitude director indicator (ADI, when it has a Flight Director), is an instrument used in an aircraft to inform the pilot of the orientation of the aircraft relative to Earth's horizon. It indicates pitch (fore and aft tilt) and bank (side to side tilt) and is a primary instrument for flight in instrument meteorological conditions.

Attitude indicators are also used on manned spacecraft and are called, Flight Director Attitude Indicator (FDAI), where they indicate the craft's yaw angle (nose left or right) as well as pitch (nose up or down), roll, and orbit relative to a fixed-space inertial reference frame. An FDAI, has different modes that allow for known positions relative to Earth or the stars, so that the engineers, scientists and astronauts can communicate the relative position, attitude, and orbit of the craft.

The essential components of the indicator are:

If the symbolic aircraft dot is above the horizon line (blue background) the aircraft is nose up. If the symbolic aircraft dot is below the horizon line (brown background) the aircraft is nose down. The fact that the horizon moves up and down and turns, while the symbolic aircraft is fixed relative to the rest of the instrument panel, tends to induce confusion in trainees learning to use the instrument; a standard mental corrective provided by flight instructors is "Fly the little airplane, not the horizon."

A 45 degree bank turn is made by placing the indicator equidistant between the 30 and 60 degree marks. A 45 degree bank turn is usually referred to as a steep turn.

The pitch angle is relative to the horizon. During instrument flight, the pilot must infer the total performance by using other instruments such as the airspeed indicator, altimeter, vertical speed indicator, directional gyro, turn rate indicator, and power instruments, e.g. an engine tachometer. "Performance = Attitude + Power".

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