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ARTIFICIAL HORIZONT

Also known as a Attitude indicator, the artificial horizont is a instrument used in aircrafts to inform the pilot of the orientation of the aircraft relative to earth. Attitude indicators also have significant application under visual flight rules, though some light aircraft do not have them installed.

The essential components of the indicator are:

• "miniature wings", horizontal lines with a dot between them representing the actual wings and nose of the aircraft.
• the center horizon bar separating the two halves of the display, with the top half usually blue in color to represent sky and the bottom half usually dark to represent earth.
• degree marks representing the bank angle. They run along the rim of the dial. On a typical indicator, the first 3 marks on both sides of the center mark are 10 degrees apart. The next is 60 degrees and the mark in the middle of the dial is 90 degrees.

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. When the dot and wings are on the horizon line, the aircraft is in level flight. Because it is the horizon that moves up and down and turns, while the symbolic aircraft is fixed relative to the rest of the instrument panel, trainees get confused; a standard corrective given by flight instructors is "Fly the little airplane, not the horizon."

Font: http://en.wikipedia.org/wiki/Attitude_indicator