by Jonathan M. Stern
The attitude indicator replicates the view that the pilot has out the windscreen if it is not obstructed by clouds or other meteorological phenomenon. The attitude indicator, as its name implies, indicates the attitude of the airplane relative to the horizon. For this reason, the attitude indicator used to be called the artificial horizon.
The attitude indicator displays airplane pitch (nose up or nose down attitude) and airplane bank (the angle the wing forms with the horizon). Marks around the top half of the instrument indicate angles of bank of 10, 20, 30, 60, and 90 degrees. Pitch is displayed in 5° increments up to 20 degrees. The attitude indicator is the only instrument in the airplane that reflects both pitch and bank.