Attitude indicator (AI), also known as Gyroscope Horizon or Artificial Horizon, is an instrument used in an aircraft to inform the pilot of the orientation of the aircraft relative to earth. It indicates pitch (fore and aft tilt) and bank or roll (side to side tilt) and is a primary instrument for flight in instrument meteorological conditions.

The Attitude Indicator shows rotation about both the longitudinal axis to indicate the degree of bank, and about the lateral axis to indicate pitch (nose up, level or nose down). It utilizes the rigidity characteristic of the gyro. It is gimballed to permit rotation about the lateral axis indicating pitch attitude, and about the longitudinal axis to indicate roll attitude. Once powered up, the indicator is maintain in a fixed position no matter what the aircraft attitude may be. 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.

Operation of Attitude Indicator

Attitude indicators use a gyroscope (powered via vacuum pump or electrical motor) to establish an inertial platform. The gyroscope is geared to a display that has two dimensions of freedom, simultaneously displaying pitch and bank. The display may be colored to indicate the horizon as the division between the two colored segments (typically blue for sky and brown for ground), and is intended to be intuitive to use. The actual bank angle is calibrated around the circumference of the instrument.