The heading indicator (also known as the directional gyro, or DG; sometimes also called the gyrocompass, though usually not in aviation applications) displays the aircraft’s heading with respect to geographical north. Principle of operation is a spinning gyroscope, and is therefore subject to drift errors (called precession) which must be periodically corrected by calibrating the instrument to the magnetic compass.
Features:
- ambient temperature: -30 – +50 °C
- ambient relative humidity: no more than 95%
- anti-vibration tensity: 1.5g
- height: 40000feet
- driving power: 15 ~18K Pa for vacuum or air pressure
- pressure for starting: 7KPa
- working range: indicating heading angle within the range of 360°
- accuracy: the drift error is not more than 4°/10 min
