Heading indicator

The gyro is an inserted in airplanes gyroscope to the direction of measurement.

In contrast to that used on ships gyrocompass - with whom he is often confused - is the directional gyro not chained, but a free gyroscope. Its vollkardanisch suspended axle but held by a righting in a plane in which the longitudinal and the transverse axis of the aircraft are. Thus, the spin axis is always perpendicular to the vertical axis of the aircraft. Its measurement principle is based on the directional stability of the axis of rotation of the rotor. It is so much the better, the larger the angular momentum of the gyro is so are the greater its moment of inertia and its rotational rate.

The top shaft can be manually set to the display of the magnetic compass. The gyro will then display the price in the horizontal plane of the earth. The angular scale of rate gyros is usually divided into 5 degrees, the reading is therefore possible to accurately about 1 to 2 degrees.

In an inclined position of the aircraft, the plane of the rotor axis is not parallel to the horizontal plane of the earth. The result is that the displayed direction deviates from the actual direction of the aircraft longitudinal axis. In a full circle she hurries the true direction twice ahead, and twice she stays behind her back. This error is the gimbal error ( in English gimbal error or Hooke 's joint error ). He disappears with the end of the inclined position again.

In addition to this error, the gyro may be subject to additional errors. Even when the top shaft clean maintains its direction, then but the earth rotates beneath it. On the pole are 15 degrees per hour. At other latitudes, this rotation rate is reduced by the sine of the latitude. Especially at the equator, ie at zero width, the effect is therefore zero. The result is thus an apparent drift of the gyro at this rate. But that can be countered by making precess opposed by an adjustable torque by the same amount the roundabout. For this gyro have a width nut ( in English latitude nut ) that can be moved along the gyroscope axis by rotation. This exhibit this apparent gyro drift does not occur if they are correctly set to the latitude. However Underkept gyro must be periodically adjusted to the magnetic compass in flight.

Another that is independent of drift is the drift transport. It is proportional to the east-west component of the velocity and the tangent of the latitude.

As long as the gyro drift remains below the specifications, the gyro is, despite its simple design, a reliable measure of air navigation and an important addition to the magnetic compass. In contrast to this it is free from its mistakes and has a quieter display so that it is also suitable for self- control of an autopilot.

The manual adjustment of the magnetic compass is taking charge Gyrosyn compass an automatic, which tracks the gyro steadily.

See also: Air navigation, Horizontal Situation Indicator, Course (navigation), Mire

• Avionics
• Gyroscope
• Navigation