artificial horizon


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artificial horizon

[¦ärd·ə¦fish·əl hə′rīz·ən]
(navigation)
A gyro-operated flight instrument that shows the pitching and banking attitudes of an aircraft or spacecraft with respect to a reference line horizon, within limited degrees of movement, by means of the relative position of lines or marks on the face of the instrument representing the aircraft and the horizon. Also known as automatic horizon.
A device, such as a spirit level or pendulum, that establishes a horizontal reference in a navigation instrument.

Artificial Horizon

 

also called gyro horizon or attitude indicator, a gyroscopic device designed to measure the roll and pitch angles of an aircraft. The pitch angle is the angle between the longitudinal axis of the aircraft and the horizontal plane, and the roll angle is the angle of inclination of the longitudinal plane of the craft to the vertical. The main parts of the artificial horizon are a gyroscope with three degrees of freedom which retains the position of its axis fixed in space and a pendulum correction system which eliminates deviations of the gyroscope rotor axis from the true vertical. Whenever a gyroscope rotor axis is out of alignment with the true vertical, the correction system, consisting of a pendulum built into the inner frame of the gyroscope and correction motors, causes precession of the gyro axis (moving it in the plane perpendicular to the direction in which the force is applied) until the axis resumes its preset position. Precession ceases as soon as the gyro axis lines up with the vertical. The most commonly encountered artificial horizon is one in which the front panel of the instrument shows a silhouette of the aircraft remaining fixed relative to the artificial horizon housing, and consequently to the aircraft as a whole. A gyro-stabilized sphere is located behind the silhouette. The bottom half of the sphere is colored blue (sky), and the top half is colored brown (earth). The interface between the two colored hemispheres serves as the artificial horizon bar. Scales are also drawn on the sphere as aids in measuring the pitch angle and the roll angle. By observing the position of the aircraft silhouette on the instrument scale relative to the moving artificial horizon bar, the pilot gains information on the presence and magnitude of those angles. A slip indicator with a zero position indicator is built into the housing of the artificial horizon. Artificial horizons with pneumatically driven gyroscopes and correction devices were used in the past; subsequently, artificial horizons with electrically driven gyroscopes and correction devices came into use. The total error in the readings of an electrically powered artificial horizon in level flight is not greater than 1°, and it is not greater than 2° when a plane is coming out of a bank turn at a 20° roll angle at a speed of 400 km/hr, an accuracy which in practice is sufficient for blind flying.

REFERENCE

Fridlender, G. O., and M. S. Kozlov. Aviatsionnye giroskopicheskie privbory. Moscow, 1961.

artificial horizon

A device for indicating the horizon, as a bubble, pendulum or the flat surface of a liquid.

artificial horizon

artificial horizon
i. A gyro-operated flight instrument that shows the pitching and banking attitudes of an aircraft with respect to a reference line horizon, within limited degrees of movement, by means of the relative position of lines or marks on the face of the instrument representing the aircraft and the horizon. The instrument normally uses an earth gyro and in some cases a tied gyro. One of the primary instruments that helps a pilot to fly at night, in cloud, or when the natural horizon is not visible.
ii. A device, such as a spirit level or a pendulum, that establishes a horizontal reference in a navigation instrument.
References in periodicals archive ?
And free or low-cost apps for your smartphone/tablet computer leverage the hardware's sensors to depict a usable artificial horizon.
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Department of Transport investigators have called for an extra artificial horizon and a voice cockpit recorder in all nine-seater aircraft.
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today announced the DMU-VGX, the industry's first high-speed solid-state true vertical gyro with the speed and accuracy necessary to accurately measure roll and pitch in dynamic environments such as camera and antenna stabilization, artificial horizon applications, automotive testing, marine motion monitoring, and unmanned vehicle orientation sensing and stabilization.
These include, of course, the artificial horizon or attitude indicator and the directional gyro, which are usually air- or vacuum-driven, plus the turn coordinator or turn and bank indicator, usually powered by the aircraft's electrical system.
Six see-through constellation outlines that overlay wide-angle views of the sky provide a nice touch for readers of all ages--though I find the added out-of-scale artificial horizons distracting.
Scientists at the National Aeronautics and Space Administration, with new appreciation for the strength of these visual illusions, are working to make the displays for artificial horizons much more obvious.
At some point these precocious kids become young adults and start to look beyond their artificial horizons.