marker beacon


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marker beacon

[′märk·ər ‚bē·kən]
(navigation)
A low-power radio beacon transmitting a signal to designate a small area, as an aid to navigation.

marker beacon

marker beaconclick for a larger image
When the aircraft flies over outer, middle, and inner markers, light in color code indicated above flashes. The frequency of audio tone is also indicated in the illustration.
The beacons serve to identify a particular location in space along an airway or an approach to an instrument runway. This is done by means of a 75 MHz transmitter, which transmits a directional signal to aircraft flying overhead. These markers generally are used in conjunction with en route navigational aids and an ILS (instrument landing system) as point designators. The three types of en route markers are fan markers (FM), low-powered fan markers (LFM), and Z markers. They transmit the letter R (.-.) as identification, or if additional markers are in the same area, the letters K, P, X, or Z. Class FMs provide positive identification of positions at definite points along the airway and have a power output of 100 watts. Class LFMs have a rated output of 5 watts, and their antenna arrays produce a circular pattern that appears elongated at right angles to the runway because of the directional characteristics of aircraft receiving the antenna. The station-location, or Z, marker gives a positive position for aircraft operating under instrument flight conditions to show the pilots when they are passing directly over a low-frequency navigational aid. There are three marker beacons: the outer marker, which is sited 4 to 5 NM from the touchdown and transmits two low-pitched dashes per s; the middle marker, which is located ¼ to ½ NM from the touchdown and transmits high-pitched dots and dashes alternately; and the inner marker, which is located at the runway threshold and transmits six high-pitched dots per second. Normally, the inner marker is not installed. The signals from the marker are beamed vertically upward in a fan shape and can be heard in the aircraft only when it is directly above the beacons.
References in periodicals archive ?
The instrument has a Swept Localizer DDM for coupled AutoPilot testing including simultaneous Localizer, Glideslope and Marker Beacon signals, as well as simulation of VOR beacon with variable bearing.
The IFR 4000 verifies the proper operation and installation of ILS, VOR and Marker Beacon receivers and VHF AM/FM and UHF AM transceivers by using eight dedicated operational modes.
In these tests the air calibration of the components of the automatic landing systems, including the localiser, glide path and marker beacons.
Components that are not standard, such as marker beacons and compass controllers, are being analyzed by Production Engineering Directorate personnel to give the depot capability to repair, overhaul and test them.
The ILS is typically complemented by distance measuring equipment showing pilots the distance to touchdown, or by marker beacons out in the approach path that signal pilots as they near the runway.
Developed in response to the demand for greater accuracy and reliability in making aerial deliveries of supplies, the new ADLS will be particularly useful during covert operations when traditional marker beacons have proved unsuccessful or cannot be used.
Under this contract, Airport Systems will supply any new navaid equipment, including Localizers, Glideslopes, Marker Beacons and DME, to the Commonwealth of Virginia.