Marker beacon

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Locator Outer Marker (LOM), a High Frequency (HF) Non-Directional Beacon, co-located with an "outer marker" (OM) 75-MHz Marker Beacon. LOM snoke.jpg
Locator Outer Marker (LOM), a High Frequency (HF) Non-Directional Beacon, co-located with an "outer marker" (OM) 75-MHz Marker Beacon.
Middle marker antenna at KONT Middle-marker-ont.jpg
Middle marker antenna at KONT

A marker beacon is a particular type of VHF radio beacon used in aviation, usually in conjunction with an instrument landing system (ILS), to give pilots a means to determine position along an established route to a destination such as a runway. [1]

Contents

According to Article 1.107 of the International Telecommunication Union's (ITU) ITU Radio Regulations (RR) [2] a marker beacon is defined as "a transmitter in the aeronautical radionavigation service which radiates vertically a distinctive pattern for providing position information to aircraft".

History

From the 1930s until the 1950s, markers were used extensively along airways to provide an indication of an aircraft's specific position along the route, but from the 1960s they have become increasingly limited to ILS approach installations. They are now very gradually being phased out of service, especially in more developed parts of the world, as GPS and other technologies have made marker beacons increasingly redundant.

Types

There are three types of marker beacons that may be installed as part of their most common application—an instrument landing system.

Outer marker

Outer-marker indicator Outer Marker Indicator.gif
Outer-marker indicator

Middle marker

Middle-marker indicator Middle Marker Indicator.gif
Middle-marker indicator

Inner marker

Inner-marker indicator Inner Marker Indicator.gif
Inner-marker indicator

Back course marker

A back course marker (BC) normally indicates the ILS back-course final-approach fix where approach descent is commenced. It is identified by pairs of Morse-code "dots" at 3000 Hz (95 pairs per minute), which will trigger the white light on a marker beacon indicator, but with a different audio rhythm from an inner marker or en-route marker. [5]

Fan marker

The term fan marker refers to the older type of beacons used mostly for en-route navigation. [6] [7] Fan-type marker beacons were sometimes part of a non-precision approach and are identified by a flashing white light and a repeating dot-dash-dot signal. [8] Recent editions of the FAA's AIM publication no longer mention fan markers. [5] [9] In August 2024 nineteen fan markers remain in the FAA database with seven listed as "DECOMMISSIONED". [10]

See also

References

  1. Wragg, David W. (1973). A Dictionary of Aviation (first ed.). Osprey. p. 186. ISBN   9780850451634.
  2. ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.107, definition: marker beacon
  3. ILS – Marker beacons Archived 2014-01-30 at the Wayback Machine ; ILS.com; retrieved .
  4. Note:Some ILS approaches have no navigation aid at all situated at the final approach fix, but use other means, such as VHF omnidirectional range (VOR) radial intersections, distance measuring equipment (DME), GPS, or radar fixes, to identify the position.
  5. 1 2 FAA AIM 1-1-9 Archived 2009-09-04 at the Wayback Machine ; article; FAA.com; retrieved .
  6. Marker beacon; Answers.com: attributed to McGraw-Hill Dictionary of Aviation.
  7. Note: The term fan marker can refer to almost any type of marker beacons used in aviation (including inner/middle/outer markers), since most of them transmit signal in the fan-shaped pattern (i.e. in a shape of a hand-held fan held up perpendicular to the flight course).
  8. Instrument Flight Training Manual; Amazon.com; accessed .
  9. Note: They are only used on a few instrument approaches anymore, to mark positions along the inbound course, when there is only one marker present: for an example, see the LOC-D document for Gillespie Field  (PDF), effective 7 Aug 2025 - here GRIGG is a fan marker. Quote regarding marker beacons –from an old edition of AIM, section 1-1-9.
  10. "ENASR".