NDB

Introduction & Background

This topic contains only those PANS-AIM requirements relevant for an NDB. For general PANS-AIM requirements valid for all kind of Radio navigation aids see topic Navaid [NAV] and subordinated pages.

A Non-directional radio beacon (NDB) is a low or medium frequency radio beacon, which transmits signals, whereby the pilot of an aircraft properly equipped can determine bearings and 'home in' on the station.

A Locator is an LF/MF NDB used as an aid to final approach.

For an NDB, PANS-AIM requires some specific properties as part of the minimum AIP data set. These are

identification, name, aerodrome served, hours of operation, magnetic variation, frequency..., position, ...

In addition, PANS-AIM ENR 4.1 and AD 2.19/AD 3.18 state as requirement

...If the operating authority of the facility is other than the designated governmental agency, the name of the operating authority shall be indicated in the remarks column. Facility coverage shall be indicated in the remarks column.

The diagram below shows the AIXM classes, including the relevant data types, needed to encode that information. The main class is the NDB which is a specialisation of the NavaidEquipment.

NDB Type

This information is not explicitly required by PANS-AIM. However, this information may be relevant for ARINC 424 coding.

In AIXM 5, the NDB.class attribute may carry the values 'ENR' for Enroute NDB,  'L' for Locator - low powered NDB used as an aid for final approach (also known as a compass locator) and 'MAR' for Marine beacon.

Enroute NDB usually refers to the beacons that are located away from aerodromes/heliports which are used for en-route navigation.

Locator (ICAO Annex 10):

An LF/MF NDB used as an aid to final approach. Note: A locator usually has an average radius of rated coverage of between 18.5 and 46.3 km (10 and 25 NM).

Several beacons are listed in "official" publications with titles such as Locator (L) beacon. These beacons are basically the same as standard NDBs, but will have a specified Instrument Approach procedure as well. These are provided as an additional approach aid during the notified hours of operation at a certain aerodrome/heliport.

When a nondirectional beacon is co-located with a marker of an ILS, the terms LO and LM generally refer to the location of the locator beacon in question, e.g. LO - at the "Outer Marker" position on the approach to the RWY, LM at the "Middle Marker" position. Sometimes these nondirectional beacons - depending on their position - are also called, "outer compass locator" or LOM and "middle marker compass locator" or LMM respectively.

Marine Beacon are usually located around the coast, provided for maritime operations but also available for aviation purposes.

ARINC 424 contains two dedicated record types for NDB. One for NDB NAVAID (DB), containing all LF and MF NDBs and selected Marine Beacons defined in the enroute structure, and one for the Terminal NDB (PN). Both record types contain the data field NAVAID Class (CLASS), that, inter alia, is used to distinguish between NDB, Locator and Marine Beacon (additional classification elements are part of this data field, which do not fully coincide with AIXM 5 concept, e.g. codes for high powered NDB, low powered NDB, etc.).

NDB Designator & Name

In general, enroute NDB will carry a three-letter character identifier. Locator may have two or one character.

The NDB.designator attribute is used to code that data.

The long name given to the NDB is coded using the NDB.name attribute.

Aerodrome Served

See topic Basic Data for Navaid.

Hours of Operation

See topic Hours of Operation for Navaid.

Magnetic Variation

For NDB, PANS-AIM Appendix 1 requires the magnetic variation to be provided. For details about the encoding including rules see the topic Magnetic Variation.

NDB Frequency

In AIXM 5, the frequency of the NDB emission is coded by using the NDB.frequency attribute.

The corresponding data type contains a uom attribute. For an NDB, only the value equal-to 'KHZ' shall be used.

According ICAO Annex 10, Volume 1  the radio frequencies assigned to NDBs shall be selected from those available in that portion of the spectrum between 190 kHz and 1 750 kHz.

Position

In case an NDB (Locator) collocated with a marker is physically located at the same position as the marker, the geographic position (latitude and longitude) of the Marker is also the geographic position of the NDB.

In case an NDB (Locator) is collocated with a Marker and the position of the NDB is different from the position of the Marker, some restrictions have to be taken into account (see coding rules for Marker Beacon).

For more details see topic Navaid Position & Elevation.

Operating Authority

See topic Operating Authority for Navaid.

Facility Coverage

See topic Facility coverage.

Navaid Collocation

An NBD instance may be collocated with a MarkerBeacon.

An NDB (and marker) may only maintain a single collocation relationship at a time, which means that it is not possible to collocate a NDB with two different markers.

Usually, the NBD collocated with a marker is a locator (see NDB type above), whereas the locator in conjunction with the collocated marker is used for ILS approaches.

In the AIP, collocated NDB and marker navaids are sometimes referred to as LOM, LMM or LIM, depending on marker position within the ILS.

An NDB may also be co-located with a DME.

For details about the coding and rules see topic Landing Systems & Navaid Collocation.

Coding Examples

 Coding examples can also be found in the AIP Data Set - Specimen (DONLON):

References