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In AIXM 5 the NDB.class attribute may carry the value; '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 NDBusually 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).
A number of 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 particular aerodrome/heliport.
When a nondirectional beacon is co-located with a marker of an ILS the terms LO, 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 2 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 powerd NDB , low powered NDB, etc.).
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For details about the coding and rules see topic Landing Systems & Navaid Collocation.
Coding Rules for NDB
| Identifier | Data Encoding Rule | Justification | Data Verification Rule (UID) | Remarks |
|---|---|---|---|---|
| NDB-101 | The DNDB.designator attribute is mandatory. | Minimum AIP data set | TBD | |
| NDB-102 | The NDB.name attribute is mandatory. | Minimum AIP data set | TBD | |
| NDB-103 | The NDB.frequency attribute is mandatory. | Minimum AIP data set | TBD | |
| NDB-104 | The NDB.location attribute is mandatory. | Minimum AIP data set | TBD | |
| NDB-105 | The NDB.magneticVariation attribute is mandatory. | Minimum AIP data set | TBD | |
| NDB-105 | The NDB.dateMagneticVariation attribute should be provided. | PANS-AIM | TBD | |
| NDB-106 | The NDB.magneticVariationAccuracy attribute should be provided. | PANS-AIM | TBD | |
| NDB-107 | The NDB.designator shall not be duplicated within 600 NM of the location of the NDB. | EAD / ICAO Annex 11 | TBD | |
| NDB-108 | The value of the NDB.frequency must be in the interval '190' to '1750' 'KHz'. | EAD / ICAO Annex 10 | TBD | |
| NDB-109 | If NDB.class equal-to 'L' and related RadioFrequencyArea.type equal-to 'COV' then CircleSector.outerDistance cannot exceed 60km. | EAD | TBD |
Coding Examples
Th efigure below shows an example of different types of NDBs published in ENR 4.1. of an AIP.
More examples TBD TBD in the scope of the DONLON AIXM AIP data set.