FAA Information Location Identifiers
1-2-1 Use of Location Identifiers
a. A Location Identifier takes the place of the name and the location of an airport, navigation aid, weather station, and manned air traffic control facility in air traffic control, telecommunications, computer programming, weather reports, and related services.
1-2-7 Assignment System
a. Three-letter identifiers are assigned as radio call signs to aeronautical navigation aids; to airports with a manned air traffic control facility or navigational aid within airport boundary; to airports that receive scheduled route air carrier or military airlift service, and to airports designated by the U.S. Customs Service as Airports of Entry. Some of these identifiers are assigned to certain aviation weather reporting stations.
NOTE- Aviation weather reporting stations in Alaska will be identified by (WS) in Sections F and G of this Order.
b. Navigation aid identifiers are assigned by the following standards:
1. Instrument Landing System (ILS) Localizers and Associated DME's. The initial ILS localizer is usually assigned the same identifier as the airport it serves. (This may be altered if the airport has not yet been assigned a three-letter identifier, or if the airport identifier begins with a ''K,''''N,'' or ''W''). If additional localizers are established, separate three-letter identifiers will be assigned each facility. This shall apply whether an additional localizer is to serve the opposite end of an ILS equipped runway or a parallel runway, even though both systems operate on the same frequencies on a non-simultaneous basis. To distinguish the ILS localizer from another VHF facility using the same identifier, the keyed ILS identifier is proceeded by the letter ''I''. When DME is installed as an integral component of an ILS, the same identifier, preceded by the letter ''I'' will be assigned to both the localizer and DME.
2. Interim Standard Microwave Landing System (ISMLS). The same criteria shall be used to assign an identifier to an ISMLS as an ILS. The identifier assigned, however, shall be preceded by the letter ''M''. If an ILS and ISMLS are installed on the same runway end, one basic identifier may be assigned preceded by an ''I'' for the ILS and an ''M'' for the ISMLS.
3. Compass Locators. The general term ''compass locator'' also covers NDB/OM, LMM, and LOM regardless of output power or type. The term is applied only to a non-direction radio facility which is located at the VHF middle or outer marker site (front course) of an ILS. It is assigned a name-code and a two-letter identifier. The two-letter identifier is derived in the following manner:
(a) The three-letter localizer identifier is considered as a base.
(b) The first and second letters of the three-letter localizer identifier are assigned to the outer marker compass locator (LOM) and the second and third letters are assigned to the middle marker compass locator (LMM).
EXAMPLE-
Raleigh-Durham
ILS
Localizer
I-RDU
LOM
RD
LMM
DD
4. Localizer Type Directional Aids (LDA). This equipment is of comparable accuracy to an ILS localizer and may be used in conjunction with a glide slope and/or markers. It usually does not meet ILS siting standards and is not part of an ILS. It is, however, assigned a three-letter identifier preceded by the letter ''I''
5. Simplified Directional Facilities (SDF). This equipment is a directional type aid that operates on localizer frequencies. It is assigned a three-letter identifier and shall not be preceded by the letter ''I''. It does not meet all localizer performance tolerances and does not have markers.
6. Non-directional Radio beacon. Non-directional radio beacons are assigned three-letter identifiers except when they are also the outer compass locator (LOM) or middle compass locator (LMM) of an ILS, or placed at a marker site of an ILS. See Compass Locators above. The same basic three-letter identifier cannot be shared by a terminal NDB and an ILS at the same location.
7. VOR, VORTAC, and TACAN Facilities. These facilities are assigned three-letter identifiers. If two or more such facilities or an NDB are established at a location, they will be assigned different identifiers. The same basic three-letter identifier can be assigned to one of these terminal facilities and to an ILS localizer at the same location.
8. Distance Measuring Equipment (DME). This equipment is used in conjunction with several type navigation aids. It is assigned the same identifier as its associated aid, whether a VOR/DME, NDB/DME, or ILS/DME.
c. Most one-number, two-letter identifiers have been assigned to aviation weather reporting and observation stations and special-use locations. Some of these identifiers may be assigned to public-use landing facilities within the United States and its jurisdictions, which do not meet the requirements for identifiers in the three-letter series. In this identifier series, the number is always in the first position of the three-character combination.
d. Most one-letter, two-number identifiers are assigned to public-use landing facilities within the United States and its jurisdictions, which do not meet the requirements for identifiers in the three-letter series. Some of these identifiers are also assigned to aviation weather reporting stations.
1. One-letter, two-number identifiers are keyed by the alphabetical letter. The letter may appear in the first, middle or last position in the combination of three characters. When the letter signifies an Air Traffic Control Center's area, the assignment will not change if the Center's boundaries are realigned.
2. Identifiers in this series, which could conflict with the ''Victor'',''Jet'' or colored airway numbers are not assigned.
e. Two-letter, two-number identifiers are assigned to private-use landing facilities in the United States and its jurisdictions which do not meet the requirements for three-character assignments. They are keyed by the two-letter Post Office or supplemental abbreviation (listed below) of the state with which they are associated. The two letter code appears in the first two, middle, or last two positions of the four character code.
