Section 2. Location Identifiers System Administration
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.
1-2-2. ASSIGNMENT AUTHORITIES
a. The Federal Aviation Administration assigns three-letter identifiers (except those beginning with the letters N, W, Y, and Z), three and four character identifiers, and five-letter name codes for the United States and its jurisdictions.
b. The Department of Navy assigns three-letter identifiers beginning with the letter N for the exclusive use of that Department.
c. Transport Canada assigns two, three, and four character identifiers, including three letter identifiers beginning with letters Y and Z, for its areas of jurisdiction.
d. The Federal Communications Commission assigns blocks of identifiers beginning with K and W for broadcast radio and television stations. The block beginning with letter Q is under international telecommunications jurisdiction and is used by FAA Technical Operations to capture National Airspace equipment not published in this order. Identifiers beginning with the letter Z are assigned to air route traffic control centers.
e. The National Weather Service assigns four-letter, one-number identifiers for certain weather requirements.
f. The U.S. Air Force Weather Agency (AFWA), acting on behalf of all the military services, assigns special use four letter “KQXX” identifiers for use by deployed units supporting real world contingencies; deployed/in-garrison unites providing support during exercises; supporting weather system testing programs requiring temporary station identifiers; and units that have requested, but not yet received a permanent location identifier.
g. The Air Traffic Safety Oversight (AOV) is requesting issuance of reserved identifier assignments in order to address future Control Tower Operator Program needs and respond to current airmen certification requirements. Identifiers beginning with the letters AV00 through AV99 are assigned to AVO.
a. In the FAA.
1. The Mission Suport Services, Aeronautical Information Management, National Flight Data Center (NFDC) Group is responsible for the coordination of requests for location identifiers within each service area.
2. Any reapplication or change in usage of a location identifier assignment must receive prior clearance from NFDC.
3. Occasions will arise where a sponsor or interested group will seek the advice of regional/service area office or field personnel concerning the assignment of a particular identifier or a change to a more preferred identifier. In these situations, no commitment shall be made. Inquiries of this nature shall be referred to NFDC for information and advice concerning appropriate handling of such matters.
b. In the Department of Navy, Naval Telecommunications System, ICO-5, is responsible for final coordination and assignment of “N” identifiers.
c. Transport Canada, Aeronautical Information Service, is responsible for final coordination and assignment of Canadian location identifiers.
a. Established three-letter identifiers are considered permanent and will not be changed without strong and documented justification, primarily concerning air safety. Other than three-letter identifiers may be changed when the status of a landing facility changes, e.g. private-use to public-use, etc.
b. Location identifiers are not interchangeable and cannot be transferred from one location to another or from one airport to another even within the same community.
c. The original identifier will remain in effect, in most instances, even though it has been necessary to change the facility's name.
a. At the same location, the same identifier may be assigned to one navigational aid (which must be located within the airport boundary), to the airport, to a manned air traffic control facility, and to an aviation weather station on the airport. With certain restrictions, variations of the airport identifier may be assigned also to landing systems.
b. Some duplication of three-letter assignments has been made between air navigation facilities in the contiguous United States, which are not associated primarily with a landing area, and U.S. Department of Defense overseas air bases. For example, the second ILS at an airport in the U.S. and an air base in Italy, or an air base in Germany and an en route VORTAC in the U.S.
c. The first and second letters or second and third letters or third and first letters of a three-letter identifier may not be duplicated with less than 200 nautical miles separation.
1-2-6. EFFECTIVE DATES
Location identifiers are published in the next edition of the order, following assignment. All segments of the aviation industry and many related activities use these codes in their daily business. The effective date of the assignment, therefore, is set by each user group according to their respective requirements.
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 staffed aviation weather reporting stations or for airports commissioning Automated Weather Observation Systems, level III (AWOS-III) or higher that have paved runways 5,000 ft or longer.
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 preceded 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).
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.
1. The following supplemental codes are used in this identifier series:
f. A single five-letter pronounceable combination serves as the fix name, assigned identifier and computer code. If a new fix is to be collocated with an existing navigation aid, ILS marker, way point, or other type fix, the original name or name-code applies to both.
g. Weather Offices and Stations, may be assigned in any of the series of Location Identifiers, depending upon type or combination of Station. Generally, a Weather Service Office at an Airport is given a three-letter identifier. AMOS equipment may be polled with any combination of three-character identifiers. Some types of Aviation Weather Reporting Stations are listed with two-number, one-letter identifiers.
1-2-8. CANCELED ASSIGNMENTS
a. All users are requested to periodically review assignments in their area of responsibility, and notify NFDC as soon as an identifier or name-code may be canceled.
b. Canceled three-letter assignments are held in abeyance for one year, usually, before becoming available for reassignment.
c. Canceled number-alpha and five-letter assignments are held in abeyance an appropriate length of time depending upon circumstances of cancellation, but not more than one year.
a. Upon receipt of this order, users are requested to verify the proper listing of identifiers in their area of responsibility. Omitted, incorrect and obsolete assignments and tie-in facilities should be reported immediately to the NFDC. If available, include the correct information. See Paragraph 1-1-4., for appropriate action dates.
b. A page is included inside the front cover for this purpose.
1-2-10. TIE-IN FACILITY
The “FAA TIE-IN FACILITY” is the telecommunications facility that handles flight plan messages for the listed landing facility or navigational aid. This also applies to Canadian facilities. Tie-in facility hours are local times. The absence of a facility in this column indicates that the location identifier is being reserved for the future commissioning of the landing facility or navigational aid.
1-2-11. ARTCC CONTROL AREA
The computer code for the U.S. Air Route Traffic Control Center or identifier of the Canadian ARTCC (see note below) of jurisdiction is shown beside the tie-in facility identifier opposite each landing facility and navigational aid listing. This information has been included to assist in routing IFR Flight Planning messages directly to ARTCC computers. The absence of a facility in this column indicates that the location identifier is being reserved for the future commissioning of the landing facility or navigational aid.
1-2-12. METROPOLITAN AREA IDENTIFIERS
A number of three-letter identifiers have been assigned in the past to designate a metropolitan area where a principal city is served by more than one airport, however, no further assignment of metropolitan codes is contemplated. Existing metropolitan codes are not exchangeable with airport codes at the same location.
1-2-13. RECORDS AND REVIEWS
a. Location Identifiers System records are retained for five years. Research of assignments beyond that time may be done only from history copies of the order.
b. Continuing reviews are conducted to update assignments in the Location Identifiers System. Assignments of more than five years are subject to over all reviews and meeting current standards.
1-2-14. RESERVED IDENTIFIERS
A number of identifiers have been reserved for the future commissioning of navigational aids and airports. These locations and identifiers will be listed without an associated tie-in facility or center code.