Designations Of U.S. Aeronautical and Support Equipment

Copyright © 2001-2023 Andreas Parsch

1 History

2 Aeronautical and Support Equipment Type Designation System

3 Designation Listings

4 Sources

1 History

From its inception in 1947 until 1952, the US Air Force designated its support equipment with arbitrary letter/number designations. This was somewhat similar to the Army Nomenclature System, except that all letters of the alphabet (instead of M only) were used. Typical designations were "K-5 Bombing System" or "E-1 Fire Control System".

On 15 March 1952, the Air Force and Navy released Air Force-Navy Aeronautical (ANA) Bulletin 420, defining the Type Designation System for Aeronautical Equipment. The system used arbitrary two-letter codes and a model number. The first letter was always an M (indicating Military Aeronautical Equipment). Examples for designations are "MA-3 Fire Control System" and "MB-2 Aircraft Towing Tractor".

The early designation systems had the drawback, that the alphanumerical designations were neither unique nor describing the type and/or purpose of the equipment. For unambiguous identification of an item, the full nomenclature was needed. Therefore, in October 1955, the USAF started to develop a new type designation system, which was intended for all types of aeronautical equipment. The result combined the Joint Electronics Type Designation System (MIL-STD-196), the Joint Photographic Type Designation System (MIL-STD-155) and ANA Bulletin 420 into a single system. The new system was proposed for joint service use but was rejected by the Joint Chiefs of Staff on 31 January 1956 as being too complicated and impractical.

The USAF then decided to develop a new type designation system for aeronautical and support equipment, which should replace ANA Bulletin 420 only. The new system closely followed the principles of the Joint Electronics Type Designation System (as will be shown below, when the system is explained). It was generally known as the Aero/Support System, but is nowadays formally called the Aeronautical and Support Equipment Type Designation System (ASETDS). The system was published on 27 August 1956 in Air Force Regulation (AFR) 81-9.

In 1957, the Navy decided to use ASETDS, too. Accordingly, the Air Force and Navy published ASETDS, in slightly modified form, in ANA Bulletin 440 on 20 March 1958. An updated system was published in ANA Bulletin 440a on 25 February 1960. In early 1966, an improved version of ASETDS was proposed, mainly to provide new type designators for modern and future non-nuclear munitions. This revision was finally published as MIL-STD-875 on 1 November 1966. A slightly expanded version was released in MIL-STD-875A on 30 April 1974.

On 28 February 1991, ASETDS was incorporated into MIL-STD-1812, together with several other type designation systems (like Aero Engines and Photographic Equipment). There was one significant change in ASETDS for this purpose, which is detailed in the description of the designations for components, groups and units. On 14 February 1997, MIL-STD-1812 was renamed as MIL-HDBK-1812. The change from "Standard" to "Handbook" meant, that the use of ASETDS (and the other systems) was no longer mandatory. Otherwise, MIL-HDBK-1812 was identical to MIL-STD-1812. However, in 2020, the document was again renamed to a mandatory "Standard", MIL-STD-1812A.

The following table summarizes the various documents containing the ASETDS:

Document IDDate
AFR 81-927 August 1956
ANA Bulletin 44020 March 1958
ANA Bulletin 440a25 February 1960
MIL-STD-8751 November 1966
MIL-STD-875A30 April 1974
MIL-STD-181228 February 1991
MIL-HDBK-181214 February 1997
MIL-STD-1812A9 October 2020

It should be noted, that only the Air Force uses ASETDS consistently for all its aeronautical and support equipment. The Navy uses its MARK/MOD numbering system for a lot of equipment used in naval aviation. The Army did never use ASETDS, relying instead on the Army Nomenclature system for all its equipment.

2 Aeronautical and Support Equipment Type Designation System

ASETDS distinguishes between complete systems and components. The US military uses detailed definitions of "Item Levels" from single "Parts" to complete "Systems", and a brief explanation of all terms relevant to the discussion of ASETDS can be found here. ASETDS does not designate parts and assemblies, and uses different designation schemes for the other item types.

2.1 Complete Equipment

These designations cover sets, subsystems and systems and also include equipment items like vehicles, shelters, etc.

Examples: A / A 24 G - 5 A
A / E 37 T - 24 (V)2
(1) (2) (3) (4) (5) (6)

All designations are prefixed by "A/" (for "Aero"). In the original (AFR 81-9) form of the system, the prefix "AF/" (for "Air Force") was used, but this was changed with the introduction of ANA Bulletin 440.

Letter (1) indicates the installation location of the equipment:

The two-digit code (2) indicates the type of the equipment. Digits 0 and 1 were originally omitted, to avoid confusion with letters O and I. MIL-STD-1812, however, introduced the new type codes 40 and 41.

Letter (3) defines the purpose of the equipment:

(4) is the model number. Each Installation-Type-Purpose combination uses its own model number sequence, starting at 1. Two blocks of high model numbers (500-599, 2500-2599) are reserved for use by Canada. Most likely the first number of the Canadian block (500) is never used, i.e. Canadian designations probably always start with 501.

The optional suffix letter (5) denotes a specific version of the equipment. The first version uses no suffix, the first modifcation uses "A", etc. The letters "I" and "O" are not used as version suffix.

(6) The "(V)" symbol indicates an equipment with variable components (sets, groups or units). A number following the "(V)" is used to designate a specific version of the equipment, i.e. with a specific component configuration. If a component of a set or system is of variable configuration, i.e. carries a "(V)" symbol, the set or system itself must also use the "(V)" symbol.


1. Installation letter "N" is only used, if the equipment is neither installed in the aerospace vehicle (letter "A") nor mission-expendable (letter "B").

2. Electronic equipment is always designated under JETDS.

2.2 Components, Groups And Units

Up to and including MIL-STD-875A, ASETDS distinguished between components and units. A component was part of an equipment, and couldn't be used on its own. A unit could function on its own and was usually used with some equipment. With the introduction of MIL-STD-1812, the component/unit differentiation was changed to group/unit. This is essentially the way JETDS does it, and is in accordance with the Item Level definitions of MIL-HDBK-505.

Examples: GB U - 10 F / B
TR K - 55 / A24J-13
MH U - 131 / E32K
GB U - 31 (V)4 / B
CN U - 80 / E25
AD G - 770 / B
AG U - 1 B / U
(2) (1) (3) (4) (6) (5)

Letter (1) indicates the category of the equipment:

The two-letter indicator (2) designates the type of equipment:

(3) is the sequential model number, starting at 1. Each type uses a single numbering sequence for all three equipment categories (e.g. if there is a MXK-856, then there is no MXU-856 or MXG-856). Two blocks of high model numbers (5000-5999, 25000-25999) are reserved for use by Canada. It seems that the first number of the Canadian block (5000) is never used, i.e. Canadian designations always start with 5001.

The optional suffix letter (4) denotes a specific version of the equipment. The first version uses no suffix, the first modifcation uses "A", etc. The letters "I" and "O" are not used as version suffix.

(5) The full type designation of a group, unit or component includes a slant bar, followed by the designation of the equipment, of which it is part of or used with. If the group, unit or component can be used with several equipment items, a more general designator is appended. E.g. the MHU-131/E32K is a munition handling unit (an ammunition transporter in this case), which is used with several A/E32K-n systems, while the CNU-80/E25 is a ground-based container, which is used for several explosive items with different purpose indicators. A designation for a general purpose group, unit or component, i.e. one that is not designed to be used in a specific environment, uses only the general installation letter "U" after the slant bar.

(6) The "(V)" symbol indicates an equipment (usually a group) with variable components. A number following the "(V)" is used to designate a specific version of the equipment, i.e. with a specific component configuration.

Aircraft Ordnance:

For aircraft-carried ordnance (bombs, rockets, etc.) designated under ASETDS, two special rules apply:


1. Nuclear bombs are not designated under ASETDS.

2. This designator is only used, if the Joint Photographic Type Designation System cannot be applied.

3. Powered versions of guided bombs are designated as guided missiles (e.g. a GBU-15/B with a rocket motor is designated as AGM-130). There are also a few unpowered guided weapons, which are nevertheless designated as missiles (AGM-62, ADM-141, AGM-154).

4. Dummy missiles can also be designated in the designation system for unmanned aerospace vehicles. E.g. DATM-9L and GDU-6/C are both dummy versions of the AIM-9 Sidewinder missile.

5. Live and dummy rockets can also be designated in the designation system for unmanned aerospace vehicles.

6. The different designators for missile components and their precedence rules are a bit confusing. The warheads are preferrably designated with WD, WE and WT. If these don't apply, WF is used. The missile shell components are designated WA, WG or WP, according to function. Other control components not covered by WG are designated WC. All remaining body parts are designated WN, if they form part of the nose, and WB otherwise.

7. The indicators EC, FN, GM and GP are missing in the current MIL-HDBK-1812A. However, it's quite likely that they were only accidentally omitted in the list and not actually removed from the system.

2.3 Miscellanea

2.3.1 Training Equipment (Complete Equipment)

Training items designed to be used with a certain equipment item are designated by adding "-Tn" to the equipment designator. E.g., the second training set for the A/A24G-6 set is designated as A/A24G-6-T2. If an item can be used for training with different equipment of a certain type, or is a general purpose training equipment of a certain type, the model number is omitted. E.g., A/E37M-T15 is the 15th training set in the E37M (Ground Electromechanical Aircraft Maintenance Equipment) category designed as a multi-purpose training set or to be used with several different A/E37M-n systems. Modifications are indicated by suffix letters, e.g. A/F37A-T26A.

Training equipment for types of equipment not covered by ASETDS (like aircraft engines or electronics), is assigned installation and type indicators as appropriate, followed by purpose letter "U". An example is the A/E37U-T34 (a fire-control trainer for F-16 aircraft).

2.3.2 Training Equipment (Groups and Units)

Training versions of groups and units are designated by adding "(T-n)" between the item designator and the slant bar. E.g., the second training version of the CDU-4/B dispenser is called CDU-4(T-2)/B.

2.3.3 Dummy Ordnance

While training versions of munitions may contain explosives, dummy versions are always completely inert. Dummy versions of live munitions are designated by adding "(D-n)" between the item designator and the slant bar. The number n is not assigned sequentially, but indicates the nature of the dummy:

An example is the BLU-7A(D-1)/B.

2.3.4 Development Indicator

During the development phase of an equipment item, a development indicator like (XN-1) may be appended to the basic equipment designation (or, for groups and units, inserted between the designator and the slant bar). The letter combination always starts with "X" and indicates the organization responsible for the development, and the number is a sequential series number (using separate series for each combination of equipment designator and developing organization). Examples include the A/E24T-189(XN-1), the first developmental model of the basic A/E24T-189 by the US Navy, and the WGU-15(XCL-1)/B, the first developmental model of the WGU-15/B by the US Naval Weapons Center, China Lake. The organization indicators are identical to those used by the Joint Electronics Type Designation System.

[Note: Up to and including MIL-STD-875, the indicators were different to those used by JETDS, but I don't have a listing of these original indicators.]

2.3.5 Suffix Numbers

ANA Bulletin 440a introduced the option to use suffix numbers to differentiate between different versions of aircraft instruments. This option was limited to indicators for aircraft instruments (e.g. AAU, ABU, etc.), and was dropped in MIL-STD-1812. An example is the AAU-31/A altimeter with versions AAU-31/A-1 and AAU-31/A-2.

3 Designation Listings

General notes for the designation lists:

3.1 Complete Equipment

I have only very few ASETDS equipment designations in my lists. All I have will eventually be provided on this site, but don't expect it to be anywhere near complete.

To view the designation listings in a frame with a separate navigation bar, click here.

A/Annx - Aerospace Vehicle Installed Equipment
A/Bnnx - Aerospace Vehicle Installed Equipment (Mission Expendable)
A/Cnnx - Ground/Airborne Combination Equipment
A/Ennx - Ground Equipment (Not Fixed)
A/Fnnx - Fixed Ground Equipment
A/Mnnx - Movable Ground Equipment
A/Nnnx - Aircraft/Missile Transported Equipment
A/Pnnx - Personal Equipment
A/Snnx - Self-Propelled Ground Equipment
A/Unnx - Multi-Installation Equipment
A/Wnnx - Water/Shipborne Equipment

3.2 Components, Groups And Units

3.2.1 Alphabetical Listing

The listings for xxU, xxK and xxG designations are organized alphabetically, one file per initial letter:

Axx, Bxx, Cxx, Dxx, Exx, Fxx, Gxx, Hxx, Jxx, Kxx, Lxx, Mxx, Nxx, Pxx, Rxx, Sxx, Txx, Vxx, Wxx

To view the designation listings in a frame with a separate navigation bar, click here. The navigation bar lists also those equipment types, for which there is no listing yet available. If the type designator is shown in light gray, I don't know a single designation for that type. For the other entries without link, at least one designation will be eventually provided.

3.2.2 Listing by General Category

The following index shows all designation listings sorted by the following general categories:

If an equipment type is listed below, but has no link, a listing is definitely planned (equipment types, for which I don't know a single designation, are not listed below). If a type designation covers items in several of the above categories, the type appears under several headings.

Aircraft Armament

Other Munitions and Related Equipment

Other Air-Dropped or Aircraft-Carried Equipment

Aircraft and Flight Instrumentation

Other Aircraft Equipment

Missile Components

Fuel Handling Equipment

Cargo Handling Equipment

Other Ground Support Equipment

Clothing and Flight Gear

Miscellaneous Personal Equipment

Electrical Equipment

Other Equipment

4 Sources

[1] Department of Defense: MIL-STD-1812A "Aeronautical and Support Equipment Type Designation System"
[2] Department of Defense: MIL-STD-875A "Type Designation System for Aeronautical and Support Equipment"
[3] Department of Defense: MIL-HDBK-505 "Handbook For Definitions Of Item Levels, Item Exchangability, Models And Related Terms"

(The designation listings were compiled using a wide variety of sources, not the least of which were the Internet and contributions by fellow researchers.)

Comments and corrections to: Andreas Parsch

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Last Updated: 11 December 2023