The Tri-Service aircraft designation system is a unified system introduced in 1962 by the United States Department of Defense for designating all U.S. military aircraft. Prior to then, the U.S. armed services used separate nomenclature systems.
Under the tri-service designation system, officially introduced on 18 September 1962, almost all aircraft receive a unified designation, whether they are operated by the United States Air Force (USAF), United States Navy (USN), United States Marine Corps (USMC), United States Army, or United States Coast Guard (USCG). Experimental aircraft operated by manufacturers or by NASA are also often assigned designations from the X-series of the tri-service system.
The 1962 system was based on the one used by the USAF between 1948 and 1962, which was in turn based on the Type, Model, Series USAAS/USAAC/USAAF system used from 1924 to 1948. The 1962 system has been modified and updated since introduction.
The designation system produces a Mission-Design-Series (MDS) designation of the form:
(Status Prefix)(Modified Mission)(Basic Mission
)(Vehicle Type)-(Design Number
Of these components, only the Basic Mission, Design Number and Series Letter are mandatory. In the case of special vehicles a Vehicle Type symbol must also be included. The U.S. Air Force characterizes this designation system as "MDS", while the Navy, and Marine Corps refer to it as Type/Model/Series (T/M/S).
These optional prefixes are attached to aircraft not conducting normal operations, such as research, testing and development. The prefixes are:G: Permanently grounded
J: Special test, temporary
N: Special test, permanent
A temporary special test means the aircraft is intended to return to normal service after the tests are completed, while permanent special test aircraft are not. The Planning code is no longer used but was meant to designate aircraft "on the drawing board". For example, using this system an airframe such as the F-13 could have initially been designated as ZF-13 during the design phase, possibly XF-13 if experimental testing was required before building a prototype, the YF-13; the final production model would simply be designated F-13 (with the first production variant being the F-13A). Continuing the example, some F-13s during their service life may have been used for testing modifications or researching new designs and designated JF-13 or NF-13; finally after many years of service, the airframe would be permanently grounded due to safety or economic reasons as GF-13.
Aircraft which are modified after manufacture or even built for a different mission to the standard airframe of a particular design are assigned a modified mission code. They are:A: Attack (i.e., air-to-surface)
C: Transport (i.e., cargo)
D: Drone director
E: Special electronic mission
H: Search and rescue, MEDEVAC
L: Equipped for cold weather operations
M: Missile carrier (1962 – c.1972), Mine countermeasures (c.1973–1976), Multi-mission (1977 onwards)
P: Maritime patrol
Q: Unmanned drone
S: Antisubmarine warfare
V: Staff transport
W: Weather reconnaissance
The multi-mission and utility missions could be considered the same thing, however they are applied to multipurpose aircraft conducting certain categories of mission. M-aircraft conduct combat or special operations while U-aircraft conduct combat support missions, such as transport (e.g., UH-60) and electronic warfare (e.g., MC-12). The vast majority of U.S. Coast Guard air assets include the H-code (e.g., HH-60 Jayhawk or HC-130 Hercules).
All aircraft are to be assigned a basic mission code. In some cases, the basic mission code is replaced by one of the modified mission codes when it is more suitable (e.g., M in MH-53J Pave Low III). The defined codes are:A: Attack aircraft (for tactical air-to-surface mission)
B: Bomber (for strategic air-to-surface mission)
C: Transport (Cargo)
E: Special electronic installation
K: Tanker (dropped between 1977 and 1985)
O: Observation (Forward Air Control)
P: Maritime patrol
S: Anti-submarine warfare
X: Special research
The rise of the multirole fighter in the decades since the system was introduced has created some confusion about the difference between attack and fighter aircraft. According to the current designation system, an attack aircraft (A) is designed primarily for air-to-surface missions (also known as "attack missions"), while a fighter category F incorporates not only aircraft designed primarily for air-to-air warfare, but also multipurpose aircraft designed also for attack missions. The Air Force has even assigned the F designation to attack-only aircraft, such as the F-111 Aardvark and F-117 Nighthawk.
The only A designated aircraft currently in the U.S. Air Force is the A-10 Thunderbolt II. The last front line A designated in the U.S. Navy and Marine Corps was the A-6 Intruder, with the only strictly A designated fixed-wing aircraft remaining is the A-29 Super Tucano leased under the Imminent Fury program.
Of these code series, no normal aircraft have been assigned a K or R basic mission code in a manner conforming to the system.
The vehicle type element is used to designate the type of aerospace craft. Aircraft not in one of the following categories (most fixed-wing aircraft) are not required to carry a type designator. The type categories are:D: Unmanned aerial vehicle (UAV) control segment
Q: Unmanned aerial vehicle
V: Vertical take-off/short take-off and landing (VTOL/STOL)
A UAV control segment is not an aircraft, it is the ground control equipment used to command a UAV. Only in recent years has an aircraft been designated as a spaceplane, the proposed MS-1A.
According to the designation system, aircraft of a particular vehicle type or basic mission (for manned, fixed-wing, powered aircraft) were to be numbered consecutively. Numbers were not to be assigned to avoid confusion with other letter sequences or to conform with manufacturers' model numbers. Recently this rule has been ignored, and aircraft have received a design number equal to the model number (e.g., KC-767A) or have kept the design number when they are transferred from one series to another (e.g., the X-35 became the F-35).
Different versions of the same basic aircraft type are to be delineated using a single letter suffix beginning with "A" and increasing sequentially (skipping "I" and "O" to avoid confusion with the numbers "1" and "0"). It is not clear how much modification is required to merit a new series letter, e.g., the F-16C production run has varied extensively over time. The modification of an aircraft to carry out a new mission does not necessarily require a new suffix (e.g., F-111Cs modified for reconnaissance are designated RF-111C), but often a new letter is assigned (e.g., the UH-60As modified for Search and Rescue missions are designated HH-60G).
Since the 1962 system was introduced there have been several instances of non-systematic aircraft designations and skipping of design numbers.
The most common changes are to use a number from another series, or some other choice, rather than the next available number (117, 767, 71). Another is to change the order of the letters or use new acronym based letters (e.g. SR) rather than existing ones. Non-systematic designations are both official and correct, since the DOD has final authority to approve such designations.RC-7B
Designation conflicted with unrelated C-7 Caribou, redesignated EO-5C in August 2004.
F/A-18 Hornet, also the transient F/A-16 and F/A-22.
Originally, the Navy planned to have two variants of the Hornet: the F-18 fighter and A-18 light attack aircraft. During development, "F/A-18" was used as a shorthand to refer to both variants. When the Navy decided to develop a single aircraft able to perform both missions, the "F/A" appellation stuck. AF-18 or FA-18 would be conformant.
F-35 Lightning II
The F designation is expected, but the series number 35 based on its X-35 designation, rather than the next available F- series number (24).
BF-111, or using a much lower number in the bomber series would have been more systematic but 111
was retained for commonality with the F-111 from the pre-1962 system.
Designated as part of series continuing from the pre-1962 system and latterly used to identify foreign aircraft acquired by the government, e.g., YF-113 was a MiG-23.
The SR-71 designator is a continuation of the pre-1962 bomber series, which ended with the XB-70 Valkyrie. During the later period of its testing, the B-70 was proposed for the reconnaissance/strike role, with an RS-70
designation. The USAF decided instead to pursue an RS-71 version of the Lockheed A-12. Then-USAF Chief of Staff Curtis LeMay preferred the SR (Strategic Reconnaissance) designation and wanted the reconnaissance aircraft to be named SR-71. Before the Blackbird was to be announced by President Johnson on 29 February 1964, LeMay lobbied to modify Johnson's speech to read SR-71 instead of RS-71. The media transcript given to the press at the time still had the earlier RS-71 designation in places, creating the myth that the president had misread the aircraft's designation.
Uses its own modified mission letter (T for Tactical) with basic mission letter (R for Reconnaissance). Later redesignated U-2R after the end of the Cold War in 1991.
Skipped hundreds of C- series numbers to use Boeing's model number. Has conformant basic mission and modified mission letters. Only used for aircraft sold to foreign air forces. The U.S. Air Force ordered the Boeing 767-based tanker KC-46, which is the expected designation following the assignment of "KC-45" to the competing Airbus A330-derived bid, which itself skipped 42-44.
The design number "13" has been skipped in many mission and vehicle series for its association with superstition. Some numbers were skipped when a number was requested and/or assigned to a project but the aircraft was never built.
The following table lists design numbers in the 1962 system have been skipped.
*: The X-23 and X-39 designations exist, but were never officially assigned. X-52 was skipped to avoid confusion with the B-52 Stratofortress.
From 1939 a manufacturer's code was added to designations to easily identify the manufacturer and the production plant. The code was a two letters for example F-15E-50-MC the MC being the code for the McDonnell Douglas plant at St. Louis, Missouri.
In 1941 block numbers were added to designations to show minor equipment variations between production blocks. The block number appears in the designation between the model suffix and manufacturers code (for example F-100D-85-NH). Initially they incremented in numerical order -1, -2, -3 but this was changed to -1, -5, -10, -15 in increments of five. The gaps in the block numbers could be used for post-delivery modifications, for example a F-100D-85-NH could be modified in the field to F-100D-86-NH. Not all types have used block numbers.