The systemThe designation system produces an MDS (or Mission-Design-Series) designation of the form:
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 options and usage of each designation elements will be discussed below. Vehicle typeThe 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:
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. Status prefixThese prefixes are attached to aircraft not conducting normal operations, such as research, testing and development. The prefixes are:
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-13 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. Basic missionAll aircraft (special and normal) 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., MH-53 Pave Low III). The defined codes are:
Of these code series, no normal aircraft have been assigned a K or R code in a manner conforming to the system. The rise of the multi-role fighter in the decades since the system was introduced has created some confusion about the difference between attack and fighter aircraft. According to this designation system, an attack aircraft is only capable of ground attack missions (e.g., the A-6 Intruder and A-10 Thunderbolt II), while a fighter need only possess minor air-to-air combat capabilities (e.g., the F-111 "Aardvark"). The Air Force prefers to refer to its attack aircraft as "fighter-bombers," thus the F-111 and F-117, which are purely attack aircraft. The only "Attack" aircraft in the USAF's current inventory is the A-10. Modified missionAircraft 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:
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., UC-12). The vast majority of U.S. Coast Guard air assets include the H-code (e.g., HH-60 Jayhawk or HC-130 Hercules). Design numberAccording 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-767A2), or have kept the design number when they are transferred from one series to another (e.g., the X-35 became the F-35). Series letterDifferent 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). Non-systematic aircraft designationsSince the 1962 system was introduced there have been a number of non-systematic aircraft designations and skipping of design numbers. Non-systematic or aberrant designationsThe 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. It should be noted that since the DOD has final authority over its own rules, even non-systematic designations are both correct and official. In other words, even though it uses the system as its guideline for naming aircraft, it can approve whatever it chooses, and whatever is approved is "correct".
Skipped design numbersThe design number "13" has been skipped in many mission and vehicle series for superstitious reasons. Some numbers were skipped when a number was requested and/or assigned to a project but the aircraft was never built. More information on the reasons behind the apparent skipping of design numbers can be found at Andreas Parsch's "Missing" USAF/DOD Aircraft Designations page. The following design numbers in the 1962 system have been skipped:
*: 24 or 36 depends on future aircraft designations of the DoD. See also
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