A NOTE ON DESIGNATIONS

US AIR FORCE / US ARMY

The Aeronautical Division of the US Army was officially opened on August 1st, 1907. Delivery of the first
aircraft, a Wright Model A biplane, was on August 2nd, 1909. The Aeronautical Division came under the
control of the Signal Corps. on July 18th, 1914, as the Aviation Section. It was separated from the Army
on May 20th, 1918 as the Air Service before becoming a part of the US Army again on June 4th, 1920.
Early Army aircraft were simply operated under their manufacturer's model numbers, there was no official
designation system in place at all. The role of most aircraft was only observation so the need for a system
didn't come about till the First World War when aircraft began to take on a wider range of duties.
Nothing however, was done about it till after the war had finished in 1918.
The following systems are based around the TYPE LETTER of a designation, more on which comes later.

The 1919 System
In September 1919, the Air Service introduced a classification system in the order of fifteen numerical types.
The Engineering Division assigned letter codes to each numbered type, there being a separate numerical
sequence within each type. Eight additional codes were eventually introduced to the system.
On June 4th, 1920, the Air Service became a part of the Army which it had been a part of originally prior to
mid 1918. The name was later changed to the United States Army Air Corps. (USAAC) on July 2nd, 1926. 
The 1924 System
The first revision took place in May 1924, aircraft in service with the old type prefixes retained them and additional
type prefixes were introduced as they became necessary. This system stayed in place basically unchanged
until after World War II.
On June 20th, 1941, the USAAC became the United States Army Air Force (USAAF) with rapid expansion in
manpower and aircraft due to the growing Japanese threat and the war already being fought in Europe.
The 1948 System
On September 18th, 1947, the USAAF became the United States Air Force (USAF), now independent from
the US Army. A second revision then took place in 1948 with many of the wartime two letter codes being
dropped and each type letter being henceforth identified by a single letter only.
The 1956 Army System
The US Army Aviation introduced a system of its own which operated from 1956 to 1962
with two letter type symbols:

The 1962 Tri-Service System
The third and most extensive revision was made on September 18th, 1962, and continues in use to the present day.
The "Unified" System saw the USAF, US Army and US Navy services all combined under one designation system with
very little changing for the USAF itself. Several new type letters were added for Army and Navy however, to bring them
into alignment with everything else.

USAF / US ARMY AIRCRAFT DESIGNATIONS

The standard US military aircraft designation may have up to six parts as in this
example of a Fairchild Provider: VC-123B-18-FA.

From this designation it can be deduced that the Fairchild Provider is the 123rd Cargo type to be
commissioned by the USAF and that it's the second variant to enter service and was probably converted
post delivery to it's primary role of VIP duties. It comes from a batch manufactured to Block 18 standards
and was built at Fairchild Hagerstown, Maryland.

Status Prefix Letter
This range of letters prefixes the Type Letter indicating the aircraft has a secondary role such as Tactical Support,
Drone Director, Staff Transport etc., this role also takes precedence over the aircraft's primary duty as indicated
by the Type Letter. For example take a CB-24J Liberator, it's primary role is Cargo transport not Bombing.
X and Y, however, always take precedence over any other Status Prefix letter (e.g. YRF-4C-MC), with Z being
the only exception to this rule (e.g. ZXB-24Q-FO).
The table below gives a list of Status Prefix Letters with those still in use today in bold type:

Type Letter
The Type Letter is the main form of aircraft designation whether it be Fighter, Bomber or Trainer etc. Early systems
quite often used a two letter code but this was dropped by 1948 for single letters only. This system has become the
basis for all US Air Force and Army designation systems since it was first introduced in 1919.
The letters H, V and Z are vehicle type designators and are only used together with a mission type prefix,
for example Helicopter types designated - AH-1 Cobra, SH-3A Sea King, UH-1 Iroquois etc.
The table below gives a list of Type Letters from the 1919 System onwards with those still in use today
in bold type:

Type Sequence Number
This is simply a numerical system denoting the number for any given Type Letter to have been commissioned by
the US armed forces. The numbers started at 1 with the 1924 system and climbed from there with each successive
type that was built, tested or put into production. For example the B-17 was the 17th Bomber design built since
1924 and the P-51 the 51st Pursuit design since 1924 etc.
Type Sequence Numbers of the 1924 system were cancelled with the 1962 Tri-Service System and all types
were again started at 1. This is why we have the Lockheed C-141 Starlifter first flown in 1963 being followed
by the Lockheed C-5 Galaxy first flown some years later in 1968.

Series Suffix Letter
A letter was applied after the Type Sequence Number to indicate a modification to the aircraft such as
an engine or armament upgrade. Design changes also denoted a new Suffix Letter such as cockpit
layout, wing or structural upgrades etc., basically a new Series Suffix Letter denoted a new variant.
The initial model of each aircraft type originally had no Suffix Letter (e.g. XP-40), with the second variant
having an A, the third a B and so on.
The 1962 Tri-Service System changed things so the letter A was always given to each types initial variant,
regardless of its status including prototypes (e.g. YF-14A, YC-17A).
The letters I and O are not used as these may be confused with numerals.

Block Numbers
These were introduced in 1941 when it was found that the Series Suffix Letters for modifications only worked
up to the end of the alphabet and in some cases modifications stretched into the hundreds.
So, Block Numbers were formed to denote minor modifications such as on board equipment like radios,
oxygen equipment, minor mechanical changes etc. In most cases major upgrades that would affect aircraft
performance would be reserved for new Suffix Letters only.
Initially started with -1, -2 etc., they became -1, -5, -10, -15 etc. in "blocks" of five, the gaps left for field and
post delivery modifications. Some aircraft such as the C-119 and C-123 were given consecutive block numbers
to denote successive production batches. Also, many aircraft relegated to second line duties but still in production
didn't use them (e.g. the last two batches of the Fairchild C-82).
Today Block Numbers have largely been done away with in favor of Lot Numbers as used on the C-17 and F-15.

Manufacturer Codes
From 1939 onwards with the growing amount of aircraft production under which several manufacturers built
the same type of variant at several different plants, it became necessary to identify which aircraft came from
which plant. Two letter codes were introduced after the Block Number to denote straight away which factory
an aircraft came from.
The Consolidated B-24J Liberator was built at five plants throughout the US from 1943 to 1944, it can be
deduced with Manufacturers Codes that those plants were: Consolidated San Diego (CO), Consolidated Fort
Worth (CF), Douglas Tulsa (DT), North American Dallas (NT) and The Ford Motor Co., Willow Run (FO).
Manufacturer Codes are to extensive to list here and are listed where appropriate in the databases.

US NAVY / US MARINES / US COAST GUARD

The US Navy flew it's first aircraft, a Curtiss A-1 Triad, on July 1st, 1911 and except for a short
period from 1917 to 1922, the US Navy identified its aircraft up to 1962 by specific designation
systems that conveyed a considerable amount of information about the aircraft type, origin and
nature. The following systems are based around the TYPE LETTER which is described in more
detail later:

The 1911-1914 System
A fairly cumbersome system that could only cope with a small amount of aircraft deliveries. Each aircraft
was given a letter to identify it's manufacturer, followed by a number to show its order of procurement.
The 1914-1916 System
On March 17th, 1914, a new system was created and all aircraft on hand were redesignated. Aircraft were
identified by type and sub-type, followed by a number to show its order of procurement, a system similar
to ship designations. On July, 1st, 1915, the Office of Naval Aeronautics was officially set up with the Naval
Flying Corps. established in August 1916.
The 1917-1922 System
No standard system was used during these years and all aircraft were operated under their manufacturers
names and model numbers.
The 1922-1962 System
The Bureau of Aeronautics (BuAer) was formed on August 10th, 1921, to assume all responsibility for matters
relating to naval aviation. On March 29th, 1922, BuAer reorganized the entire designation system for naval
aircraft which also applied to the US Marine Corps. and the US Coast Guard from 1935.
A further revision was made on March 10th, 1923, with this system being the one that stayed in practice until
the "Unified" System was introduced on September 18th, 1962, which saw all Naval, Marine and Army aircraft
placed under the same designation system as that of the USAF.

US NAVY / US MARINE AIRCRAFT DESIGNATIONS

The standard US Navy aircraft can have up to six parts as in this example
of a Grumman Hellcat: XF6F-3N.

From this designation it can be deduced that this Grumman Hellcat is a prototype Fighter aircraft,
the sixth Fighter design to be produced by the Grumman Aircraft Corp. and is the third variant to
be produced and has a special purpose role of being a Night-fighter.

Status Prefix Letter
A first letter was only applied if an aircraft had a changed status such as being built or converted
to a prototype aircraft which saw the use of X as the designator for this role. Y was used when
an aircraft was undergoing service tests.

Type Letter
This is the main designation system that is the primary means of identifying an aircraft type,
whether its a Fighter, Patrol Bomber or Trainer etc. This is the system that applied to aircraft from
1922 to 1962 and is presented in the table below:

Manufacturer Type Sequence Number
This reflects the delivery of different models of the same Type Letter from the same manufacturer.
for example the Grumman F4F Wildcat was the fourth Fighter Type produced by Grumman with
the single F5F Skyrocket being the fifth Grumman Fighter design etc. Of course the next aircraft
was the F6F Hellcat which like the F4F became legend. 

Manufacturer Codes
Simply a single letter that denotes the aircraft's manufacturer. Unlike the two letter codes used for
the USAF, which determine the actual plant, the Navy single letters tend only to identify the overall
manufacturer. So for example the PBY-5A was produced at two plants but the Y code applied to
both the Consolidated San Diego plant and also the Consolidated New Orleans one.
Situations where a different manufacturer was license building an aircraft type, a different code
would of course be used. Hence, the TBF Avenger applied to aircraft produced by Grumman and
the TBM Avenger designation applied to the same aircraft, but produced by General Motors.
Manufacturer Codes are to extensive to list here and are listed where appropriate in the databases.

Type Series Number
This number basically denotes the number of variants produced of an aircraft type. The first variant
of an aircraft would be -1, the second -2 etc. The Navy used this numbering sequence whereas the
USAF and Army used a Suffix Letter to denote their progressive variants.

Special Purpose Suffix Letter
Similar to the Air Force Status Prefix Letter, this goes at the end of the designation in the Navy,
not at the start as is the case with the Air Force. It indicates a special purpose mission role or secondary
duty that the aircraft was modified to perform. For example the photographic reconnaissance version
of the F4F Wildcat was designated as the F4F-4P Wildcat.
In some cases a further modification made to an aircraft my result in a second sub-variant identified by
a number 2 following the Suffix Letter (e.g. TBM-3S2).
In rare cases during World War II, aircraft designated from Army aircraft versions used Suffix Letters to
indicate the variant of the aircraft. So the North American B-25D Mitchell was designated in US Marine
Corps. service as the PBJ-1D and the B-25J the PBJ-1J etc.
The table below is the Special Purpose Suffix Letters in use from 1922 to 1962:

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