Japanese Aircraft Designation System

From The Air Combat Wiki

Contents 1 Japanese Army Air Force 1.1 Kitai Numbers 1.2 Type Numbers 1.3 Popular Names 2 Japanese Navy Air Force 2.1 Experimental Shi Numbers 2.2 Short Designation System 2.3 Type Number System 2.4 Popular Names 2.5 Navy Short Designation Function Letters 2.6 Navy Short Designation Manufacturer Letters 3 Allied Intelligence

Japanese Army Air Force

The Japanese Army Air Force (JAAF) started using the "type number" desgination system in 1927 and added the Kitai number system in 1932. Some aircraft had popular names and research aircraft used a special designation.

Kitai Numbers

Airframes were given a Kitai (Ki-) number starting in 1932. New types were assigned a number in sequence until 1944 when numbers were mixed up in an attempt to confuse Allied intelligence.

• Subsequent models retained the same Ki- number and used a roman numeral (e.g. Ki-61-I) to differentiate between models.

• Versions of the same model (usually different weaponry) were given a Japanese character (e.g., Ko, Otsu, Hei, etc.), which is usually replaced by a lower-case Roman letter (e.g., Ko = a, Otsu = b, Hei = c).

• The Kaizo (Kai) designation indicated a Modified prototype (no letter suffix, e.g., Ki-61-II KAI) or production (e.g., Ki-61-II KAIa) model.

• Gliders initially received a Kitai (Ki-) number but were later changed to a Guraida (Ku-) sequence.

• Aircraft not originated through the Koku Hombu received designations based on their manufacturer's name (e.g., Kayaba Ka-1).

• Missiles used a special designation, but the Kawasaki Igo-1-B was known as the Ki-148 to confuse Allied intelligence.

Type Numbers

Aircraft accepted for production and operation service were given a type number beginning in 1927 consisting of a brief description of the plane's function and a type number. The type number was based on the last two digits of the Japanese year (up to 2599) in which the aircraft was accepted. 1939 AD was 2599 in the Japanese calendar and thus a fighter accepted in that year would be a "Type 99 Fighter", while one produced the next year would be a "Type 100 Fighter" and the next year's would be a "Type 1 Fighter".

• Additional models of the same type were given a model number and versions resulted in a letter suffix (e.g., Type 97 Light-Bomber Model 1A).

• Foreign designed aircraft were given a type letter based on their country of origin instead of a type number (e.g., the Italian Fiat B.R.20 was known as the Type I Heavy Bomber).

Popular Names

Shortly after the war started the Koku Hombu realized that using the Kitai and Type systems were both too complicated for daily use and revealed too much to Allied intelligence. Therefore, popular names were given to principle types, with names chosen haphazardly.

Japanese Navy Air Force

Experimental Shi Numbers

From 1931 onward a Shi (experimental) number based on the current year of the Imperial reign was assigned to all new naval aircraft projects.

• Different projects in the same year were distinguished by using a description of the aircraft function.

For example, a reconnaissance seaplane designed in 1932 (7th year of Hirohito's reign) was referred to as the Navy Experimental 7-Shi Reconnaissance Seaplane.

Short Designation System

During the 1920s the JNAF adopted a shortened designation system similar to what the US Navy used until 1962.

• The first capital letter was a Type symbol indicating the primary function of the plane.

• The first number was a sequence based on the number of planes of that type designed up until that time.

• The second capital letter indicated the company responsible for the design.

• The second number indicated subsequent models of the same type.

• A lower-case letter suffix indicated minor modifications not signidficant enough to warrant a new model number.

For example, A6M5c referred to the 3rd minor modification to the 5th model of the 6th type of Carrier Fighter designed.

• If an aircraft was modified for another purpose, the function was indicated as a capital letter dashed suffix (e.g., A6M2-K was a Zero Trainer).

Type Number System

From 1921 onward the Navy assigned a type number to most planes. Until 1928 the number was based on the year of the reign of the current Emperor (e.g., 1926=Taisho 15 and 1928=Showa 3).

• Starting in 1929 the type number was based on the last two digits of the Japanese calendar year. The system was thus identical to the Army system described above, except that a Type 0 was used instead of a Type 100 for the year 2600.

• Initially additional models within a type were distinguished by a single digit (e.g., Model 1) and minor modifications were given a dash number suffix (e.g., Model 1-1). In the late 1930s a two-digit model system was adopted. The first digit would change when the airframe was modified and the second would change when a new engine was adapted for use. Under the new system, the first version would be Model 11 and the second would be Model 21 if only the airframe changed, Model 12 if only the engines were changed and Model 22 if both engines and airframe were modified.

• Minor modifications within a Model would be distinguished using a Japanese character (Ko, Otsu, Hei, etc.), which in Western use is usually changed to a Roman letter suffix (e.g., Model 51 Hei is known as Model 52c in Western usage).

• In 1942 the Type system was modified for security purposes to a popular name (described below), while retaining the Model and modification system.

Popular Names

In 1943 the Navy reversed its long-standing aversion to the use of popular names and officially designated popular names in place of the Type number. Names were selected based on the following schedule:

• Fighters - named after meteorological phenomena

* Carrier and Seaplane Fighters - named after meteorological phenomena ending in pu or fu (wind)

* Interceptor Fighters - named after meteorological phenomena ending in den (lightning)

* Night Fighters - named after meteorological phenomena ending in ko (light)

• Attack Aircraft - named after mountains

• Reconnaissance Aircraft - named after clouds

• Bombers - named after stars (sei) or constellations (zan)

• Patrol Planes - named after seas and oceans

• Transports - named after skies

• Trainers - named after trees, plants and flowers

• Miscellaneous Aircraft - named after landscape effects

Navy Short Designation Function Letters

A - Carrier Fighter

B - Carrier Attack Bomber

C - Reconnaissance Plane

D - Carrier Bomber

E - Reconnaissance Seaplane

F - Observation Seaplane

G - Attack Bomber

H - Flying Boat

J - Land-based Fighter

K - Trainer

L - Transport

M -Special Floatplane

MX - Special Purpose Aircraft

N - Fighter Seaplane

P - Bomber

Q - Patrol Plane

R - Land-based Reconnaissance

S - Night Fighter

Navy Short Designation Manufacturer Letters

A - Aichi Kokuki K.K.

G - Hitachi Kokuki K.K.

H - Hiro Dai-Juichi Kaigun Kokusho

He - Ernst Heinkel, A.G.

J - Nihon Hogata Hikoki K.K.

K - Kawanishi Kokuki K.K.

M - Mitsubishi Jukogyo K.K.

N - Nakajima Hikoki K.K.

P - Nihon Hikoki K.K.

S - Sasebo (Dai-Nijuichi Kaigun Kokusho)

Si - Showa Hikoki K.K.

W - K.K. Watanabe Tekkosho

Y - Yokosuka (Dai-Ichi Kaigun Koku Gijisusho)

Z - Mizuno Guraida Seisakusho)

Allied Intelligence

At the start of the war all Japanese fighters were referred to by the Allies as "Zeros" and all bombers were identified as "Mitsubishis". Because of the confusion, the Allied Air Technical Intelligence Unit (ATIU) was assigned the task of coming up with a better system.

Captain Frank T McCoy of Nashville, Tennessee was assigned to Australia as the Intelligence Officer for the 38th Bombardment Group in early 1942 and in June became the founder and head of the Materiel Section of the Directorate of Intelligence, Allied Air Fores, Southwest Pacific Area, in Melbourne. His staff consisted entirely of two men: Technical Sergeant Francis Williams and Corporal Joseph Gratton. They were assigned the task of identifying all Japanese aircraft.

Code names were assigned based on the following schedule:

• Male first names - Fighters and Reconnaissance Seaplanes

• Female first names - Bombers, attack bombers and dive-bombers, Land- and carrier-based Reconnaissance Planes and Flying-boats

• Tree names - Trainers

• Bird names - Gliders