Japanese military aircraft designation systems

Japanese military aircraft, especially of the Imperial (pre-1945) period, are rather difficult to keep track of by their Japanese designations, primarily because multiple designation systems were in use by each armed service. This is what led to the Allies' use of codenames during World War II, and these codenames are still better known in English-language texts than the real Japanese names for the aircraft. Articles on Japanese aircraft in Wikipedia are titled by the manufacturer and short designation code.

Thus, the following may prove helpful. The confusion is not so much that any of the designation schemes are difficult, but that a number of different schemes were simultaneously in use.

Table of contents

1 Imperial Japanese Navy 1.1 Specification Shi numbers 1.2 Long Type and Model Number system 1.3 Short system 2 Popular names 3 Imperial Japanese Army 4 Postwar Japanese self-defence forces

Imperial Japanese Navy

The Imperial Japanese Navy used several different aircraft designation systems simultaneously. Between 1931 and 1945, aircraft had Shi numbers designating the specification they were designed to. They also had a long form of Type and Model Number system used between 1920 and 1943, a short designation system akin to that of the United States Navy in use between the late 1920s and 1945, a system of popular names introduced to replace type numbers from 1943 through 1945, and finally a SADP (Service Airplane Designation System) number used from 1939 onward.

Specification Shi numbers

Japanese Navy specifications from 1931 were given an experimental, or Shi number, based on the year of the Emperor's reign the specification was issued in. Since multiple specifications could be issued in a year, the number was disambiguated with the aircraft purpose.

During the period this designation system was in use, the Emperor in question was Hirohito, the Showa Emperor, thus the years of Showa were those used, which began in 1926.

Thus, the Mitsubishi Zero was designed to meet the 1937 specification called 12-shi carrier fighter.

Long Type and Model Number system

After 1920, aircraft types were given a type number based on the last two digits of the Japanese year. Added to this was a brief description of the aircraft's function. The Mitsubishi Zero was so-called because entered service in 1940 which was the Japanese year 2600, thus it was designated Type 0 Carrier Fighter.

Model numbers were added to show subtypes. By the late 1930s these were two digits, the first being airframe revisions, the second engine revisions.

The system was abandoned in 1943, when it was decided that it gave away too much information about the aircraft.

Short system

In the late 1920s a short designation scheme was adopted, which was strikingly similar to the United States Navy's 1922-64 system. This scheme used a letter or two letters to designate a type of aircraft, a number to indicate the number in series of that type of aircraft, and finally a letter to designate the manufacturer. Unlike the US Navy system, the Japanese system did not have a different number series for each manufacturer; also, the number 1 was not omitted.

Thus, the Zero's type in this designation system was A6M, which meant the sixth type of carrier fighter under this designation system, and that it was built by Mitsubishi.

Variants were indicated by an additional number at the end; repurposing an aircraft was indicated by a dash and then the new type letter.

Sometimes two aircraft were ordered from different manufacturers to the same specification at the same time, generally as insurance against the primary design not working out. In this case, the same series number was used for both.

Aircraft type letters Letter Type of Aircraft A Carrier fighter B Carrier attack bomber C Reconnaissance D Carrier dive bomber E Reconnaissance seaplane F Observation seaplane G Attack bomber (land-based) H Flying boat J Fighter (land-based) K Trainer L Transport M Special seaplane N Fighter seaplane P Bomber Q Patrol R Reconnaissance (land-based) S Night fighter

Manufacturer Letters Letter Manufacturer A Aichi North American Aviation B Boeing C Consolidated Aircraft D Showa Douglas Aircraft G Hitachi Kokuki Grumman H Hiro Hawker He Heinkel J Nihon Kogata Hikoki Junkers K Kawanishi Kinner M Mitsubishi N Nakajima P Nihon S Sasebo Si Showa V Vought-Sikorsky W Watanabe W Kyushu Y Yokusuka Z Mizuno Guraida Seisakusho

Popular names

After July 1943, names were given to Navy aircraft instead of type designations. These names were given according to a scheme based on the aircraft's role.

• Fighters: Weather and meteorological names
  • Carrier fighters and seaplane fighters: Wind names (ending with pu or fu)
  • Interceptors: Lightning names ending in den
  • Night fighters: Light names ending in ko
• Attack planes: Mountains
• Bombers: Star (ending in den) or constellation (ending in dan) names
• Patrol: Sea or ocean names
• Reconnaissance: Cloud names
• Trainers: Trees, plants and flowers
• Transports: Sky names
• Miscellaneous: Landscape names

Two special cases were the Ohka ("Cherry blossom") and the Kikka ("Orange blossom"). Both types were designated "special attackers", meaning kamikaze weapons - named for the fruit trees in the gardens of the imperial palace.

Imperial Japanese Army

Postwar Japanese self-defence forces