# Japanese aircraft engine identification systems

Japanese aero-engines for military aircraft were given a wide variety of designations depending on the customer. This led to much confusion, particularly among the Allied forces, where a single engine type could have up to six different designations. This situation emerged because of the almost total lack of co-operation in weapons procurement between the IJAAS (大日本帝國陸軍航空隊 - Dai-Nippon Teikoku Rikugun Kokutai - Imperial Japanese Army Air Service) and the IJNAS (大日本帝國海軍航空隊 - Dai-Nippon Teikoku Kaigun Koukuu-tai - Imperial Japanese Navy Air Service).
Engines could have designations in any or all of these designation systems:

## Army Hatsudoki experimental designation

    (Kawasaki Ha40)

## Army long designation

    (e.g. Army Type 99 900hp Air Cooled Radial)

## Navy experimental designation

    (Nakajima NK9B)

## Navy Name designation

    ( Nakajima Homare 11)

## Manufacturers designation

    (Nakajima NBA)

## Unified system introduced by the Ministry of Munitions in April 1942

    (Kawasaki Ha-60)
Data from:Japanese Aircraft 1910–1941 & Japanese Aircraft of the Pacific War & Japanese Aircraft Engines

## Army Hatsudoki system

Experimental engines for Army aircraft were given ハ Ha – (エンジン - Hatsudoki) numbers whilst under design and testing. The Army Ha numbers had no intrinsic meaning and were only sequentially allocated. Sub types could be identified by suffixes -kai, -ko etc., or -I, -II etc.. e.g.:Nakajima Ha115

## Army long designation system

Once an engine had been accepted for service in Army aircraft it was given a long designation which denoted the year of introduction, power, cooling method and layout:
e.g.:Army Type 100 1,450hp Air Cooled Radial – (Nakajima Ha111) The two or three digit Type number denoted the Japanese Imperial year (皇紀, kōki) that the engine was introduced, identical to the Type numbers used in Japanese aircraft long designations from 1925 (From 1927 to 1930 the Type number sometimes denoted the Shōwa or Taisho year ):
After the Type number the power of the engine was denoted in horsepower:
* 1250 hp
After the power designator the type of engine was denoted:
* Air-cooled Radial
Sub-types were designated by suffixes.
* Model 1

## Navy experimental designation

The IJNAS introduced a designation system for experimental engines and those under development / test before production. Once the engine entered service this designation was replaced by the name or unified system. Formed from four character groups the IJNAS experimental designation system consisted of e.g. Nakajima NK9B

### First character for manufacturer

    A - Aichi
    G - Hitachi
    I - Ishikawajima
    K - Kawasaki
    M - Mitsubishi
    N - Nakajima
    Y – Naval Air Technical Arsenal (Yokosuka and Hiro)

### Second Character for engine attributes

    K - Air cooled
    E - Liquid Cooled
    D - Diesel

### Fourth Character for the revision code

    A - first revision

### B - second revision, and so on.
## Navy name designation

The simplest of all the systems the IJNAS allocated name characters to engines combined with Model and revision numbers, introduced to reduce confusion and also to reduce the intelligence value of the designation to enemies. e.g. Nakajima Homare 11 - (praise" or, more usually, "honour (誉, Homare))

## Manufacturers designation

Some engines were never allocated a designation or there is no record of such. In which case they are usually identified by the manufacturers designation. e.g. Mitsubishi A4

## Unified IJAAS / IJNAS designation system

From 1942 the Ministry of Munitions in Japan instituted a Unified aero-engine designation system in an attempt to reduce confusion caused by previous systems. The new system prefixed engine designations with ハ Ha – (エンジン - Hatsudoki) followed by code numbers identifying each engine in terms of layout, no of cylinders, cooling method and sub-series model numbers.
Thus the Mitsubishi Ha-33-62 金星 Kinsei
* Mitsubishi - manufacturer
* ハ Ha (エンジン Hatsudoki) - engine.
* 3 - air-cooled 14-cylinder double-row radial engine.
* 3 - 140 mm bore, 150 mm stroke.
* 62 - 60 series engine, second revision.
* 金星 Kinsei - name
Each engine designation in this system started with the Hatsudoki short hand character, represented by Ha in English, followed by two numbers classifying the engine:
The first digit represented the engine classification:
* Air-cooled inline engine.
* Air-cooled single-row radial engine.
* Air-cooled 14-cylinder double-row radial engine.
* Air-cooled 18-cylinder double-row radial engine.
* Air-cooled, more than 18-cylinders, multi-row radial engine.
* Liquid-cooled 12-cylinder engine.
* Liquid-cooled, more than 12-cylinders engine.
* Diesel engine.
* Special engine.
The second digit represented the bore and stroke of the engine:
* 130/160
* 140/130
* 150/170
* 140/150
* 140/160
* 130/150
After the classification digits a two digit number gave the model number and revision state.
Model numbers were given as:
* 00 – baseline Model, usually prototypes
* 10
* 20
* 30
* 40
* 50
* 60
etc.etc.
A revision (or modification) state number replaced the second digit of the model number:
* 10 – Model 10 baseline version
* 11 – Model 10 revision 1
* 12 – Model 10 revision 2
* 23 – Model 20 revision 3
* 62 – Model 60 revision 2
Coincidentally one engine was assigned the same numerical designation in the IJAAS and joint designation systems; Nakajima Ha-45 Homare.

## Calendars and Type numbers

Data from:
| Gregorian calendar year | Type number (Army and Navy) | Imperial Japanese Calendar Year | Nengo Calendrical era | Navy exp.Shisaku number |
| 1921 | Type 10 (Taisho) | 2581 | Taisho 10 | |
| 1922 | Type 11 (Taisho) | 2582 | Taisho 11 | |
| 1923 | Type 12 (Taisho) | 2583 | Taisho 12 | |
| 1924 | Type 13 (Taisho) | 2584 | Taisho 13 | |
| 1925 | Type 14 (Taisho) | 2585 | Taisho 14 | |
| 25/12/1926 | Type 15 (Taisho) | 25/12/2586 | Taisho 15 | |
| 26/12/1926 | | 26/12/2586 | Showa 1 | |
| 1927 | Type 87 | 2587 | Showa 2 | |
| 1928 | Type 88 | 2588 | Showa 3 | |
| 1929 | Type 89 | 2589 | Showa 4 | |
| 1930 | Type 90 | 2590 | Showa 5 | |
| 1931 | Type 91 | 2591 | Showa 6 | 6-Shi |
| 1932 | Type 92 | 2592 | Showa 7 | 7-Shi |
| 1933 | Type 93 | 2593 | Showa 8 | 8-Shi |
| 1934 | Type 94 | 2594 | Showa 9 | 9-Shi |
| 1935 | Type 95 | 2595 | Showa 10 | 10-Shi |
| 1936 | Type 96 | 2596 | Showa 11 | 11-Shi |
| 1937 | Type 97 | 2597 | Showa 12 | 12-Shi |
| 1938 | Type 98 | 2598 | Showa 13 | 13-Shi |
| 1939 | Type 99 | 2599 | Showa 14 | 14-Shi |
| 1940 | Type 100 / Type 0 | 2600 | Showa 15 | 15-Shi |
| 1941 | Type 1 | 2601 | Showa 16 | 16-Shi |
| 1942 | Type 2 | 2602 | Showa 17 | 17-Shi |
| 1943 | Type 3 | 2603 | Showa 18 | 18-Shi |
| 1944 | Type 4 | 2604 | Showa 19 | 19-Shi |
| 1945 | Type 5 | 2605 | Showa 20 | 20-Shi |

## Table of japanese aero-engine designations

| Manufacturer | Army exp. | Army long | Navy exp. | Navy Name | Manuf desig. | Unified | Notes |
| Nakajima | Ha1 | Army Type 97 650hp Air-cooled Radial | | longevity (寿, Kotobuki) | AH | | |
| Nakajima | | | | | NZ | | 110 kW (150 hp) 7-cylinder radial |
| Mitsubishi | Ha2 | Army Type 93 700hp Water Cooled In-line | | | | | |
| Nakajima | Ha5 | Army Type 97 825hp Air Cooled Radial | | | | | |
| Mitsubishi | Ha6 | | MK1 | heavens name (震天, Shinten) | A6(7) | | 14 cyl. radial |
| Nakajima | Ha8 | Army Type 94 550hp Air Cooled Radial | | | | | |
| Kawasaki | Ha9 | Army Type 98 850hp Liquid Cooled In-line | | | | | liquid-cooled V-12 (BMW VI) |
| Hitachi | Ha12 | Army Type 95 150hp Air Cooled Radial | | encampment wind (陣 風, Jimpu) | | | |
| Hitachi | Ha13 | Army Type 95 350hp Air Cooled Radial | | encampment wind (陣 風, Jimpu) | | | |
| Hitachi | Ha13a | Army Type 98 450hp Air Cooled Radial | | encampment wind (陣 風, Jimpu) | | | |
| Nakajima | Ha20 | | | light (光, Hikari) | | | |
| Lorraine-Dietrich | | | | | Lorraine 1 | | IJN designation for imported Lorraine-Dietrich 12D V-12 engines |
| Lorraine-Dietrich | | | | | Lorraine 2 | | IJN designation for imported Lorraine-Dietrich 12Eb W-12 engines |
| Lorraine-Dietrich | | | | | Lorraine 3 | | IJN designation for imported geared Lorraine-Dietrich 12Eb W-12 engines |
| Nakajima | Ha25 | Army Type 99 975hp Air Cooled Radial / Army Type 99 950hp Air Cooled Radial | NK1 | prosperity (栄, Sakae) | | Ha-35 | |
| Mitsubishi | Ha26 | Army Type 99 900hp Air Cooled Radial | MK2 | holy star (瑞星, Zuisei) | A14 | Ha-31 | |
| Hitachi | Ha38 | | | | | | 600 hp 9-cyl radial |
| Nakajima | Ha39 | | | | | | |
| Kawasaki | Ha40 | Army Type 2 1,100hp Liquid Cooled In-line | | | | Ha-60 | liquid-cooled V-12 |
| Nakajima | Ha41 | Army Type 100 1,250hp Air Cooled Radial | | | | | |
| Hitachi | Ha42 | | | | | | 9-cyl radial |
| Nakajima | Ha45 | Army Type 4 1,900 hp Air-cooled Radial | NK9 | honour / praise (誉, Homare) | NBA | Ha-45 | |
| Hitachi | Ha47 | Army Type 4 110hp Air Cooled Inline | GK4 | fresh wind (初風, Hatsukaze) | | | |
| Nakajima | Ha51 | | | 22cyl Homare | | Ha-51 | Air-Cooled 22-Cylinder 2-Row Radial |
| Yokosuka Naval Air Arsenal | Ha73 | | | Ken No. 3 | YE2 | | W-18 |
| Yokosuka Naval Air Arsenal | Ha74 | | | | YE3 (Ken No. 1) | | 2,500 (or 3,200) shp horizontal X-24 liquid-cooled engine, known as Yokosuka Naval Air Arsenal YE3B (Ha 74 Model 01) or YE3E (Ha 74 Model 11) |
| Mitsubishi | Ha101 | Army Type 100 1,450hp Air Cooled Radial | MK4 | Mars (火星, Kasei) | A10 | Ha-32 | |
| Mitsubishi | Ha102 | Army Type 100 1,050hp Air Cooled Radial | MK2 | holy star (瑞星, Zuisei) | A14 | Ha-31 | |
| Nakajima | Ha103 | | NK7 | protector (護, Mamoru) | NAK | Ha-36 | |
| Mitsubishi | Ha104 | Army Type 4 1,900hp Air Cooled Radial | | | | | |
| Nakajima | Ha105 | | | | | | |
| Nakajima | Ha109 | Army Type 2 1,450hp Air Cooled Radial | | | | Ha-34 | |
| Mitsubishi | Ha111 | Army Type 100 1,450hp Air Cooled Radial | MK4 | Mars (火星, Kasei) | A10 | Ha-32 | |
| Mitsubishi | Ha112 | Army Type 4 1,500hp Air Cooled Radial | MK8 | golden star (金星, Kinsei) | A8 | Ha-33 | |
| Nakajima | Ha115 | Army Type 1 1,150 Air Cooled Radial | | | | | |
| Nakajima | Ha117 | | | | | | |
| Kawasaki | Ha140 | | | | | | liquid-cooled V-12 |
| Nakajima | Ha145 | | | | | | |
| Kawasaki | Ha201 | | | | | Ha-72 | liquid-cooled inverted V-24 |
| Mitsubishi | Ha211 | | MK9 | | | Ha-43 | |
| Mitsubishi | Ha214 | | | | | | |
| Nakajima | Ha217 | | | | | Ha-46 | |
| Nakajima | Ha219 | | | | | Ha-43 | |
| Nakajima | Ha315 | | | | | | |
| Nakajima | Ha505 | | | 36 cyl Kotobuki | | Ha-54-01 | projected 5,000 hp Air-Cooled 36-Cylinder 4-Row Radial |
| Aichi | | | Aichi AE1 | | Aichi Atsuta | | |
| Aichi | | | Aichi Type 91 | | | | W-12 water-cooled 500–650 hp (370–480 kW) |
| Aichi | | | | | | Ha-70 | Coupled Atsuta 30 engines |
| Hiro | | Hiro Type 14 620 hp | | | | | |
| Hiro | | Hiro Type 90 600 hp water-cooled W-12 | | | | | 500 hp W-12 (Lorraine 12F Courlis development) |
| Hiro | | Hiro Type 91 520 hp water-cooled W-12 | | | | | 500 hp W-12 (Lorraine 12Eb development) |
| Hiro | | Type 94 900 hp liquid-cooled in-line | | | | | 40 degree angle W-18 |
| Hitachi / Gasuden | | | | breeze (端風, Hatakaze) | | | |
| Hitachi / Gasuden | | | | divine wind (神風, Kamikaze) | | | 160 hp 7-cyl. radial |
| Hitachi | | | GK2 | heavenly wind (天風, Amakaze) / heavenly father (天父, Tempu) | | | |
| Hitachi | | | | | | Ha-23 | 4-cyl inverted in-line |
| Ishikawajima Shibauru Turbine Company / Yokosuka (Kugisho) | | | | | Ishikawajima Ne-20 (Japanese: 石川島 ネ-20) | | turbojet |
| Ishikawajima Shibauru Turbine Company | | | | | Ne-30 | | turbojet |
| Ishikawajima Shibauru Turbine Company | | | | | Ne-130 | | turbojet |
| Kawasaki | | Army Type 95 800hp Liquid Cooled In-line | | | | | liquid-cooled V-12 (BMW VI) |
| Maru Industries | | | | | Maru Ka-10 | | pulse-jet |
| Mitsubishi | | | | | A2 | | 320 hp |
| Mitsubishi | | | | | A4 | | 760 hp |
| Mitsubishi | | | | | A9 | | |
| Mitsubishi | | Army Type 92 400hp Air Cooled Radial | | | A5 | | |
| Mitsubishi | | | MK10 | | | | |
| Mitsubishi | | | | | Ne-330 | | turbojet |
| Nakajima | | | NK11 | | | | |
| Mitsubishi | | | | | Mitsubishi Tokuro-1 Ro.1 | | |
| Mitsubishi | | Army Type3 Rocket | KR10 | | Mitsubishi Tokuro-2 Ro.2 | | Walter HWK 109-509 |
| Mitsubishi | | Army Type 2 Rocket | | | Mitsubishi Tokuro-3 Ro.3 | | |
| | | | | | Ne-12 | | turbojet |
| Nakajima - Hitachi | | | | | Ne-230 | | turbojet |
| | | | | | Tsu-11 | | Thermojet |
| | | Navy Type 4 Model 1 solid fuel rocket | | | | | |
| Kobe | | | | | Argus As 10 | | |
| | Ka-10 | | | | Argus As 109-014 | | Pulsejet |