Japanese aircraft engine identification systems

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Japanese aircraft engine designation systems

Data from:Japanese Aircraft 1910–1941[1] & Japanese Aircraft of the Pacific War[2] & Japanese Aircraft Engines[3]

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
(Nakajima Ha41)
Army long designation
(e.g. Army Type100 1250hp Air Cooled Radial)
Navy experimental designation
(Nakajima NK9B)
Navy Name designation
( Nakajima Homare 11)
Manufacturers designation
(Nakajima NBH)
Unified system introduced by the Ministry of Munitions in April 1942
(Kawasaki Ha-60)

Army Hatsudoki system[edit]

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[edit]

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 Type100 1250hp Air Cooled Radial – (Nakajima Ha41) 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[edit]

The IJNAS introduced a designation system for experimental engines and those under development / test before production. Once the engine entrred 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
Third Character for the design number
Fourth Character for the revision code
A - first revision
B - second revision, and so on.

Navy name designation[edit]

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 ( Homare?))

Manufacturers designation[edit]

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[edit]

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:

  1. Air-cooled inline engine.
  2. Air-cooled single-row radial engine.
  3. Air-cooled 14-cylinder double-row radial engine.
  4. Air-cooled 18-cylinder double-row radial engine.
  5. Air-cooled, more than 18-cylinders, multi-row radial engine.
  6. Liquid-cooled 12-cylinder engine.
  7. Liquid-cooled, more than 12-cylinders engine.
  8. Diesel engine.
  9. Special engine.

The second digit represented the bore and stroke of the engine:

0. 130/160
  1. 140/130
  2. 150/170
  3. 140/150
  4. 140/160
  5. 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


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[edit]

Data from: [1]

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[edit]

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
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
Hitachi Ha13 Army Type 95 350hp Air Cooled Radial
Hitachi Ha13a Army Type 98 450hp Air Cooled Radial
Nakajima Ha20
Nakajima Ha25 Army Type 99 975hp Air Cooled Radial / Army Type 99 950hp Air Cooled Radial NK1 prosperity ( 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 ( 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 ( 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-44
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 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 encampment wind (陣 風 Jimpu?) 150 - 160 hp 7 cyl. radial
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 light ( Hikari?)
Nakajima NK11
Nakajima NZ
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

See also[edit]


  1. ^ a b Mikesh, Robert; Shorzoe Abe (1990). Japanese Aircraft 1910–1941. london: Putnam. ISBN 978-0-85177-840-2. 
  2. ^ Francillon, Rene (1979). Japanese Aircraft of the Pacific War. London: Putnam & Company Limited. ISBN 0 370 30251 6. 
  3. ^ Mawhinney, Robert. Japanese Aircraft Engines. Washington D.C.: NASM. 


External links[edit]