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Nakajima Sakae.jpg
Nakajima Sakae engine on a Mitsubishi Zero

The Nakajima Sakae ( Prosperity?) was a two-row, 14-cylinder air-cooled radial engine used in a number of combat aircraft of the Imperial Japanese Navy and Imperial Japanese Army before and during World War II.[1]

Design and developmentEdit

The engine was designed by Nakajima Aircraft Company after acquiring a license for the French Gnome-Rhone 14K. The Imperial Japanese Army Air Force called the first of the series the Ha-25 (ハ25) and later versions were designated Ha35, Ha105 and Ha115, while the Imperial Japanese Navy Air Service designation was Nakajima NK1, with sub-types identified by Model numbers; thus Nakajima NK1 Sakae 10, 20 and 30 series.

A total of 21,166 were made by Nakajima; 9,067 were manufactured by other firms.


Army Type 99 975 hp Air-cooled Radial
Long Army designation for the Nakajima NK1 radial engine named Sakae.
Nakajima Ha25
Short Army designation for the initial production version of the Nakajima NK1 radial engine named Sakae.
Nakajima Ha35
Nakajima Ha35 Model 11
Nakajima Ha35 Model 12
Nakajima Ha35 Model 23 - 1,150 hp (858 kW)
Nakajima Ha105
Nakajima Ha115
Nakajima Ha115-I
Nakajima Ha115-II
Nakajima NK1
NK1C Sakae 12 - 925 hp (690 kW) , 940 hp (701 kW) , 975 hp (727 kW)
NK1D Sakae 11 - 970 hp (723 kW) , 985 hp (735 kW)
NK1F Sakae 21 - 1,115 hp (831 kW) , 1,130 hp (843 kW)
NK1E Sakae 31 - 1,130 hp (843 kW) , boosted to 1,210 hp (902 kW) with water-methanol injection


Surviving enginesEdit

A small number of original Sakae powerplants are on display in aviation museums, usually mounted into the airframes of restored Mitsubishi A6M Zeros - only one airworthy Zero worldwide still flies with a restored Sakae powerplant, the Planes of Fame Museum's A6M5 example, bearing tail number "61-120".[2][3]

Specifications (Sakae 21)Edit

CVE27 Kamikaze engine parts

USS Suwannee after the Kamikaze attack of 25 October 1944. Parts of the A6M5 Kamikaze-Zero's Nakajima Sakae 21, 14-cylinder radial engine were found in the vicinity of the hit. Cylinder heads are destroyed, connecting rods and crankshaft are visible.

Data from Jane's.[4]

General characteristics

  • Type: 14-cylinder air-cooled two-row radial engine
  • Bore: 130 mm (5.1 in)
  • Stroke: 150 mm (5.9 in)
  • Displacement: 27.8 L (1,700 in³)
  • Length: 1,600 mm (63 in)
  • Diameter: 1,144 mm (45.0 in)
  • Dry weight: 533 kg (1,175 lb)


  • Valvetrain: Overhead valve
  • Supercharger: Gear driven, two speed.
  • Fuel system: Nakajima twin choke carburettor, automatic mixture and boost control.
  • Cooling system: Air-cooled


  • Power output: 761 kW (1,020 hp) at 2,600 rpm at 6,400 ft (1,950 m)
  • Specific power: 30.2 kW/L (0.66 hp/in³)
  • Compression ratio: 7:1
  • Power-to-weight ratio: 1.43 kW/kg (0.87 hp/lb)

See alsoEdit



  1. Gunston 1989, p.105.
  2. Seaman, Richard. "Aircraft air shows." Retrieved: 13 October 2010.
  3. "Flight Demo of Genuine Japanese Zero with ORIGINAL WWII Sakae 31 Engine!". YouTube. 2009. Archived from the original on December 14, 2009. Retrieved May 6, 2013. 
  4. Jane's 1989, p.298.


  • Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
  • Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1989. ISBN 0-517-67964-7
  • Peattie, Mark R., Sunburst: The Rise of Japanese Naval Air Power 1909-1941, Annapolis, Maryland: Naval Institute Press, 2001, ISBN 1-55750-432-6

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