The engine was designed by Nakajima Aircraft Company with code name NAM, as a scaled-down and advanced version of the previous NAL design (Army Type 97 850 hp radial engine, Nakajima Ha5).[2] The Imperial Japanese Army Air Force called the first of the series the Ha25 (ハ25) and later versions were designated Ha105 and Ha115, in the Hatsudoki designation system and Ha-35 in the unified designation system, 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.
Variants
Army Type 99 975 hp Air-cooled Radial
Long Army designation for the Nakajima NK1 radial engine named Sakae.
Nakajima Ha25 (Hatsudoki designation)
Short Army designation for the initial production version of the Nakajima NK1 radial engine named Sakae.
Nakajima Ha105 (Hatsudoki designation)
Nakajima Ha115 (Hatsudoki designation)
Nakajima Ha115-I
Nakajima Ha115-II
Nakajima Ha-35 (unified designation)
Nakajima Ha-35 Model 11
Nakajima Ha-35 Model 12
Nakajima Ha-35 Model 23 - 1,150 hp (858 kW)
Nakajima NK1 (Navy designation)
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 - 1,130 PS (831 kW; 1,115 bhp)
NK1E Sakae 31 - 1,130 hp (843 kW), boosted to 1,210 hp (902 kW) with water-methanol injection
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".[3][4]
Specifications (Sakae 21)
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.
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