The was a two-row, 14-cylinder air-cooled

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...

used in a number of combat aircraft of the

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrender ...

and

Imperial Japanese Army The was the official ground-based armed force of the Empire of Japan from 1868 to 1945. It was controlled by the Imperial Japanese Army General Staff Office and the Ministry of the Army, both of which were nominally subordinate to the Emper ...

before and during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

Design and development

The engine was designed by

Nakajima Aircraft Company The was a prominent Japanese aircraft manufacturer and aviation engine manufacturer throughout World War II. It continues as the car and aircraft manufacturer Subaru. History The Nakajima Aircraft company was Japan's first aircraft manufactur ...

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). The

Imperial Japanese Army Air Force The Imperial Japanese Army Air Service (IJAAS) or Imperial Japanese Army Air Force (IJAAF; ja, 大日本帝國陸軍航空部隊, Dainippon Teikoku Rikugun Kōkūbutai, lit=Greater Japan Empire Army Air Corps) was the aviation force of the Im ...

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 The was the air arm of the Imperial Japanese Navy (IJN). The organization was responsible for the operation of naval aircraft and the conduct of aerial warfare in the Pacific War. The Japanese military acquired their first aircraft in 1910 ...

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 - 1,115 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

Applications

Kawasaki Ki-45 The Kawasaki Ki-45 ''Toryu'' (屠龍, "Dragonslayer") was a two-seat, twin-engine heavy fighter used by the Imperial Japanese Army in World War II. The army gave it the designation "Type 2 Two-Seat Fighter"; the Allied reporting name was "Nic ...

(prototype) * Kawasaki Ki-48 * Kawasaki Ki-56 *

Mitsubishi A6M The Mitsubishi A6M "Zero" is a long-range carrier-based fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries, and was operated by the Imperial Japanese Navy from 1940 to 1945. The A6M was ...

* Mitsubishi C5M2 * Nakajima B5N2 *

Nakajima J1N The is a twin-engine aircraft used by the Japanese Imperial Navy during World War II and was used for reconnaissance, night fighter, and ''kamikaze'' missions. The first flight took place in May 1941. It was given the Allied reporting name "Irvi ...

* Nakajima Ki-43 * Nakajima Ki-115 *

Tachikawa Ki-77 The Tachikawa Ki-77 was a Japanese very long-range experimental transport and communications aircraft of World War II derived from a design commissioned by a newspaper to break the flight distance record set by a rival. It was a low-wing cabin mo ...

Surviving engines

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 Planes of Fame Air Museum is an aviation museum in Chino, California,World Wa ...

's A6M5 example, bearing tail number "61-120".