The Nakajima Ha5 is a twin row, 14 cylinder

air-cooled Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures. In all combustion engines, a great percentage of the heat ge ...

radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric), a line * Radius, adjective form of * Radial distance, a directional coordinate in a polar coordinate system * Radial set * A bearing f ...

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many ...

built by the

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

ese

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 manufacture ...

. The engine was a development of earlier single-row Japanese engines, the Kotobuki and

Hikari may refer to: Places *Hikari Station, a station on Sanyō Main Line in Hikari, Yamaguchi * Hikari, Chiba, a former town in Sousa District, Chiba, Japan *Hikari, Yamaguchi, a city in Yamaguchi Prefecture, Japan People *Hikari (name), people and ...

, which had combined features of the

Bristol Jupiter The Bristol Jupiter was a British nine-cylinder single-row piston radial engine built by the Bristol Aeroplane Company. Originally designed late in World War I and known as the Cosmos Jupiter, a lengthy series of upgrades and developments turn ...

and

Pratt & Whitney R-1340 Wasp The Pratt & Whitney R-1340 Wasp is an aircraft engine of the reciprocating type that was widely used in American aircraft from the 1920s onward. It was the Pratt & Whitney aircraft company's first engine, and the first of the famed Wasp series ...

designs. First introduced in a 1,000 PS prototype in 1933, about 7,000 civilian and 5,500 military Ha-5's were built 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 vast majority of the world's countries—including all of the great powers—forming two opposin ...

. The Ha-5 had separate

cam Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bin ...

-discs for the front and rear rows of cylinders like American designs, rather than using a single, front-mounted cam-disc with long and short pushrods to operate both rows of cylinder valves. The Ha-5 was a twin-row development of the

Nakajima Hikari The Nakajima Hikari (Japanese: 光 "Light") was a nine-cylinder, air-cooled, radial aircraft engine developed in Japan for Navy use during World War II by the Nakajima Aircraft Company. It was a development of the Nakajima Kotobuki and Wright ...

, which was itself a development of the

Nakajima Kotobuki The Nakajima Ha1 Kotobuki (寿, "Longevity") was an aero-engine developed by Nakajima. It was a radial piston developed under licence from the Bristol Jupiter. Design and development In 1917, Chikuhei Nakajima set up the "Airplane Institute" a ...

. It spawned several improved variants, namely the Ha-41, with a single stage

supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement. The current categorisation is that a supercharger is a form of forced induct ...

, and the Ha-109, which featured a two-speed, single stage supercharger. The later Ha-219 was based on the same cylinder design, but was increased in size to 18 cylinders.

Design and development

In 1917, Chikuhei Nakajima set up the "Airplane Institute" at Ojima Town in

Gunma Prefecture is a prefecture of Japan located in the Kantō region of Honshu. Gunma Prefecture has a population of 1,937,626 (1 October 2019) and has a geographic area of 6,362 km2 (2,456 sq mi). Gunma Prefecture borders Niigata Prefecture and Fukushima ...

. In 1918 they built their first airplane; the "Nakajima Type 1" with a U.S.A. made engine.Engine development at Nakajima 1923–1945 In 1920 the company sent Kimihei Nakajima to France to study European advances, and in 1922 started their own engine factory in Tokyo. This led to production of engines based on the

Lawrance A-3 The Lawrance A-3 or Lawrance Model A was an American twin-cylinder aircraft piston engine. Designed by Charles Lawrance in the mid-1910s the engine was produced by the Lawrance Aero Engine Company and under license by Excelsior. Weighing 200&nb ...

two-cylinder air-cooled horizontally opposed engine. At the time the Lawrance was an oddity. Most air-cooled engines at that time were

rotary engine The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and i ...

s, using cylinders that rotated together with the

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

with a fixed crankshaft, in order to improve cooling but Kimihei overheard that an engine with good cooling capability with stationary cylinders was being developed in England: a

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 ca ...

. He observed the English

Gloster Gamecock The Gloster Gamecock was a biplane fighter designed and produced by the British aircraft manufacturer Gloster. The Gamecock was a development of the earlier Grebe Mk III, an early interwar fighter procured by the Royal Air Force (RAF). Wor ...

fighter with its

engine, which was an advanced design for the era with an automatic adjustment device for

tappet A tappet is most commonly a component in an internal combustion engine which converts the rotating motion of the camshaft into linear motion of the valves, either directly or indirectly. An earlier use of the term was for part of the valve gear ...

clearance, spiral intake piping for even charge air distribution, and a four-valve intake and exhaust system. He acquired a manufacturing license for the Jupiter in 1925. In 1927, after inviting two production engineer instructors from the Bristol company, the Jupiter Type 6 of 420 PS and Type 7 of 450 PS with a supercharger were put into production at the Nakajima factory. After studying the

Pratt & Whitney Wasp The Pratt & Whitney Wasp was the civilian name of a family of air-cooled radial piston engines developed in the 1930s, 1940s, and 1950s.Gunston 1989, p.114. The Pratt & Whitney Aircraft Company (P&W) was founded in 1925 by Frederick B. Rentsc ...

9-cylinder radial, Nakajima tried to combine the good points found in Jupiter design with the

rational Rationality is the quality of being guided by or based on reasons. In this regard, a person acts rationally if they have a good reason for what they do or a belief is rational if it is based on strong evidence. This quality can apply to an abi ...

design of the Wasp. Nakajima then produced a series of engine types, named "AA", "AB", "AC", and "AD", as engineering exercises. The next engine design, the "AE", was innovative, with a bore of 160 mm and a stroke of 170 mm.

Prototypes A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and software programming. A prototype is generally used to ...

were made and performance tests were done, but this engine was not adopted due to its very complex engineering. Nakajima continued testing different cylinder designs. In 1929, the "AH" design, with bore and stroke of 146 × 160 mm and a total displacement of 24.1 L, was completed. This was to be the final version of this basic engine design. In June 1930 the first prototype of was completed and it passed the durability test for the type approval in the summer. Then flight tests were started using a

Nakajima A2N The Nakajima A2N or Navy Type 90 Carrier Fighter was a Japanese carrier-borne fighter of the 1930s. It was a single-engined biplane of mixed construction, with a fixed tailwheel undercarriage. Design and development The A2N was originally dev ...

carrier plane. Nakajima had successfully designed the first original Japanese air-cooled 9-cylinder engine, the 450 PS " Kotobuki", which would over time be developed into the Ha-5 and its successors. In December 1931, this engine was approved and adopted by the Navy for the Navy Type 96 Carrier fighter. The engine was named, in connection with the Jupiter engine, "Kotobuki". The "Kotobuki" engine was improved and developed into the "

(light)" engine with the bore and stroke expanded to the limit of the cylinder (160 × 180 mm for a displacement of 32.6 L), with the power was increased to 720 PS. The "Hikari" was used in Type 95 carrier fighters and Type 96 Carrier Attack Plane. Nakajima knew that engines of higher power would be needed and began work on the Ha-5, a new 14-cylinder, twin-row design that was based on the 160 × 180 mm cylinder of the Hikari. The Ha-5 prototype engine was completed in 1933, producing 1,000 PS. An improved Ha-5 was developed as a 1,500 PS engine. In all about 5,500 Ha-5 engines were produced for the military. Later on, as the weights of aircraft rose and higher speeds were required, Nakajima continued to improve the Ha-5 design, creating the "Ha-41" and "Ha-109", which shared the same 146mm x 160mm bore and stroke as the Ha-5, but were increased from the 950 hp of the Ha5 to 1,260 hp and 1,440 hp, respectively. The unified code for the Ha-41 was "Ha-34". Later the engine was developed into an 18-cylinder, twin-row engine called the "Ha-219", but this never got into mass development phase before the war ended a total of 10 were built. All these engines used essentially the same cylinder heads, the differences being in supercharging systems and maximum engine revolutions per minute. The Ha-5 and Ha-41 shared the same weight of 630 kg, while the Ha-109 weighed 720 kg due to its larger, twin-stage supercharger system. The Ha-41 was the primary engine of early variants of the

Nakajima Ki-49 The Nakajima Ki-49 ''Donryu'' (呑龍, "Storm Dragon")Francillon, 1970, p.223 was a twin-engine Japanese World War II heavy bomber. It was designed to carry out day bombing, daylight bombing missions, without the protection of escort fighters. Con ...

"Helen" bomber, and the

Nakajima Ki-44 The Nakajima Ki-44 ''Shoki'' (鍾馗, " Devil Queller") was a single-seat fighter- interceptor which was developed by the Nakajima Aircraft Company and operated by the Imperial Japanese Army from 1942 to 1945 during World War II. Its official d ...

"Tojo" fighter, later versions of both planes using the more powerful Ha-109 engine. Early versions of the

Mitsubishi Ki-21 The (Allied reporting name: "Sally" /"Gwen") was a Japanese heavy bomber during World War II. It began operations during the Second Sino-Japanese War participating in the Nomonhan Incident, and in the first stages of the Pacific War, including ...

"Sally" used the Ha-5. The Ha-41 would have been an ideal power plant in aircraft that used the

Mitsubishi Kasei The was a two-row, 14-cylinder air-cooled radial engine built by Mitsubishi Heavy Industries and used in a variety of World War II Japanese aircraft, such as Mitsubishi J2M and Mitsubishi G4M.Gunston 1989, p.104. The Mitsubishi model designa ...

, being of smaller dimensions and displacement, yet making equivalent power levels. Nine of the Ha 219 engines where issued to the Kitai Squadron to use for the new KI 84 N. According to two surviving IJAAF mechanics in 1987, the Ki 84 N had a recorded speed of 448–450 mph at a ceiling of 42,254 ft when using war emergency power. The engine required much maintenance to keep running, and it overheated when flying at low speeds.1987 JTVD documentary: ''The Last Men''

Variants

;Ha5:634 kW (850 hp), Base design, (used on

Army Type 97 Heavy Bomber)Francillon pg 162 ;Ha5-KAI:634 kW (850 hp), (used on

Mitsubishi Ki-30 The was a Japanese light bomber of World War II. It was a single-engine, mid-wing, cantilever monoplane of stressed-skin construction with a fixed tailwheel undercarriage and a long transparent cockpit canopy. The type had significance in bein ...

)Francillon pg 167 ;Ha5:660 kW (890 hp) (used on Nakajima Ki-19)Mikesh & Abe pg 221 ;Ha5-KAI:708 kW (950 hp), (used on

Mitsubishi Ki-57 The Mitsubishi Ki-57 was a Japanese passenger transport aircraft, developed from the Ki-21 bomber, during the early 1940s. Development In 1938, when the Ki-21 heavy bomber began to enter service with the Imperial Japanese Army, its capability ...

and Ki-57-I Army Type 100 Transport Model 1)Francillon pg 184 ;Ha5-KAI:708 kW (950 hp) take-off, 805 kW (960 hp) at 3,000 m (11,810 ft), (used on Mitsubishi Ki-30 and on first prototype

Donryu)Francillon pg 228 ;Ha5-KAI:708 kW (950 hp) take-off, 805 kW (1,080 hp) at 4,000 m (13,125 ft), (used on Mitsubishi Ki-21-I Army Type 97 Heavy Bomber Model 1 and Ki-21-Ia, Army Type 97 Heavy Bomber Model 1A) ;Ha41:1,260 hp at 2,500rpm takeoff, 1,260 hp at 2,450 rpm at 3,700 m ;Ha109:1,500 hp at 2,650rpm takeoff, 1,440 hp at 2,600 rpm at 5,200 m ;Ha219: 1,895 kW (2,541 hp) ( 10 built used on Tachikawa Ki-94-2, Ki-87 and Ki-84-N late war prototypes most destroyed after war with documents.

Applications

The Ha5 engine was used to power: *

"Sally" *

The Ha41 engine was used to power: *

-I ''Donryu'' ("Helen") *

-I ''Shoki'' ("Tojo") The Ha109 engine was used to power: *

-II *

-II

Specifications (Nakajima Ha-5)

References

Notes

Bibliography

* Francillon, R. ''Japanese Aircraft of the Pacific War''. Annapolis: Putnam, 1970. SBN 370 00033 1 * * Gunston, Bill. World Encyclopaedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. * Mikesh, Robert C. and Abe, Shorzoe. ''Japanese Aircraft 1910–1941''. Naval Institute Press, 1990.

External links

Nakajima Aircraft Industries History

The Pacific War Online Encyclopedia
{{Imperial Japanese Army aeroengines Ha5 Aircraft air-cooled radial piston engines 1930s aircraft piston engines