| Ha5 | |
|---|---|
| Type | 14-cylinder, air-cooled, two-row radial piston engine |
| National origin | Japan |
| Manufacturer | Nakajima Aircraft Company |
| Major applications | Mitsubishi Ki-21 Mitsubishi Ki-30 Mitsubishi Ki-57 Nakajima Ki-49 (Ha-41/Ha-109) Nakajima Ki-44 (Ha-41/Ha109) |
| Developed into | Nakajima Ha219 |
TheNakajima Ha5 is a twin row, 14 cylinderair-cooledradialaircraft engine built by theJapaneseNakajima Aircraft Company. The engine was a development of earlier single-row Japanese engines, theKotobuki andHikari, which had combined features of theBristol Jupiter andPratt & Whitney R-1340 Wasp designs.
First introduced in a 1,000 PS prototype in 1933, about 7,000 civilian and 5,500 military Ha-5's were built duringWorld War II. The Ha-5 had separatecam-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 theNakajima Hikari, which was itself a development of theNakajima Kotobuki. It spawned several improved variants, namely the Ha-41, with a single stagesupercharger, 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.
In 1917, Chikuhei Nakajima set up the "Airplane Institute" atOjima Town inGunma Prefecture. In 1918 they built their first airplane; the "Nakajima Type 1" with a U.S.A. made engine.[1] 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 theLawrance A-3 two-cylinder air-cooled horizontally opposed engine.
At the time theLawrance was an oddity. Most air-cooled engines at that time wererotary engines, usingcylinders that rotated together with thepropeller 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: aradial engine. He observed the EnglishGloster Gamecock fighter with itsBristol Jupiter engine, which was an advanced design for the era with an automatic adjustment device fortappet clearance, spiral intake piping for even charge air distribution, and afour-valve intake and exhaust system. He acquired a manufacturing license for the Jupiter in 1925.[2] 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 thePratt & Whitney Wasp 9-cylinder radial, Nakajima tried to combine the good points found in Jupiter design with therational design of the Wasp. Nakajima then produced a series of engine types, named "AA", "AB", "AC", and "AD", as engineering exercises.[1] The next engine design, the "AE", was innovative, with a bore of 160 mm and a stroke of 170 mm.
Prototypes 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.[1]
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 aNakajima A2N 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 theNavy Type 96 Carrier fighter. The engine was named, in connection with the Jupiter engine, "Kotobuki".[1]
The "Kotobuki" engine was improved and developed into the "Hikari (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 inType 95 carrier fighters andType 96 Carrier Attack Plane.[1]
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.[1]
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 theNakajima Ki-49 "Helen" bomber, and theNakajima Ki-44 "Tojo" fighter, later versions of both planes using the more powerful Ha-109 engine. Early versions of theMitsubishi Ki-21 "Sally" used the Ha-5. The Ha-41 would have been an ideal power plant in aircraft that used theMitsubishi Kasei, 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-84N. According to two surviving IJAAF mechanics in 1987, the Ki-84N 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.[3]
The Ha5 engine was used to power:
The Ha41 engine was used to power:
The Ha109 engine was used to power:
Data fromEngine development at Nakajima 1923–1945,Engine History of Nakajima Aircraft.[9]
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