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The Nakajima Homare (誉, "praise" or, more usually, "honour") was an air-cooled twin-row 18-cylinder radial Japanese aircraft engine manufactured during World War II. Producing almost 2,000 horsepower, it was used widely by both the Imperial Japanese Army and the Imperial Japanese Navy. Given the Navy service designation NK9, the "Homare" was also given the company designation NBA, Army experimental designation Ha-45 (ハ45) or, Army long designation Nakajima Army Type 4 1,900&nbsp;hp Air-Cooled Radial and, (coincidentally) unified designation code of Ha-45.

Design and development

Development of the Homare started in 1940, and certification was completed in 1941. It succeeded Nakajima's previous 14-cylinder Sakae (Ha-25) engine, which had its own forward seven cylinders staggered from the rear seven for efficient cooling.

The design was exceptionally compact, with an external diameter of 118&nbsp;cm, a mere 3&nbsp;cm larger than the Sakae. With a bore and stroke of 130&nbsp;mm x 150&nbsp;mm, it was classified as a short-stroke engine. It was designed to output around 1800&nbsp;hp (1340&nbsp;kW), or 100&nbsp;hp (75&nbsp;kW) per cylinder. However, the tight design of the engine made it difficult to maintain quality in manufacturing, and unreliability in the field was a significant problem; actual output of early models at altitude was in the range of 1300&nbsp;hp (970&nbsp;kW), far below the designed capability. Later models had improved performance, and it became one of the predominant powerplants of Japanese military aircraft in the latter part of the war. A total of 9089 were produced.

Variants

  • Homare 11 - 1,650&nbsp;hp (1,230&nbsp;kW), 1,820&nbsp;hp (1,357&nbsp;kW), 1,900&nbsp;hp (1,417&nbsp;kW)
  • Homare 12 - 1,825&nbsp;hp (1,361&nbsp;kW)
  • Homare 21 - 1,990&nbsp;hp (1,460&nbsp;kW)
  • Homare 23 - 2,000&nbsp;hp (1,491&nbsp;kW)
  • Homare 25 - 2,000&nbsp;hp (1,491&nbsp;kW)
  • Homare 42 - 2,200&nbsp;hp (1,640&nbsp;kW)

Applications

  • Aichi B7A
  • Kawanishi N1K-J
  • Mitsubishi A7M
  • Nakajima C6N
  • Nakajima G8N
  • Nakajima J5N
  • Nakajima Ki-84
  • Yokosuka D4Y5
  • Yokosuka P1Y1

Specifications (Ha-45-21)

See also

References

Notes

Bibliography

  • Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1998.