Aichi Ha-70

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Aichi Ha-70
DB 610 gearbox end, showing same two-engine arrangement
Type Piston X 2 inverted V12 aircraft engines
National origin Japan
Manufacturer Aichi
First run 1945
Major applications Yokosuka R2Y
Developed from Aichi Atsuta

The Aichi Kokuki KK Ha-70 was a compound engine composed of two 1,700 hp 12-cylinder liquid-cooled inverted V-12 Aichi Atsuta aircraft engines mounted to a common gearbox. The only aircraft powered by the Ha-70 was the Yokosuka R2Y, an Imperial Japanese Navy Air Service (IJNAS) prototype reconnaissance aircraft that was designed and built near the end of World War II.

Design and development[edit]

In common with Daimler-Benz, Aichi Kokuki KK joined two Aichi Atsuta engines to drive a single propeller through a combining gearbox in very similar fashion to the Daimler Benz DB 606 (two Daimler-Benz DB 601 engines coupled to a gearbox),

The Yokosuka R2Y prototype reconnaissance aircraft required a new engine of 3,400 hp (2,535 kW) and after studying the Daimler-Benz DB 606A-2 engine that powered the Heinkel He 119 single-engine reconnaissance bomber, Aichi determined that the required horsepower could be attained by coupling two Atsuta engines with a common gearbox. To obtain the required power the Atsuta would require up-rating by at least 300 hp (224 kW) horsepower; Aichi continued to improve the Atsuta 32, eventually extracting the required 1,700 hp (1,268 kW)

The two inverted Vee Atsuta engines were mounted side-by-side, each rotated outboard from the centre-line so that the inner banks were upright, with sufficient room between them for the exhaust manifolds. The engines were attached to a gearbox that combined the two separate engine drives into a single output shaft.[1]


Fitted to the R2Y the Ha-70 was mounted behind the pilot, requiring a long drive shaft to drive the nose-mounted gear box that mounted the six-bladed propeller.


Data from The First Naval Technical Arsenal, August 22, 1945[2]

General characteristics

  • Type: Two coupled twelve-cylinder liquid-cooled supercharged 60° inverted Vee aircraft piston engines
  • Bore: 150 mm (5.91 in)
  • Stroke: 160 mm (6.30 in)
  • Displacement: 33.93 L (2,070.5 in³) each, 67.86 L (4141 in³) total



  • Power output: Takeoff: 2,500 kW (3,350 horsepower)

See also[edit]

Comparable engines
Related lists



  1. ^ Daimler-Benz DB 606
  2. ^ The First Naval Technical Arsenal, August 22, 1945
  3. ^ Wilkinson, Stephan (Jan 2003). "With the Noise of a Stone Crusher". Popular Science. 


  • Monogram Close-Up 13 ISBN 0-914144-13-8
  • R. J. Francillon, Japanese Aircraft of the Pacific War (1970 Putnam & Company) SBN 370 00033 1

External links[edit]