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Aichi Ha-70

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Aichi Ha-70
DB 610 gearbox end
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 engine 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 near the end of World War II.

The IJNAS's Atsuta was based on the engine that powered Germany's Messerschmitt Bf 109 fighter.[1]

Design and development

Daimler-Benz granted Aichi Kokuki KK, a part of the Aichi Clock and Electric Co. (Aichi Tokei Denki KK), a license to manufacture the DB 600A through D models in November, 1936. Aichi's new engine was known as the AE1A, its experimental designation, and Atsuta 12 when accepted by the IJN. It was rated at 1,200 hp. This engine was used to power the Yokosuka_D4Y1 dive bomber and the first prototype Aichi_M6A1 Special Attack aircraft.

By early 1938 the Japanese Navy had also acquired the German He 118 V4 two-seat dive bomber aircraft, along with its production rights. This aircraft was powered by the DB 601A, the direct fuel injection version of the DB 600. By 1939, eleven of the more advanced model DB 601A engines were imported. Manufacturing rights were updated for Aichi to build this model. The new engine received AE1P as its experimental designation, and became the Atsuta 32 when accepted by the IJN. It was rated at 1,400 hp. This engine was used to power the Yokosuka_D4Y2 dive bomber and the remainder of the Aichi M6A1 Special Attack aircraft.[1]

The Yokosuka R2Y prototype reconnaissance aircraft required a new engine of 3,400 hp to drive its twin three-blade contra-rotating propellers. After studying the Daimler-Benz DB 606A-2 engine (two Daimler-Benz DB 601 engines coupled to a gearbox) that powered the Heinkel He 119 single-engine reconnaissance bomber, Aichi determined that the required horsepower could be attained by coupling two of the Atsuta engines with a common gearbox, if they could increase the Atsuta by 300 horsepower. Aichi continued to improve the Atsuta 32, eventually increasing it to the required 1,700 hp.

The two inverted Vee Atsuta engines were mounted side-by-side, each rotated outward from the center line so that the inner banks were upright, with sufficient room between them for the exhaust manifolds. The engines were bolted to a gearbox that combined the two separate engine drives into a single output shaft.[2]

The engine in the R2Y was mounted behind the pilot, and that required a long drive shaft forward to a nose-mounted gear box that drove the contra-rotating propellers.[2]

Specifications

Data from The First Naval Technical Arsenal, August 22, 1945[3]

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

Components

Performance

  • Power output: Takeoff: 2,500 kW (3,400 horsepower)

See also

Comparable engines

References

Notes

  1. ^ a b Monogram Close-Up 13
  2. ^ a b Daimler-Benz DB 606
  3. ^ The First Naval Technical Arsenal, August 22, 1945
  4. ^ Wilkinson, Stephan (2003). "With the Noise of a Stone Crusher". Popular Science. {{cite journal}}: Unknown parameter |month= ignored (help)

Bibliography

  • 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
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