The radial 22 cylinder engine "HA51" and genealogic survey of the Gas-Den aero-engine

Abstract

Hitachi Aero Plane Co. former Tokyo Gas Electric Industry Co. (Gas-Den), who also predecessor of Hino Motors, Ltd. developed an unique radial 22 cylinder aero-engine "HA51" by order of imperial army at the time of later period of the World War II. Although the engine could not be applied to test flight due to the end of the war, it has some advanced design features. For searching the design and the philosophy of this engine, brief history of the Gas-Den aero-engines was described in first part on this paper. That includes Japanese first own designed unique Shimpu (or Jimpuu) in 1928, Tempu (or Amakaze) and also Military Tank engine and others. The "HA51" engine was compared with "Homare" one of the Japanese high power engine and American P & W R2800. Unfortunately, some hypothesizes have to made on the engine, because it was missing at the war's end.