ISBN 978-1-86126-447-3. Suzuki, Takeshi; et al. (2008). "「ハ51型 」星型22シ リンダエンジンとガス電航空エンジンの系譜" [The Radial 22 Cylinder Engine "HA51" and Genealogic Survey of the
Aircraft Engines Experimental engines for Army aircraft were given ハ Ha – (エンジン - Hatsudoki) numbers whilst under design and testing. The Army Ha numbers