Malcolm V Lowe explains how Japan’s uniquely powered Ki-61 Hien gave Allied aircrew a headache in World War Two
Among the world’s major military powers of the 1930s, the USA and Japan specialised in the design and manufacture of air-cooled radial piston engines, rather than investing in liquid-cooled inline powerplants. Although US engine builder Allison eventually produced the V-1710, which proved to be a perfectly workable inline option, the Japanese struggled to develop an indigenous inline unit of comparable performance to those being produced in Europe. Consequently, almost all major Japanese combat aircraft during World War Two employed radials.
The only Japanese wartime inline engine of real significance was Kawasaki’s Ha-40 and the related Ha-140. The former was developed with considerable help from Nazi Germany, and it eventually powered the sole non-radial Japanese fighter of note during the war, the Kawasaki Ki-61.
