The Hirth HM 504 is a four-cylinder air-cooled inverted inline engine. The HM 504 was a popular engine for light aircraft of the 1930s-1940s, and it was used to power a number of Germany's trainer aircraft of World War II. The engine featured a cast magnesium alloy crankcase made of Elektron The Hitachi Hatsukaze Model 11 was a Japanese licensed version.