the was a 14-cylinder, supercharged, air-cooled, two-row radial engine used in a variety of early world war ii japanese aircraft. it was one of the smallest 14-cyl. engines in the world and the smallest diameter japanese engine. the mitsubishi model designation for this engine was a14 while it was an experimental project, in service it was known as the mk2, followed by the revision code letter, and known as the ha26 & ha102 by the army and "zuisei" by the navy. unified designation code was [ha-31].