Mitsubishi B4M

The Mitsubishi B4M, also called the Ka-12, was a carrier-based biplane torpedo bomber of 1934, of which Mitsubishi built two prototypes for the Imperial Japanese Navy. It developed the company's earlier 3MT10, replacing the heavy Rolls-Royce Buzzard V-12 with a lighter experimental Mitsubishi radial engine and using aluminium wings, which cut the weight by 590 kilograms. Designer Hajime Matsuhara gave it inverse gull lower wings and a wide-track undercarriage for an 800 kilogram torpedo. The first prototype flew in August 1934, but the wing proved inefficiently stiff and could not safely reach its theoretical speed, the aircraft was unstable, and the Navy chose the Yokosuka B4Y instead.