Nakajima
G5N Shinzan
The Nakajima G5N Shinzan was Japan’s only four‑engine bomber to reach production, conceived in the late 1930s to rival contemporary Allied heavy bombers. Development began in 1939 under the Imperial Japanese Navy, and the first prototype flew in June 1941. Although its design borrowed heavily from the American Douglas DC‑4 and incorporated a sleek low‑wing monoplane layout, the Shinzan suffered from chronic reliability problems in its Nakajima Ha-5 radial engines and was under‑powered for its size. Only fifteen aircraft were completed before the program was canceled in 1943, after the emergence of more capable twin‑engine designs such as the Mitsubishi G4M. Key features included a reinforced all‑metal airframe, a dorsal and ventral gun turret, and a bomb payload of up to 2,000 kg. Its long wingspan of 27 m gave it a respectable range of roughly 3,600 km, allowing limited strategic missions over the Pacific. Although it never saw large‑scale combat, the G5N Shinzan provided valuable data on multi‑engine aerodynamics and structural engineering that informed later Japanese designs, marking a brief but pivotal step in the nation’s attempt to field a true heavy bomber during World War II.
