Ki-57

The Mitsubishi Ki‑57, known to the Allies as 'Topsy,' was a twin‑engine transport aircraft developed in the late 1930s from the Ki‑55 advanced trainer. Mitsubishi Aircraft Company began its design in 1939, adapting the proven Ki‑21 bomber airframe to create a high‑speed, long‑range passenger and cargo carrier for the Imperial Japanese Army Air Service. First flown on 5 August 1940, the Ki‑57 entered service in 1941 and saw extensive use throughout World II on routes across China, Southeast Asia and the Pacific, often ferrying troops, equipment, and high‑ranking officials.

Key features included a low‑wing monoplane layout, two Mitsubishi Ha‑26 14‑cylinder radial engines delivering 850 hp each, a spacious, fully enclosed cabin that could accommodate up to 12 passengers or a mixed load of freight, and retractable landing gear. The aircraft’s all‑metal construction, relatively simple control system and good handling characteristics made it a reliable workhorse in diverse climates.

Although only around 500 units were built, the Ki‑57 demonstrated Japan’s ability to adapt combat designs for logistical roles, influencing post‑war civil transport concepts and providing a template for later twin‑engine transports worldwide.

Mitsubishi

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Design & Classification