The Mitsubishi Ki-57 was a Japanese passenger transport aircraft, developed from the Ki-21 bomber, during the early 1940s.

In 1938, when the Ki-21 heavy bomber began to enter service with the Imperial Japanese Army, its capability attracted the attention of the Imperial Japanese Airways. In consequence, a civil version was developed and this, generally similar to the Ki-21-I and retaining its powerplant of two 708 kW (950 hp) Nakajima Ha-5 KAI radial engines, differed primarily by having the same wings transferred from a mid- to low-wing configuration and the incorporation of a new fuselage to provide accommodation for up to 11 passengers. This transport version appealed also to the navy, and following the flight of a prototype in August 1940 and subsequent testing, the type was ordered into production for both civil and military use.^[1]

This initial production Ki-57-I had the civil and military designations of MC-20-I and Army Type 100 Transport Model 1, respectively. A total of 100 production Ki-57-Is had been built by early 1942, and small numbers of them were transferred for use by the Japanese navy in a transport role, then becoming redesignated L4M1. After the last of the Ki-57s had been delivered production was switched to an improved Ki-57-II, which introduced more powerful 805 kW (1,080 hp) Mitsubishi Ha-102 14-cylinder radial engines installed in redesigned nacelles and, at the same time, incorporated a number of detail refinements and minor equipment changes. Civil and military designations of this version were the MC-20-II and Army Type 100 Transport Model 2, respectively. Only 406 were built before production ended in January 1945. Both versions were covered by the Allied reporting name "Topsy".^[2]

• Ki-57-I Army Type 100 Transport Model 1: Powered by two 708 kW (950 hp) Nakajima Ha-5 KAI radial engines and a redesigned fuselage to accommodate 11 passengers. About 100 aircraft of this type were built including the civil version.
• MC-20-I: Same as above but built for civil use with Imperial Japanese Airways (Dai Nippon Koku KK).
• Ki-57-II Army Type 100 Transport Model 2:Powered by two 805 kW (1,080 hp) Mitsubishi Ha-102 Zuisei 14-cylinder radial engines installed in redesigned nacelles. Minor equipment and detail refinements were also incorporated. 306 aircraft of this type were produced before the end of production in January 1945.
• MC-20-II: Same as above but built for civil use with Imperial Japanese Airways (Dai Nippon Koku KK).
• L4M1: A small number of Ki-57-Is were transferred for test by the Japanese navy as transports and were redesignated L4M1.

• On 20 December 1940, an Imperial Japanese Airways MC-20-I (J-BGON, Myuko) crashed into Tokyo Bay off Chiba during CAB's test flight, killing all 13 on board including 8 CAB inspectors.^{[citation needed]}
• On 21 June 1941, a Manchurian Air Transport MC-20 (M-604) crashed into the Sea of Japan, killing all 18 on board.^{[citation needed]}

Data from Japanese Aircraft of the Pacific War ^[4]

General characteristics

• Crew: 4 (pilot, co-pilot, navigator and radio operator)
• Capacity: 11 passengers
• Length: 16.1 m (52 ft 10 in)
• Wingspan: 22.6 m (74 ft 2 in)
• Height: 4.86 m (15 ft 11 in)
• Wing area: 70.08 m² (754.3 sq ft)
• Empty weight: 5,585 kg (12,313 lb)
• Gross weight: 8,173 kg (18,018 lb)
• Max takeoff weight: 9,120 kg (20,106 lb)
• Powerplant: 2 × Mitsubishi Ha-102 Zuisei 14-cylinder air-cooled radial engine, 805 kW (1,080 hp) each for take-off
• Propellers: 3-bladed variable-pitch propellers

Performance

• Maximum speed: 470 km/h (290 mph, 250 kn) at 5,800 m (19,000 ft)
• Range: 3,000 km (1,900 mi, 1,600 nmi)
• Service ceiling: 8,000 m (26,000 ft)
• Time to altitude: 5,000 m (16,000 ft) 15 minutes 45 seconds
• Wing loading: 116.6 kg/m² (23.9 lb/sq ft)

Related development

• Mitsubishi Ki-21

Related lists

• List of aircraft of Japan during World War II
• List of aircraft of the Japanese Navy
• List of aircraft of World War II
• List of military aircraft of Japan