The Mitsubishi Ki-57 was a Japanese passenger transport aircraft, developed from the
Ki-21 bomber, during the early 1940s.
Development
In 1938, when the
Ki-21heavy 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]
Variants
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.
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]
1 X as second letter is for experimental aircraft or imported technology demonstrators not intended for service,
2 Hyphenated trailing letter (-J, -K, -L, -N or -S) denotes design modified for secondary role, 3 Possibly incorrect designation, but used in many sources