Plans of
Mitsubishi Ki-57 'Topsy'
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The Mitsubishi Ki-57 was the main personnel transport aircraft used by the Imperial Japanese Army during the Second World War, and was developed from the Ki-21 twin engined heavy bomber.
Work on the Ki-57 began early in 1939 at the request of Nippon Koku K.K. (Japan Air Lines). The company had been impressed by the performance of the Ki-21 in China, and asked Mitsubishi to produce a design for a civil version of the same aircraft. This was completed by the summer of 1939, by which time the airline had been reorganised as Dai Nippon Koku K.K. (Great Japan Airlines Co.), with 37.25% of the company owned by the Japanese government. The new design interested the Imperial Japanese Army, which gave it the designation Ki-57 and ordered it into production. The civil version was given the designation MC-20.
While the Ki-57 was being developed a number of spare Ki-21-Ias, replaced in front line service by more recent versions of the aircraft, were converted into transport aircraft as the MC-21.
The prototype Ki-57 made its maiden flight in July 1940. It used the wings, engines, tail and cockpit of the Ki-21-I, but with a new fuselage that contained a cabin that could carry eleven passengers. The wings were moved down from the middle of the fuselage on the bomber to the base on the transport aircraft. Despite a fatal crash involving the fourth prototype the Ki-57 was ordered into production as the Army Type 100 Transport Model 1, or Ki-57-I. A small number went to the Navy, where they were known as the Mitsubishi L4M1. One hundred Ki-57-Is were produced.
They were followed by 406 Ki-57-IIs. These were given two 1,080hp Mitsubishi Ha-102 radial engines and the revised engine nacelles adopted on the Ki-21-II, and were 25mph faster than the -I, and had a higher service ceiling. Production began in May 1942 and continued until January 1945.
The Ki-57 was used as a communications aircraft, for logistical transport and as a paratroop transport, and served on every front where the Japanese Army was involved. Its biggest success came on 14 February 1942 when aircraft from the 1st Raiding Air Regiment were used to transport paratroops to attack the oil refineries at Palembang on Sumatra, preventing the Allies from destroying them before they fell into Japanese hands.
Ki-57-I
Engine: Two Nakajima Ha.5 radial engines
Power: 950hp at take-off, 1,080hp at 13,125ft
Crew: 4 + 11 passengers
Wing span: 74ft 2in
Length: 52ft 10in
Height: 15ft 8in
Empty Weight: 12,174lb
Loaded Weight: 17,328lb
Maximum Weight: 18,600lb
Max Speed: 267mph at 11,155ft
Cruising Speed: 199mph at 9,840ft
Service Ceiling: 22,965ft
Range: 1,865 miles
Ki-57-II
Engine: Two Mitsubishi Ha.102 14-cylinder radial engines
Power: 1,080hp at take-off, 1,050hp at 9,185ft
Crew: 4 + 11 passengers
Wing span: 74ft 2in
Length: 52ft 10in
Height: 15ft 8in
Empty Weight: 12,313lb
Loaded Weight: 18,018lb
Maximum Weight: 20,106lb
Max Speed: 292mph at 19,028ft
Service Ceiling: 26,250ft
Range: 1,865 miles
