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-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 eleven 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.

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 one-hundred 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.
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Specifications (Ki-57-II)
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)
(Text from Wikki)