Country of origin:

Japan

Description:

Medium bomber

Power Plant:

Two 1,119 kw (1,500 hp) Mitsubishi Ha-101 fourteen-cylinder two-row air-cooled radial engines

Specifications:

Armament:

7.7 mm (0.303 in) Type 89 machine guns in nose, ventral and dorsal positions; one in tail and on each side of fuselage; one 12.7 mm (0.50 in) machine gun in dorsal turret; max bomb load 1,000 kg (2,205 lb)

History:

In 1936 the Japanese Air Headquarters issued a specification for a twin-engined monoplane heavy bomber and, to meet this requirement, a number of aircraft designs were proposed by Japanese manufacturers. Nine months after the issue of the specification, two prototypes of the Ki-21 were built at Mitsubishi’s No 5 Airframe Works at Nagoya, and the first prototype made its first flight on 18 December 1936. The two prototypes then were placed in competition with the Nakajima Ki-19 and subsequently the Ki-21 won the competition, and was placed in production as Army Type 97 Heavy Bomber Model 1.

In 1937, after the second Sino-Japanese incident broke out, production was accelerated and the 60th Sentai was the first unit to receive the type. Japanese Army units equipped with the Ki-21 supported the invasion of Thailand, Burma and Malaya, operating from bases in French Indo China. ‘Sallys’ were used in operations in south-east Asia and Netherlands East Indies and were involved in the fall of Hong Kong and Rangoon, meeting RAF Hawker Hurricanes and Curtiss P-40s of the American Volunteer Group over Burma and China. As the war progressed and allied fighter numbers increased, it received a mauling at the hands of RAAF and USAAF fighters.

Mitsubishi produced 143 Ki-21-Ias and then switched to the Ki-21-Ib which had increased armament and a larger bomb bay. Development led to the Ki-21-Ic, the Nakajima Ha-5 engines being replaced by Mitsubishi Ha-101s, and later the Ki-21-II in 1940. Development continued up to the Ki-21-IIb, the last of which was delivered in September 1944. Total Ki-21 production, including prototypes and those aircraft built by Nakajima, was 2,064 aircraft.

It was to be replaced by the Nakajima Ki49 ‘Donryu’ but this aircraft was found to be more difficult to operate and had a smaller effective warload. The ‘Sally’ only began to be replaced with the introduction of the Ki-67 Hiryu in 1944.  However, bombing of Japanese factories caused considerable disruption to aircraft production and the 58th Sentai continued to operate the Ki-21 until the final surrender, by which time it was somewhat obsolescent. Examples remained in service in the training role and a number were converted for use as transports. A number were used for suicide attacks.

The Ki-21 saw extensive service in the Pacific Theatre. It is known the ‘Sally’ was involved in bombing raids on Australia during World War II. One of these was on 20 June 1943 when a force of 21 Ki-21 ‘Sallys’, escorted by 21 Mitsubishi A6M ‘Zeros’ and Nakajima ‘Oscars’ of the Japanese Army 7th Air Regiment, raided Darwin, NT. On this occasion they were intercepted by 46 Supermarine Spitfires of No 1 Fighter Wing and 14 enemy aircraft were claimed as shot down. At least two Ki-21 Sallys were shot down, one flown by Lieutenants Ohta Katshuhiro and Matsuhara, crashing near Koolpinyah, NT. Another ‘Sally’ was shot down near Millingimbi, NT during an air raid on 9 May 1943.

At the end of World War II a preliminary list of enemy aircraft to be brought to Australia was prepared, and it included two examples of the ‘Sally’. In fact one was recovered and was flown south for eventual display in the Australian War Memorial. This aircraft was noted as the machine used by Lt General Ichi, Supreme Commander of the Japanese forces in the Celebes, to fly from Langoen to Morotai where he surrendered command. It was in the markings of the Headquarters Flight of the 3rd Kokugun, with the name Tokyo Rose (in English) painted on the nose.

With a crew of five from No 481 Maintenance Squadron, captained by Fl Lt M W Baker, it was flown to Laverton, VIC in February 1946. Other members of the crew were Warrant Officer Frederick Pitts, Flt Lt Dai Walthaus DFC, Flt Sgt Derrick Hosking, LAC Norman Hill and LAC Arthur Barr. The flight commenced at Labuan on 1 February 1946, first stop being Balikpapan on the east coast of Borneo. Some problems were encountered with the engines, electrics, and leaking fuel tanks. The flight continued, stops being made at the former Japanese airfield at Penfoie in Timor, Darwin, NT, Cloncurry, QLD and Bourke, NSW to attend to electrical problems and obtain fuel, arriving at Laverton on 8 February 1946. It was later flown to Canberra, ACT where it was placed in storage.

Although not in good condition, at the time it was complete and was noted in RAAF records as ‘Sally Serial No 1’. There it remained for some years but for some reason which has never been explained, the Ki-21, along with a number of other aircraft, including a Handley Page Hampden which served with a RAAF unit in Russia, was sold for scrap metal and broken up, this ‘Sally’ aircraft in a dismantled condition being noted near Duntroon Military College at the back of Fairbairn RAAF Base, ACT in 1957. The wrecks of a number are still in New Guinea; one regularly visited by tourists being at the Lakunai airstrip at Rabaul, New Britain.