Country of origin:

Japan

Description:

Medium range bomber

Power Plant:

Two 1,380 kw (1,850 hp) Mitsubishi MK4T Kasei 25 14-cylinder two-row air-cooled radial engines

Specifications:

Armament:

One 20 mm Type 99 cannon in hydraulically operated dorsal turret; hand held Type 99 cannon in each of two lateral positions and one in tail; one 7.7 mm (0.303 in) Type 97 machine gun in nose. Max bomb load 998 kg (2,200 lb).

History:

The Mitsubishi G4M1 type 1 Land Attack Aircraft Model 11 was encountered in the Pacific campaign by the Allies in some numbers and is the most well known Japanese bomber. The prototype was built at Nagoya and rolled-out in September 1939, making its first flight at Kasumigaura Airfield on 23 October 1939. After manufacturers trials it was taken to Yokosuka for service trials. However, the Japanese Navy declined to order the type into production for some time and the first production aircraft was not completed until October 1940. Some 1,200 examples of the Model 11 were built at the Nagoya Third Airframe Works between October 1940 and January 1944.

In 1942 a new model, the Navy Type 1 Attack Bomber Model 21 was introduced, incorporating recommendations for improvements made following combat experience. This model differed externally in having flush glazed panels in lieu of lateral fuselage machine-gun blisters, and a modified tail cone with a cut-out to improve operation of the 20 mm cannon. The power plant was now the MK4E Kasei 15 which had a higher altitude rating and this permitted a cruise above the effective ceiling of light anti-aircraft guns. Fuel tank protection was introduced, as was a fire extinguisher system.

Mitsubishi then developed the G4M2 with a view to improving range and speed, and also to increase armament. In this regard the Mitsubishi MK4P Kasei 21 engine with water methanol injection driving four-blade propellers was installed, and fuel capacity increased to 6,490 litres (1,428 Imp gals). However, due to delays in the production of the Kasei 21 engine, production did not commence until July 1943 and eventually 1,154 examples of the G4M2 were completed. A number of variants of the G4M2 were completed and these differed mainly in the model engine and armament installed. Total production of the type was 2,446 aircraft.

In addition to bombing missions, the ‘Betty’, as it was known to the Allies, was used for other purposes. One variant, known as the G6M1, was built as a convoy fighter. This was to escort groups of bombers and had extra armament, but was not a success. The G4M2e Model 24J was modified to carry the Navy Suicide Attacker Ohka Model 11 under the belly of the aircraft.

The type was operated by Japanese units in the Dutch East Indies, New Guinea, Papua and New Britain, units involved including the 1st and 4th Kanoya and Takao Kokutais, and were involved in the planned Japanese invasion of Australia. The first raid by the type on Darwin, NT was made on 19 February 1942 and subsequently further attacks were made on northern Australia up until June 1944.

One of the most successful attacks against Darwin was on 2 May 1943 when G4M1 Model 21s of the 705th Kokutai, escorted by A6M3 ‘Zero’ fighters, dropped 100 bombs on the old Darwin RAAF station. On this occasion three Spitfires from Nos 54, 452 and 457 Squadrons being shot down by the escorting fighters, five more making forced landings, for the loss of five ‘Zeroes’ but no bombers. On 30 June a flight of 27 G4M1s escorted by 23 ‘Zeroes’ was intercepted by 38 Spitfires over Fenton, NT. Three US Liberators were destroyed on the ground and seven others were damaged. Losses were four Spitfires, but three A6M3s and six G4M1 bombers were shot down.

On 19 March 1942 Kittyhawks strafed Japanese aircraft based at Lae, NG. Twelve aircraft were destroyed and five damaged, including a number of ‘Bettys’. The G4M bombers carried out attacks on Darwin from their bases on Timor, one attack being made on 22 March 1942 penetrating 322 km (200 miles) inland to bomb Katherine, NT. Such operations were carried out through to July 1943.

Towards the end of the war a number were captured, and at least one was tested by the United States Technical Air Intelligence unit and painted in US markings. One was used as a transport for the surrender delegation from Japan to Ie Shima Island near Okinawa on 19 August, 1945.

One of the most famous G4M1 ‘Bettys’ was that of Admiral Isoroku Yamato who, with his staff on board, was intercepted by USAAF Lockheed P-38 Lightnings on 18 April 1943. The aircraft was shot down 32 km (20 miles) from Kahiu on Bougainville Island. The type made many raids on northern Australia and one (serial 5415) was shot down on 23 November 1942 by Sqdn Ldr R Cresswell of No 77 Squadron. The wreck of this aircraft was taken to Melbourne, VIC for intelligence assessment. Many wrecks remain in New Guinea, the Solomon Islands, and islands in the Pacific where they fell after being shot down, or were abandoned by retreating Japanese forces.

At the conclusion of World War II consideration was given to the obtaining of a number of Japanese aircraft for display in the Australian War Memorial collection. A ‘Bett was at the forefront of aircraft to be obtained but in the event, although aircraft were available, no ‘Betty’ was obtained but a ‘Sally’ was obtained and flown to Laverton, VIC by a RAAF crew but has not survived  In recent years consideration has been given by private organisations to the location and recovery of one, it being well known that a number are still in the islands, particularly in the Shortland Islands, part of the Solomon Islands Group, at their crash sites or where they were abandoned but to date none have been considered to be in a good enough state to warrant their recovery.

The wreck of one has been recovered from the islands and conveyed to Japan where it is privately being restored to static display for a museum, being the only surviving ‘Betty’.  In recent times the wrecks of a few have been recovered from the Solomon Islands for restoration for museums. One has been recovered from a Pacific island through Australia for restoration.