G4M 'Betty', Mitsubishi (Japan)

The G4M was the result of an Imperial Japanese Navy specification for a long range land based bomber in 1937. This called for a bomber that could carry a heavy torpedo or bomb load over 3,000 miles (4800km), as even at this early stage the Japanese recognised the vast distances that they would have to fight over if they were to realise their Imperial ambitions. Left alone the Mitsubishi team would have designed an excellent four engine bomber but the Navy insisted that the aircraft have only 2 engines which would lead to serious short comings in the final bomber.

Mitsubishi G4M1 at Munda Airfield
Mitsubishi G4M1
at Munda Airfield

The main problem was that with only two engines an aircraft that had the required range had to forego any armour and nearly all fire protection, with the resulting G4M design caught fire so easily that the US Navy pilots called it 'the one shot lighter'. The first prototype flew in 1939 and much time was wasted when Mitsubishi were ordered to convert it for escort duties with many guns and and a crew of ten.

Mitsubishi G4M2 'Betty' from above Mitsubishi G4M2 'Betty' from above

This flawed concept (especially in a still unarmoured aircraft) was eventually dropped but not before 30 of the escorts (G6M) had been built, these were later used as troop transports.In December 1940 the first G4M1 reached the flight test stage and despite its fragile airframe met all the criteria originally specified. By June 1941 they were operating against targets in China and 120 were available by the time of Pearl Harbour. On the 10 December 1941 several were involved in the sinking of the British ships Prince of Wales and Repulse. The plane proved popular at first but this soon changed when it started to meet real fighter opposition. the Allies gave it the code name Betty following the policy of giving Japanese bombers girls names. By August 1942 and the Solomon's campaign the Betty was receiving almost devastating casuality rates in encounters with Allied fighters. New models quickly followed adding fire suppression but no armour. Production continued up until 1944 with the Betty becoming the most important Japanese land based bomber, taking part in many almost suicidal attacks against Allied ships and a G4M2e version being the launch vehicle for the MXY7 Ohka piloted rocket missile. The only properly armoured variant the G4M3 flew in Jan 1944 which dropped range for more weapons and armour and fire suppression but only 60 were built and few saw active service.

Plan of Mitsubishi G4M 'Betty'
Plan of Mitsubishi G4M 'Betty'

Crew; 7. Max Speed; 428km/h (266 mph). Max range 6033km (3,749 miles). Weapon load; 800 Kg (1,764lbs) of bombs or torpedo, 3x7.7mm machine guns, 1x20mm cannon.

Japanese Aircraft of World War II 1937-1945, Thomas Newdick. A useful shorter reference work looking at the combat aircraft fielded by the Japanese during the Second World War, along with those jet and rocket powered aircraft that got closest to being completed. A useful guide to the aircraft of the Japanese Army and Navy, a key element in the rapid expansion of Japanese power, and in the increasingly desperate defence of their expanded Empire as the war turned against them. Organised by type of aircraft, with enough information on each type for the general reader, and longer sections on key aircraft such as the Zero (Read Full Review)
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How to cite this article: Dugdale-Pointon, TDP. (16 September 2001), G4M 'Betty', Mitsubishi (Japan), http://www.historyofwar.org/articles/weapons_G4m_betty.html

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