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Mitsubishi Type 1 Attack Bomber Hamaki / G4M Betty
Technical Information

The Imperial Japanese Navy (IJN) Mitsubishi Type 1 Attack bomber. In Japanese, 一式陸上攻撃機, 一式陸攻 (Isshiki rikujō kōgeki ki, Isshikirikkō). Allied code name "Betty". Japanese crews nicknamed it Hamaki (Cigar) due to the cylindrical shape of the fuselage. Built by Mitsubishi, the G4M1 Betty redefined Naval bomber operations because of its extremely long range. By comparison, RAF crews struggled 900 miles to Germany, Japanese Navy crews hauled similar bomb loads to targets twice as far away in spacious, well equipped Betty bombers, making it one of the outstanding bombers of its time.

Notorious for its tendency to catch fire due to the bomber's large unprotected fuel tanks that tended to explode when hit by even short burst of enemy fire. Later, attempts were made to protect the fuel tanks.

The tail position was armed with a 20mm cannon Type 99 flexible cannon type 1 (99 Shiki 20mm Senkai-kiju 1gata). The weapon had a circular magazine with 45 rounds that weighed 16.5 kg (36.38 pounds). Alternately, there was a smaller circular 30 round magazine.

Model 11
The first bomber model of series, with 1,140 kW (1,530 hp) Mitsubishi MK4A Kasei Model 11 engines driving three-blade propellers. The following modifications were made during production

Model 12
The Model 12 was possibly an interim model or designation that ultimately disappeared. The Model 12 is cited in Japanese plan for production aircraft, September 1943 from plant Suzuka, yet in October 1943 delivering Model 11 only.

G4M2 Model 22
The first prototype made in November 1942 and flew in December 1942.

G6M1-L Betty (Transport Version)
The G6M1-L Betty was a transport version of the Type 1 / G4M1 Betty. This variant had several differences, including lack of a middle row of windows on the sides of the nose. The pitot tube was more forward on the nose. The waist blister were nearer to the wing and struts different. The position of the antennas on the top of the fuselage was different and this model lacked a loop antenna. The fuselage door was oval shaped and the type lacked defensive armament or ordnance.

A total of 2,446 Bettys were built.

Thanks to Yoji Sakaida, Jim Long and Richard Dunn for additional information.

Technical Details
Crew  7-10 (pilot, co-pilot, navigator, mechanic, gunner, gunner, gunner)
Engine  2 x Mitsubishi MK4P Kasei 21 fourteen-cylinder air-cooled propellers (G4M2)
Span  25m
Length  20m
Height  6m
Maximum Speed  236 km/h
Range  3,270 miles
Armament  (nose, turret, waist) 7.7mm machine guns (tail) 20mm cannon
Bomb load  1 x 800 kg aerial torpedo or up to 1,000 kg of bombs

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