G4M1
- G4M1 Prototypes: Japanese Navy land Based Bomber Type 1. Two prototypes built.
- G4M1 Model 11: Japanese Navy Land Attack Bomber Type 1. The first bomber model of series, with 1,530 hp (1,140 kW) Mitsubishi MK4A Kasei Model 11 engines driving three-bladed propellers. The first aircraft (241st production example) fitted with MK4E Kasei Model 15 engines with larger superchargers for better high altitude performance, became standard in August 1942 from 406th aircraft onwards. These MK4E-engined aircraft have been often, erroneously, referred as the G4M1 Model 12. In summer 1942 propeller spinners were introduced. In march 1943 from 663rd machine onwards, 30 mm rubber ply sheets installed beneath the wing outer surfaces to protect the undersides of the fuel tanks (speed reduced by 9 km/h and range by 315 km), 5 mm armour plates added into tail gunner's compartment. In spring 1943 outer half of the tail cone cut away in order to improve tail gunner's field of fire. Production of the G4M1 ended in January 1944.
G4M2
The first of the four G4M2 prototypes flew in December 1942. It differed from the preceding model in having MK4P Kasei Model 21 engines with VDM Electric four-blades capable of full feathering function, re-designed main wings with LB type laminar flow airfoil[3] and widened tail horizontal stabilizer wing area, which improved service ceiling to 29,360 ft (8,950 m) and maximum speed to 271.5 mph (437 km/h, 236 knots). Main wing fuel tanks were enlarged to 6,490 L (1,715 US gallon) which enabled range of 3,790 mi (6,100 km / 3,294 nm overloaded, one way). An electric motor power-operated dorsal turret featuring a 20 mm cannon was introduced in place of G4M1's dorsal position with a 7.7 mm machine gun, total guns armed were 2 x 20 mm Type 99 cannon (1 x tail turret, 1 x top turret), 4 x 7.7 mm Type 92 machine gun (1 x nose, 2 x waist, 1 x cockpit side). External differences also included increased nose glazing, flush side gun positions instead of blisters, and rounded tips of wings and tail surfaces. These major improvements also made G4M2 possible to carry more powerful bombs; 1 x 1,055 kg (2,326 lb) Type 91 Kai-7 (improved model 7) aerial torpado bomb or 1 x 800 kg (1,764 lb) bomb or 2 x 500 kg bombs or 1 x Type 3 - 800kg (1,764 lb) no.31 ray-detective type bomb + 12 x 60kg (132 lb) bombs. This model G4M2 was into service in mid-1943.
- G4M2 Model 22: The base model, the first production example completed in July 1943. Introduced bulged bomb bay doors from 65th aircraft onwards, and an optically flat panel in the nose cone from the 105th aircraft onwards.
- G4M2 Model 22 Ko: Very similar to previous model. Carried Type 3 Ku Mark 6 search radar and was armed with two Type 99 20 mm Mark 1 cannons replacing the 7.7 mm machine guns in the lateral positions.
- G4M2 Model 22 Otsu: Dorsal turret cannon changed to longer-barreled Type 99 20 mm Mark 2.
- G4M2a Model 24: Modified Model 22, MK4T Kasei 25 1,800 hp (1,340 kW) engine, with bulged bomb bay doors as standard for larger bomb capacity. Externally distinguishable from the Model 22 by a carburetor air intake on the top of the engine cowling.
- G4M2a Model 24 Ko/Otsu: Armament similar to Model 22 Ko/Otsu respectively.
- G4M2a Model 24 Hei: Modified 24 Otsu, with one 13 mm Type 2 machine gun mounted in tip of the nose cone, radar antenna relocated from that position to above the nose cone.
- G4M2b Model 25: One G4M2a modified to MK4T-B Kasei 25 Otsu 1,825 hp (1,360 kW) engines. Only experimental.
- G4M2c Model 26: Two G4M2a modified to MK4T-B Ru Kasei 25b 1,825 hp (1,360 kW) engines with Turbo compressors.
- G4M2d Model 27: One G4M2 modified to MK4V Kasei 27 1,795 hp (1,340 kW) engines.
- G4M2e Model 24 Tei: Special version for the transport of the ramming attack bomb plane - Kugisho/Yokosuka MXY-7 Ohka ("Baka") Model 11, conversions of G4M2a Models 24 Otsu and 24 Hei. Had armour protection for the pilots and fuselage fuel tanks.
- MXY11 Yokosuka Navy Type 1 Attack Bomber: Ground Decoy Non-flying replica of Mitsubishi G4M2 developed by Yokosuka