Mitsubishi G4M Part I

 

The bulbous G4M was the most numerous and best-known Japanese medium bomber of World War II. It possessed incredible range, but its unarmored fuel tanks led to the unenviable nickname “Flying Lighter.”

In 1937 the Imperial Japanese Navy issued an incredibly difficult specification mandating production of land-based bombers with even greater range than the superb G3M. Although such performance was usually attained by four-engine designs, the new craft was restricted to only two. That year Kiro Honjo commenced work on a machine whereby fuel capacity was emphasized to the exclusion of all other considerations. In 1939 the G4M prototype was flown as an all-metal, midwing design with rakish wings and tail surfaces melded to a rotund fuselage. As expected, the airplane performed well and possessed impressive range. However, this was achieved by stuffing as much fuel as possible into wing tanks that remained unarmored to save weight; crew armor was also deleted for the same reason. Nonetheless, the navy was highly pleased with the G4M, and in 1940 it entered production. The following year they were baptized under fire in northern China, performing well against limited opposition. When the Pacific war broke out in December 1941, roughly 160 G4Ms were in service. Allied forces gave them the code name Betty.

The G4M came as quite a surprise to British and American forces, who believed themselves beyond the reach of medium bombers. But in quick succession, G4Ms helped sink the battleships HMS Repulse and Prince of Wales, and they plastered airfields throughout the Philippines. It was not until the spring of 1942 that the Betty’s weakness was revealed. The very attributes endowing it with such long range caused it be destroyed by a few tracer rounds. The G4Ms took staggering losses during the Guadalcanal campaign, and the Japanese finally introduced self-sealing tanks and crew armor in subsequent versions. One of the last roles of the G4M would be to carry the Yokosuka MXY 7 Oka suicide rocket. Production totaled 2,416 of all versions.

Production
G4M1 Model 11: 1172 examples (including prototypes.)
G4M2 Models 22, 22 Ko and 22 Otsu: 429 examples.
G4M2a, Models 24, 24 Ko, 24 Otsu, 24 Hei, and 24 Tei: 713 examples.
G4M3 Models 34 Ko, 34 Otsu, and 34 Hei: 91 examples.
G6M1: 30 examples.
Total production of all versions: 2,435 examples.

Specifications (G4M1, Model 11)
General characteristics
    Crew: 7 (main-pilot, co-pilot, navigator/bombardier/nose gunner, captain/top turret gunner, radio operator/waist gunner, engine mechanic/waist gunner, tail gunner)
    Length: 19.97 m (65 ft 6¼ in)
    Wingspan: 24.89 m (81 ft 7¾ in)
    Height: 4.9 m (16 ft 1 in (in a horizontal position))
    Wing area: 78.13 m² (840.9 ft²)
    Airfoil: Mitsubishi type
    Empty weight: 6,741 kg (14,860 lb)
    Loaded weight: 9,500 kg (20,944 lb)
    Max. takeoff weight: 12,860 kg (28,350 lb)
    Powerplant: 2 × Mitsubishi MK4A-11 "Kasei" (Fire star) 14 cylinder radial engines, 1,141 kW (1,530 hp) each
    Propellers: 4-bladed Hamilton Standard licensed Sumitomo constant speed variable-pitch
Performance
    Maximum speed: 428 km/h (230 kn, 265 mph)
    Cruise speed: 315 km/h (175 kn, 196 mph)
    Stall speed: 120 km (75 mph)
    Range: 2,852 km, one way (1,540 nmi, 1,771 mi, one way (overloaded: 5,040 km (2721 nmi, 3,132 mi)))
    Service ceiling: 8,500 m (27,890 ft)
    Rate of climb: 550 m/min (1,800 ft/min)
Armament
    Guns: 1× 20 mm Type 99 cannon (tail turret), 4× 7.7 mm Type 92 machine gun (nose turret ×1, waist positions ×2, top turret ×1)
    Bombs: 1× 858 kg (1,892 lb) Type 91 Kai-3 (improved model 3) aerial torpedo or 1× 800 kg (1,764 lb) bomb or 4× 250 kg (551 lb) bombs