Mitsubishi G4M (Betty) Navy Land-Based Medium Bomber Aircraft
The Mitsubishi G4M Betty will forever be linked to the ill-fated flight which saw the death of Japanese Admiral Yamamoto at the hands of American Lockheed P-38 Lightning fighters over Bougainville in 1943.
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Like most of Imperial Japan's aircraft in the early stages of World War 2, the Mitsubishi G4M (codenamed "Betty" by the Allies) was a potent performer in operation as a twin-engined, land-based naval medium-class bomber. The aircraft was of a well-thought out design, showcasing excellent range for the period and would see combat action throughout the entire war. Though appearing in relatively limited numbers (just over 2,400 were built), the G4M - at least for a time - was a medium bomber of considerable value to the Empire of Japan when attempting to retain its holdings across the vast Pacific.
Despite this early wartime success, the series is mainly remembered as one of two "Betty" aircraft shot down by a pair of American P-38 "Lightning" fighters on April 18th, 1943. One of the bombers was of particular note for its passenger was none other than Japanese Admiral Isoroku Yamamoto - mastermind of the Pearl Harbor attack of December 1941 - a disastrous blow to Imperial Japanese operations in the Pacific Theater. The P-38 pilots credited with the attack were 1st Lt. Rex T. Barber and Captain Thomas G. Lamphier intercepting from Henderson Field, Guadalcanal.
Mitsubishi engineers developed their G4M to fulfill a 1937 requirement calling for an all-modern long-range bombing platform. The prototype recorded a first-flight on October 23rd, 1939 and did not disappoint - proving the design capable of possessing both above average speed as well as range. Defensive armament consisted of a combination of cannon and machine guns: 1 x 7.7mm Type 92 machine gun was positioned at the nose and one at the dorsal turret. One gun was managed at each beam position (side blisters). 1 x 20mm Type 99 automatic cannon was featured at a gunner's position in the tail to protect the aircraft's critical "six". The crew commitment was seven (2 x pilots, nose gunner-bombardiers-navigator, dorsal gunner, 2 x waist gunners, tail gunner) and an internal bomb load of up to 2,205 pounds could be carried. With the bomber being developed for the Imperial Japanese Navy, and therefore charged with attacking naval targets of interest, the G4M was also cleared to carry a 1,858lb Type 91 torpedo in place of the traditional conventional drop bomb load.
The G4M prove its worth immediately in early entanglements that included the sinking of the British warships HMS Repulse and HMS Prince of Wales, both occurring in the first year of the aircraft's combat service career. In addition to successful action against the Allies, the G4M was also used in anger against neighboring China in their long-running war.
The primary weakness of the G4M, a weakness common to many of the Japanese aircraft of the Second World War, was armor protection of crew spaces and fuel stores. Lacking these qualities, the aircraft proved highly susceptible to small bursts of gunfire. Any sort of dominance that the G4M exhibited in the early phases of the conflict were soon reversed as newer and better Allied fighters became available in quantity. The days of the G4M as a frontline attack system were numbered though the series saw action into the war's final weeks (August 1945
Variants included the G4M1 (encompassing prototypes and the first production model), the G4M2 (various sub-marks produced for Navy service), the G4M3 (self-sealing fuel tanks and armor protection added) and the G6M1 (improved defensive armament, 30 built).
With its pair of Mitsubishi MK4A-11 "Kasei" 14-cylinder radial engines of 1,530 horsepower each, the G4M1 (Model 11) managed a maximum speed of 265 miles per hour (cruising at 195mph), a range out to 1,770 miles and a service ceiling up to 28,000 feet. Rate-of-climb was 1,800 feet-per-minute.
The Betty stocked some 37 Japanese bomber groups during the war. Post-war operators became China and Indonesia. Both the United States and United Kingdom tested the aircraft extensively.
Production totaled 2,435 units. This included 1,172 of the definitive G4M1 mark, 429 examples of the G4M2, 713 additional aircraft in the G4M2a guise and 91 examples of the G4M3. The G6M1 numbered thirty aircraft.