| Mitsubishi G4M | |
|---|---|
| Mitsubishi G4M1 of 801st Kokutai | |
| Role | Twin-engine medium bomber |
| Manufacturer | Mitsubishi |
| Designer | Kiro Honjo |
| First flight | 23 October 1939 |
| Introduction | June 1941 |
| Retired | 1945 |
| Primary user | Imperial Japanese Navy Air Service |
| Number built | 2,435 |
The Mitsubishi G4M (or "Type 1 land-based attack aircraft")一式陸上攻撃機, 一式陸攻 Isshiki rikujō kōgeki ki, Isshikirikkō was the main twin-engine, land-based bomber used by the Imperial Japanese Navy Air Service in World War II. The Allies gave the G4M the reporting name Betty. The Allies usually gave Japanese fighters and floatplanes male names, while giving female names to bombers and reconnaissance aircraft. These code names did not come into general use until mid-1943.[1]
The G4M had a one-way range of about 3,700 miles which was achieved by its structural lightness and an almost total lack of protection for its crew, with no armor plating or self-sealing aviation fuel tanks. These omissions proved to be its weakness when opposition from American fighter aircraft increased during the second half of the Pacific War of World War II.[2]
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The G4M was designed for a long range and high speed at the time of its introduction. Consequently, several weight-saving measures were incorporated into the design, such as dispensing with self-sealing fuel tanks, which caused Allied fighter pilots to give it derisive nicknames such as "the one-shot lighter", "the flying Zippo" and "the flying cigar" because of their tendency to explode or catch on fire from any slight damage to the fuel tank wings after being hit by aerial machine gun fire or ground antiaircraft fire. Similarly, pilots of the Imperial Japanese Navy despairingly called the G4M "Betty" the "Type One Lighter", "The Flying Lighter" of the "Hamaki" ("cigar"). This was partially due to the fact that on many occasions, the G4M was used for low-altitude torpedo attacks on shipping in which their performance advantages were negated, and the G4M was frequently shot down by antiaircraft artillery fire, and even by small arms. The "Betty"'s relatively large size made it an easy gunnery target, and the predictable approach path required for a torpedo run made for a generally easy interception by Allied fighter aircraft.
When used for medium to high-altitude bombing against stationary land targets like a supply depots, seaports, or airfields, "ease of interception" was another matter entirely. Using its long range and high speed, the G4M could appear from any direction, and then it could be gone before many fighters intercepted them. The 20 mm cannon in its tail turret was much heavier armament than was commonly carried by bombers of either side, making aerial attacks from the rear quite dangerous for the Allied fighter aircraft. Sometimes, assuming they did not catch fire in the first place after being hit in the wings by flak from the ground or machine gun bullets from enemy fighters, G4Ms also proved to be able to remain airborne despite being badly shot up. For example, after the attack of the 751 Kokutai attack on the USS Chicago during the Battle of Rennell Island, three out of four survivors (out of 11 aircraft committed to the attack) returned flying on only one engine.
Towards the end of World War II (1945), the "Betty" bomber was commonly used for carrying and launching kamikaze aircraft, and was the usual aircraft for carrying the Ohka kamikaze manned rocket-powered bombs.
The G4M was similar in performance and missions to other contemporary twin-engine bombers such as the German Junkers Ju 88 and Heinkel He 111 medium bombers, and also the American North American B-25 Mitchell and Martin B-26 Marauder bombers. These were all commonly used for antiship roles. The G4M Model 11 was prominent in attacks on Allied shipping in the 1941 to early 1944 time frame, but after that time, it was increasingly easy prey for Allied fighters.
The G4M's baptism by fire occurred on 13 September 1940 in Mainland China, when 27 "Bettys" and Mitsubishi C5Ms of 1st Rengo Kokutai (a composite force including elements of the Kanoya and Kizarazu Kokutais (Air Groups)) departed from Taipei, Omura, and Jeju City to attack Hankow. The bombers and reconnaissance aircraft were escorted by 13 A6M Zeros of 12st Kokutai led by the I.J.N. lieutenant, Saburo Shindo. A similar operation occurred in May 1941. In December 1941, 107 G4Ms based on Formosa of 1st Kokutai and Kanoya Kokutai belonging to the 21st Koku Sentai (Air Flotilla) crossed the Luzon Strait en route to bombing the Philippines, and this was the beginning to widespread invasion of the islands of the Southwest Pacific Theater.
As a torpedo bomber, the G4M's most notable use was in the sinking of the HMS Prince of Wales and the HMS Repulse off the eastern coast of British Malaya on 10 December 1941. These carried out the attacks alongside the older Japanese bombers, the Mitsubishi G3M "Nells" which were doing high-level bombing runs. The battleship Prince of Wales and the battlecruiser Repulse were the first two capital ships ever to be sunk exclusively by air attack during a war, while on the open ocean. Those bomber crews were a handful of selected Imperial Japanese Naval Air Force (IJNAF) aviators in prewar Japan, who had skills not only in torpedo-attacks at an altitude of less than 30 ft (9 m), but also in being able to navigate long-range flight over the ocean to pinpoint naval targets moving quickly on the sea. This same squadrons in Kanoya Air Group of Kanoya Kokutai (751 Ku), Genzan Air Group of Genzan Kokutai (753 Ku), and the Mihoro Air Group of Mihoro Kokutai (701 Ku). These sank the British capital battle ships, and they later carried out an extended series of attacks against U.S. Navy and Allied ships, and on land targets during the six-month-long Battle of Guadalcanal (in the Solomon Islands), in late 1942.
On 8 August 1942, the second day of the U.S. Marines landing on Guadalcanal, IJNAF's 23 G4M1s conducted a torpedo attack against American ships at Lunga point, Guadalcanal. A total of 18 of the attacking G4M1s were shot down, due to very heavy antiaircraft fire, and air cover from Grumman F4F Wildcat fighters based on three American aircraft carriers. In all, 18 Japanese crews – approximately 120 aviators– were missing at the beginning of the month. More than 100 Japanese G4M1s and their best crews (with no substitutes available) were shot down during the many following battles around Guadalcanal, from August through October 1942.[3] In the two days of the Battle of Rennell Island on 29 and 30 January 1943, 10 out of 43 Japanese G4M1s were shot down during night torpedo attacks, all by the U.S. Navy's antiaircraft fire. About 70 Japanese aviators, including Lieutenant Commander Higai, were killed during that battle.
Probably the best-known incident involving a G4M during the war was the attack resulting in the death of Isoroku Yamamoto. The G4M with tail number T1-323 - which was carrying the Imperial Japanese Navy Admiral Isoroku Yamamoto - was attacked and shot down by Lockheed P-38 Lightnings from 339th Fighter Squadron of the 347th Fighter Group, Thirteenth Air Force, USAAF on 18 April 1943.
The G4M Model 11 was replaced by Models 22,22a/b,24a/b,25,26 and 27 after June 1943, following service in New Guinea, the Solomons, and the South Pacific area, in defense of the Marianas and finally in Okinawa. Others had field modifications resulting in the Model 24j which carried suicide flying bombs Yokosuka MXY7 Ohka Model 11 beginning on 21 March 1945, with disastrous results due to extensive Allied fighter opposition.
From November 1944 to January 1945, G4Ms were one of the main types of aircraft used in the Japanese air attacks on the Mariana Islands, and plans to use converted G4Ms to land commandos on the islands were developed in mid-1945 and only cancelled at the end of the war.
Following the loss of Okinawa, G4Ms constituted the main weapon of the land-based Japanese naval bomber force, consisting of 20 Kokutais at the end of the war, including the testing air group equipped in 1944–45 with the latest version G4M3 Model 34 and 36 which arrived too late to have an impact on the war.
As part of the negotiations for the surrender of Japan, two demilitarized G4Ms, given the call-signs Bataan 1 and Bataan 2 were sent to Ie Shima carrying the first surrender delegations as the first leg of their flight to Manila, the Philippines.
Production of the G4M1 ended in January 1944.
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-blade propellers capable of full feathering function, redesigned main wings with LB type laminar flow airfoil.[N 1] and widened tail horizontal stabilizer wing area, which improved service ceiling to 8,950 m (29,360 ft) and maximum speed to 437 km/h (236 kn, 272 mph). Main wing fuel tanks were enlarged to 6,490 L (1,715 US gal) which increased the range to 6,100 km (3,790 mi/ 3,294 nmi overloaded, one way). An electrically powered 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 × 20 mm Type 99 cannon (1 × tail turret, 1 × top turret), 4 × 7.7 mm Type 92 machine gun (1 × nose, 2 × waist, 1 × 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 it possible for the G4M2 to carry more powerful bombs; 1 × 1,055 kg (2,326 lb) Type 91 Kai-7 (improved model 7) aerial torpedo or 1 × 800 kg (1,760 lb) bomb or 2 × 500 kg (1,100 lb) bombs or one Type 3 – 800 kg (1,760 lb) no.31 ray-detective type bomb + 12 × 60 kg (130 lb) bombs. This model, G4M2, was put into service in mid-1943.
There are no flyable or intact Mistubishi G4Ms left. Several wrecks remain scattered in southeast Asia and on Pacific islands, although only one complete aircraft is known to be on display;[7] a G4M1 Model 11, built in Nagoya Works No.3 on 16 April 1942, tail number 370, which had likely crash landed before mid-1944[8], was recovered from Babo Airfield, Indonesia, in 1991, with the wreck on display in a diorama at the Planes of Fame Air Museum.[9] Several other locations display pieces of the G4M.
Data from Airreview's Japanese Navy Aircraft In The Pacific War[10]
General characteristics
Performance
Armament
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