Mitsubishi G4M, part four

 

The Mitsubishi G4M2 was the replacement variants of the G4M1. The first prototype of the G4M2 flew for the first time in December 1942. It differed from the previous G4M1 in being powered by two Mitsubishi MK4P 'Kasei' radial engines rated at 1.775 hp, driving a four-bladed propeller and capable of full feathering function. Its main wings were also redesigned with LB type laminar flow airfoil and widened tail horizontal stabiliser wing area. All those changes increased type's maximum speed and service ceiling. Main fuel tanks were enlarged, so maximum range was increased too. 

Various sub-variants were made:

• G4M2 Model 22: The main production model. It was introduced in July 1943 and, from 65th aircraft onwards, bulged bomb bay doors were introduced. An optically flat panel in the nose cone, was also featured from 105th aircraft onwards. The total number of produced machines is unknown, as sources vary, but it's placed between 816 and 839.
• G4M2 Model 22 Ko, AKA Model 22A: A sub-variant equipped with a Type 3 Ku Mark.6 search radar and armed with 20 mm Type 99 cannons in the lateral positions.
• G4M2 Model 22 Otsu: Another sub-variant, this time the gun in the dorsal turret was a Type 99 Model 2. 
• G4M2a Model 24: A variant equipped with uprated Kasei MK4P engines, which delivered up to 1.800 hp of power, and bulged bomb bay doors to carry a larger payload. It also had a carburetor air intake on top of the engine cowling. A total of 514 G4M2a Model 24 were manufactured, though that number is not completely certain. The prototype flew for the first time on 31st May 1944. 
• G4M2a Model 24 Ko: Same armament as G4M2 Model 22 Ko.
• G4M2a Model 24 Otsu: Same armament as G4M2 Model 22 Otsu
• G4M2a Model 24 Hei: A modified Model 24 Otsu with a single 13.2 mm Type 2 machine gun placed in tip of the nose cone. Radar antena was also placed above nose cone.
• G4M2b Model 25: A experimental version fitted with MK4T-B Kasei engines, rated at 1.820 hp of power.
• G4M2c Model 26: Another experimental model fitted with the same engines as the G4M2b, but with superchargers added.
• G4M2d Model 27: Yet another experimental model, this fitted with another variant of the Kasei engines.
• G4M2e Model 24 Tei: A special modification made to transport a Yokosuka MXY-7 Kamikaze airplane. It featured armoured cockpit and fuel tanks. The exact number of converted is unknown, but it must've been a minimum of 65 and a maximum of 70 between 1944 and 1945. 

There were also some non-flying decoys of the G4M2, which received the name of MXY11.

The next main variant of the G4M, was the G4M3. This version was a redesigned G4M2 with self-sealing fuel tanks, improved armour protection and a redesigned tail turret, with a gunner's compartment similar to that present in the Martin B-26 Marauder. Wings were also redesigned and the horizontal tailplane was given dihedral. It was armed with two 7.7 mm (0.303 in) Type 92 machine guns in nose cabin, and both side positions, plus one 20 mm Type 99 cannon both in dorsal turret and tail. The first prototype flew for the first time on 1st January 1944 and it entered production in October. It was produced until August 1945, when Japan surrended and a total of 60-65 machines were built. Most of them featured 20 mm Type 99 cannons at the sides, instead of machine guns.

After the loss of Okinawa, the G4M was the main land-based bomber of the Imperial Japanese Navy (IJN). Most of them were assigned to the 20th Kokutai, which included the Testing Air Group, which was equipped in 1944-1945 with the latest G4M3 Model 34 and 36, though these arrived too late and too little to have any impact in the course of the war. 

From November 1944 to January 1945, G4Ms were the main type of aircraft used by the Japanese to strike the Mariana Islands. Plans to use converted G4Ms to land commandos on the islands were developed in mid-1945 and cancelled later, due to the end of the war.

Two de-militarized G4Ms carried the first Japanese surrender delegation on the first leg of their flight to Manila. They were painted in green, with green crosses and were escorted by two P-38 Lightnings. 

The intended successor of the G4M was the Yokosuka P1Y Ginga, however, due to production problems, the changeover was just began when the war ended.

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_G4M

2. https://www.valka.cz/Micubisi-G4M2-22-Betty-t8550

3. https://www.valka.cz/Micubisi-G4M2a-24a-Betty-t81394

4. https://www.valka.cz/Micubisi-G4M2e-Betty-t35059

5. https://www.valka.cz/Micubisi-G4M3-34-Betty-t29176

Mitsubishi G4M, part three

 

As the war kept going on, bomber designs intended to replace the G4M failed to materialise and Mitsubishi created additional versions to cope with various new roles needed and to eliminate weaknesses in the design, including various engine and weapons.

The first version, the G4M1, suffered some alterations throughout its operational history. In March 1942 new machines were fitted with a supercharger in their Mitsubishi Mk4E 'Kasei' radial engines, in order to improve high altitude performance. These superchargers became standard in August that same year from 406th production aircraft onwards. That same summer, propeller spinners were introduced and in March 1943, aircraft's armour was reinforced though its maximum range and speed was slightly reduced due to the extra weight.

Shortly later, that same spring, the outer half of the tail cone was cut away to improve tail gunner's field of fire. In August, a completely redesigned tail cone was introduced with reduced framing and wide V-shaped cut out. This form of tail cone was standard for every G4M2. In September, individual exhaust stacks were introduced from 954th airframe onwards.

A total of 1.264 G4M1 were manufactured from September 1937 (when the two prototypes were completed) until January 1944 when production of the G4M1 ceased. 

The second version, named G4M2, whose prototype flew for the first time in December 1942, was powered by two Mitsubishi Mk4P 'Kasei' Model 21 engine, rated at 1.775 hp of power driving four-bladed propellers, capable of achieving full feathering function. Main wings were redesigned as well to include LB type laminar flow airfoil and tail horizontal stabilizer area was widened, which improved service ceiling and maximum speed. This version had also larger fuel tanks, which made for longer range. It also featured a new electrically powered tail turret armed with a single 20 mm Type 99 cannon plus a dorsal turret armed with another Type 99 cannon, in lieu of the G4M1's Type 92 7,92 mm machine gun. The remaining posts, nose, waists and cockpit side, were provided each with a single Type 92 machine gun. External differences from the G4M1 included also increased nose glazing, flush side gun positions instead of blisters and rounded wing tips and tail surfaces. These improvements allowed the G4M2 to carry bigger payloads either in bombs or torpedoes. It entered service in July 1943.

Another famous action involving a G4M during World War 2, was the attack that resulted in the death of Admiral Yamamoto. On 18th April 1943 sixteen Lockheed P-38 Lightnings shot down a G4M1 carrying Admiral Yamamoto. In that same battle, another G4M1 carrying Chief of Staff Vice-Admiral Matome Ugaki was also shot down, though Ugaki survived the crash.

The G4M1 was gradually replaced by the G4M2 from June/July 1943 onwards, serving this way in the campaigns of New Guinea, the Solomon Islands and the South Pacific Area, defence of Marianas and, finally in Okinawa. 

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_G4M

2. https://www.valka.cz/Micubisi-G4M1-13-Betty-t31301

3. https://www.valka.cz/Micubisi-G4M1-12-Si-t64994

4. https://www.valka.cz/Micubisi-G4M2-22-Betty-t8550

5. https://www.valka.cz/Micubisi-G4M1-11-Betty-t1284

6. Bunrin Do - Famous Airplanes Of The World 59 - Mitsubishi G4M Betty (translated as much as we could)

Mitsubishi G4M, part two

 

The Mitsubishi G4M, when used against fixed ground targets like supply depots, naval ports or airfields, it was a much harder target to intercept. Owing to its long range and high speed, the G4M could appear from any direction, and be gone before any fighter intercepted them. The 20 mm Type 99 cannon present at the tail was a much heavier defensive weapon for the time and made attacks from the rear quite dangerous. Sometimes, if they were not hit (and caught fire) in the wings' fuel tanks, by anti-air fire or by machine gun bullets from an enemy fighter, they proved to remain airborne despite being heavily damaged. An example of this sturdiness showed when four G4M attacked the American Heavy Cruiser USS Chicago (CA-29) on 30th January 1943, and three of the four surviving G4Ms returned to their bases flying on one engine only. 

The most famous action of the war performed by an G4M was the torpedo attack on the Battleship HMS Prince on Wales (53) and Battlecruiser HMS Repulse (34) off the Eastern shore of Malaya, shortly after Pearl Harbor, on 10th December 1941. The G4M stroke together with older G3M bombers which made high-level bombing rounds. HMS Prince of Wales and HMS Repulse were the first two capital ships to be sunk exclusively by aerial attacks during a war while in open waters. The G4Ms belonged to the Kanoya Kokutai (Kanoya Air Group), Genzan Kokutai and Mihoro Kokutai. All these groups were trained in low-level torpedo attacks (less than 10 m -30 ft- high) and in long-range over-ocean navigation, so they could hit naval targets while moving quickly at sea. 

G4Ms were employed later for attacking Allied shipping and land targets during the six-months-long Guadalcanal Campaign, in the Solomon Islands in late 1942. More than 100 G4M1s and their crew were lost, with few replacements available, during the many battles around Guadalcanal area, from August to October 1942. On 8th August 1942, during the second days of American Marine landings on the island, 23 Imperial Japanese Navys (IJN) G4M1s attacked American ships at Lunga point, but 18 of them were shot down by heavy anti-air fire or carrier-based Grumman F4F Wildcat fighters. A total of 18 Japanese crews (120 aviators) were lost at Lunga Point. 

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_G4M

2. https://www.valka.cz/topic/view/1284

3. Bunrin Do - Famous Airplanes Of The World 59 - Mitsubishi G4M Betty (translated as much as we could)

MItsubishi G4M, part one

 

The G4M was designed as a long range and high speed bomber at the time it was introduced. In order to meet the ambitious specifications issued by the Imperial Japanese Navy (IJN) which called for a bomber capable of achieving a top speed of 398 km per hour (247.306 mph), a service ceiling of 3.000 m (9.800 ft), a range of 4.722 km (2.934 milles) unloaded and 3.700 km (2.300 milles) when loaded with 800 kg (1.800 lb) of payload, Mitsubishi's team, lead by Kiro Honjo, did not incorporate self-sealing fuel tanks and armour plating in order to save weight to achieve a longer range. This decision made both the A6M Zero and the G4M vulnerable to machine gun and anti-air fire. 

Japanese pilots nicknamed the G4M as "Hamaki" (cigar) because of its shape and Allied pilots nicknamed it as "the flying lighter", "the flying zippo" or "the one-shot lighter" because of its easiness to ignite when hit in the wing fuel tanks. 

Given some defensive deficiencies observed on the previous model, the G3M, the first production variant, the G4M1 included a single 7.7 mm (0.303 in) Type 92 machine gun in the nose. This first variant carried also a dorsal Type 92 machine plus two additional ones located in lateral beams. The tail was guarded by a single 20 mm Type 99 cannon placed inside a cupola. The whole machine was powered by two Mitsubishi Mk4A Kasei 11 radial engines which delivered 1.530 hp of power and had a payload of up to 1.000 kg (2.204 pounds) of bombs or a single 858 kg (1891.57 pounds) aerial torpedo.

In retrospective, the G4M was, in terms of performance, similar to other contemporary medium bombers such as the German Heinkel He.111, the North American B-25 Mitchell or the Vickers Wellington. Just like these bombers, the G4M was extensively in anti-shipping strikes from 1941 until 1944 when it became a rather easy prey for Allied fighters.

It was used for the first time in combat on 13th September 1940 in mainland China, in a bombing raid against the city of Hankow. Twenty-seven G4M of the 1st Rengo Kokutai departed from Taipei, Omura and Jeju escorted by 12 A6M Zero fighters. Similar bombing operations took place in May 1941. In December 1941 one hundred and seven G4Ms departed from Taipei, Formosa, crossed the Luzon strait and bombed the Philippines, opening the Japanese invasions in the South-Western Pacific Theatre. 

During the first year of combat, the G4M was a success. They bombed Clark Field, the main US Army Air Base in the Philippines on 8th December 1941 and was instrumental at the aerial raid that sank both HMS Prince of Wales (53) and HMS Repulse (34) Battleship and Battlecruiser respectively. Two days later, they took part in the bombing of Katherine, in Australia, being that the deepest inland attack on Australian territory during the whole war at over 200 milles (322 km). The G4M took advantage of the Allied weak fighter opposition during the earliest stages of the War in the Pacific, and attacked targets ranging from the Aleutian Islands to Australia, thanks to its long range. The flaw of not having self-sealing fuel tanks wasn't an inconvenience at this early point of the theatre.

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_G4M

2. https://www.valka.cz/topic/view/1284

3. Bunrin Do - Famous Airplanes Of The World 59 - Mitsubishi G4M Betty (translated as much as we could)

Mitsubishi G4M, foreign users

 

The Mitsubishi G4M was a Japanese twin-engined medium bomber designed to success to former G3M. Its main user was the Imperial Japanese Navy (IJN), but as the war went on, it saw service with some other countries as well:

• Communist China: Apparently, among the many aircraft left over by the Japanese, the Communists managed to capture some machines, probably in the Southern part of the country, as that's where the IJN had some aerial bases at the end of the conflict. As we couldn't find neither graphical nor text information about the G4M serving with the Chinese, the drawing should be considered as speculative.
• United Kingdom: The British Allied Technical Air Intelligence Unit South East Asia (ATAIU SEA) operated one captured G4M2 Model 22, registered as FI-11 for evaluation purposes at Tebrau airfield, in Malaysia. It belonged originally to the 13th Koku Kantai Yuso Tai. Its ultimate fate is unknown, but it was most probably scrapped.
• Indonesia: Among the aircraft used by the Indonesian Air Force, was, apparently, at least one G4M captured by Indonesian guerrillas, left over by the Japanese in some remote area of the country. It was probably used by the Indonesians during their Independence War, but its ultimate fate is unknown. As we couldn't find information on the subject, the drawing and the information written here should be considered as speculative.
• United States: The Technical Air Intelligence Unit, operated some captured G4M for evaluation purposes at Eagle Farm airfield, in Brisbane, Australia in 1945. The evaluated bomber was painted with exaggerated American markings and rudder stripes even if they were eliminated three years earlier. 

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_G4M

2. https://captured-wings.wikia.org/wiki/FI-11

3. https://captured-wings.wikia.org/wiki/ATAIU-SEA

4. https://en.wikipedia.org/wiki/Indonesian_Air_Force#Before_Indonesian_independence_(1941–1945)

5. https://ww2db.com/photo.php?list=search&sp&startRow=40&keyword&source=colorall&color&foreigntype=A&foreigntype_id=12&dt&image_id

6. https://j-aircraft.com/captured/capturedfrom/TAIC/TAICSG4M/mitsubishi_g4m2_betty.htm