THE 456th FIGHTER INTERCEPTOR SQUADRON
THE PROTECTORS OF S. A. C.
The Mitsubishi G4M 'Betty' Bomber
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The Betty Bomber
Few would know it by its official designation, the Navy Type 1 Attack Bomber. The Allies called it the BETTY but to the men that flew the airplane, it was popularly, but unofficially, the 'Hamaki,' Japanese for cigar, in honor of the airplane's rotund, cigar-shaped fuselage. The Japanese built more of them than any other bomber during World War II. From the first day of war until after the surrender, BETTY bombers saw service throughout the Pacific and Indian Oceans. Like its stable mate, Mitsubishi's Zero Fighter the Hamaki soldiered on long after it became obsolete, even dangerous, to fly wherever Allied interceptors prowled.
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In July 1937, the new Mitsubishi G3M bomber (Allied codename NELL) went into service in China. Only two months later, the Navy issued a specification to Mitsubishi for a NELL replacement. At that time, the requirements were unprecedented for a twin-engine, land-based attack bomber: flying at a top speed of 398 kph (247 mph) and an altitude of 3,000 m (9,845 ft), the new bomber had to fly a distance of 4,722 km (2,933 miles) without a torpedo or equivalent weight in bombs. When carrying an 800 kg (1,768 lb) torpedo or the same weight in bombs, the Navy needed the bomber to fly at least 3,700 km (2,300 mi).
To meet the requirements, a Mitsubishi design team led by Kiro Honjo crafted an airplane called the G4M with fuel tanks in the wings that were not resistant to explosion when punctured during combat. These tanks were much lighter in weight than explosion-proof (also called 'self-sealing') gas tanks. The decision not to incorporate the heavier, safer fuel tanks was necessary to meet the Navy's range requirements. Mitsubishi incorporated this same design feature in the Zero, for the same reasons and with the same results. Both aircraft had unprecedented range but they were also extremely vulnerable to the machine gun and cannon fire from Allied fighter aircraft. The BETTY was so prone to ignite that the Allies nicknamed it the 'flying lighter.'
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The fuselage was streamlined but rotund to allow space for a bomb bay within the wing center section and to allow the 7 to 9-man crew to move about. About half the crew were gunners who manned the defensive armament positions. Bomber crews flying the NELL were virtually incapable of defending themselves from concentrated fighter attacks, so Honjo paid special attention to this aspect of the G4M. He incorporated 7.7 mm (.30 cal.) guns in the nose, atop the mid-fuselage behind the cockpit, and on both sides of the fuselage behind the wing. In the tail, he introduced a 20 mm cannon. Although the G4M now had a more potent sting, Honjo again sacrificed crew protection to the Navy's demands for great range. He omitted amour plate.
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The first G4M prototype left the factory in September 1939 and made the trek to Kagamigahara Airfield for Mitsubishi's Nagoya plant had no company airstrip. Kagamigahara was 48 km (30 miles) to the north. Japan's newest and most advanced bomber made the trip, disassembled and stacked on five ox-drawn farm carts, over unpaved roads! After arriving at the airfield, the first G4M was reassembled and flown by test pilot Katsuzo Shima on October 23, 1939. Initial results were impressive, but the Navy shelved the bomber for a time in favor of a variant to be called the G6M1. Navy leaders hoped that by increasing the number of defensive cannons, the G6M1 could become a heavy escort fighter for other bombers but this diversion failed to live up to expectations, and the Navy ordered the G4M1 into production. The U. S. Army Air Corps conducted a similar experiment using a modified Boeing B-17 bomber designated the B-40 but this idea too failed to survive operational testing and was soon abandoned. The first production G4M rolled off the line in April 1941. For the remainder of the war, the BETTY assembly line continued to run.
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Built in larger numbers than any other Japanese bomber and flown in action from Australia to the Aleutians, the G4M Navy Type 1 Attack Bomber was the most famous Japanes bomber. The Allied code name was "Betty".
Operationally, BETTY crews achieved much in their first year of combat. They devastated Clark Field, Philippine Islands, on December 8, 1941, and participated in sinking the British battleships HMS "Prince of Wales" and HMS "Repulse" on December 10. They ranged across the length and breadth of the Pacific theatre, attacking targets from the Aleutians to Australia. Against limited fighter opposition, the lack of armour and self-sealing fuel tanks was no hindrance. The savings in airframe weight allowed the G4M to attack targets at unprecedented ranges. But as Allied fighter strength increased, the BETTY began to reveal its fatal vulnerabilities. Admiral Isoroku Yamamoto, architect of the Pearl Harbor attack, died on April 18, 1943, along with his entire staff when U. S. Army Air Corps P-38 Lightnings intercepted and destroyed the two BETTY bombers that carried them. Six escorting Zeros flew guard but in a matter of seconds, the Air Corps pilots shrugged off the escorting fighters and sent both BETTYs crashing down in flames.
As the war dragged, improved bombers failed to materialize so Mitsubishi fielded different versions of the G4M to fulfill new missions, and to eliminate the various weaknesses in the basic design. Front-line combat units operated many variants and sub-variants with different engines and armament packages. The G4M2 was a complete redesign but it did not overcome the airplane's vulnerability to Allied firepower. Mitsubishi tried again to reduce the bomber's tendency to burn. The firm changed the wing to a single-spar configuration and installed self-sealing fuel tanks with a capacity about one-third less than earlier versions. The capacity dropped because of the material inserted in the tank to block leaking fuel when gunfire perforated the tank. Armour plate was also added to all crew positions and the tail turret was redesigned. As a result of these modifications, the fuselage was shortened and the center-of-gravity shifted forward. To re-balance the bomber, dihedral was added to the horizontal stabilizer. This version was called the G4M Model 34.
Designation / Design Bureau
Mitsubishi G4M 'Betty'
Seven crew land-based navy bomber
Two 1,800 hp ( 1343 kW ) Mitsubishi MK4P Kasei 21 radial pistons
272 mph ( 438 km/h ) at 15,090 ft (4600 m)
32.4 minutes to reach 26,245 ft (8000 m)
29,365 ft (8950 m)
3,765 miles (6059 km)
70 ft, 4¼ in ( 21.44 m )
48 ft, 6½ in ( 14.80 m )
13 ft, 5½ in ( 4.10 m )
718.0 sq ft ( 66.7m2 )
17,990 lb (8160 kg)
Loaded Take-off Weight
27,558 lb (12500 kg)
Armament (Defensive )
2,205 lb (1000 kg) of bombs or one 1,764 lb (800 kg) torpedo
Total production 2,414
The G4M- Allied reporting-name 'Betty' - was the main 'heavy' bomber of the Japanese Navy during World War II. It was remarkable for its long range, but this was achieved by depriving the aircraft of armour while providing it with huge fuel tanks in the wings. Since the tanks were not self-sealing the Betty was extremely vulnerable, tending to go up in flames whenever hit. This led to its receiving the derisive nicknames 'One-Shot Lighter' and 'the Flying Cigar'. Despite its range and speed, it was therefore - not surprisingly - unpopular with its crews.
The G4M's single outstanding success was achieved at the start of the Pacific War when, on 10 December 1941, only three days after Pearl Harbor, G3M Nell's and G4Ms of the 22nd Air Flotilla sank two British capital ships - the new battleship Prince of Wales and the old battlecruiser Repulse - off the coast of Malaya. This action - sometimes referred to as 'The Battle of the Gulf of Siam' - is more generally known as 'The Destruction of Force Z'.
Prince of Wales and Repulse were the first capital ships ever to be sunk while at sea and free to manoeuvre. In fact, only three other dreadnoughts were ever sunk by air attack under such conditions - the Japanese giants Yamato and Musashi which were destroyed by US carrier aircraft towards the end of the war,and the Italian fast battleship Roma which was attacked (immediately after the Italian surrender) by German land-based aircraft using radio-controlled glider-bombs.
The first attacks on Allied forces to be made following the Guadalcanal landings were carried out by G4Ms flying from Rabaul. An attack on the US transports by 26 Betties was to demonstrate to Allies and Japanese alike the vulnerability of the G4M to anti-aircraft fire. At least 17 Betties were shot down. One aircraft damaged by gunfire made a suicide crash on the transport George F. Elliott. The resulting fire destroyed the ship - this was the only damage inflicted by Japanese air attacks in reaction to the Allied landings.
G4Ms operated throughout the six months of fighting on Guadalcanal, suffering heavy losses. By early 1943 the Japanese Navy had developed new techniques for night torpedo attack. These were put into effect on the night of 29/30 January 1943 in the Battle of Rennell Island, in which Betties torpedoed and sank the heavy cruiser Chicago. G4Ms repeatedly harassed US task groups in night attacks from this time until almost the end of the war, occasionally inflicting heavy damage - for example in February 1944 when a Betty torpedoed the Essex Class carrier Intrepid after Task Force 58's raid on the Japanese base of Truk in the Caroline Islands.
The G4M had been designed to meet a very demanding Navy specification of 1938. Mitsubishi repeatedly advised the Navy that a four-engined design would be preferable, but the Navy insisted on the restriction to two engines. The G4M1 flew its first missions in China in May 1941. Engine-power and fuel capacity were increased with the G4M2, the version produced in the greatest numbers. In the G4M3 the balance of the design was dramatically changed, with full protection being provided and fuel capacity being drastically reduced.
In 1945 specially-modified G4Ms were employed to carry the Ohka rocket-propelled piloted bomb. This development was in general a disastrous failure, since the modified G4Ms when carrying the Okha were hopelessly vulnerable to fighter attack - although if the G4M succeeded in launching the Okha within range of allied ships the weapon then often proved devastating.
Total production of the G4M was 2,479 - a remarkably high figure for a Japanese medium or heavy bomber.
The Mitsubishi G4M 'Betty' Bomber
The Mitsubishi G4M Role Twin-engine medium bomber Manufacturer Mitsubishi Designed by Kiro Honjo First flight 23 October 1939 Introduced June 1941 Retired 1945 Primary user IJN Air Service Number built 2,435
The Mitsubishi G4M or 一式陸攻 Ichishiki rikujō kōgeki ki, Isshikirikkō ("Type 1 land-based attack aircraft") was the main twin-engine, land-based bomber aircraft used by the Imperial Japanese Navy Air Service in World War II. The Allies gave the G4M the identification name of Betty,
Design And Development
The G4M had a long range and high-speed at the time of its introduction. However, it was known for its poorly-protected fuel tanks, which caused Allied fighter pilots to give it the derisive nicknames "one-shot lighter", "flying Zippo" and "flying cigar". Similarly, pilots of the Imperial Japanese Navy called the G4M the "Type One Lighter" and Hamaki (Cigar). This was due to the fact that on many occasions, it was used for low-altitude torpedo attacks where its performance advantages were negated. The "Betty"'s relatively-large size made it a large target to shoot at, and the simplified approach path on a torpedo run to attack a ship, meant for a generally easy interception.
When used for medium- to high-altitude bombing against stationary 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 be gone before many fighters could intercept them. The 20 mm cannon in the tail turret was much heavier armament than commonly installed in bombers, making dead astern attacks very dangerous. Sometimes, assuming they did not catch fire in the first place, G4Ms also proved to be able to remain airborne despite being badly shot up. For example, after 751 Kokutai's attack during the Battle of Rennell Island, three out of four survivors (of eleven aircraft that went to attack) returned flying on one engine only. Near the end of the war the "Betty" was used as a common kamikaze-carrying and launching platform, and was the usual aircraft for carrying the Ohka kamikaze rocket aircraft.
- Total production of G4M1 Model 11: 1172 examples including prototypes.
- Total production of G4M2 Models 22, 22 Ko and 22 Otsu: 429 examples.
- Total production of G4M2a, Models 24, 24 Ko, 24 Otsu, 24 Hei, and 24 Tei: 713 examples.
- Total production of G4M3 Models 34 Ko, 34 Otsu, and 34 Hei: 91 examples.
- Total production of G6M1: 30 examples.
- Total production of all versions: 2,435 examples.
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Mitsubishi G4M1 of 801st Kokutai 721st Kokutai's G4M2e bomber carrying Ohka IJN aviators pressed home a torpedo attack against American ships off Guadalcanal on August 8 1942, suffering heavy losses. Crashed G4M1 floating at Tulagi. An early-production Mitsubishi G4M1 Model 11 without the propeller spinners G4M2e Model 24 Tei launching suicide bomb Yokosuka MXY-7 Ohka "Baka" Betty bombers during an air raid over Darwin, Australia.. Mid- or late-production G4M1 Model 11s with the propeller spinners and rubber ply beneath the wing fuel tanks Early production G4M1s of Kanoya Kokutai with the original shape tail cones
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, the North American B-25 Mitchell, and the American Martin B-26 Marauder. These were all commonly used in the anti-shipping role, and all but the B-25 were used as torpedo-bombers. The G4M Model 11 was prominent in attacks on Allied shipping in the 1941 to early 1944 time-frame, but beyond that time, it was increasingly the easy prey of the ever-improving enemy fighters.
The G4M's baptism by fire occurred September 13, 1940 in Mainland China, when 27 Bettys and Mitsubishi C5M1 of 1st Rengo Kokutai (a composite force including elements of Kanoya and Kizarazu Kokutais) departed from Taipei, Omura and Cheju to attack Hankow. The bombers and reconnaissance aircraft were escorted by 13 Mitsubishi A6Ms of 12st Kokutai led by Navy Lt. Saburo Shindo. A similar operation occurred in May 1941. In December 1941, 120 Taiwan-based G4Ms of 1st Kokutai and Kanoya Kokutai belonging to the 21st Koku Sentai crossed the Luzon Strait en route to bombing the Philippines, the beginning to widespread Southeast Asia operations.
As torpedo bombers, the G4M's most notable use was in the sinking of Prince of Wales and the Repulse off the coast of Malaya on December 10 1941. They carried out the attacks alongside the older Japanese bombers, the Mitsubishi G3M "Nells" who were doing high-level bombing runs. The Prince of Wales and the Repulse were the first two capital ships ever to be sunk exclusively by air attack during a war, while at sea. 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-attacking at less than 30 ft high but also in being able to navigate long range flight over the ocean to spot a pinpoint target moving fast on the sea. The same squadrons in Kanoya AG (751 Ku), Genzan AG (753 Ku) and Mihoro AG (701 Ku), which sunk the British capital battle ships, later staged an extended series of attacks against American ships and land targets in Battle of Guadalcanal in the Solomon Islands, late 1942.
On August 8 1942, the 2nd day of US Marine's landing at Guadalcanal, IJNAF's 23 G4M1s conducted a torpedo attack against American ships at Lunga point, Guadalcanal. 18 of the attacking G4M1s were lost, due to extraordinarily heavy antiaircraft fire and air cover from F4F fighters. In all, 18 Japanese crews of approximately 120 aviators were missing in the beginning of the months. Over 100 Japanese G4M1s and their best crews with no substitute were thoroughly lost in the following battles of Guadalcanal, between August and October, 1942. In two days of the Battle of Rennell Island on January 29 and 30, 1943, 10 out of 43 Japanese G4M1s were lost in the night torpedo-attacks, again to American anti-aircraft fire. About 70 Japanese aviators including Lt Cdr Higai were killed in action.
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 IJN Admiral Isoroku Yamamoto, was attacked and shot down by American P-38 Lightnings on April 18, 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 Marianas and finally in Okinawa, with 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 heavy Allied fighter opposition.
Following the loss of Okinawa, G4Ms constituted the main weapon of the land-based Japanese naval bomber force, consisting of 20 Kokutais when at war's end, including the testing air group equipped in 1944-45 with the latest version G4M3 Model 34 and 36, arriving too late to change the course of 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.
In 1945, Indonesian guerrillas captured numerous ex-Japanese air bases including Bugis Air Base in Malang (repatriated 18 September 1945). Several G4Ms were seized and flown by the Indonesians. Most of the aircraft were destroyed during 1945–1949 when the former Dutch East Indies and the Netherlands were engaged in a military conflict in Indonesia.
- 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. Following modifications were made during the production:
- March 1942: 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.
- Summer 1942: Propeller spinners introduced.
- 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.
- Spring 1943: Outer half of the tail cone cut away in order to improve tail gunner's field of fire.
- August 1943: A completely redesigned tail cone, with reduced framing and wide V-shaped cut out; this form of tail cone was also used in all G4M2 models.
- September 1943: Individual exhaust stacks from 954th airframe onwards.
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-blades capable of full feathering function, re-designed main wings with LB type laminar flow airfoil 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
- G4M3 Model 34
- Redesigned G4M2 with added self-sealing fuel tanks, improved armor protection and an entirely new tail gunner's compartment which was quite similar to that of late model American B-26 Marauders. Wings were also redesigned and horizontal tail plane was given dihedral. Armed with two Type 92 7.7 mm machine guns in nose cabin and in both side positions, and one type 99 model 1 20 mm cannon in dorsal turret and tail. Entered production in October 1944 in G4M3a Model 34 Ko form with 20 mm cannon in side positions instead of machine guns.
- G4M3a Model 34 Otsu and Hei
- Similar modifications as in corresponding Model 24 variants.
- G4M3 Model 36
- Prototype. Two G4M2 Model 34 modified to Mitsubishi MK4-T Kasei 25b Ru 1,825 hp (1,360 kW) engines.
- G6M1 Japanese Navy Long Range Heavy Fighter Type 1
- Initial model of the series, armed with Type 99 20 mm cannons between each side of fuselage and in tail, one 7.7 mm machine gun in nose cabin and one 30 mm cannon in front ventral position. Thirty built.
- G6M1-K Trainer, Japanese Navy Type 1
- Converted G6M1s.
- G6M1-L2 Transport Type 1, Japanese Navy
- Modified as transports.
Specifications (G4M1, Model 11)
Data from Airreview's Japanese Navy Aircraft In The Pacific War.
- Crew: Seven (main-pilot, co-pilot, navigator/bombardier/nose gunner, captain/top turret gunner, radio operator/waist gunner, engine mechanic/waist gunner, tail gunner)
- Length: 65 ft 6 in (19.970 m)
- Wingspan: 81 ft 7 in (24.9 m)
- Height: 16 ft 1 in (4.900 m (in a horizontal position))
- Wing area: 840.9 ft² (78.125 m²)
- Airfoil: Mitsubishi type
- Empty weight: 15,430 lb (7,000 kg)
- Loaded weight: 20,940 lb (9,5000 kg)
- Powerplant: 2× Mitsubishi "Kasei (Fire star)" Type 11, 14 cylinder radial engine, 1,530 hp () each
- Propellers: Three-bladed Hamilton licensed Sumitomo constant speed variable-pitch
- Maximum speed: 264.7 mph (426 km/h, 230 knots)
- Cruise speed: 195.7 mph (315 km/h, 175 knots)
- Stall speed: 74.6 mph (120 km/h)
- Range: 2,664 mi, (overloaded, one way) (2,852 km, one way (overloaded: 4,288 km, 2,315 nm))
- Service ceiling: 27,890 ft (8,500 m)
- power (detail):1,530 hp / 2,450 rpm at take-off, 1,410 hp / 2,350 rpm at 2,000 m, 1,340 hp / 2,350 rpm at 4,000 m (13,120 ft)
- Guns: 1 x 20 mm Type 99 cannon (tail turret), 4 x 7.7 mm Type 92 machine gun (nose turret x 1, waist turret x 2, top turret x 1)
- Bombs: 1 x 858 kg (1,892 lb) Type 91 Kai-3 (improved model 3) aerial torpedo bomb or 1 x 800 kg (1,764 lb) bomb or 4 x 250 kg (551.2 lb) bombs
- 1 The Allies usually gave Japanese fighters and floatplanes "male" names, while giving "female" names to bombers and reconnaissance aircraft. These did not come into general use until mid-1943.
- 2 Iwaya Fumio, Chuko (Medium Attack Bomber), 1958, Hara Shobo, Tokyo, Japan
- 3 LB type laminar airfoil: designed by Prof. Tani of Tokyo Univ. in 1937
- 4 Captured USAAF Mitsubishi G4M Betty
- 5 pp.128–136, Aoki, Hideo, Mitsubishi Type 1 Attack Bomber (G4M) <Betty>, AIRREVIEW's JAPANESE NAVY AIRCRAFT IN THE PACIFIC WAR, 1972, Kantosha.
- 6 Serial no. 603 and later had 30 mm (1.2 in) thick natural rubber plates covered their outside bottoms of wing fuel tanks but lost their service range by 10 % instead.
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- Aoki, Hideo, p.128–136, Mitsubishi Type 1 Attack Bomber (G4M) <Betty>, p.147-149, Kugisho Suicide Attacker "Oka" (MXY7) <Baka>, AIRREVIEW's JAPANESE NAVY AIRCRAFT IN THE PACIFIC WAR, Kantosha, Tokyo, 1972.
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