Japanese Aircraft of the Sino-Japanese and Pacific War

Nakajima Experimental Ki-12 Fighter.

No sooner had production begun in France of the advanced Dewoitine D.510 fighter in 1935, than Mitsubishi imported two for study by September of that year. The outstanding appeal of this aeroplane was its new engine-mounted 20mm cannon which fired through the propeller shaft. Taking into consideration this and other features of the Dewoitine, Nakajima designed a comparable fighter but went a major step further by adding a retractable undercarriage, the first to be built in Japan.

Heading this project were two French engineers, Roger Robert and Jean Beziaud who were hired by Nakajima, with Shigenobu Mori as the chief Japanese designer. Although the D.510 served as a reference aircraft in creating the new Nakajima fighter, a number of details were further refined. Using the same 690hp Hispano-Suiza 12Xcrs engine with its 20mm engine-mounted cannon which was imported separately for this project, an oval-shaped radiator was mounted in front of the nose instead of beneath as on the D.510. This reduced the frontal area of this aeroplane as with the similar D.513. The hydraulically-operated undercarriage retracted inwards into the elliptically shaped wing which also had split flaps. The tailwheel was fully retractable. The headrest behind the open cockpit was extended aft to become part of the fin. The result was perhaps one of the most refined fighter airframes in the world at that time.

The aeroplane was completed in October 1936 and moved immediately into the flight-test phase. It was tested against the Mitsubishi Ki-18 which had been completed fourteen months previously, as well as the Mitsubishi Ki-33, Kawasaki Ki-28 and the Nakajima Ki-27, the last of these being finished about this time. The Nakajima Ki-12 was found to be inferior to all in manoeuvrability, a quality which the Japanese Army placed above all others. Failing this most important test, the design was doomed because it was not thought that a licence manufacturing agreement for the Hispano-Suiza 12Xcrs would be granted, and Japan did not want to rely upon imported engines for its combat aircraft. Consequently, the Ki-12 programme ended with but one prototype, and Nakajima's Ki27 won the Army's approval to become its next standard fighter. On a trial basis, two Hispano-Suiza 12Xcrs were tested in the normally radial-engined Mitsubishi A5M3a, greatly enhancing its fighter-like lines and adding a little more speed.

Single-engine low-wing cantilever monoplane fighter with retractable undercarriage. All-metal monocoque fuselage, with all-metal multi-spar stressed skin wing. Pilot in open cockpit.

610-690hp Hispano-Suiza 12Xcrs twelve-cylinder vee liquid-cooled engine, driving a fixed-pitch three-bladed metal propeller.

One 20mm engine-mounted cannon firing through propeller shaft, two 7.7mm machine-guns mounted in the Wing.

Span 11 m (36ft 1in); length 8.30m (27ft 2 3/4in); height 3.30m (10ft 10in); wing area 17sq m (182. 992sq ft).

Empty weight 1,400kg (3,086Ib); loaded weight 1,900kg (4,188Ib); wing loading 111.9kg/sq m (22.9lb/sq ft); power loading 2.75kg/hp (6Ib/hp).

Maximum speed 260kt (229.2mph); cruising speed 200kt (230mph); landing speed 65kt (74.8mph); climb to 5,000m (16,404ft) in 6min 30sec; service ceiling 10,500m (34,448ft); range 433nm (498sm).

One built in October 1936.

Kawanishi was a leader in flying boat development and had gained most of its experience in designing large sea going aircraft. Two of their most successful designs were the Kawanishi H6K (codenamed Mavis by the Allies) and the H8K (Emily), with the latter arguably the best flying boat of World War 2. The company was also not lacking in cargo flying boat design having modified the H6K to serve as a transport as the H6K2-L and H6K4-L. Even the H8Kwas adapted as a transport, the H8K2-L Seikū (or Clear Sky). Kawanishi had also been working on the design of the K-60, a long-range transport flying boat. With these credentials, Kawanishi was able to capitalise on their knowledge to begin the design of the H11K Soku (Blue Sky) for the IJN.

Kawanishi was instructed by the UN to use as much wood as possible in the construction of the Soku since a flying boat of such size would have consumed a large amount of precious alloys needed for other aircraft such as fighters. Within Kawanishi, the Soku was called the KX-8 and the initial design draft was processed rapidly. The aircraft drew heavily from the H8K being a high-wing, cantilever monoplane but overall, the Soku was much larger. The keel of the Soku was nearly identical to the H8K. To power the flying boat four Mitsubishi MK4Q Kasei 22 (Ha-32-22) radials, each developing 1,850hp, were selected with two per wing. As ordered by the UN, both the fuselage/hull and the wings were to be built of wood and under each wing would be a non-retractable float. The Soku had two decks. The lower deck could accommodate up to eighty fully equipped soldiers including a number of vehicles or a comparable amount of cargo. A smaller, upper deck housed quarters for the crew of five. The main departure from the H8K transports was that the Soku utilised a split nose that was hinged to allow the two nose sections to be opened outward to each side of the fuselage, providing ready access to the lower deck. This facilitated easier loading and unloading increasing the speed and ease of these procedures. As a measure of protection the Soku was to be fitted with three 13mm Type 2 machine guns.

Kawanishi presented the KX-8 to the IJN and the design was accepted. Authorisation was given to construct a full scale wooden mock-up of the Soku now designated the H11K1 for inspection before Kawanishi could proceed with the actual prototype. Construction of the mock-up commenced at the port of Komatsujima in the city of Komatsushima on the island of Shikoku (the smallest of the four main islands making up Japan). This area was selected by Kawanishi because it had access to the Seto Inland Sea which, once the prototype was built, would be needed to undertake sea and flight trials. Unfortunately for the Soku, the deteriorating war picture saw delay after delay affect the construction of the mock-up. To add to the problem, Kawanishi was instructed by the IJN in 1945 to reduce production of the H8K and instead, concentrate on building the Kawanishi NI K2-J Shiden-Kai fighter. Together, these factors would see the mock-up approaching its completion in April 1945, well over a year after the design had been initiated.

On 1 April 1945, bombing raids conducted on targets along the Seto Inland Sea saw the nearly completed Soku mock-up destroyed. With this loss, all further work on the Soku design was shelved.

Type Transport Flying Boat

Crew: Five

Powerplant: Four Mitsubishi MK4Q Kasei 22 (Ha·32-22) 14-cylinder, air-cooled radial engines developing 1,850hp for take-off, 1,680hp at 6,886ft and 1,550hp al 5,500m/18,044ft: each engine drove a 4.3m (14.lft) diameter, four-bladed, alternating stroke propeller

Dimensions

Span: 47.97m 157.4ft

Length: 37.70m I23.7ft

Height: 12.55m 41.2ft

Wing area: 289.95m2 3,121ft2

Wing loading: 156.72kg/m2 32.1 lb/ft2

Power loading: 6. I2kg/hp 13.51blhp

Weights

Empty: 26,405kg 58,213lb

Loaded: 45,550kg 100,420 Ib

Useful load 19,095kg 42,097lb

Performance

Max speed: 470km/h 292mph at 5,000m at 16,404ft

Cruise speed: 369km/h 229mph

Landing speed: 144km/h 89mph

Range: 3,890km 2,417 miles

Climb: 11 min 30 sec to 3,000m (9,842ft)

Armament: Three 13mm Type 2machine guns with 200 rounds of ammunition per gun

As the Washington (Disarmament) Treaty of 1922 limited the tonnage for capital ships for the US Navy, the Royal Navy and the Japanese Navy, so did the London (Disarmament) Treaty of 1930 limit the number of smaller ships including aircraft carriers and cruisers. Japanese Navy planners recognized the capability of Navy land-based bombers that could be used to supplement and reinforce fleet activities and thus were responsible for the development of the Hiro Navy Type 95 Land-based Attack Aircraft.

To meet this new requirement for air power starting in 1932, Rear Admiral Isoroku Yamamoto, Chief of Engineering Department, Naval Air Headquarters, called for a land-based long-range attack bomber that could fly more than 2,000nm and carry two tons of bombs. The Hiro Arsenal was selected for the project, for at that time it was the most experienced in the design of all-metal large aircraft. Chief designer was Lieut-Cdr (Ordnance) Jun Okamura who had served in this capacity for the preceding Type 91 Flying-boat project. This land-based bomber became the primary concern at the Hiro Arsenal, diverting attention from the development of the flying-boats previously described.

At the start of the project, the prototype's designation was the Hirosho 7-Shi Special Attack Aircraft, with the short designation G2HI. Structurally, it was a combination of a large wing of traditional Wagner diagonal tension-field structure and a slender fuselage of monocoque construction. The twin fins and rudders were similar to those of the final design of the Type 90-1 Flying-boats, and the ailerons were of the Junkers double-wing variety. One of the innovative features of the armament installation was a cylindrical belly gun turret which retracted into the fuselage. This feature was carried over into early versions of the Mitsubishi Navy Type 96 Land-based Attack Aircraft, that were code-named Nell by the Allies during the Pacific War.

To power the new bomber, two 900-1,180hp Type 94 water-cooled engines were selected, the most powerful aircraft engines available at that time. They were being developed by the Hiro Arsenal as a scaled-up version of the 600hp Type 90 Engine. It was felt that with these new engines, the aeroplane would be equivalent to a three- or four-engined aircraft of the time. Although the airframe dimension, wing area, and empty weight were almost identical to the Type 90-1 Flying-boat, aircraft range and payload were increased by nearly 50 percent. This was the largest land-based aeroplane in the Navy at that time, second only to the Army's Type 92 Heavy Bomber (Ki.20) of the Junkers-G 38 design, yet it was the first of such a large size to be designed from the beginning as a land-based attack bomber. With two engines, its wing span was 103 ft 11 1/4in, marginally bigger than the four-engined Boeing B-17 Flying Fortress with 103ft 9in wingspan.

The first prototype was completed on 29 April, 1933, at the Hiro Arsenal and moved by ship to Yokosuka. There it made its first flight in mid-May 1933 in the presence of Rear Admiral Yamamoto who had originated this bomber concept for the Navy. Making the first flight were Lieut-Cdr Shinnosuke Muneyuki and Lieut-Cdr Toshihiko Odahara, both of the Flight Experiment Group of the Yokosuka Kokutai. After taking off, Muneyuki made one pass over the field for the spectators and proceeded to Kasumigaura Air Base where testing was to take place.

As flight evaluations continued, it was found that the aeroplane possessed outstanding performance as the Navy's largest land-based aeroplane at that time. But shortcomings became evident, including tail vibrations caused by the light structure of the fuselage, aileron flutter, and unreliable engines. One aircraft was lost during test flying because of aileron and tail flutter, causing it to ditch in Tokyo Bay. Corrections were made to the design enough to justify production.

In June 1936, the aeroplane was officially accepted by the Navy as the Type 95 Land-based Attack Aircraft, at the same time as the Navy accepted the Type 96 Land-based Attack Aircraft (G3M 1), Nell. To avoid identity confusion between the two, the G3Ml was referred to as the Type 96 Chu-ko (Medium Attack) or simply 'Chuko,' while the G2H was called the Type 95 Dai-ko (Large Attack) or 'Dai-ko.'

After six of the G2H bombers had been produced at Hiro Arsenal, production was transferred to Mitsubishi. Before long, however, the Navy asked that production be concentrated on the smaller G3M, curtailing the G2H because of maintenance difficulties with the Type 94 Engines and the aeroplane's low-speed flying characteristics. Consequently, production ended with only two having been manufactured by Mitsubishi.

With the activation of the Kisarazu Kokutai on 1 April, 1936, all remaining G2H1s (a total of eight were built) were assigned to this unit but were regarded as second-line aircraft because of the better performance of the G3Ms.

Heavy losses were experienced by G3Ms over Nanjing in August 1937, resulting in the deployment of the G2Hs to an airfield on Saishuto Island (now Cheju Do, off the southern coast of South Korea), and while en route, and for unexplained reasons, one G2H dropped out of formation and crashed near the coast of Sagami Bay southwest of Tokyo. Once in place, and established as the 1st Combined Kokutai with other forces from Kanoya, they made their first mission into China in support of ground forces in the Shanghai area on 30 September, 1937, under the command of Lt Motokazu Mihara. They made further attacks against nine major combat areas and received considerable damage from AA fire but no aeroplanes were lost.

Disaster did catch up with these G2Hs on 24 October, 1937, when one aircraft caught fire while its engines were being started and soon exploded. The fire spread to the other G2Hs, each loaded with three 250kg, five 60kg and five 50kg bombs, exploding successively until four aircraft were destroyed and the fifth badly damaged.

Specifications (G2H1)

Twin-engined land-based mid-wing monoplane bomber. All-metal stressed skin construction.

Crew of seven.

Two 900-1, 180hp Hiro Type 94-1 eighteen-cylinder W-type water-cooled engines, driving four-bladed wooden propellers.

One nose-mounted flexible 7.7mm machine-gun, twin dorsal 7. 7mm machine-guns retractable turret-mounted, one retractable turret-mounted ventral 7.7mm machine-gun. Bomb load: six 250kg (551Ib) bombs or four 400kg (881Ib) bombs.

Span 31.68m (103ft 11 1/4in); length 20.15m (66ft 1 1/4in); height6.28m (20ft 7 1/4in); wing area 140sq m (1,506.996sq ft).

Empty weight 7,567kg (16,682Ib); loaded weight 11,000kg (24,250Ib); wing loading 78.5kg/sq m(16Ib/sq fr); powerloading 6.11 kg/hp (13.4lb/ hp).

Maximum speed 132kt (152mph) at 1,000m (3,280ft); cruising speed 90kt (104mph); climb to 3,000m (9 ,843ft) in 9min 30sec; service ceiling 5,130m (16,830ft); range 1,080 to 1,557nm (1,245 to 1,800sm).

Hirosho built six from 1933 and Mitsubishi built two from 1936.

In September 1922, a patriotic organisation known as the Teikoku Kaibo Gikai (Imperial Maritime Defence Volunteer Association) recognised that an all-metal aircraft of the quality being demonstrated by other countries, had not been manufactured in Japan, and therefore undertook such a project. For the design they organised the All Metal Aeroplane Committee which consisted of leading authorities of the Aeronautical Research Institute of Tokyo Imperial University, the Army, and the Navy. Although this was a joint effort, the design was identified with the PMBRA since the main component the hull, was built by the Army Arsenal.

The committee was led by Dr. Sc. Aikichi Tanakadate, the other members being Narihisa Yokota who became the chief designer, Yuzo Hishida, Matsutaro Honda, Shuhei Iwamoto, Yoshitake Ueda, Haruhiko Uemura, Hisakichi Akaishi, Masayuki Hori, Fumio Murase and Kyohei Arisaki. Joining the committee at a later date were two engineers, Keikichi Satake and Jun Okamura. The basic design for what was at first called the All Metal Seaplane was undertaken at the Aeronautical Research Institute, Tokyo Imperial University. Detail design, tooling and manufacturing of components and airframe were provided by the Army Artillery Arsenal, Army Ordnance Arsenal, Tokyo. Wind-tunnel model testing, powerplant and control system installations became the responsibility of the Aeroplane Factory, Department of Ordnance, Yokosuka Naval Arsenal.

The planned performance was a operational altitude of 3,000 m (9,843 ft) with a maximum speed of 108 kt (125 mph) provided by two 200 hp engines, giving a range of more than 1,080 nm (1,250 sm). A unique feature of this parasol-wing design was that the wing was supported by two massive wide-chord outward sloping structures in place of the more normal pylon connecting the hull to the wing. This feature was later patented, along with the type of metal propellers developed as well as the all-metal metal hull. A spare hull was built for additional tests purposes.

Although the work was suspended temporarily by the severe Kanto earthquake in September 1923, the airframe was nearly completed by March 1924, with the exception of the engine installation and other systems. In July of that year, the airframe was transported to the Department of Ordnance, Yokosuka Naval Arsenal, where the engines and other systems were installed. Because of development delays with the Japanese engines which were to deliver 200 hp at 3,000 m (9,843 ft), it was decided to use two 185 hp BMW IIIa engines instead. With these installed, the KB Flying-boat (KB for Kai Bo) as it was now called, was completed in December 1924.

The Kaibo Gikai KB was a twin-engined parasol-wing monoplane flying boat with a two-step hull and sponsons. It was of all-metal construction with metal stressed skin covering apart from some fabric covering on the wings and control surfaces.

After the aircraft was donated to the Navy by the Kaibo Gikai, flying trials began at Taura Beach, Yokosuka, with Navy test pilot Lieut-Cdr Hisakichi Akaishi, at the controls. As a result of minor modifications, the aircraft showed excellent take-off and alighting performance under light load conditions. The preliminary performance in speed and range gave strong indications that the desired performance would be met at the intended operational altitude. However, on 22 March, 1926, during its seventh test flight, the aircraft was seen in a glide with both engines stopped, its gliding angle continued to steepen and it crashed into the water nearly vertical, killing all four crew members on board. The cause of the crash was attributed to a malfunction of the flight control system.

With this loss, further development of the design was ended; however tests did continue with the second hull that was built for structural analysis. Considerable experience was gained thorough the design of this aircraft and it greatly influenced the 1928 Giyu No.3 flying-boat sponsored by the Kaibo Gikai and built by Kawasaki.

Technical Data

Manufacturer:

Type: Twin-engined flying-boat.

Crew(4):

Powerplant: Two 185-230 hp BMW IIIa six-cylinder water-cooled inline engines, driving two-blade metal (Later wooden) propellers.

Dimensions: Span 21.78 m (71 ft 5 1/2 in); length 13.95 m (45 ft 9 in); height 4 m (13 ft 1 1/2 in).

Weights: Empty 2,012 kg (4,435 lb); loaded 3,086 kg (6,803 lb); power loading 6.7 kg/hp (14.7 lb/hp).

Performance: maximum speed 109 kt (125 mph); minimum speed 50 kt (58 mph); climb to 3,000 m (9,843 ft) in 15 min; service ceiling 6,500 m (21,325 ft).

Production: Only a single prototype was built in 1924.

Based upon experience in satisfying the needs of the Japanese Navy, Herbert Smith undertook a new design for a carrier attack bomber, reverting to the biplane configuration. The first of this type (Company designation 2MT1) was completed in 1923, and a year later was accepted as the Navy Type 13 Carrier Attack Aircraft, of which several versions were produced.

The first production version was powered by a 450 hp Napier Lion W-type water-cooled engine, and designated Type 13-1 carrier Attack Aircraft (B1M1). It was of wooden construction with fabric covering. It had a fixed wide-track undercarriage which allowed the following military load to be carried; one 800 kg (1,764 lb) 457 mm (18 in) torpedo or two 240 kg (529 lb) bombs. The aircraft had a crew of two, consisting of pilot and observer, both in open cockpits. The observer had a 7.7 mm (0.303 in Lewis machine-gun in the rear cockpit. Most aircraft also had a fixed synchronised forward-firing Vickers machine-gun operated by the pilot. All could be equipped with either wheel undercarriage or twin floats to meet different mission requirements.

Within the Type 13 Carrier Attack Series was the Model 2MT4 Ohtori (Wild Goose) Type Reconnaissance Seaplane (3 built). This was a twin-float long-range reconnaissance aircraft completed in 1925. it was evaluated by the Navy at Kasumigara along with the Nakajima-Breguet 19A.2B and the Kawasaki-Dornier Do D, but none of the three were accepted by Navy.

As an experiment the 2MT5 Tora (Tiger) Type Carrier Aircraft was fitted with the 450 hp Mitsubishi Type Hi (Hispano-Suiza) water-cooled engine instead of the Napier Lion. Completed on 4 February, 1926, it recorded a maximum speed of 122 kt () and a rate of climb of 17 min to 3,000 m (9,843 ft) during tests flights at Kagimigahara. On a closed-course distance test from Kasumigaura and return with stop-overs, Mitsubishi pilot Sumitoshi Nakao flew this aircraft 3,108 km () from 25 May to 31 May, 1926. This model became the prototype of the Type 13-2 Carrier Attack Aircraft (B1M2) although production aircraft were built as three-seaters.

the Model 3MT2 was also powered by the Type Hi engine had Farman reduction gear fitted to improve take-off and climb performance. The propeller was either a four-blade or a larger diameter two-blade unit to absorb the added power. This model was officially accepted by the Navy as the Type 13-3 Carrier Attack Aircraft (B1M3) in January 1931 and served as an all-round combat aircraft for the Japanese Navy. it was relied upon as the main strike force aircraft until the early stages of the Sino-Japanese Conflict. It was never considered inferior to its Western counterparts and was therefore highly respected within the operational units. Many remained in operational service until 1938, some having been donated as Hokuku-go aircraft.

When the Shanghai Incident broke out in January 1932 the carriers Akagi and Hosho were in Chinese waters and the Imperial Japanese Navy's 1st Air Wing deployed 32 Type 13 Carrier Attack Aircraft against targets in and around Shanghai. On 5 February, 1932 two Mitsubishi Type 13s escorted by three Nakajima Type 3 Carrier Fighters were engaged in aerial combat with some Chinese Vought Corsairs. While on 22 February, 1932, over Suchou, three Mitsubishi Type 13-3s, escorted by three Nakajima Type 3-2 (A1N2) Carrier Fighters from the Kaga were attacked by a single Chinese Boeing Model 218 (export version of the Boeing P-12E), flown by the American volunteer pilot Robert Short. The Boeing was shot down by the combined fire of the six Japanese aircraft. The unit commander Lieut Susumu Kotani, was killed and his radio-operator/gunner, was badly injured. However, Sub-Lieut Yoshiro Sakinaga flew the aircraft back to its base at Shanghai.

Technical Data

Manufacturer: Mitsubishi Nainenki Seizo KK (Mitsubishi Internal Combustion Engine Co Ltd).

Type: Single-engined Carrier Attack Bomber.

Crew (2 or 3): Pilot and radio-operator/gunner in open cockpits.

Powerplant: (Type 13 -1) One 450 hp Napier Lion twelve-cylinder W water-cooled engine with reduction gearing, driving a two-blade wooden propeller, (Type 13-2) one 450 hp Mitsubishi Type Hi (Hispano-Suiza) twelve-cylinder vee water-cooled direct drive engine, driving a two-blade wooden propeller.

Armament: (Type 13-1) twin rear-firing 7.7 mm (0.303 in) machine-guns flexibly mounted in open dorsal position, (Type 13-2) two fixed forward-firing 7.7 mm (0.303 in) machine-guns and twin flexibly mounted 7.7 mm (0.303 in) machine-guns in open dorsal position. Bomb-load: One 800 kg (1,764 lb) 457 mm (18-in) Torpedo, or two 240 kg (529 lb) bombs.

Dimensions: Span 14.766 m (48 ft 5 1/2 in); length (Type 13-1) 9.773 m (32 ft 1 in), (Type 13-2) 10.06 m (33 ft); height (Type 13 -1) 3.505 m (11 ft 6 in), (Type 13-2) 3.52 m (11 ft 6 1/2 in); wing area (Type 13 -1) 59 sq m (635 sq ft), (Type 13-2) 57 sq m (613.5 sq ft).

Weights: Empty (Type13-1) 1,442 kg (3,179 lb), (Type 13-2) 1,765 kg (3,891 lb); loaded (Type 13-1) 2,697 kg (5,945.7 lb), (Type 13-2) 2,850 kg (6,283 lb); wing loading (Type 13-1) 45.6 kg/sq m (9,339 lb/sq ft), (Type 13-2) 50 kg/sq m (10,241 lb/sq ft); power loading (Type 13-1) 6 kg/hp (13.227 lb/hp), (Type 13-2) 6.33 kg/hp (13.955 lb/hp).

Performance: Maximum speed (Type 13-1) 113 kt (130 mph), (Type 13-2) 105 kt (121 mph); landing speed (Type 13-2) 75 kt (86 mph); climb to (Type 13-2) 3,000 m (9,843 ft) in 20 min; service ceiling (Type 13-1) 4,500 m (14,763 ft); endurance (Type 13-1) 2.6 hr, (Type 13-2) 5 hr.

Production: A total of 402 Type 13s were built as follows:

Mitsubishi Nainenki Seizo KK as follows:

197 - 2MT1-3 (Type 13-1) from 1923.

1 - 2MT4 Ohtori - 1925

1 - 2MT5 Tora - 1926

115 - 2MT5 (Type 13 -2) from 1926

88 - 3MT2 (Type 13-3) from 1930

Hiro Kaigun Koshol as follows:

Approx 40 - Type 13-3