. Kawasaki Ki-88 – data

. Kawasaki Ki-88 - data

image11Performance (specifications are estimations by Kawasaki)

Max speed at 19,685ft 600km/h 373mph

Range 1,198km 745 miles

Climb 6 min 30 sec to 5,000m (16,404ft)

Ceiling 11,000m 36,089ft


One 37mm Ho-203 cannon and two 20mm Ho-5 cannons


None. The Ki-88 did not progress past a mock-up and partially completed prototype.


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This story centres on the failure of a bomber that inspired the development of another new type. The Nakajima Ki-68 and the Kawanishi Ki-85, both four-engine, long – range bomber designs, hinged on the success of the UN’s Nakajima G5N Shinzan (Mountain Recess). The G5N would prove to be a failure and in turn led to the termination of the Ki-68 and Ki-85 programs; therefore the IJA was left without a long-range bomber project. It was Kawasaki who stepped in to fill the gap with their own design.

In 1938, the UN was enamoured with the idea of a bomber that was capable of operat­ing up to 6,486km (4,030 miles) from its base. In part, this was due to the initial desire to strike targets deep in Russia from Manchurian bases. Later, when Japan went to war with the United States, a need to attack the US mainland was identified and it was recog­nised that a two-engine design would not suf­fice – four engines would be required. On the understanding that the Japanese aircraft industry had very little experience in building such aircraft, the UN used the Mitsui Trading Company as a cover to acquire a Douglas DC-4E four-engine airliner, ostensibly for use by Japan Air Lines. The development of the

DC-4E four-engine passenger aircraft was funded by five airlines and Douglas with United Airlines building and testing the one prototype. While the DC-4E was impressive, in terms of its operating costs it did not add up. The aircraft was complex and this resulted in maintenance issues, which increased the cost of using the plane. Support for the DC-4E was withdrawn and Douglas was asked to simplify the design. As a conse­quence, the DC-4 saw operational use with the US Army as the Douglas C-54 Skymaster.

In early 1939, the sale of the DC-4E was completed and arrived in Japan to be reassembled. By this time, the UN had informed Nakajima to be ready to study the DC-4E to produce a suitable bomber devel­opment from it. After having been flown sev­eral times, the DC-4E was then reported as having ‘gone down in Tokyo Bay’, but in real­ity had been handed over to Nakajima whose engineers took it apart. Within a year, Naka­jima had built the prototype G5N1 which first flew on 10 April 1941. The G5N1 used only the landing gear layout, wing design and radial engine fittings from the DC-4E coupled to a new fuselage, tail design and a bomb bay. The IJA planned to produce the G5N1 and

Nakajima submitted the Ki-68 version using either the Mitsubishi Ha-101 or Nakajima Ha-103 engines in place of the Nakajima NK7A Mamom 11 units on the G5N1. Kawan­ishi also submitted their Ki-85 which was to use the Mitsubishi Ha-111M engines.

As it was, the G5N1 proved to be a dismal failure. The NK7A engines were problematic and underpowered and the aircraft was too heavy and complex. These difficulties con­tributed to the overall poor performance of the G5N1. Despite the problems, three more G5N1 aircraft were built followed by a further two air­craft that replaced the NK7A engines for four Mitsubishi Kasei 12 engines. The two addi­tional aircraft were designated G5N2, but even the Kasei 12 engines could not resuscitate the design and the problems remained. Due to its complications, the G5N1 was never used as a bomber. Two G5N1 (using Kasei 12s) and two G5N2 aircraft were converted to transports and served in this role until the end of the war. The Allies gave the G5N the codename Liz.

By May 1943, the cancellation of the G5N had also brought the demise of both the Ki-68 and the Ki-85 (of which Kawanishi had a mock-up constructed by November 1942), leaving the IJA with no active four-engine

bomber designs on the table. Kawasaki, see­ing the opportunity, immediately got to work on designing a new bomber. The man behind the Ki-91 was Takeo Doi, an engineer employed by Kawasaki. It was his goal to see the development of a successful four-engine

bomber and engineer Jun Kitano would work with Doi to help turn the aircraft into reality. In June 1943, Doi and Kitano began their initial research and by October, work on the first design concept for the Ki-91 was underway.

The Ki-91 was slightly larger than the Boe­
ing B-29 Superfortress which was to be mass produced in late 1943. Four Mitsubishi Ha-214 18-cylinder radial engines were chosen to power the Ki-91. As the plane was expected to operate at high-altitude, provisions were made to utilise superchargers with the

engines and the projected maximum speed was 580km/h (360mph). To provide for the anticipated 10,001km (6,214 mile) range, each wing carried eight fuel tanks with a fur­ther two mounted in the fuselage above the bomb bay. For weapons, the Ki-91 was to carry a heavy armament of twelve 20mm can­nons. Five power-operated turrets were to be used; one in the nose, one on the underside of the forward fuselage, one above and below the aft portion of the fuselage, and the last in the tail. The bottom turrets were remotely controlled while the remainder were manned. The tail turret was to mount four cannons while the rest had two cannons each. As far as bombs, a total payload of 4,000kg (8,8181b) was envisioned and the Ki-91 was to have a tricycle landing gear with the nose gear using a single tyre and the main landing gear using dual tyres. A semi – recessed tail wheel was also installed.

Another feature of the Ki-91 was to be the use of a pressure cabin for the eight man crew. But the development of such a large pressurised cabin for the Ki-91 was expected to take some time to implement, even using knowledge from another of Doi’s designs, the Kawasaki Ki-108, a twin-engine high-altitude fighter fitted with a pressure cabin for the pilot. Therefore, it was decided that the initial Ki-91 prototype would be built without pres-
surisation so as to avoid holding up develop­ment and allow its flight characteristics to be measured. Once the pressurised crew cabin for the Ki-91 was ready, subsequent aircraft were to have it installed.

In April 1944, a full-scale wooden mock-up was completed and Kawasaki invited IJA offi­cials to come and review the Ki-91. Up until this time, the project was a private venture by Kawasaki to which considerable company resources has been allocated. If the IJA did not find the bomber to their liking, it would have been a waste of time, effort and money. Fortunately, the IJA saw potential in the Ki-91 and work continued. In May, the IJA inspected the Ki-91 mock-up and immedi­ately ordered production of the first proto­type. Kawasaki planned to construct the Ki-91 at a new plant in Miyakonojo in Miyazaki Prefecture. However, the IJA did not want to wait for the construction of a new plant and directed Kawasaki to use their established factory in Gifu Prefecture. By June 1944, the construction of the prototype Ki-91 had begun at the Gifu factory, together with the necessary tools and jigs to produce further aircraft.

However, June would see the first B-29 raids over Japan, but as the attacks were few and far between, work on the Ki-91 continued despite the worsening situation for the coun­
try. This would change by the close of 1944 when B-29s began to operate from the Mari­ana Islands and by 1945 bombing raids were far more frequent. In February 1945, a raid heavily damaged the factory in which the Ki-91 prototype was being constructed. The damage was extensive, ruining the tools and jigs. With the loss of equipment needed for future production coupled with dwindling supplies of aluminium, the IJA decided that fighters to combat the marauding B-29s had become a higher priority than bombers. Any hope of utilising such bombers was at best slim. With the Ki-91 at 60 per cent comple­tion, Kawasaki stopped further work on the bomber and the project was officially can­celled in February 1945.

Had the Ki-91 achieved service, plans to attack the US mainland were in place to oper­ate the bomber from the Kurile Islands using temporary bases, while another plan to strike Hawaii was formulated using bases in the Mar­shall Islands. The second plan was rendered obsolete when the Japanese lost the Marshall Islands to the Allies in February 1944. As a note, contemporary images sometimes show the Ki-91 as having a bomb bay battery of down­ward firing cannons for a ground-attack role. While the Japanese were interested in such concepts, there is no evidence that Kawasaki envisioned such a task for the Ki-91.

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Mitsubishi T. K.4 Type 0

At the outset of hostilities in the Pacific, Amer­ican intelligence had very little information on just exactly what aircraft the Japanese were fielding. In part this lack of knowledge sprang from poor intelligence management and cen­sorship of periodicals and other publications by the Japanese authorities. In scrambling to document Japanese aviation, invariably US intelligence officers turned to Japanese mag­azines as a means of gaining information. However, there were pitfalls to using such sources and the Mitsubishi T. K.4 Type 0 was just one example.

The T. K.4 appeared in a section of the Japanese aviation magazine Sora entitled ‘Dreams of Future Designers’. The issue was published in April 1941. The T. K.4 was depicted as a twin-engine fighter whose design was rather similar to the German Messerschmitt Bf 110. The aircraft, although a fighter, was shown with a glazed nose along with the expected glazing over the pilot and crew positions. Each of the low mounted wings sported an inline engine in a very streamlined cowling, each motor driving a three-bladed propeller. What weapons the T. K.4 carried was unknown nor was the crew compliment listed, although two or three could be estimated. Also lacking was any data on the performance of the T. K.4.

Information on the T. K.4 would also appear in a US magazine. The 25 December 1941 issue of Flight mentioned the aircraft as a twin-engine, twin-tail monoplane fighter. From these sources, the US intelligence determined that the T. K.4 was a bona fide fighter that would be encountered in combat. Major Frank T. McCoy, Jr., the head of the Material Section of the Directorate of Intelli­gence, Allied Air Forces, Southwest Pacific

Area, would assign the T. K.4 the codename Frank, taking his own first name. It was McCoy who arrived at the method of assign­ing names to Japanese aircraft in order to simplify identification.

At some point, the T. K.4 Type 0 fighter took on a completely different appearance. When the Japanese Aircraft Manual, O. N.l. 249 (Office of Naval Intelligence), was first pub­lished in December 1942, the Mitsubishi Type 0 was no longer called the T. K.4. Although no illustration was provided in the manual, the Type 0 was described as an army fighter based on the Dutch Fokker D. XXIII. The D. XXIII was a twin-engine fighter that mounted the engines in the fuselage in a push-pull configuration. It was also a twin – boom design that was under development and in flight-testing until the German inva­sion. The manual stated that the Type 0 used two German BMW engines, each developing 750hp, but that a redesign of the aircraft would see it using two l,000hp Mitsubishi Kinsei air-cooled radial engines. No further information was made available.

When the original T. K.4 Frank failed to materialise in combat, McCoy removed his name from the T. K.4 and reassigned it to the Nakajima Ki-84 Hayate (meaning ‘Gale’) which was a fighter very much in use, being first encountered in combat in early 1944. The Type 0, as described in the O. N.l. 249 manual, was given the codename Harry after Colonel Harry Cunningham, a friend of McCoy’s, who was the intelligence officer for General Ennis Whitehead. At the time it was believed that the Type 0 would eventually be seen in action but, just like the T. K.4, it never would and the Type 0 was dropped from the intelligence publications.

The T. K.4 was not the only Japanese aircraft uncovered in the pages of Sora. The same ‘Dreams of Future Designers’ article in which that image was unearthed also included the Nakajima AT27. Several months later, the 25 December 1941 issue of Flight, a US maga­zine, would also feature these planes, along with several others, lending credence to the idea that they were genuine aircraft in use by the Japanese.

The AT27 was novel in a number of ways. On the outside, the fuselage was sleek and well streamlined. The wings were low-mounted with a conventional tailplane. Inside, however, the AT27 featured two 12-cylinder inline engines each rated at 1,250hp and was reported to obtain a maxi­mum speed of 660km/h (410mph). One engine was in the nose while the other was situated behind the cockpit. Contra­rotating propellers were used, the rear engine driving its propeller via an extension shaft. To maintain the excellent aerodynamic prop­erties, the engines were reported to have been provided with a ‘steam cooling’ system. This may have been a surface evaporation system. Such a system took the steam created after the water had passed through the engine and ran it through piping in the wings where the cooler airflow would con­dense the steam back into water that was cycled back through the engine. The pilot
was afforded some protection by the engines in front and behind him but the AT27 could also carry additional armour not only for the pilot but for the engines as well. What type of weapons the AT27 was to carry were not known.

Based on its appearance in the magazines, the AT27 was believed to be a bona fide fighter that could be encountered and thus Allied intelligence gave the AT27 the code – name Gus. However, the AT27 would never be seen or met in battle since, as was later discovered, the aircraft was Fictitious. Gus was soon dropped from the Japanese aircraft intelligence rolls.

Interestingly, the AT27 was very similar to the very real Kawasaki Ki-64 whose develop­ment began in October 1940. Both used 12- cylinder inline engines, one in the nose and the other behind the cockpit, driving contra­rotating propellers. In addition, both used a surface evaporation system. Perhaps by sheer coincidence, one of the Japanese illus­trations of the AT27 that was published in Sora and later in Flight showed it sporting the number 64 on the fuselage.

The З-view illustration of the AT27 is in the markings and colouration of an aircraft of the 244th Sentai operating in the defence of Tokyo, 1944-1945. The side view below depicts the AT27 as it appeared in Sora magazine."


As we have already seen, the April 1941 issue of Sora misled Allied intelligence over the nature and extent of Japanese aircraft design. As the war continued, none of the four aircraft that feature in the April issue were encoun­tered and subsequently dropped from Allied intelligence publications. However, Sora con­tinued and so did the section responsible. How often the ‘Dreams of Future Designers’ portion of the magazine appeared is not known but one issue from either 1944 or 1945 contained a design that was nothing short of fantastic. This was the S-31 Kurowashi, or Black Eagle.

The Kurowashi was a four-engine heavy bomber concept. What was unique about the aircraft was that all of the engines were housed within the fuselage and the Kurowashi used a push-pull configuration. Both in the front and the rear of the fuselage were two 2,500hp, 24-cylinder, liquid cooled, inline X-engines, driving a pair of contra-rotat­ing, three-bladed propellers via a gearbox. With this powerplant the Kurowashi was to boast a top speed of 689km/h (428mph), but such a powerful engine of this type would not see service with the Japanese air forces. However, this was not for a lack of trying: it may or may not be that the originator of the Kurowashi was aware of the Yokosuka YE3 series of engines.

In 1940, the UN initiated development of the YE3A, a 24-cylinder, liquid-cooled, X-engine that was to produce 2,500hp. An X-engine is produced by having paired V – block engines horizontally opposed to each other with the cylinders in four banks driving a common crankshaft and thus, when viewed head-on, appearing as a ‘X’. The major benefit to using such a configuration is that the engine is more compact than a com­parable radial engine or standard V-engine. However, X-engines are far more complex to construct and service and are heavier. It was not be until October 1943 that the first YE3B [Ha-74 Model 01] (also known as the Ken No. l) was completed and tested. The YE3B was designed to be housed inside the wing. A second model, the YE3E [Ha-74 Model 11) (Ken No.2), was rated at 3,200hp and was slated to be completed in March 1944. Unlike the YE3B, the YE3E was designed to be housed within the fuselage. As it was neither engine would see service by the time the war ended. Interestingly, a surviving YE3B engine was fitted with a two-stage reduction gear and a extension shaft that would have been used to drive two, contra­rotating propellers.

With a wingspan of just over 33m (107ft), the Kurowashi was by no means a small air­craft. The plane was just under 21m (70ft) in length and a height just shy of 6m (20ft). These dimensions were very similar to the Boeing B-l 7 bomber. The Kurowashi sported horizontal stabilisers which ended in ovoid shaped vertical stabilisers.

The Kurowashi was certainly not lacking for weaponry. A total of eight 7.7mm machine guns and four 23mm cannons were carried by the bomber. 7.7mm was a calibre used by both the IJA and the UN, but on the other hand, the Japanese did not field a 23mm can­non in any form, either in aircraft or on the ground. The UN did use a 25mm anti-aircraft cannon (Type 96) but did not apply the weapon to aircraft. The IJA also experi­mented with a 25mm aircraft cannon but abandoned it in favour of the 30mm cartridge. Why the creator of the Kurowashi decided to use 23mm as the calibre for the cannons remains unknown.

What is known is the novel arrangement of the defensive armament. Fitted directly into the leading edge of each wing were two ball turrets. The outer turret contained one 23mm cannon while the inner turret sported two 7.7mm machine guns. Directly opposite these front-facing turrets was another set of ball turrets. As the trailing edge of the wing was too thin to allow the turrets to be inter­nally mounted, each turret was fitted into the end of a nacelle that extended from the back of the wing. Therefore, each wing was fitted with four turrets for a total of two 23mm can­nons and four 7.7mm machine guns. To con­trol these turrets the Kurowashi relied on two gunners, the bombardier and co-pilot. Both gunners had positions facing to the rear of the aircraft behind the bomb bay. The first gunner station was in the upper portion of the fuse­lage while the second was in a ventral station. Weapon sights were provided along with the controls to manipulate and fire the turrets. The bombardier and the co-pilot stations were also provided with a sight and turret controls so that if they were not occupied with other duties they could man the weapons. It is likely that the bombardier and co-pilot had control of the forward facing tur­rets while the two gunners maintained con­trol over the rear facing weapons.

For its war load the Kurowashi could carry just over 7,257kg (8 tons) of bombs, about 1,814kh (2 tons) less than the Boeing B-29. The bomb bay was divided into two and each section could hold six bombs to give a total of twelve. Beneath the main bomb racks were

hinged panels, one per side. Each panel held four bombs for total of eight. When the bomb bay doors opened, the bombs suspended from the panels would be released and the panels swing aside so the remainder of the bombs could drop. This arrangement was created to maximise the payload space avail­able. Situated directly above the bomb bay were fuel tanks and it was likely the wings also housed fuel.

The Kurowashi used a tricycle landing gear system with the nose wheel retracting into the fuselage while the main landing gear went up into the wings. However, because of the heavy tail and to prevent damage to the rear propellers while on the ground or during take-off and landing, a large, retractable tail wheel was fitted to the back of the fuselage.

For its crew the bomber had five men: pilot, co-pilot, bombardier and two gunners. One of the gunners served as the radio operator as the radio station was situated in front of the upper gunner’s position.

It may very well be that Allied intelligence was aware of this design and it was also likely that by 1944-1945, intelligence officers were no longer taking aircraft illustrated in the ‘Dreams of Future Designers’ section in Sora magazine at face value. The Kurowashi was a creation that would have been very difficult to execute in reality and may not even have been feasible.

S-31 Kurowashi – data


Daimler-Benz Schnellbomber mit DB P83 Gruppenmotor (Germany)


Heavy Bomber



Powerplant Four 24-cylinder, liquid-cooled X-engines, each developing 2,500hp, each pair driving two, metal 3-bladed contra­rotating propellers


Span Length Height Wing area





107.7ft 69.2ft 19.3ft 1,431.6ft2






Max speed



Cruise speed



Landing speed





3,666 miles




Fuel Weight




Eight 7.7mm machine guns and four 23mm cannons (see text for arrangement); up to 8,000kg (17,6361b) of bombs

Deployment None. The S-31 Kurowashi was purely a paper, if not impractical, design in a magazine.

Junkers Ju 90 transport

On 25 July 1938, Mitsubishi entered into nego­tiations with Junkers on behalf of the IJA to work with the German company to produce a bomber version of the Ju90 transport. Ten were to be completed and flown to Japan. The IJA even allocated the designation Ki-90 for the bomber. However, Junkers eventually declined Mitsubishi’s proposal citing its involvement in filling domestic orders for air­craft.

Junkers Ju 160 transport

The Ju 160 was an improved Junkers Ju60, the latter having lost to the Heinkel He 70 in the fast, small airliner market. Lufthansa pur­chased 11 Ju 160A-0 and 10 Ju 160D-0 6-pas – senger aircraft, putting them into service in 1935-36. Two would end up in Manchuria, registered as civilian aircraft. The UN pressed them into service as the LXJ.


The D. IX provided the inspiration for the Seishiki-1 which used an imported Mercedes Daimler lOOhp engine, later licence-built in Japan. The Seishiki-1 was completed in 1916 but the biplane’s poor performance resulted in further development being cancelled.

Rohrbach R flying boat

The Navy was very interested in the metal air­craft construction techniques used by the German company Rohrbach. Mitsubishi was asked to study the techniques and the two companies would form Mitsubishi-Rohrbach GmbH in Berlin in June 1925. A total of three Rohrbach flying boats were to be imported, the R-l, R-2 and R-3, known collectively as the Mitsubishi Experimental Type-R flying boats. Although these aircraft would prove to have poor take-off and alighting that denied them military service, they did provide invaluable experience to Mitsubishi when it came to metal stressed skin construction.

Kayaba Katsuodori


The Katsuodori depicted here is shown in the colours and markings of the 71st Sentai. It is intercepting Tokyo-bound Northrop B-35 bombers of the 44th Bomb Squadron, 40th Bomb Group operating from Tinian.



Kayaba envisioned that his design for a fast, point defence interceptor would sweep through the Allied bombers like the kat­suodori bird hunts for fish. Impressed with the prowess of the katsuodori, Kayaba named his design after the bird. But as we will see, his vision was to meet with a harsh reality.

The genesis of the Kayaba Katsuodori began as far back as 1937 with the Kayaba Ramjet Study Group, a collection of engineers and scientists who sought to investigate ram­jet propulsion in Japan. The concept of the ramjet was actually patented in 1908 by French engineer Rene Lorin, but it was the Russian I. A. Merkulov who first built and tested one, the GIRD-04 in 1933. A ramjet is a very basic engine with few moving parts. In simple terms, it uses the high pressure air generated by the aircraft’s forward motion and forces it through the inlet. The air is then mixed with combusted fuel – this heats the air and is forced out of the rear of the engine, pro­viding forward propulsion. Unlike pulsejets (which were to be used on the Kawanishi Baika, see Page 61), the fuel flow is continu­ous. Without getting into the specifics of a ramjet, adjustments in the design of the inlet (to maximise the intake of air), combustor (to ensure effective operation during flight move­ments) and the outlet nozzle (to effect accel­eration increases) all come into play on
designing such an engine. The main draw­back with a ramjet engine is that at subsonic speeds its performance is poor. Below 612km/h (380mph), a ramjet suffers signifi­cant loss in speed and becomes highly ineffi­cient in terms of fuel consumption. The ramjet typically requires another power source to bring the aircraft up to the speed at which the ramjet can operate efficiently. Typ­ically, this speed is at least 966km/h (600mph). Once the ramjet reaches that speed the engine is self-sufficient and, with­out fuel injection moderation, would propel the plane to speeds far in excess of the design’s ability to handle the high tempera­tures and Mach number.

The Kayaba Ramjet Study Group saw the benefits of high speed with a relatively easy to manufacture engine. The group produced two test models before the final product, the Kayaba Model 1 ramjet, was realised. The Model 1 was projected to be able to offer speeds of 900km/h (559mph). With the engine complete, all that was needed was the aircraft to fit it into.

The airframe design began with Kumazo Hino. Hino was an officer in the IJA and had been the first Japanese to unofficially make a flight on 14 December 1910 when he acci­dentally took to the air in a Hans Grade mono­plane while he was taxiing. This aircraft had
been purchased from Germany. His interest in aviation saw him produce four aircraft designs: the Hino No. 1, No. 2 and the No. 3 and No. 4 Kamikaze-go airplanes. However, each of these designs was a failure. Pressure from his military superiors saw Hino give up on aviation by 1912.

However, in 1937, Hino was inspired to cre­ate a tailless glider. The project was taken over by the Kayaba Seisakusho (Kayaba Man­ufacturing Works) and then by Dr. Hidemasa Kimura who worked for the Aeronautical Research Institute of the Tokyo Imperial Uni­versity under Dr. Taichiro Ogawa. The result was the HK-1. The HK-1 (standing for Hino Kumazo) was built by the Ito Нікбкі K. K. and was completed in February 1938. It was purely a research glider to test the tailless concept. Testing commenced in December 1938 with ground towing at Kashima in Ibaraki Prefecture and the first air released flights began in September 1939 at Tsu – danuma in Chiba Prefecture. Because it showed positive results, the IJA took an inter­est in the concept. The HK-1 was purchased by the Rikugun Kokugijutsu Kenkyujo in April

1940 for continued testing. However, a subse­quent test flight on 16 April by an IJA officer pilot resulted in a hard landing that damaged the HK-1 beyond repair. In all, 182 flights had been made in the HK-1.

With the IJA still interested, the Rikugun Kokugijutsu Kenkyujo set aside 200,000 yen to continue the project. Kimura, along with Kayaba’s chief development designer Dr. Shigeki Naito, set about the task of producing a new tailless aircraft, this time with a possi­ble military application. The result was the Ku-2. The Ku-2 had no tail but rudders were fixed to the wing tips and the design was tested extensively from November 1940 through to May 1941 making 270 flights in all before it was damaged in a crash on 10 May. To further test the concept, Kimura (with the aid of Joji Washimi) produced the Ku-3 which had no vertical control surfaces at all and fea­tured a cranked delta wing form to test vari­ous angles of sweep. The only control came from the flaps arranged along the wings. 65 flights were carried out with the single Ku-3 before a crash in 1941 wrecked the glider.

The last design put forward by Kimura was the Ku-4. At the request of the Rikugun Kokugijutsu Kenkyujo, the Ku-4 was to be powered and a rear mounted 120hp de Hav – illand Gipsy 4-cylinder, air-cooled, inline engine was selected, turning a two-bladed propeller. Unfortunately for Kimura, the IJA lost interest in the entire concept. With the loss of the Ku-2 and the Ku-3, the IJA can­celled the Ku-4 before it could be finished. With no backing, Kayaba could not afford the 100,000 yen to finish the Ku-4 alone. The IJA had paid Kimura and Kayaba 17,000 yen out of the 200,000 yen project money for costs associated with the Ku-2, Ku-3 and what was already paid into for the Ku-4. The remaining funding was not released. Shiro Kayaba, how­ever, still had hopes that the concept could be a potent weapon and from this came the Kat- suodori.

The roots of the Katsuodori come from the Ku-2. Unlike the Ku-2, the wings were moved higher on the fuselage and the wing form had a rearward sweep. The Katsuodori retained the vertical wingtip rudders used on the Ku-2. The ramjet filled most of the fuselage which meant there was no room for landing gear. Instead, a main skid was incorporated on the underside of the fuselage along with a small wheel mounted at the rear of the aircraft. Without integral landing gear, the Katsuodori was to be fitted with a simple, sprung set of landing gear that could be jettisoned when the aircraft took to the air. The pilot sat towards the front of the fuselage and was pro­vided with a one piece canopy that offered respectable visibility to the front and sides.

In order to get the Katsuodori off the ground, Kayaba envisioned the use of four rocket booster units. Secured to each side of the fuselage under the wings were two rocket units and together all four could provide an estimated 7,200kg (15,8731b) of thrust. The planned procedure for using the rockets was to have one on each side being fired first, and when these had burned out the next pair would be fired. Each rocket contained pro­pellant for five seconds of thrust and, all told, the scheme would give the Katsuodori a total of ten seconds of thrust with which to get the plane off the ground and the ramjet function­ing. Kayaba estimated that the Katsuodori would need to achieve 367km/h (228mph) before the ramjet would operate and cer­tainly the speed provided by the rocket units would have been sufficient for this to happen. The rockets, once used, may or may not have been releasable but the latter is likely in order to minimise drag.

With the ramjet operating, the estimated performance of the Katsuodori was a speed of 900km/h (559mph) and a climb rate of three minutes to reach an altitude of 10,000 (32,808ft). Fuel load was 1,500kg (3,3061b) and with a fuel consumption of 50kg (1101b) per minute would grant a combat endurance of thirty minutes. Once the fuel was exhausted, the Katsuodori would use its glid­ing properties to return to base.

For weapons, Kayaba planned on mount­ing two 30mm cannons externally, one under each wing near the wing root. Kayaba did not wish to use existing 30mm cannon designs such as the Ho-155 preferring to produce a 30mm version of the 40mm Ho-301 cannon which his manufacturing facilities were con­structing for use in the Ki-44-П Hei Shoki fighter. The Ho-301 used caseless ammuni­tion with each round being, in effect, a rocket. The propellant cavity was partially lined with a thin aluminium cap. When the primer was struck, the propellant was ignited and the pressure would build up until the cap burst, the exhaust gas being vented out the back of the round to move the projectile forward. The main advantage of the weapon was its light weight for such a heavy calibre.

The design of the Katsuodori was nearly complete by 1943 and Kayaba anticipated that he could have had a flying prototype by

1944. By this time, however, the IJA was already involved with the rocket powered Ki-200 (the IJA version of the UN’s Mitsubishi J8M1 Syusui – see Page 96) and so paid no attention to the Katsuodori. Kayaba, in trying to salvage the design, stated that he could adapt the Katsuodori to accept the Kugisho Ne20 turbojet or the KR10 rocket motor as used in the Ki-200. And since his design was

nearly complete a prototype Katsuodori could be ready for testing before the Ki-200.

The advantages of the Katsuodori included a ramjet that was far less complex to con­struct than a turbojet. This would have been a critical asset in a Japanese war industry that was devastated by US bombing. It could also use standard aviation fuel, unlike the Ki-200 that required special fuels, and by extension, could operate from any airfield without the need of special fuelling apparatus and proce­dures. While the speed of the Katsuodori was on par with the Ki-200, the Katsuodori’s com­bat endurance was far superior to the Ki-200 and the IJA’s own planned rocket intercep­tor, the Rikugun Ki-202 Sytisui-Kai (see Page 40).

However, the Katsuodori had several draw­backs. The first was the use of the rocket boosters to get the plane up to speed. The Japanese did not have a successful track
record for using such units. Improper place­ment of rocket boosters was the reason behind the aborted second flight of the Naka – jima Kitsuka (Page 114), heavily damaging the aircraft. Attempts to use rocket boosters on the Mitsubishi Ki-109 to boost take-off and climb met with such poor results that the rockets were removed from the Ki-109 devel­opment all together. A misfire or variation in the thrust output might result in the plane careering out of control. Like the Ki-200, once fuel was exhausted the Katsuodori lost its speed advantage, and on the ground its recovery would take longer since the Kat­suodori could not move on its own without means of wheeled apparatus. This made it vulnerable to intruder aircraft dedicated to airfield interdiction missions. Kayaba’s elec­tion to use a 30mm version of the Ho-301 can­non would have been a recipe for disaster. The 40mm version, as used in combat by the

Japanese, had an incredibly short range – only 149.5m (490ft) since it had a muzzle velocity of 241m/sec (790ft/sec). Coupling the very short range of such a weapon with a high closure rate due to the speed of the Kat­suodori against a slow bomber, the pilot would have had mere seconds or less to line up the target, fire, and then bank to avoid col­lision. Since Kayaba did not proceed with a 30mm variant of the Ho-301, the muzzle velocity for the round is unknown but it can­not have been substantially more than the Ho-301.

Despite the potential advantages over the Ki-200, the Katsuodori would never see life outside plans on Kayaba’s design board. The IJA was looking to the Ki-200 and their own Ki-202 for their interceptor needs and thus ended Kayaba’s dream of seeing his Kat­suodori taking to the skies to defend Japan.

Kayaba Katsuodori – data




Handley Page H. P.75 Manx (UK), BOK-5 (Russia), Blohm und Voss P.210/P.215 (Germany), Heinkel P.1078 (Germany), Northrop XP-56 Black Bullet (US), Northrop XP-79 Flying Ram (US), Skoda-Kauba SK P.14.01 (Germany), Lippisch Li Р. ІЗа (Germany), Messerschmitt Me P. l 101L (Germany), Heinkel He P.1080 (Germany), Stockel Rammschussjager (Germany), Leduc Model 010 (France), Kostikov 302 (Russia)


Point Interceptor




One Kayaba Model 1 (or possibly later) ramjet producing 300kg (661 lb) of thrust at 367km/h (228mph), 420kg (925 lb) of thrust at 490km/h (304mph), 550kg (1,2121b) of thrust at 612km/h (380mph) and 750kg (1,6531b) of thmst at 734km/h through 1,103km/h (456mph through












Wing area



Wing sweep










Max speed



Landing speed





248 miles


3 min to 10,000m (32,808ft)





Two 30mm cannon


None. The Katsuodori did not advance beyond the drawing board.



Т. К.19

It was difficult for the US and her Allies to acquire intelligence about the Japanese war industry as far as HUMINT (HUMan INTelli – gence) was concerned. This was due to the relative difficulty associated with either turn­ing a Japanese source or inserting a foreign spy into Japan who was capable of avoiding detection. Once it was broken, the PURPLE code (as used by Japanese foreign offices) and the later JN-25 code (as it was labelled by the US) used by the 1JN provided a wealth of information and intelligence, but human intelligence and cipher cracking were only a part of the overall processes. One avenue used prior to the war was the gathering of publications such as books and magazines. Besides being relatively innocuous to pur­chase in Japan, such sources could be obtained outside of Japan and were therefore easier to gather. It was one such publication issued just prior to the start of hostilities that revealed the T. K.19 to intelligence officers.

The illustration of the T. K.19 appeared in the April 1941 issue of the Japanese aviation magazine Sora in a section entitled ‘Dreams of Future Designers’. The T. K.19 showed a fuselage that was elongated and ovoid in shape. More interestingly, it showed a canopy that could be lowered to fit flush with the top of the fuselage thereby eliminating the drag of a standard canopy. This same concept was seen in the Russian Bisnovat SK and Bartini Stal’-6, both of which were high-speed air­craft whose designers were seeking military
applications for their charges. Each wing of the T. K. 19 showed what appeared to be three weapon ports, totalling six machine guns or cannons. There were also ducts in each of the wing roots, ostensibly to cool the engine. A radiator bath may have been located in the nose of the aircraft. Given the flush canopy, the T. K.19 may have used a system similar to the Stal’-6 in which for take-off and landing the canopy hood was hinged upwards and the pilot would raise his seat. Whether the T. K.19 used a periscope vision system for the pilot once in flight as was proposed in the Soviet Lavochkin LL fighter was not known.

Like many of the other aircraft in this sec­tion, the T. K.19 would later appear in the American magazine Flight in the 25 Decem­ber 1941 issue. The description made no mention of the more striking features of the plane as described and shown in the Japan­ese magazine. Instead, the article, which con­tained no illustration, reported the T. K.19 was of orthodox appearance save that the aircraft had a twin row radial engine in the rear of the fuselage and was cooled via ducts. From this, a drawing evolved that took the basic shape of the Japanese T. K. 19 and made it more con­ventional, to the point that it bore a slight resemblance to the Curtiss P-40 Warhawk, a plane that first flew in 1938 and one that Japanese pilots first encountered in combat in late 1941. The changes from the Japanese T. K.19 included doing away with the flush canopy (providing a more standard style seen

The T. K.19 depicted here is shown in the colours of the 77th Hiko Sentai during operations in Burma, 1941-1942.

in many aircraft), moving the wings higher up the fuselage, adding pronounced wing root fairings that extended from the nose of the aircraft to rear of the cockpit (the latter being set behind the wings) and having a main landing gear reminiscent of the Brewster F2A but with landing gear doors. No weapons were shown but air intakes were illustrated in the wing roots.

From reviewing the information, US intelli­gence made the assumption that the T. K.19 was a bona fide Japanese fighter that was in service or was soon to be in service. Thus, it was codenamed Joe after Corporal Joe Grat­tan, one of the team members responsible for assigning codenames to Japanese aircraft. The T. K.19 failed to appeare in Japanese sources despite remaining in US intelligence bulletins. It eventually became clear that the T. K.19 was nothing more than a fictional air­craft and Joe was removed from future intel­ligence publications.

T. K.19-data

No information, if any, on the specifications are aoailable for the T. K. 19. Deployment

None. The T. K.19 existed only as an illustration in a magazine.

Rumpler Taube

The Imperial Flying Association purchased two Rumpler Taube aircraft prior to the out­break of World War 1. As Japan was part of the Entente Powers, and thus against Ger­many, the Japanese Army bought the two Taubes from the Association for use in action in the Tsingtao campaign. With no aircraft, the Imperial Flying Association built their own version of the Taube calling it the Isobe Kaizo Rumpler Taube. The solitary aircraft first flew in 1915 before being wrecked in a crash later in the year. The remains were cannibalised and used in the Ozaki Soga-go of 1917.

Arado Ar 196 float plane

It was reported by Allied intelligence services that the Japanese received two Arl96 float planes. However, there is no evidence to sug­gest this occurred. The Germans operated a submarine facility at Penang, Malaysia, and the unit used the Arl96 in Japanese colours which may have led to the confusion in the intelligence report.

Arado Ar 234 Blitz

jet reconnaissance bomber

The Ar234 was a twin-turbojet, single-seat reconnaissance bomber that entered service with the Luftwaffe in September 1944. Allied intelligence intercepted a communication between Germany and Japan in March 1944 that confirmed that the Japanese had data on the Ar234. It was assumed that the data related to the Ar234A, which was not as advanced as the subsequent Ar 234B models. Another report went so far as to say produc­tion plans were in place to build the latest Ar 234 aircraft but this was based solely on the fact another report stated that the FuG 136 Nachtfee visual command indicator equip­ment (used in the Ar234P series night fight­ers) had been delivered to Japan in January 1945. It would become clear that the Ar234 was never produced in Japan and it is unknown exactly what data Japan did receive on this aircraft.

Kokusai Ta-Go





Подпись: The profile depicts the Kokusai Та-Go prototype in the colours it actually sported.

In 1943, the Allied island-hopping campaign was underway and in 1944 the Japanese would see their island outposts, bases and strongholds destroyed and lost to them for­ever. In 1945, the Japanese lost their holdings in Burma, Borneo, Iwo Jima and Okinawa. Japanese military planners had no doubts that the Allies would continue their progress and land forces on the main islands of Japan. The Allies did indeed have such a plan known as Operation Downfall. The Japanese, to defend against the invasion they felt was coming, put into motion Ketsugo Sakusen or Operation Decision.

Operation Decision’s main component was the use of shimpu and shimbu missions targeting the Allied naval force, specifically landing craft, troop ships and support ships. To repel the invaders, all manner of craft were assembled for the Japanese defender of kokutai, the national polity of self sacrifice. Midget submarines such as the Kairyu, Koryu and the crude U-Kanamono, the Kaiten human torpedo, small explosive laden powerboats like the Maru-Ni (IJA) and Shinyo (UN), and even frogmen (the Fukuryu) were prepared for the final showdown. Even the best tanks, the Type 3 Chi-Nu and Type 4 Chi- To, were held in Japan to counter Allied armour. Aircraft would also play a significant role in the defence of Japan. It was estimated that 10,000 aircraft of every type would be available to throw at the Allied invasion fleet. It was thought that the mass wave tactics would result in a tremendous loss of aircraft which the Japanese industry in 1945 would be unable to keep pace with unless steps were taken to remedy such a situation. The Та-Go was one such remedy.

By 1945, Japanese industries were under regular bombardment from US airpower. In
addition to war factories being razed to the ground, Japan was being starved of materials needed to sustain weapon production. Alu­minium was a key material in aircraft pro­duction and it was estimated that by December 1945, even with strict control, the supply of this metal would be exhausted. Consequently, wood was to become the main material for aircraft construction, regardless of the type of aircraft concerned. Examples included the Tachikawa Ki-106 (a wooden version of the Nakajima Ki-84 Hay – ate) and the Kugisho D3Y Myojo (which was the wood derivative of the Aichi D3A Val). With the loss of heavy industrial machinery, it fell more and more to smaller workshops to produce components and sub-assemblies for aircraft. Often the labour force was not as skilled as before and working with wood was easier as it did not require the sophisticated tools and jigs necessary for construction of more conventional aircraft using metal com­ponents.

Captain Yoshiyuka Mizuyama, an officer in the IJA’s aviation equipment section, was the man behind the Та-Go (Та being short for take-yari, or bamboo spear). It was his desire to design and build a plane that was simple in constmction, used the bare minimum of war critical materials and could be produced rapidly. By doing so, the Та-Go could quickly populate the aircraft pool available to units destined for shimbu missions and also replenish losses in short order. He hoped that the Та-Go could be used to defend the seaside cities of Osaka and Kobe. In an effort to help realise the Та-Go, Mizuyama approached the Tachikawa Hikoki K. K. with his concept. Despite Mizuyama being an IJA officer, Tachikawa refused to assist him as his plan had no official sanction and was not

approved by the Koku Hombu. As such, Tachikawa could not spare the capacity to develop the aircraft.

Undeterred, Mizuyama discovered a small shop in the city of Tachikawa within which he and his fellow men went about the task of designing and constructing the first proto­type. Once the concept was completed, work began on building the Та-Go. Using wood lathes to construct the fuselage and other components, the aircraft was made from ply­wood while fabric was used for some of the skinning and coverings for the control sur­faces. The pilot was given a simple acrylic glass canopy. Instrumentation was kept to the bare minimum. The landing gear was fixed. For a motor, a Hitachi Ha-13 Ко 9-cylinder, air­cooled radial engine developing 450hp was selected, the cowling for it being made from plain sheet steel. The only armament was a single 500kg (1,1021b) bomb. In February 1945, the Та-Go prototype was nearly com­plete when Tachikawa was subjected to a bombing raid. In the ensuing attack, the shop was burnt to the ground and the Та-Go inside destroyed.

Despite the setback Mizuyama forged ahead, going to Nippon Kokusai Kogyo K. K. (Japan International Air Industries Co. Ltd.) to pitch his Та-Go. In the end the project was accepted and in part this may have been due to Kokusai’s experience with light aircraft such as the Ki-76 (known as Stella by the Allies) and the Ki-86 Ко (codenamed Cypress), the latter of which Kokusai had built as the prototype all-wood Ki-86 Otsu. Of course, Kokusai was not as heavily taxed by wartime demands from either the IJA or the UN and could thus allocate some assets to the development of the Та-Go. Despite Kokusai taking on the Та-Go project, it still remained an unofficial design and thus bore no Ki number.

Mizuyama’s design for Kokusai differed from the one he proposed to Tachikawa because the new version was significantly scaled down and much smaller. In so doing, this reduced the amount of assemblies needed to produce the aircraft which, by extension, lowered the man-hours required to build it. Fewer assemblies meant less use of construction materials. With the resizing, the Ha-13 radial became too large for the pro­posed airframe and so the Hitachi [Ha-47] 11 inline engine, rated at 1 lOhp, was selected as a replacement. This same engine was used in the Tokyo Koku Ki-107 all-wood two-seat trainer which was to be the replacement for the Ki-86 had the former made it into service.

In addition to the size reduction, steps were taken to simplify the Та-Go even more. Gone was the canopy and the pilot sat in a open cockpit with only a small acrylic glass wind­screen as protection from the elements. For instrumentation, only the absolute basics were used consisting of a speedometer, altimeter, compass and the essential engine related gauges such as fuel and oil. The fuse­lage was slab sided and box shaped. While this granted easier construction, it was not the most aerodynamic design. Much of the fuselage used wood sparring and structure while the skinning was of plywood. The wings were low mounted with squared wing tips and they were hinged just outside of the landing gear to enable them to fold upwards to allow the aircraft to be hidden in caves as well as facilitate their construction within the confines of caves or small manufacturing lines. Both the vertical stabiliser and the hori­zontal stabilisers were rectangular in shape.

The landing gear was fixed, being made of steel tubing and fitted with rubber wheels, each gear supported by a single strut. To pro­vide a modicum of streamlining the tubing that made up the landing gear was faired over using aluminium. The only measure of shock absorption came from the tyres and the tail skid, the latter also being built from steel tub­ing with a portion rubberised.

The [Ha-47] 11 engine was fitted with an angular plywood cowling, the engine driving a fixed-pitch, two-bladed wooden propeller. A metal engine mount was used while the fuel tank was situated on top of the engine and used a gravity feed system. Behind the tank and in front of the windscreen was a sim­ple oil cooler, mounted flush in the fuselage. Given the much smaller dimensions of the revised Та-Go, it was no longer able to carry the 500kg (1,1021b) bomb Mizuyama’s origi­nal version was designed for. Instead, it could only carry a 100kg (2201b) bomb. The bomb was fitted to the underside of the fuselage and once in place could not be released by the pilot.

Mizuyama, with the assistance of his own men and Kokusai, had completed the first prototype of the new Та-Go by the middle of June 1945 and it was made ready for flight. On 25 June, the Та-Go took to the air for the first time with a Kokusai test pilot at the controls. Not surprisingly, the pilot reported handling concerns. After a number of additional test flights, revisions were made to the design. Once complete, Kokusai created a complete set of working blueprints for the production version. However, with the cessation of hos­tilities in August 1945, the Kokusai Ta-Go never entered production. The close of the war also saw the end of two Kokusai devel­opments of the Та-Go, known as the Gi-Go and Tsu-Go. Both remain shrouded in mys­tery because no information on them has sur­faced to date.

Ironically, Tachikawa would return to the Та-Go when the Gunjusho (Ministry of Muni­tions) authorised development of Mizuyama’s initial design following the com­pletion of the Kokusai Та-Go prototype. The end of the war would find the Tachikawa Та-Go prototype incomplete. As a note, with the acceptance of the Та-Go by the Koku Hombu, a project number (meaning a Ki number) was assigned to the Та-Go – Ki-128. It has not yet been confirmed whether this Ki number applied to the Kokusai Та-Go, the Tachikawa Та-Go or both.

Та-Go – data


Messerschmitt P. l 104 Sprengstofftrager (Germany) Specifications are for the Kokusai Ta-Go.

Type Special Attack Aircraft

Crew One


One Hitachi [Ha-47] 11,4-cylinder, air-cooled inline engine developing 1 lOhp for take-off driving a wooden, two-bladed propeller 7.1ft in diameter


Span Length Height Wing area Wing loading






29.2ft 24.3ft 12.7ft 54.9ft2 7.1 lb/ft2









Max speed



Cruise speed





93 miles





One 100kg (2201b) bomb


None. A total of three Ta-Go aircraft were constructed: Mizuyama’s own prototype aircraft that was destroyed by fire prior to flight, the one built and flown at Kokusai, and the Tachikawa Ta-Go which remained incomplete at the end of the war.

Weapon Systems

Japanese Missile and Guided Munitions Projects

The aim of tactical missiles, specifically guided munitions, is to increase accuracy. It takes a considerable amount of conventional bombs or torpedoes to strike a ship and inflict enough damage to cripple or sink the vessel. Likewise, anti-aircraft cannons have to put a significant amount of shells into the air to bring down a single plane. Another benefit of using missiles is the measure of protection afforded to the user by way of range. A fighter combating bombers has to attack at such a range that his weapons are effective and therefore within range of the defensive arma­ment of the target. The fighter also has to con­tend with escorting fighters before he even has a chance to press home an attack on the bomber. The same is true of attacking ships. To improve accuracy, a torpedo or dive – bomber has to be close enough to the ship to ensure a hit. Of course, this also puts the air­craft in the uncomfortable position of being within range of the many anti-aircraft can­nons and machine guns carried by the ship, as well as attack by fighters providing cover for the vessel. Guided munitions eliminate some or all of these problems.

Without doubt, the undisputed leader in World War 2 missile development was Ger­many. Missiles such as the Fieseler Fi 103 (the V-l), EMW A4 (better known as the V-2), Ruhrstahl-Kramer X-l Fritz X and the Hen – schel Hs 293A were used operationally with a measure of success. This was just the tip of the iceberg. Many more designs came close to seeing service or were in the latter stages of testing at the war’s end. Such weapons included the EMW C2 Wasserfall, Rhein – metall-Borsig Rheintochter, Henschel Hs 117 Schmetterling, Ruhrsahl-Kramer X-4 and many more. The US was not lacking in missile and guided munition technology of its own. Operational weapons included the ASM-N-2 Bat, GB-l/GB-4 and the VB-1 AZON (AZimuth ONly). Projects included ‘Little Joe’ (intended as a ship-borne missile to combat kamikazes), the McDonnell LBD-1 Gargoyle and the JB series of missiles. Other Allies, such as the British and the Russians, would not spend nearly as much resources on the subject as did the Germans and Americans. The British would squander the potential of the Brakemine surface-to-air missile and stall the Fairey Stooge while the Russians would only test and reject the promising Korolev Type 212A (built in 1937), waiting until the close of World War 2 to revive its missile development work. In some cases the Soviets used the fruits of German labour as their basis, for example, developing the R-l/SS-1 Scunner from the V-2 missile and the Type lOCh from the V-l flying bomb.

An example of the greater accuracy of mis­siles and guided munitions can be seen in the 27 December 27 1944 mission flown by the US to attack the Pyinmana rail bridge in Burma. Nine VB-1 AZON guided bombs were enough to destroy a bridge that for two years previ­ously had failed to be hit by thousands of con­ventional bombs. Likewise, the Germans were able to successfully attack shipping tar­gets using the Henschel Hs293A and Fritz-X using less aircraft and with a higher hit and kill ratio than if the same attacks had been made using conventional bombs and torpedoes.

With these benefits in mind, it is not sur­prising that Japan also devoted considerable effort to producing such weapons themselves (while Japan did receive some German mis­sile technology, it is unknown how much of it found its way into the IJA and UN missile pro­grams). Both the IJA and UN funded the development of missiles as a means to both combat the bombers that tormented the homeland and to attack Allied shipping.

Bachem Ba349 Natter rocket interceptor

The Natter (meaning ‘Viper’ in German) was a rocket powered point defence interceptor – in essence, a manned rocket launched verti­cally towards enemy bombers where it would use its high speed to avoid enemy fighters and launch a salvo of either 73mm Hs217 Fohn or 55mm R4M rockets at the attacking bombers. The pilot would then eject from the Ba 349 and return to earth via parachute along with the engine portion of the aircraft. The Ba 349 required little in terms of critical war materials and could be con­structed by semi-skilled workers. Several unmanned test flights were flown but the only recorded manned flight ended in the death of the pilot. Despite a handful being deployed, none saw action. Allied intelligence surmised that the Japanese were provided with infor­mation on the Ba 349 and they were correct. The RLM ordered Erich Bachem to give the Japanese a complete set of plans for the Ba349. However, the submarine carrying the data was lost at sea. When this transfer occurred is unknown but it would likely have been late in the war.

Blohm und Voss Ha 142 heavy bomber

The Ha 142 (later the BV142) was the land version of the Ha 139 float plane. Unlike the successful Ha 139, the Ha 142 was, ultimately, a failure when converted from a transport to a reconnaissance bomber aircraft in 1940. Despite this, the Blohm und Voss P.48 project was listed as a bomber version of the Ha 142 for Japan. Most likely, this remained a paper concept with no further action being taken as only four BV142 aircraft were built before the type was withdrawn from service in 1942.

Bticker Bii 131 Jungmann trainer

In August 1942, the Japanese obtained the licence to produce the Jungmann trainer (meaning ‘Young Man’ in German). The Bii 131 had been demonstrated to the Japan­ese in 1938 and a total of 22 aircraft were pur­chased from 1938 to 1939. The Japanese attempted to make their own version of the Bii 131 but the results paled in comparison to the German aircraft and this resulted in the 1942 acquisition of production rights. The Bii 131 was produced for the IJA as the Koku – sai Ki-86a and for the UN as the Kyushu K9W1 Momiji (meaning ‘Maple’). One all-wood Ki-86b was completed in February 1945 but remained a prototype. All told, 339 K9W1 and 1,037 Ki-86a aircraft were built from 1942 through 1945. The Allies codenamed both air­craft Cypress.

Maeda Ku-6

Interest in airborne forces can be traced as far back as 1917 because they can provide sev­eral tactical advantages. Being air dropped, parachute troops can be deployed into areas not easily accessible by ground forces as well as bypassing defences meant to hinder or repel attacks from specific avenues of approach. Also, the ability to place troops anywhere on the battlefield requires the enemy to use assets to protect against such operations, thereby spreading defending forces thinner. Such advantages come at a cost, however. Airborne forces typically do not have the firepower of comparable ground forces nor the ability to remain independent for long before outside support must be obtained.

Airborne troops were used by all of the major warring powers in World War 2 and special equipment and weapons were cre­ated for use by these units in an attempt to provide them with heavier firepower. Artillery such as the US Army M1A1 75mm pack how­itzer and the German 7.5cm LG 40 recoilless gun were air-droppable and the troops used modified or special small arms such as the US

M1A1 ,30cal carbine and the Japanese Type 2 Paratroop rifle. Despite such weapons, air­borne forces were deficient in one critical area: armoured vehicles. The ability to pro­vide airborne troops with armoured support such as tanks was one sought by all the war­ring powers and tank designs did emerge. The key problem was how to send in the tanks with the troops during an operation. One of the first solutions was the glider tank.

The Japanese would create and utilise air­borne forces during World War 2. The IJA called their forces the Teishin Dan (Raiding Brigades) while the UN had the Rikusentai. Both would be used first in 1942 during the fighting in the Dutch East Indies. Unlike the Germans, British and Americans, the Japan­ese did not provide their paratroopers with a significant amount of specialised heavy weapons. In part, this may have been due to the fact that the Japanese parachute forces would rarely be used in their designated role. Instead, much of their fighting would be done as light infantry (much like the German Fallschirmjagers). Nevertheless, the IJA and UN were considering ways to improve the
striking power of their paratroopers and one such plan was a tank borne into battle on wings.

In 1943, the IJA set the wheels in motion to investigate a flying tank. The Army Head Avi­ation Office in league with the Fourth Army Research Department drafted the initial con­cept for the weapon. The aviation research section of Maeda was tasked with producing the wings that would form the glider portion of the weapon and the Army Head Aviation Office assigned the designation Ku-6 to the glider. The tank was to be designed and built by Mitsubishi and called the So-Ra (or Sora – Sha, literally ‘sky tank’). To ensure there was no confusion, the Army Head Aviation Office called the entire combination the Kuro-Sha (taking the ‘Ku’ from Ku-6 with ‘ro’ meaning 6 and the ‘Sha’ for tank).

Mitsubishi’s So-Ra was, due to the purpose for which it was intended, a tankette design. With a crew of two (driver/pilot and the com – mander/gunner), the So-Ra was to weigh 2,812kg (3.1 tons). The turret was set behind the driver/pilot compartment and was pro­vided with three large, hinged ports to allow



some measure of vision for landing. Armour was likely very light and was certainly less than the 6mm-12mm armour protection of the Type 95 На-Go light tank then being used by Japanese airborne forces. Three weapon fits were proposed for the So-Ra. The first was a 37mm cannon (such as the 37mm Type 94 used in the На-Go), the second consisted of a machine gun armament (either a light weapon like the 7.7mm Type 97 machine gun or a heavier calibre) and the third was a flamethrower. Power was to come from an air-cooled engine producing 50hp that was estimated to give the So-Ra a maximum road speed of 42km/h (26mph).

The glider portion, the Maeda Ku-6, has been interpreted in at least two ways since the original design is not known, the docu­ments either having not survived the war or have yet to be discovered. One version shows the wings secured to the So-Ra at the hull, on either side of the turret, with a tail boom fitted to the rear of the tank. A horizontal stabiliser sat on top of the vertical stabiliser. The dri – ver/pilot moved the control surfaces via wires that ran into the tank. On the hull front was the tow cable attachment point. The second version has the So-Ra fitted with struts on the hull sides. Atop the struts was the main wing to which twin tail booms were fitted with a low mounted horizontal stabiliser connecting the vertical stabilisers. In essence, the So-Ra would hang below the wing. On landing, the tank would shed the wings and move into action with the paratroopers.

By 1945, the Ku-6 had been completed and Mitsubishi had produced a full scale mock-up of the So-Ra. Flight testing was conducted for a brief period and it is likely that the mock-up was used, suitably weighted to simulate the 2,812kg (3.1 tons) of an operational So-Ra. The So-Ra was to be towed by a Mitsubishi Ki-21 bomber. Tests soon showed the diffi­culty of the concept. The Kuro-Sha suffered from in-flight control problems, the driver/ pilot had poor vision and landing was extremely difficult. Another concern was that the So-Ra could not stand up to heavier and more powerful tanks. Any usefulness the Ku-6 may have possessed was minimised with the advent of the Kokusai Ku-7 Man – azuru (meaning ‘Crane’) glider that began development in 1942. First flown in August 1944, the Ku-7 was able to carry a 7,257kg (8 ton) tank within its fuselage which was more than enough to hold the 6,713kg (7.4 tons) of the На-Go light tank. With the Kuro-Sha’s problems evident, the 1JA terminated any fur­ther work on the Kuro-Sha favouring the Ku-7.


Antonov A-40 (or KT for КгуГуа Tanka, flying tank) (Russia), Raoul Hafner’s Rotabuggy and Rotatank (UK), Baynes Bat (UK), John Walter Christie’s M1932 (US)

Specifications are based on the second variation of the Kuro-Sha, with the So-Ra beneath the wing.


Glider (Ku-6)













Wing area




Loaded (with the So-Ra)




Max glide speed





Type Tankette (So-Ra)

Crew Two


One 4-cylinder, air-cooled, gasoline engine developing 50hp at 2,400rp
















Max speed




One 37mm cannon, machine gun or flamethrower




None. Only one prototype built and flown.

In late 1942, the Koku Hombu was looking for a number of new aircraft types as improve­ments on those in service. These included a heavy fighter capable of conducting ground attack operations and a high-altitude fighter. Nakajima and Tachikawa were tasked with the latter, coming up with designs that would later result in the Ki-87 and Ki-94 respectively (see Pages 28 and 53). For the former, Kawasaki attracted the interest of the Koku Hombu with their multi-role Ki-102. However, Kawasaki’s design was not to go uncontested and the competition would come from a rela­tively small aviation company.

Manshukoku Hikoki Seizo K. K. – the Manchurian Aeroplane Manufacturing Com­pany Ltd., and better known as Manshu, a contraction of the kanji ‘Man’ in Manshtikoku and ‘Hi’ in Hikoki-was founded in 1938. Man – sliu was a subsidiary of Nakajima Hikoki K. K. and produced the Nakajima Ki-27 (code – named Nate by the Allies) and the Nakajima Ki-84 [Frank) for the company. Manshu would produce few of their own designs and only one ever saw service, the Ki-79
advanced trainer. Manshir’s main plant was located in Harbin in the Japanese puppet state of Manzhouguo. On learning of the Koku Hombu’s desire for new aircraft, Manshu sought to put together a proposal to meet the fighter requirement. The company assigned their two best men to the project, engineers Noda and Hayashi, and what resulted was an aircraft that was far from the conventional types Manshu had worked on in the past.

The aircraft was a single-engine fighter with a pusher, twin-boom configuration. The heart of the plane was to be a Mitsubishi Ha-211-III 18-cylinder, air-cooled radial engine fitted within the fuselage and behind the cockpit. The four-bladed propeller, situ­ated at the very rear of the fuselage, was dri­ven by a 2m (6.5ft) long extension shaft. In order to maintain a well streamlined airframe no air scoops were used; instead, flush inlets were fitted along the top of the fuselage behind the canopy. To increase the flow of air to the engine, a fan driven by the engine was installed. Flush outlets forward of the pro­peller completed the air circuit across the

engine. The thin wings were mounted low and on each wing was a boom that ended in an ovoid vertical stabiliser. A single, high mounted horizontal stabiliser connected the two tails.

A tricycle landing gear system was used, the nose gear retracting backwards into a wheel well that ran underneath the cockpit. Each of the two main wheels retracted into their respective tail booms. As the aircraft sat very high off the ground, the pilot had to access the cockpit via a hatch in the nose wheel well. If the pilot had to bail out, he had two choices. He could leave in a conventional fashion, but had to contend with both the twin tails and horizontal stabiliser along with the propeller. Manshift recommended that the pilot egress through the hatch out of the bottom of the air­craft. This method allowed the pilot to avoid being dashed on the tail but still had to con­tend with the propeller. Nevertheless, the chances of lowering the nose gear, sliding down and out through the hatch in a stricken plane were slim and Manshu were aware of this flaw in the design. The canopy was a bub­ble type that afforded an excellent field of view. For weapons, two Ho-5 20mm cannons and one Ho-204 37mm cannon were installed in the nose. Due to the short length of the fuse­lage, the barrels for the cannons, especially the Ho-204, protruded out from the nose.

Once the preliminary design for the fighter had been completed, Manshu submitted it to the Koku Hombu. Despite the unorthodox approach, it was accepted as the Ki-98 and work was allowed to proceed. Interestingly, the Koku Hombu rejected Tachikawa’s Ki-94-I that was similar in concept to the Ki-98. With approval in hand, the draft for the Ki-98 was finalised by July 1943. Work then commenced on a wooden mock-up that was completed in December. Design work con­tinued into the beginning of 1944 further refin­ing the Ki-98. A scale model of the aircraft were constructed and sent to Japan for wind tunnel testing at Rikugun Kokugijutsu Kenkyfjjo. Unfortunately for Manshu, the worsening war situation saw some of their personnel called into service or shifted to other departments and this, coupled with a plethora of design revisions, saw work on the Ki-98 slow down. Nevertheless, wind tunnel tests showed excellent results and Manshu began to make the preparations to construct the first prototype.

In the spring of 1944, the Koku Hombu instructed Rikugun Kokugijutsu Kenkyfijo to tell Manshtj that the Ki-98 should be adapted to serve as a high-altitude fighter. This they did, sending Manshu suggestions for design changes to the Ki-98 to make it suitable for the new role. On receiving the news Manshu had to substantially alter its initial design to meet the new demands. With strained manpower and resources, the mandated changes set the Ki-98 program further back and scuppered plans to build the prototype.

One of the most important changes was the need to fit an engine with a turbosupercharger resulting with the Ha-211-III being replaced by the Mitsubishi Ha-211 Ru which incorporated this feature. As the turbosupercharger was exhaust driven it required the appropriate additional piping, which, of course, was not originally included. The new engine was therefore larger than the original and this made it necessary for the fuselage to be lengthened and slightly widened. As the new propeller had a larger diameter, the twin booms had to be moved further apart to accommodate the blades and, by extension, the wings had to be reworked as well. Finally, the airframe had to be strengthened to support the heavier weight. Another alteration was to offer the pilot a more suitable way to bail out of the aircraft. Given the extreme difficulty in having to drop the nose wheel to gain access to the well hatch, the revised Ki-98 incorpo­rated explosive bolts that shed the tail unit to allow the pilot to exit more conventionally. The weapon fit remained unchanged.

With the new specifications in hand, the Ki-98 design was reworked and redrafted but it would not be until October 1944 that the redesign was completed to be followed by a mock-up of its revised fuselage. Manshu expected to have the first prototype finished and ready for flight testing by early 1945. These plans were dashed following a US bombing raid on Manshift’s Harbin factory on 7 December 1944. It was not until January 1945 when work commenced on the Ki-98. Despite Manshu attempts to increase the pace of construction work, progress still lagged.

At the start of August 1945, the fuselage, wings and the tail booms were completed and were ready to be assembled. However, on 8 August 1945, the Soviet Union declared war on Japan and initiated its invasion of Manzhouguo the next day. With the Manzhouguo Imperial Army and the Japan­ese Kwantung Army unable to stem the tide of Soviet forces, Manshu ordered all relevant documentation including models, mock-ups, jigs, tools and the incomplete Ki-98 to be destroyed to prevent the aircraft and informa­tion on it being captured by the Soviets.


Arkhangelskiy BSh (Russia), Saab 21 (Sweden), Vultee V.78 (US), Bel! XP-52 (US)

Performance specifications are estimates based on Manshu’s projections.


High Altitude Fighter




One Mitsubishi Ha-211 Ru 18-cylinder, air-cooled radial engine with a turbosupercharger developing 2,200hp for take-off, l,960hp at 2,000m/6,561ft and l,750hp at 8,500m/27,887ft driving a four-bladed,

metal, 3.6m/l 1.8ft diameter propeller





Length (total)



Boom length






Wing area



Wing loading


38.4 lb/ft2

Power loading











Max speed



at 10,000m

at 32,810ft


5 min 30 sec to 5,000m (16,404ft)



776 miles


2 hours 15 min at 499km/h (310mph)





One Ho-204 37mm cannon and two Ho-5 20mm cannons


None. The only prototype was never completed and was destroyed to prevent capture.

Подпись: RONNIE OLSTHOORNimage25image26


Mitsubishi Ki-73 – data


Consolidated Vultee XP-81 ‘Silver Bullet’ (US), North American P-5 ID ‘Mustang’ (US), Lavochkin La-11 (NATO codename Fang) (Russia), Westland Wyvem (UK)


Outside of the intended engine and the aircraft’s role, specifications on the Ki-73 are unknown


None. The Ki-73 never advanced past the concept stage.

In 1943, the Koku Hombu issued a specifica­tion for a fighter capable of operating for long distances in order to act as an escort for bomber formations. Despite the defensive weapons Japanese bombers carried, they were still vulnerable to interception. If a fighter had the extended range, it would be able to protect the bomber formations by being able to engage enemy interceptors and allow as many bombers as possible to survive and deliver their bomb loads. It was this desire that fuelled the Koku Hombu to issue their specification and from which Mitsubishi would build the aircraft to meet it.

Mitsubishi’s Tomio Kubo, along with engi­neers Kato, Sugiyama and Mizuno, began the investigation on how best to meet the specifi­cations. They settled on using a single engine design and the heart of it would be the Mit­subishi На-203-II engine. This was a 24-cylin­der, horizontal-H, liquid-cooled engine that was projected to generate 2,600hp. The На-203-II was chosen due to its horizontal-H configuration – in essence, two flat engines placed one on top of the other and geared together (a flat engine is one in which the pis­tons move horizontally). Each flat engine had its own crankshaft. Although horizontal-H engines have a poor power-to-weight ratio, they offer the advantage of being more com­pact, which made the На-203-II the ideal choice for the aircraft, now designated the Ki-73.

Unfortunately, Mitsubishi was having a very difficult time with the На-203-II. In fact, because of the relative complexity of the hor­
izontal-H design the engine experienced near constant problems during its development. Ultimately Mitsubishi was unable to over­come these difficulties and abandoned the На-203-II. Due to the delays and eventual can­cellation of the engine, Kubo’s Ki-73 design was abandoned even before he and his team could produce a mock-up, let alone a proto­type. Even though the Ki-73 went nowhere, Allied intelligence was aware of this new pro­ject. Information obtained from various sources, including captured documents, led intelligence officers to conclude that the Ki-73 would see service. As such, in 1944, the Ki-73 was assigned the codename Steve. As it was, no Allied pilot would ever encounter the Ki-73 in any form.

What Allied pilots might have encountered had the war gone on would have been the Mit­subishi Ki-83. Not discouraged by the Ki-73’s demise, Kubo would go on to design the twin – engine Ki-83 to meet Koku Hombu’s specifi­cation. The result was a highly capable aircraft that would have provided a challenge to Allied air power. However, only four Ki-83 proto­types were built before the end of the war.

Very little is known to show what the Ki-73 looked like. The artwork depicted for the Ki-73 in this book is based on an interpreta­tion of the Ki-73 printed in Richard Bueschel’s 1966 book Japanese Code Names. The illus­tration was based on the Ki-83 on the assumption that Tomio Kubo would have used aspects of the Ki-73 in the Ki-83. Steve is shown here in the markings and colours of the 101st Sentai.

Altitude is a major factor in an engine’s per­formance and, by extension, the aircraft as a whole. Known as density altitude, the higher the altitude, the less dense the air. The effects of this manifest themsleves in lower wing lift, a reduction in propeller efficiency and reduced horsepower output from the engine. As such, a plane that was not designed to operate in such conditions suffers accord­ingly. The Koku Hombu sought an answer to the problem and Nakajima looked to provide the solution. The result was the Ki-87.

In mid-1942, the Koku Hombu drew up a set of specifications for a high-altitude fighter. These called for a plane capable of operating at high altitude, heavily armed with a maxi­mum range of 3,000km (1,864 miles) and capable of 800km/h (497mph). Examination of the specifications called into question the viability of meeting such performance expec­tations. After deliberation, they were revised. The role remained the same but the speed requirement was dropped entirely to the point that no mention was made at all for a minimum or maximum speed. The range requirement was adjusted to one hour of loi­
ter flight time in addition to a half hour of combat flight time up to 800km/h (497 miles) from the airfield that the aircraft operated from. Finally, a heavy armament requirement called for two 30mm cannons and two 20mm cannons.

With these new specifications, Nakajima was contracted in November 1942 to produce three prototypes and seven pre-production aircraft for the IJA. The prototypes were to be completed between November 1944 and Jan­uary 1945 with the pre-production planes fin­ished between February and April 1945. The design of the Ki-87 was headed by Kunihiro Aoki.

Nakajima initially selected the Nakajima [Ha-44] 11 18-cylinder radial engine as the heart of the Ki-87. The [Ha-44] 21 (known also as the Ha-219 Ru) was also considered but the [Ha-44] 11 would be the engine used in the first prototype. Both engines were rated at 2,400hp and each used a turbosupercharger that would maintain and enhance the engine’s power output at altitude. A turbosu­percharger is an air compressor used to force air induction to the engine. It does this by
having a turbine and a compressor linked together via a shared axle. Engine exhaust spins the turbine which in turn spins the com­pressor which draws in outside air, com­presses it and then directs the air to the intake manifold of the engine. This compressed air, delivered at high pressure, results in more air reaching the cylinders for combustion. The net effect of this is that at higher altitudes where the air is thinner, the turbosuper­charger allows the engine to function as if it was at a lower altitude where the air is heav­ier and thus engine performance is not adversely affected. A benefit of this is that because the air is thinner at higher altitudes, there is less drag on the aircraft and since the turbosupercharger preserves the horsepower of the engine, overall speed is improved.

A sizable portion of the aircraft’s forward fuselage was taken up by the [Ha-44] 11 engine assembly and the large turbosuper­charger was fitted to the starboard side of the fuselage, just ahead of the cockpit. To cool the engine, a sixteen-bladed fan was mated to the four-bladed, constant speed propeller, turning at 150 per cent of the propeller speed.

The engine reduction gear ratio was set at 0.578. As the Ki-87 was designed for high alti­tude operation, the pilot was to be provided with a pressurised cockpit (though the proto­type was not equipped with one).

For weapons, Nakajima kept to the specifi­cations mounting a 20mm Ho-5 cannon in each wing root, synchronised to fire through the propeller, and a 30mm Ho-155 cannon in each wing to the outside of the main landing gear wheel wells. Ammunition was stored in the inner wing near the fuselage. Hydraulic pressure was used to load the cannons and they were fired by electrical triggers. If required, provision was made to carry a 250kg (551 lb) bomb or a drop tank along the centreline. Because of the heavy weapon fit and to ensure enough room for the self-seal – ing wing fuel tanks, Nakajima designed a landing gear arrangement that was rare in Japanese aircraft development – the main landing gear struts would retract backwards and the wheels would rotate 90° to fit flush into the wheel wells.

Given the task the Ki-87 had to perform, Nakajima provided a degree of protection for the pilot in the form of 66mm thick, bullet proof glass in the front of the canopy and back protection via armour plate 16mm thick. To extend the range of the Ki-87, two 300 litre (79 gallon) drop tanks could be fitted under each wing beside the landing gear wells. The pilot could jettison them via electrically controlled releases and these could be used in conjunc­tion with centreline payloads.

Подпись: MUNEO HOSAKAimage29


As work progressed on the Ki-87, the IJA saw fit to change the design by insisting that the turbosupercharger be placed in the rear of the fuselage beginning with the third pre – production Ki-87. Nakajima protested against

Подпись: MUNEO HOSAKAimage31

Contemporaries Sukhoi Su-1 (Russia)

Because the Ki-87 was not flown to its full ability, the performance statistics are estimates made by Nakajima.

Type High-Altitude Interceptor

Crew One

Powerplant One Nakajima [Ha-44] 11,18-cylinder, air-cooled radial developing 2,400hp for take-off, 2,200hp at l,500m/4,920ft, 2,050hp at 6,000m/l 9,685ft and 1,850hp at 10,500m/34,450ft and driving a constant speed, 4-bladed propeller










Wing area



Wing loading


44.3 lb/ft2

Power loading


5.2 lb/hp












Max speed



at 11,000m

at 36,090ft


2 hours


14 min 12 sec to 10,000m (32,810ft)






Two 30mm Ho-155 cannons, Two 20mm Ho-5 cannons and provision for one 551 lb bomb


None. Only one Ki-87 was completed and test flown with two others incomplete before the war ended.


Nakajima Ki-87 (FE-153)

This was the only Ki-87 to fly, having the serial 8701. Captured at the IJA air base at Chofu, the Ki-87 (nicknamed ‘Big Boy’ by the men who saw the large aircraft) was crated and shipped to the US, appearing on 10 March 1946 at MAMA Under restoration for the museum, the Ki-87 was soon moved to Park Ridge. However, after 1 May 1949 (the last written report documenting the aircraft) all trace of the Ki-87 disappeared, a likely victim of the cutter’s torch.

Nakajima Ki-87 (FE-155)

It has been surmised that FE-155 was, in fact, a typographical error made on a later report concerning FE-157 (see below). On the flip side, it may be that the FE-155 entry was a correction and that FE-157 as listed on the earlier report was designated in error. In either case, only two of the Ki-87 aircraft reached the US.

Nakajima Ki-87 (FE-157)

FE-157 was, most likely, the second of the two remaining Ki-87 prototypes found incomplete when the war ended. Listed as FE-157 on 10 March 1946 at MAMA, the plane would later reappear on a 1 August 1946 report as FE-155 and was located at the AOAMC in Newark, New Jersey.

No further trace of this Ki-87 exists after the August report and the aircraft was most probably scrapped.

the change but could do little to sway the IJA on the matter. In addition, the third prototype Ki-87 would have a reduction gear ratio set at 0.431 and the seventh pre-production Ki-87 was to feature a cooling fan that spun faster to facilitate enhanced engine cooling.

Despite the worsening war situation, Naka­jima was able to complete the first prototype, c/n 8701, by February 1945 rolling it out from their Ota Plant. Problems with the electrical system that operated the landing gear and dif­ficulties with the turbosupercharger delayed flight testing. It was not until April 1945 that the Ki-87 was able to take to the air. Due to the issues with the landing gear, Nakajima for­bade the test pilot from retracting the main gear lest it fail in the up position, thereby dam­aging or destroying the Ki-87 with the resul­tant belly landing. This, however, prevented any chance of a thorough evaluation of the Ki-87’s top speed and full manoeuvrability. Consequently, there was no attempt to mon­itor and collect performance data. During the five flights the prototype did make, the pilot
reported good handling characteristics and it was thought that the Ki-87 was superior in comparison to the Nakajima Ki-84 Hayate (Gale).

Even as testing of the Ki-87 was underway with work continuing to meet the IJA turbo­supercharger position requirement, Naka­jima designers developed the Ki-87-II. Replacing the [Ha-44] 11 would be the Naka­jima [Ha-46] 11 (known also as the Ha-219) that could provide 3,000hp. The turbosuper­charger was situated in the belly of the fuse­lage as demanded by the IJA. Performance estimates showed a 4 per cent increase in speed compared to the Ki-87.

Ultimately, the Ki-87’s design team failed to overcome the problems with its engine. Because they were unable to solve difficulties with both the turbosupercharger and the [Ha-44] 11 as well as the temperamental land­ing gear system, the Ki-87 would make no more test flights. When hostilities ceased the other two prototypes remained incomplete and the Ki-87-II was still on the drawing board.



By 1945, Japan was reeling from one defeat after another in the face of the Allied advance. With the possibility of an Allied invasion looming in the minds of Japanese military leaders and planners, several means to repel the invaders were considered, investigated, and in some cases, allowed to proceed towards a finalisation. One of the ideas devel­oped was to use aircraft for shimbu (suicide) missions against the invasion fleet. Airworthy aircraft of any type were to be thrown against Allied shipping. In order for the missions to succeed, wave attacks were envisioned, involving scores of aircraft. Sheer numbers would ensure successful hits on naval ships and landing craft even in the face of heavy anti-aircraft fire and combat air patrols. Even one aircraft that struck a ship had the poten­tial to cause significant damage. Such mass attacks, however, led to the conclusion that the available pool of aircraft would quickly be depleted. Thus, it was clear that an airplane had to be designed that could be built rapidly to swell the number of aircraft available for these shimpu missions. It was Nakajima that would provide one answer.

On 20 January 1945, the 1JA issued specifi­cations for an aircraft that could be built by semi-skilled labour, would use very few war critical materials, had the ability to accept any radial engine with a 800hp to 1,300hp rating, was easy to maintain in the field, was able to carry at least one bomb and had a maximum speed of at least 340km/h (211mph) with landing gear and 515km/h (320mph) without landing gear. Nakajima was tasked with mak­ing the specifications a reality and engineer Aori Kunihiro was assigned the project. Kuni – hiro would have assistance from the Mitaka Kenkyujo (Mitaka Research Institute) and Ota Seisakusho K. K. (Ota Manufacturing Co Ltd).

Because semi-skilled workers would be used to build Kunihiro’s aircraft, the Ki-115 Ко was simplicity itself. The fuselage used a steel
structure with steel panelling and centre sec­tions with tin used for the engine cowling. The tail was made of wood with fabric cover­ing while the slightly swept wings were of metal with stressed skinning on the outer wing surfaces. The И-115 Ко could accept a variety of radial engines and to simplify the installation only four bolts were used to secure the engine to the fuselage. The Naka­jima [Ha-35] 23 (Ha-25) radial engine was used on the prototype Ki-115 Ко and would be found on the subsequent production air­craft. The pilot was provided with an open cockpit with simple instruments and con­trols. A crude aiming sight was provided as well. The landing gear could be jettisoned after take-off, had no suspension outside of the balloon tyres and was made out of pipes. For weapons, the Ki-115 Ко carried only a sin­gle bomb and this was held in a recess under the fuselage between the wings. The heaviest bomb that could be carried weighed 800kg (1,7641b) and the bomb had no provision for release from the cockpit.

In March 1945, the prototype of the Ki-115 Ко, called the Tsurugi (which means ‘sword’ or ‘sabre’), was rolled out and flight testing commenced. As soon as the trials had started problems began to surface. The landing gear contributed to poor ground handling and this was compounded by the poor view afforded the pilot. Once in the air, the flight character­istics of the Ki-115 Ко were anything but stel­lar and even skilled test pilots had some difficulty in flying the aircraft, let alone a pilot with minimal training. Nevertheless, given the mission of the Ki-115, flight trials contin­ued while modifications were investigated to improve the aircraft. By June 1945, the initial flight testing was completed. Two further changes were made to the Ki-115 Ко and this involved adding suspension to the landing gear and including auxiliary flaps to the inboard trailing edge of the wings. Production
models of the Ki-115 were to be fitted with two solid-fuel rockets, one under each wing. The purpose of the rockets was to boost the speed of the aircraft during the final, terminal dive on the target. With the Ki-115 Ко deemed acceptable, Nakajima began production of the Tsurugi at both their Iwate and Ota plants. The IJA anticipated that 8,000 aircraft per month would be assembled from production lines scattered throughout Japan.

Even with production underway, steps were being taken to further simplify the Ki-115. To save on precious metals, the wings of the Ki-115 Ко would be replaced with wooden versions and the wing area increased. To better address pilot vision, the cockpit would be moved forwards. The ver­sion of the Tsurugi was to be designated the Ki-115 Otsu. A variation of the Ki-115 Ко was the Ki-115-III (also known as the Ki-115 Hei). The only two modifications was the provision of a bomb release and cockpit being moved even further forwards. But even these models would not be the end because the Ki-230, a further development of the Ki-115, was also investigated.

The UN, having learned of the new plane, became interested in the Ki-115 and sought to produce it for themselves. To facilitate this, Nakajima provided Showa Hikoki K. K. (Showa Aeroplane Co Ltd) with two Ki-115 Ко aircraft. In UN service, the aircraft was to be called the Toka, meaning Wisteria. Showa was to adapt the design to accept any num­ber of UN radial engines from older, refur­bished motors to ones then in current service.

By the time the war ended, Nakajima had only been able to produce 104 of the Ki-115 Ко (22 from the Iwate plant and 82 from the Ota plant) and none would be used in anger. Neither the Ki-115 Otsu, КІ-115-ІІІ or the Ki-230 would be constructed, remaining for­ever as design board projects. Likewise, Showa had no time to produce the Toka.



Nakajima Ki-115 Ко Tsurugi (FE-156)

One of four captured at Nakajima’s No. l plant in Ota, Gunma Prefecture, this Ki-115 Ко (serial 1002) was listed on the MAMA 1 August 1946 report as being in storage and was moved to Park Ridge in September 1949. Lucky enough to survive the scrap heap, the Ki-115 Ко is currently in storage, unrestored and in poor condition at the Paul. E. Garber facility in Suitland-Silver Hill, Maryland (pictured left).

Nakajima Ki-115 Ко

Apparently another surviving Ki-115 Ко is being restored in Japan but there are few, if any details, on who is restoring the aircraft nor the history of the Ki-115 involved.

In 1991, two other Ki-115 aircraft were reported to be found in Japan, one in Kanda and the other in Koganei. Who has them and in what condition is neither known nor confirmed.

Nakajima Ki-230 – data (estimated)


Span Length Height Wing area

















Max speed



at 2,800m

at 9,185ft



745 miles




The Ki-201 depicted here sports the colours of the 244th Sentai, one of the more successful Japanese home defence air units.

As a result of the development of the Naka­jima Kitsuka for the UN, Japan’s first turbojet – powered aircraft to fly (see Page 114), Nakajima was in the position of being the leader in the fledgling jet aircraft field. Seek­ing to expand on that position, Nakajima took it upon themselves to offer a jet that would be superior to the Kitsuka. This was to make the most of what little data was received from Germany on the Messerschmitt Me 262. With the Kitsuka under development for the UN, Nakajima provided the IJA with their proposal for what was to be the definitive Japanese version of the Me 262, the Ki-201 Karyu, the Fire Dragon.

Depending on the source, the IJA was or was not interested in developing its own jet aircraft. However, evidence supports the fact that the IJA wished to have its own jet-pow­ered fighter or was looking to have an option should the Ki-202 and fighter variant of the Kitsuka not meet their expectations. In Octo­ber 1944, the Japanese embassy informed the Germans that the IJA would be the producer
of the Me 262 and requested reports and pro­jections for the production of 100 and 500 air­craft a month. It was known that the wartime manufacturing capability of Japan could not produce an exact copy of the Me 262 and adaptations would have to be made to accommodate Japanese capabilities. Naka­jima sought to provide that answer.

The genesis of the Ki-201 took place on 12 January 1945 with the formation of the design team led by Nakajima engineer Iwao Shibuya. Unlike the Kitsuka project, from the outset Shibuya designed the Karyu as a fighter. In addition, Shibuya realised that the aerodynamics of the Me 262 had been tested and felt assured that by applying as much of the design of the Me 262 into the Karyu as was possible would result in an aircraft that would need minimal testing before production was started. This idea was shown to good effect in the development of the Mitsubishi J8M Syusui.

Shibuya had the same access to the Me 262 information as the UN. It consisted of sketches

Imperial Japanese Army



Messerschmitt Me 262A-la (Germany), Avia S-92

Turbina (Czechoslovakia)






Two Ne 230 axial-flow turbojets rated at 885kg (1,951 lb) of static thrust each; later, two Ne 130 axial-flow turbojets rated at 908kg (2,0021b) of

static thrust each











Wing area














Max speed



(Ne 230) at 10,000m

at 32,808ft



(Ne 130) at 10,000m

at 32,808ft

Landing speed


1 OOmph

Max dive speed



Take-off distance


3,100ft loaded


5,209ft in overload

Range at 60% thrust


613 miles

at 7,995m

at 26,230ft

Fuel capacity

2,200 to 2,590 litres 560 to 684 gallons


(Ne230) 6 min 54 sec to 6,000m (19,685ft) (Ne 130) 6 min 17 sec to 6,000m (19,685ft) (Ne 230) 14 min 56 sec to 10,000m (32,808ft) (Ne 130) 13 min 15 sec to 10,000m (32,808ft)





Two Но-155-II 30mm cannons and two Ho-5 20mm cannons; one 1,763 lb bomb or one 1,102 lb bomb; proposed Navy version to be fitted with two Type 5 30mm cannons and two Type 99 20mm cannons


None. The prototype Ki-201 was incomplete by the close of the war.

and drawings of the Me 262A-1 and little else. Whereas the Kitsuka only bore a superficial resemblance to the Me 262, Shibuya’s design would seek to match the Me 262 as much as possible. Shibuya and his team may have had little, if any, contact with the Kitsuka develop­ers despite being in the same company. The first draft of the Karyu nearly matched the dimensions of the Me 262. However, it fea­tured a straight wing as opposed to the swept wing of the German jet. This was quickly changed and the revised Кагуй was larger and heavier than the Me 262, but replaced the straight wing with a gently swept wing.

Initial design work, including wind tunnel testing, was completed in June 1945. For all intents and purposes, the Ki-201 was a larger derivative of the Me 262. That it was bigger and heavier than the German jet may point to adaptations the Japanese had to make in order to produce the Кагуй. For example, the Japanese did not have the experienced fabri­cators to make the thin, sheet steel used in the nose of the Me 262. The result was that the KaryO’s nose had to make do with duralumin which was heavier. In addition, it is certain that the Кагуй incorporated simplifications to accommodate production by semi-skilled labour and construction using less critical war materials. The latter was borne out by the intense interest by the Japanese in obtaining the German process for making plywood (and likely the bonding glues as well) which the Germans used in their aviation industry because, although Japan was lacking in avia­tion metals by the close of the war, they had ample access to wood.

The Кагуй was initially slated to be fitted with Ne 230 axial-flow turbojet engines each rated at 85kg (1,951 lb) thrust. These were cal­culated to push the Кагуй at a maximum speed of 812km/h (504mph). However, it was also planned that once they became avail­able, the Ne230 engines would be switched for the improved Ne 130 axial-flow turbojets. Projected to produce 908kg (2,001 lb) of thrust each, the calculated speed of the Кагуй with the Ne 130s was a maximum 852km/h (529mph).

For armament, the Кагуй was fitted with two Ho-155-11 30mm cannons and two Ho-5 20mm cannons. On the chance that the UN might acquire the Ki-201, provision was also made to use two Type 5 30mm cannons and two Type 99 20mm cannons. More notable was that the Кагуй was slated to be equipped with the Ta-Ki 15 airborne intercept radar. Used in conjunction with the Ta-Chi 13 ground control radar, the Кагуй could be guided to its targets by ground controllers with a 153km (95 mile) radius. Such a system would have been a benefit in low-light, night or poor flying weather interceptions. In addi­tion to the cannon fits, the Кагуй was to be capable of carrying a 800kg (1,7631b) or 500kg (1,1021b) bomb.

With the initial progress of the UN’s J8M SyCisui program, which would provide the IJA with the Ki-200 and the subsequent IJA Ki-202 SyOsui-kai project, IJA interest in the Ki-201 looked to have waned. The result was delays in further developing the Кагуй. Nakajima wanted to have the final design of the Ki-201 completed by July 1945 with more advanced testing underway by August. The first proto­type of the Кагуй was to be completed and ready for flight trails by December 1945, and in addition, a further 18 examples of the Ki-201 were to be built and delivered by March 1946.

Despite the delays, work commenced on the prototype. Nakajima’s Mitaka plant, which was located on the western edge of Tokyo, was the facility for the prototype Ki-201’s constmction. Regular production of the Ki-201 was intended to be carried out at the Kurosawajiri Research Works No.21 situ­ated near Kitakami, in Iwate Prefecture, in Honshfl. The fuselage for the Кагуй was nearly complete when Japan surrendered on 15 August 1945. With the surrender, work on the Ki-201 ceased. It would be nearly 30 years before the next Japanese designed and built jet fighter would fly, this being the Mitsubishi F-l which first flew on 3 June 1975.

At the time the Ki-93 was conceived the war situation for Japan was dire. The mainland was suffering from near daily B-29 raids and looming on the horizon was the anticipated US invasion of Japan. A means to counter the B-29s as well as to attack Allied invasion ships was needed. The resulting Ki-93 would be a first and a last for Rikugun and Japan.

When Rikugun Kokugijutsu Kenkytijo began the design research for the Ki-93, the goal was to provide an aircraft that could pro­vide a platform for anti-bomber operations and anti-shipping missions. In both cases the aircraft had to be able to absorb damage when flying in the face of interceptors, the defensive machine guns of the bombers, and the anti-aircraft weapons of ships.

Two versions of the all-metal Ki-93 were to be constructed. The first, the Ki-93-I Ко, was the heavy fighter that would combat bombers. The second was the Ki-93-I Otsu and this was the anti-shipping model. The Mitsubishi Ha-211 radial engine was consid­
ered at first to power the Ki-93 but both mod­els were ultimately powered by two Mit­subishi Ha-214 18-cylinder, air-cooled radial engines, each providing a maximum of 2,400hp. In order to give the aircraft a mea­sure of survivability in the face of enemy fire, armour plating was used. The pilot was pro­vided with five armour plates, each 12mm thick. Two plates were placed just forward of the cockpit in the nose, one on each side of the pilot and the fifth would protect his back. The front glazing was composed of 70mm thick bullet proof glass. The rear gunner was also protected by a 12mm armour plate, offer­ing defence from rounds being fired at the Ki-93 from behind. Likewise, the fuselage fuel tanks were given a measure of protection from incoming fire via an 8mm thick armour plate. Each engine was also provided with armour plating in the nacelles. Should the armour protecting the fuel tanks be pene­trated, each tank was self-sealing and, to prevent fuel fires, had an automatic fire



Henschel Hs 129B-3/Wa (Germany), Messerschmitt Me410A-l/U4 (Germany), Tupolev ANT-46 (Russia), North American B-25G Mitchell (US), Bell YFM-1 Airacuda (US), Curtiss XP-71 (US), de Havilland Mosquito FBMMVIII (UK)

Type Heavy Fighter (Ki-93-1 Ко) and

Ground Attack Aircraft (Ki-93-1 Otsu) Crew Two


Two Mitsubishi Ha-214,18-cylinder, air-cooled radials, developing 2,400hp for take-off, l,970hp at l,500m/4,920ft and l,730hp at 8,452m/27,729ft; each engine drove a 6-bladed, metal propeller











Wing area



Wing loading



Power loading


4.9 lb/hp







23,501 lb


Max speed



at 8,300m

at 27,230ft

Cruise speed





1,864 miles


6 hours


4 min 18 sec to 3,000m (9,840ft)

9 min 3 sec to 6,000m (19,685ft)





One 57mm Ho-401 cannon with 20 rounds of ammunition, two 20mm Ho-5 cannons with 300 rounds of ammunition per gun and one 12.7mm Ho-103 machine gun with 400 rounds of ammunition (Ki-93-I Ко); One 75mm Type 88 cannon, one 12.7mm Ho-103 machine gun and two 250kg (551 lb) bombs (Ki-93-1 Otsu)


None. Two Ki-93 prototypes (one of each version) were produced but did not enter production before the end of the war.

extinguishing system. Finally, a defensive armament, consisting of a single 12.7mm Ho-103 machine gun was Fitted in a rear firing position to be operated by the second crew­man.

The difference in the two versions was in the offensive weapon fits, both mounted in ventral gondolas. The Ki-93-1 Ко was equipped with a powerful 57mm Ho-401 can­non and this was backed up by two 20mm Ho-5 cannons (although one initial design did away with the two Ho-5 cannons and used a single 37mm cannon with 40 rounds of ammunition). It was anticipated that the Ho-401 cannon would inflict enough damage with a single hit to cripple or shoot down a B-29. The Ho-401 could fire 90 rounds per minute with a muzzle velocity of 518.2m/sec (l,700ft/sec). For the Ki-93-1 Otsu, the large 75mm Type 88 cannon was fitted. The weapon was an adaptation of the Type 88 anti-aircraft gun that had been modified for use on aircraft. Besides the Ki-93, this weapon was also used operationally in the

Mitsubishi Ki-109 (flown by the 107th Sentai). The Type 88 had to be hand loaded by the second crewman. In addition to the cannon the Ki-93-I Otsu would carry two 250kg (551 lb) bombs.

Rikugun had Dai-Ichi Rikugun Kokusho, located in Tachikawa (which is about 24 miles from the centre of Tokyo), construct the Ki-93. The first prototype in the Ki-93-1 Ко con­figuration was completed by April 1945. In the same month the aircraft successfully took to the air making it the first Rikugun aircraft to be built and flown. However, further flight testing was hampered by the war situation, so much so that the test program was never com­pleted. Despite the worsening conditions in Japan and delays with the flights of the first prototype the second aircraft in the Ki-93-I Otsu configuration was completed. However, it would never fly.

With the surrender of Japan, the Ki-93 would become the last heavy fighter and ground attack aircraft to be built during the war.


The IJA was not satisfied with the Ki-200 (the IJA designation for the Mitsubishi J8M1 Syusui – See Page 96). They felt that the UN’s plans to adopt and adapt the Messerschmitt МеІбЗВ as the J8M1 would amount to the same, if not more, effort and development compared to creating a new design based on, but not a direct adaptation of, the Me 163B. Although the IJA attempted to make the IJN see their point – of-view, the IJN pushed aside such plans, forg­ing ahead with their J8M program. Thus, the IJA took it upon themselves to design the bet­ter aircraft they had wanted from the outset.

The IJA saw a main flaw in the Ki-200 that resulted in aspects of the plane’s performance that they found unacceptable: the limited fuel capacity. Because of this, combat endurance was reduced and fuel was rapidly consumed by the KR10 (Toku-Ro 2) engine. Even with the UN’s proposed J8M2, which removed a Type 5 30mm cannon to make way for more fuel, the IJA felt that the endurance was still insufficient. Starting in 1945, Rikugun Kokugijitsu Kenkyujo began the process of developing the IJA’s own rocket aircraft using the Me 163B as a template. This development was in secret and the desig­nation given to the aircraft was the Ki-202 Sytisui-Kai which meant ‘Autumn Water – Improved’.

The IJA took the obvious route and increased the fuel capacity by stretching the fuselage to make room for larger fuel tanks. They also planned to use an improved motor, but exactly what power plant depends on which source is referred to. Two main options appear. One was the KR10 as used in the Ki-200 that developed 1,500kg (3,3061b) of thrust, but with a secondary rocket added pro­viding a further 400kg (881 lb) of thrust. The other motor was the KR20, which may also be known as the Mitsubishi Toku-Ro.3. The KR20 promised 2,000kg (4,409 lb) of total thrust and may have been fitted with a cruise chamber. This is a secondary combustion chamber which was typically mounted above or below the main combustion chamber. The purpose of having two such chambers is that the main one (or both if necessary) can be used for full power needs such as take-off and rapid ascent, while the cruise chamber has a lower thrust output and can be employed for normal cruise speeds once the plane is aloft and the main chamber shut off. The benefit of this is the conservation of fuel, allowing the plane to remain airborne and in action longer. Wartime Allied intelligence reports stated that the Germans had provided data to the Japan­ese on the Walther HWK 509C rocket motor which used a cruise chamber. If this was so, then the KR20 was most likely the Japanese development of the HWK 509C motor and the answer the IJA was looking for in extending the range of the Ki-202. Contemporary illustra­tions of the Ki-202 clearly show some form of a secondary means of thrust. As a stop-gap measure, the Ki-202 could have accepted the KR10 motor if problems arose with the devel­opment and production of the KR20 and thus any delays in flight testing could have been avoided.

Although the Ki-202 was larger than the Ki-200, no attempt was made to include a landing gear system. Like the Ki-200, the Ki-202 retained a central landing skid, tail wheel and would use the jettisonable wheeled dolly for take-off and ground han­dling. No provision for catapult launching is known to have been considered as a means to conserve fuel that would have been con­sumed during normal take-off procedures.

For weapons, the Ki-202 was slated to use two Ho-155 30mm cannons, one mounted in the each wing root, the same as the Ki-200.

Insofar as the larger size and motor, the Ki-202 was estimated to have an endurance of 10 minutes and 28 seconds, whereby the Ki-202 was calculated to achieve 5 minutes and 30 seconds. With a near doubling of the endurance time, this would have allowed the Ki-202 to remain in combat for a longer period or, at the least, extend its operational radius. It was projected that the final design of the Ki-202 would be completed by February 1945 with construction of the first prototype com­mencing shortly afterwards. The first test flight was scheduled for August 1945.

As it was, the Ki-202 design would remain just that, a design. When the war ended, no metal had been cut on the Ki-202 prototype nor was a mock-up even constructed. In part, the Ki-202 program may have hinged on the success or failure of the J8M1. The technical issues in producing the KR10 in a reliable form most likely stymied work on the KR20, which was to be the main powerplant for the Ki-202. The problems with the KR10 delayed flight testing of the J8M1 until July 1945 and even then, a fuel system failure caused the crash of the Syusui during its maiden flight. This set back the J8M1 further still and although the fuel system problem was corrected, the war ended before any further flights could be made. Had the J8M1 succeeded and the IJA version, the Ki-200, entered service, it is likely development of the Ki-202 would have rapidly proceeded and had it succeeded, the IJA would have offered it to the UN. If accepted, the designation would have been the J8M3.


Messerschmitt Me 163C-la (Germany)

Type Interceptor/Fighter

Crew One

Powerplant (planned)

One Toku-Ro.3 (KR20) bi-fuel rocket motor producing 2,000kg (4,409 lb) of thrust with supplementary rocket or cruise chamber producing 400kg (8801b) of thmst











Wing area



Wing loading










Maximum loaded



Performance (estimated by Rikugun)

Max speed



at 10,000m

at 32,808ft

Landing speed




10 min 28 sec of endurance


1 min 21 sec to 2,000m (6,561ft)

2 min 0 sec to 4,000m (13,123ft)

2 min 34 sec to 6,000m (19,685ft)

3 min 2 sec to 8,000m (26,246ft)

3 min 26 sec to 10,000m (32,808ft)





Two Ho-155 30mm cannon


None. The Ki-202 did not advance beyond the design board.