Category JAPANESE SECRET PROJECTS

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.

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.

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.

Contemporaries

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. Type Glider (Ku-6) Powerplant None

Dimensions
Span	21.97m	72.1ft
Length	14.96m	41.9ft
Height	2.98m	9.8ft
Wing area	59.99m2	645.83ft2
Weights
Loaded (with the So-Ra)	4,200kg	9,2591b
Performance
Max glide speed	174km/h	108mph
Armament	None

Type Tankette (So-Ra) Crew Two

Powerplant One 4-cylinder, air-cooled, gasoline engine developing 50hp at 2,400rp Dimensions Width Length Height 1.43m 4.05m 1.88m 4.7ft 13.3ft 6.2ft Weights Loaded 2,900kg 6,3931b Performance Max speed 42km/h 26mph Armament One 37mm cannon, machine gun or flamethrower Armour Unknown Deployment 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.

Contemporaries Arkhangelskiy BSh (Russia), Saab 21 (Sweden), Vultee V.78 (US), Bel! XP-52 (US) Performance specifications are estimates based on Manshu’s projections. Type High Altitude Fighter Crew One Powerplant 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 Dimensions Span 11.24m 36.9ft Length (total) 11.39m 37.4ft Boom length 8.26m 27.1ft Height 4.29m 14.1ft Wing area 23.99m 258.3ft2 Wing loading 187.48kg/m2 38.4 lb/ft2 Power loading 2.72kg/hp 61b/hp Weights Empty 3,500kg 7,7161b Loaded 4,500kg 9,9201b Performance Max speed 731km/h 454mph at 10,000m at 32,810ft Climb 5 min 30 sec to 5,000m (16,404ft) Range 1,249km 776 miles Endurance 2 hours 15 min at 499km/h (310mph) Ceiling 10,000m 32,808ft Armament One Ho-204 37mm cannon and two Ho-5 20mm cannons Deployment None. The only prototype was never completed and was destroyed to prevent capture.

Mitsubishi Ki-73 – data

Contemporaries

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

Specifications

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

Deployment

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.

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

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

Span	13.41m	44.0ft
Length	11.79m	38.7ft
Height	4.48m	14.7ft
Wing area	25.99m!	279.8ft2
Wing loading	216.29kg/m!	44.3 lb/ft2
Power loading	2.35kg/hp	5.2 lb/hp
Weights
Empty	4,387kg	9,6721b
Loaded	5,632kg	12,4161b
Maximum	6,100kg	13,4481b
Performance
Max speed	707km/h	439mph
	at 11,000m	at 36,090ft
Endurance	2 hours
Climb	14 min 12 sec to 10,000m (32,810ft)
Ceiling	12,855m	42,175ft

Dimensions

Armament

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

Deployment

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

Survivors

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.

PHOTOGRAPHS BY TIM HORTMAN

Survivors

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)

Dimensions Span Length Height Wing area	39.69m 8.47m 3.29m 13.09m2	1.8ft 27.8ft 10.8ft 141.0ft2
Weights
Empty	1,700kg	3,7471b
Loaded	2,400kg	5,2911b
Performance
Max speed	557km/h	346mph
	at 2,800m	at 9,185ft
Range	1,199km	745 miles
Ceiling	6,500m	21,325ft

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

DANIEL UHR

Contemporaries	Messerschmitt Me 262A-la (Germany), Avia S-92
Turbina (Czechoslovakia)
Type	Fighter
Crew	One
Powerplant
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
Dimensions
Span	13.68m	44.9ft
Length	11.49m	37.7ft
Height	4.05m	13.3ft
Wing area	23.96m2	258ft2
Weights
Empty	4,495kg	9,9101b
Loaded	7,021kg	15,4781b
Overload	8,492kg	18,7221b
Performance Max speed	812km/h	504mph
	(Ne 230) at 10,000m	at 32,808ft
	845km/h	525mph
	(Ne 130) at 10,000m	at 32,808ft
Landing speed	161knVh	1 OOmph
Max dive speed	l,006km/h	625mph
Take-off distance	945m	3,100ft loaded
	1,588m	5,209ft in overload
Range at 60% thrust	987km	613 miles
	at 7,995m	at 26,230ft
Fuel capacity	2,200 to 2,590 litres 560 to 684 gallons
Climb	(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)
Ceiling	12,000m	39,370ft
Armament
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
Deployment
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

MUNEO HOSAKA

Contemporaries

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

Powerplant 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 Dimensions Span 18.98m 62.3ft Length 14.20m 46.6ft Height 4.84m 15.911 Wing area 54.74m! 589.3ft2 Wing loading 184.80kg/m2 39.9lb/ff Power loading 2.22kg/hp 4.9 lb/hp Weights Empty 7,686kg 16,9451b Loaded 10,660kg 23,501 lb Performance Max speed 625km/h 388mph at 8,300m at 27,230ft Cruise speed 350km/h 217mph Range 3,000km 1,864 miles Endurance 6 hours Climb 4 min 18 sec to 3,000m (9,840ft) 9 min 3 sec to 6,000m (19,685ft) Ceiling 12,049m 39,530ft Armament 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)

Deployment

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.

DANIEL UHR

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.

Contemporaries

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 Dimensions Span 9.72m 31.9ft Length 7.68m 25.2ft Height 2.74m 9ft Wing area 18.39m! 198ft2 Wing loading 272.43kg/m2 55.81b/ft2 Weights Empty 1,619kg 3,5691b Loaded 3,384kg 7,4601b Maximum loaded 5,015kg 11,0571b Performance (estimated by Rikugun) Max speed 900km/h 559mph at 10,000m at 32,808ft Landing speed 132km/h 82mph Range 10 min 28 sec of endurance Climb 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) Ceiling 12,000m 39,370ft Armament Two Ho-155 30mm cannon

Deployment

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

The Funryu (‘Raging Dragon’) was the name given to the UN’s missile program that com­menced in 1943. The initial study for the Fun­ryu was conducted by the Kaigun Gijyutsu Kenkyujyo (Navy Technology Laboratory) but three other groups would review the study soon afterwards and they were the Dai-Ichi Kaigun Koku Gijutsu-sho, Dai-Ni Kayaku-Sho (2nd Bureau of Gunpowder) and the Kure Kosho (Kure Arsenal). Ultimately, it would be Kugisho that was given the Funryu project in early 1944. To accomplish the task, Kugisho formed the Funshin Kenkyu-Bu (Rocket Research Bureau) and was staffed with up to 200 technicians led by a research team made up of 40 officers (all engineers and/or techni­cians) from the UN. In all, Kugisho would investigate and put forward four Funryu designs.

The first was the Funryu 1 and the design was an air-to-surface missile (ASM) whose specific role was anti-shipping. Funryu 1 was much like a miniature airplane. The warhead contained 8821b of explosive and guidance was via radio control. Testing of the Funryu 1 was conducted with the missile being dropped from a modified Mitsubishi G4M bomber. However, it was seen that the means to effectively control the missile in flight would require a significant amount of time to perfect and with the increase in US bombing raids against Japan, it was decided that efforts should be directed towards sur – face-to-air missiles (SAMs). Thus, the Funryu 1 was shelved and was to be the only ASM of the Funryu family.

The Funryu 2 was to be a SAM built around a solid fuel rocket using a radio guidance system. Despite three rocket motors being available already (the Ro-Tsu, Ro-Sa and Ro-Ta), it was decided that a new motor was required. This motor was capable of produc­ing 2,400kg (5,291 lb) of thrust during its 3.5 second burn time. The shape of the missile was relatively simple. Four wooden wings were fitted to the body of the missile and each was equipped with an elevon (elevons con­trol both pitch and roll). Four fins, making up the tail, were fitted to the outside of the noz­zle for the motor. This final shape and config­uration was a result of numerous tests of various missile bodies and wing/fm arrange­ments in a wind tunnel. The radio guidance system was initially to consist of a single transmitter but a second was fitted to ensure a measure of accuracy. The first transmitter was used for target detection while the sec­ond would control and steer the missile to the target. To maintain attitude, the Funryu 2 con­tained two gyrocompasses and 50kg (1101b) of explosive was housed in the nose. The basic operation consisted of the Funryu 2 being launched from a rail set at an angle of 80°. Once launched, radio receivers fitted in the wings would receive signals from the ground transmitter, steering the missile onto the target.

The war situation in 1944 was starving Japan of critical war materials and KQgisho found they were unable to obtain the neces­sary quantity of duralumin to build the Funryu 2 prototypes. It took theft from a warehouse to obtain the required metals. Using the absconded material, a number of Funryu 2 missiles were constructed with one being used for continued wind tunnel testing and the remainder used for actual field tests, the latter being conducted near Mount Asama (located near Ueda). Testing commenced in the spring of 1945. The first launches of the Funryu 2 were unguided, conducted solely to evaluate the rocket motor performance and the general flight characteristics of the mis­sile. In July 1945, the first test of the Funryu 2 was undertaken using the radio guidance sys­tem. With UN personnel in attendance, the Funryu 2 successfully lifted off from the launch rail and was directed towards a ground target. Using the radio signals, the Funryu 2 was guided to within 20m (65ft) of the target when impact was made. Although a direct hit was not achieved, the test was considered a success. It was to be, however, the last flight of the Funryu 2 because the war ended before any further launches could be made.

The Funryu 2 was 2.2m (7.2ft) long, ,28m (0.9ft) in diameter and had a span of.88m (2.9ft). Total launch weight of the missile was 370kg (8161b) and its maximum ceiling was 5,000m (16,404ft). The maximum speed of the missile at full burn was 845km/h (525mph).

Even as the Funryu 2 was being investi­gated, a variant of the missile, the Funryu 3, was proposed using a liquid fuel rocket in place of the solid fuel motor. However, initial discussions on the new rocket engine led to the conclusion that there was no time or resources available to study, design, con­struct and test such a propulsion method. As such, the Funryu 3 was shelved.

With the commencement of flight testing of the Funryu 2, work got underway on another SAM that was to be far more advanced. This missile was designated the Funryu 4. Design work was carried out by engineers from Mitsubishi and from the Air­craft Equipment Factory of Tokyo, all based in a facility in the Izu Peninsula, west of Tokyo. The Funryu 4 was to be built around the Toko Ro.2 (KR10) rocket engine, the very same engine used in the Mitsubishi J8M Svusui rocket fighter. As testing of the Toko Ro.2 was already underway and would soon be put into production, Mitsubishi could devote less time to engine concerns. The Funryu 4 was to use a mixture of the Ко fuels (concentrated hydrogen peroxide) and Otsu (hydrazine hydrate solution in methyl alcohol) as used by the J8M. The engine would provide up to 1,500kg (3,307 lb) of thrust and move the Fun­ryu 4 to a maximum speed of l,099km/h (683mph).

The guidance system selected for the Fun­ryu 4 was far more sophisticated than that used in the Funryu 2. Whereas the latter relied on radio, the Funryu 4 would use radar. Two stations would be used to deliver the Funryu 4 to the target. One station would track the target while the second would track and control the missile. The intention was that the two radar signals would coincide on the target, thus bringing the missile to impact. To control the missile, a radio signal of 1,000MHz was to be used with five frequen­cies. Each frequency corresponded to con­trolling the pitch and the roll with the fifth being the detonation command. A variation of this system is used today known at retrans­mission homing or Track-via-Missile (TVM).

Funryu 4, like the Funryu 2, used two gyro­compasses and carried wing radio receivers for the commands sent to it from the ground. It carried a far heavier warhead of 200kg (4401b) in comparison to the 50kg (1101b) warhead of the Funryu 2. The shape of the Funryu 4 was also more streamlined and it only had two of the elevon-equipped wings and two tail fins. Launch would occur from a rail set at a 45° angle.

The Funryu 4 was 4.0m (13.1ft) long, .6m (1.9ft) in diameter and its span was approxi­mately,8m (2.5ft). Fully loaded its weight was 1,900kg (4,1891b), range 30km (18.6 miles) and ceiling of 15,000m/49,215ft.

Nagasaki Arsenal was tasked with building the Funryu 4 and this did not begin until the late summer of 1945. The first ground test of the missile and its motor commenced on 16 August, but the close of the war prevented the Funryu 4 from being launched or its guidance system fully tested.

To prevent the Allies from learning of the Funryu developments, the UN forbade any of the personnel involved with the Funryu from discussing the project with anyone. In addi­tion, documents, test data, constructed mis­siles, the launching apparatus and the facilities in which the Funryu was developed were all burned and destroyed.

It was reported the Japan received two Do 217 aircraft in January 1943, and that by July 1943 the Japanese had purchased the manufacturing licence for the bomber. How­ever, no record exists of any Do 217 being sent to Japan, nor the purchase of the licence, and so the report may have been made in error.

Dornier Do 335 Pfeil fighter bomber

The Pfeil (‘Arrow’) was a twin engine, puller – pusher fighter and one of the fastest piston – engine fighters of World War 2. Although a number of Do 335s of various makes would eventually be built (and ten Do 335A-0 aircraft were used in the field by Erprobungs- kommando 335), the type did not enter ser­vice with the Luftwaffe. Nevertheless, it was believed that the Japanese were provided with a description of the Do 335 in March 1945 but no substantive information was released to them.

Dornier Do 635

long-range reconnaissance aircraft

The Do 635 was basically two Do 335 aircraft mated together by way of a centre wing sec­tion. Conceived in mid-1944, the design of the Do 635 was completed soon afterwards and the RLM ordered four prototypes and six pre – production aircraft. By the close of 1944, the Do 635 was shared with the Japanese who found the design intriguing but outside of their interest. The Japanese made no further moves to obtain the aircraft. Although wind tunnel models were completed and tested and a mock-up of the cockpits were built, the Do 635 was cancelled on 5 February 1945.

Heinkel He 100D-0 fighter

In 1940, Japan paid 2.8 million Reichsmarks for three He 1OOD-O aircraft and the manufac­turing rights. It was planned to produce the Неї OOD-O as the AXHel but the war pre­vented Heinkel from delivering the required jigs and tools and so production was aban­doned. Nevertheless, the Japanese were very impressed with the fighter and the design was a major influence for the successful Kawasaki Ki-61 Hien. Interestingly, Allied intelligence thought that details of a ‘He 113’ were received by Japan in July 1943. The ‘He 113’ was actually the He 100. A propa­ganda ruse using the few He 100s built tried to make it appear that the type was in German service and this succeeded in fooling Allied intelligence who used the ‘He 113’ designa­tion in their reports.

Kogiken Plan I – data (estimated)

Contemporaries Arado P.530 light bomber (Germany), Bell P-39 Airacobra fighter (US), Caudron C.670 light bomber (France), Farman N. C.223 heavy bomber (France), Messerschmitt Me 210 and 410 heavy fighter (Germany), Piaggio P. l 19 fighter (Italy), Potez 63 heavy fighter (France), Yakovlev Yak-2 light bomber (Russia).

Type Type A Heavy Fighter

Crew One

Powerplant One Nakajima Ha-4518-cylinder, air-cooled radial engine developing l,480hp for take-off and 1,460hp at 5,800m (19,028ft), driving a four-bladed metal propeller Dimensions Span Length Height Wing area 9.32m 8.71m 3.29m 14.59m! 30.6ft 28.6ft 10.8ft 157.1ft2 Weights Empty 2,291kg 5,0501b Loaded 3,140kg 6,9221b Performance Max speed 699km/h 434mph at 5,800m at 19,028ft Max range 599km 372 miles plus 1 hour Armament One 37mm Ho-203 cannon or one 20mm Ho-5 cannon and four 12.7mm Ho-103 machine guns

Kogiken Plan I – data

Type Type В Heavy Fighter

Crew One

Powerplant One Nakajima Ha-4518-cylinder, air-cooled radial engine developing l,480hp for take-off and l,460hp at 5,800m/19,028ft, driving a four-bladed metal propeller Dimensions Span Length Height Wing area 9.32m 8.86m 3.68m 14.59m! 30.6ft 29.1ft 12.1ft 157.1ft2 Weights Empty 2,295km/h 5,0591b Loaded 3,205kg 7,0651b Performance Max speed 699km/h 434mph at 5,800m at 19,028ft Max range 599km 372 miles plus 1 hour Armament One 20mm Ho-5 cannon, four 12.7mm Ho-103 machine guns and two 7.7mm Type 89 Model 2 machine guns

Without doubt, war often provides for rapid advancements in military technology. The key driver of this is the need for a weapon that is superior to those used by the opposition. In the majority of cases, improvements in weapons come about because one partici­pant fields a weapon that the other partici­pants have no answer for or cannot adequately counter with currently available weapons. This, then, spurs development of an equal or better weapon and the cycle repeats – an arms race! In some cases, devel­opment of a weapon does not result from actually encountering new developments on the battlefield. Instead, study of what could be encountered in the future, coupled with what can reasonably be advanced in terms of technology, provides the required emphasis for development – in essence, an attempt to second-guess likely developments so that if and when they manifest themselves the answer will already be in place. It was the lat­ter that prompted the IJA’s Rikugun Kokugi – jutsu Kenkyujo to initiate a series of studies and plans for a host of aircraft suitable to meet different roles.

In the summer of 1941, Kogiken (a con­traction of Kokugijutsu Kenkyujo) formed a group headed by aeronautical engineer Lieu­tenant Commander Ando Sheigo. The task put to Sheigo and his group of engineers was to study Japanese aviation technology in terms of what was possible at present and in the near future. In addition, some effort was to be spent on reviewing the aircraft technol­ogy of other countries. From the results of these studies, the group was to assemble and draft proposals for aircraft to fill various roles that could take advantage of future innova­tion. In all there were four roles or classes of aircraft the Kogiken group had to produce designs for: heavy fighter, light bomber, heavy bomber and reconnaissance. There was a fifth class, that of high speed, but meth­ods to achieve high speed aircraft were often
incorporated into designs in the other four classes. In addition to Kogiken, the IJA’s two biggest aircraft providers, Tachikawa and Kawasaki, were also invited to participate in some of the studies and tender their own designs.

A central theme in all of the Kogiken air­craft was the use of only a select group of engines. The two most prominent were the Nakajima Ha-45 and the Mitsubishi Ha-211-II, both of which were 18-cylinder, air-cooled radial engines. At the time of the Kogiken study, these engines were still in develop­ment but were expected to be operational in the very near future. Another factor concern­ing the engines was that, in some cases, the designs were built around the ability to replace the radial power unit with an inline engine without significant modifications. The primary inline engines were the Daimler – Benz DB601 and DB605. The former was licence built in Japan as the Kawasaki Ha-40.

By the close of September the designs were nearing completion. Since there were no performance requirements or specifica­tions applied to any of the classes of aircraft, this essentially left the engineers and designers with free rein to come up with aircraft they thought would be suitable for the roles. In many cases this led to aircraft concepts that featured, at least for the Japanese, unconventional mechanisms and approaches. Each aircraft was designated as a plan with each plan grouped by their respective class.

The first class, the heavy fighter, had four main designs, all Kogiken creations. Two were for a single-engine aircraft while the other two were twin-engine concepts. The first was the Kogiken Plan I Type A heavy fighter. Outwardly it was a fairly conventional aircraft. It used low mounted, thin laminar flow wings but in order to reduce drag the Ha-45 engine was placed within the fuselage, along the aircraft’s centre of gravity. This, in

per. Both were twin-engine designs and fitted with the Ha-21 l-II radial although the Ha-145 and the Kawasaki Ha-140 12-cylinder, liquid cooled inline engine were also considered. At this time, the latter was a projected develop­ment of the Ha-40 engine, which as noted was a licence-built version of the German Daimler-Benz DB601A. They each carried a crew of two. The Kogiken Plan I Type A Long Range Heavy Fighter carried an armament of one 20mm Ho-5 cannon and two 12.7mm Ho-103 machine guns in the nose with a rear firing Ho-103 for the second crewman. The Kogiken Plan I Type В Long Range Heavy Fighter was identical to the Type A but fea­tured a slightly different weapon fit. It retained the two forward firing Ho-103 machine guns but would either add a second Ho-5 in the nose or swap both Ho-5 weapons for two 30mm cannons, perhaps based on the 30mm Ho-155 that would eventually

Kogiken Plan V – data
evolve from the Ho-5. A variation of the Type B, the Plan II Long Range Fighter, had a slightly redesigned wing that reduced the wing area from 44.99m2 (484.3ft2) down to 41.99m2 (452ft2). A final variation, the Plan III Long Range Fighter, reduced the crew glaz­ing and fitted a remote controlled Ho-103 machine gun in the tail.

The light bomber plans would feature an approach that would not be repeated in sub­sequent Japanese designs. The Kogiken Plan II Light Bomber used two airframes con­nected by a wing centre section. The vertical stabilisers were connected by a single hori­zontal stabiliser. The pilot and crewman sat in a cockpit on the left airframe while a third crewman had a station in the right. The main landing gear retracted outwards into the outer wing panels. Buried in each airframe was a Nakajima Ha-39, 18-cylinder, water cooled radial engine that developed l,760hp

Kogiken Plan V – data

Dimensions
Span	14.23m	46.7ft
Length	10.63m	34.9ft
Height	3.71m	12.2ft
Wing area	26.59m2	286.3ft2

Armament

One 7.7mm Type 89 machine gun, one 12.7mm Ho-103 machine gun and fourteen 50kg (110 lb) bombs, eight 100kg (220 lb) bombs, two 250kg (551 lb) bombs or one 500kg (1,1021b) bomb

Kogiken Plan I Type A – data

Type High Speed Heavy Bomber

Crew Four

Powerplant

Four Mitsubishi Ha-21 l-II 18-cylinder, air-cooled radial engines, each developing 2,100hp driving a four-bladed metal propeller

Dimensions Span 826.33m 6.4ft Length 19.78m 64.9ft Height 5.09m 16.7ft Wing area 88.00m2 947.2ft2 Wing loading 219.7kg/m! 45 lb/ft2 Power loading 2.76kg/hp 6.1 lb/hp Weights Empty 12,540kg 27,6451b Loaded 19,340kg 42,6371b Useful load 6,800kg 14,9911b Performance Max speed 684km/h 425mph at 8,500m at 27,887ft Cruise speed 515km/h 320mph at 8,500m at 27,887ft Climb 3 min 9 sec to 3,500m (11,482ft) 6 min 3 sec to 5,000m (16,404ft) Max range 3,000km/l,864 miles

Armament

Two 7.7mm Type 89 machine guns, one 12.7mm Ho-103 machine gun and up to 1,500kg (3,306 lb) of bombs

Armament One 7.7mm Type 89 machine gun, three 12.7mm Ho-103 machine guns and up to 1,500kg (3,3061b) of bombs

and drove a four-bladed propeller via an extension shaft. It was proposed that a sur­face evaporation cooling system be used which consisted of a network of piping that would take the steam produced by the engines as the water circulated through them out into the wings where the cooler air would condense the steam back into water that was then recycled through the engines. The main benefit from this method of cooling was that it allowed for a more streamlined fuselage which increased air speed. Typical of early
war Japanese light bombers, the armament was light consisting of two 7.7mm Type 89 machine guns. For bombs, a regular payload of 300kg (661 lb) could be carried with a max­imum of 400kg (881 lb).

The Kogiken Plan III Light Bomber was basically identical to Plan II. The main change was the replacement of the Ha-39 engines with the Ha-45 and the latter were situated deeper into the fuselages requiring a.83m (2.7ft) long extension shaft. Without the com­plex cooling system of Plan II, Plan III was

smaller, lighter and faster. In addition, the canopy for the third crewman was made flush with the fuselage and was provided with a ventral fairing to facilitate bombing or reconnaissance duties. The propellers were fitted with ducted spinners to help cool the engines. The Kogiken Plan III Revised Light Bomber was a version of the Plan III but with the Ha-45 radials placed in a conventional fashion in the nose – the ducted spinners were left out. Another light bomber, the Kogiken Plan V Light Bomber, shared a simi­larity to the Plan III Revised but whereas the twin airframes were of the same length, the Plan V had the right airframe shorter to the point that the propeller spun behind the one on the left airframe. The canopy for the pilot and second crewman was also length­ened. The Kogiken Plan V Revised Light Bomber broke away from the previous designs. The twin airframe scheme was dropped and an engine was placed in a large nacelle in each wing. The Ha-211-II engine was specified but the Ha-45 could also be used. The crew was reduced to two and the armament was dropped to a single 7.7mm Type 89 machine gun while the bomb pay – load was lowered to 250kg (551 lb).

Kawasaki – data Type High Speed Heavy Bomber Crew Four to Five Powerplant Two Kawasaki Ha-140 24-cylinder, liquid-cooled inverted V engines, each developing 1,350hp driving a four-bladed metal propeller Dimensions Span 19.17m 62.9ft Length 14.87m 48.8ft Height N/A Wing area 48.00m2 516.6ft2 Wing loading I99.69kg/m! 40.9 Ib/ft2 Power loading 3.40kg/hp 7.5 lb/hp Weights Empty 6,170kg 13,6021b Loaded 9,590kg 21,1421b Useful load 3,420kg 7,5391b Performance Max speed 580km/h 360mph at 6,000m at 19,685ft 610km/h 379mph at 7,500m at 24,606ft Cruise speed 400km/h 248mph at 7,500m at 24,606ft Climb N/A Max range 3,000m 1,864 miles Armament Two 7.92mm Type 98 machine guns, one 12.7mm Ho-103 machine gun and up to 1,000kg (2,2041b) of bombs

In the heavy bomber class, only one stan­dard heavy bomber design was completed by Kogiken and this was the Kogiken Plan VI Heavy Bomber. The fuselage was conven­tional and was reminiscent of the solid nosed Junkers Ju 88 bombers although the Plan VI had longer glazing over the compartment for the crew of four. The similarities ended there. Set into each wing was a nacelle that housed two engines driving two propellers in a push- pull configuration. Originally Ha-45 radial engines were planned but the Ha-211 -II was the engine of choice. The design could have been adapted to take the forthcoming Mit­subishi Ha-214 18-cylinder air cooled radial or the Kawasaki Ha-201 which was made from two Ha-40 12-cylinder inline engines mounted in tandem and was under development at the time. Defensive armament was light consist­ing of a single 7.7mm Type 89 machine gun and a 12.7mm Ho-103 machine gun. A vari­able bomb load could be carried depending on the mission. A slight variation of the Plan VI increased the wing area to 69.99m2 (753.4ft2).

There was far more activity in the high speed heavy bomber category. Here, Tachikawa and Kawasaki made proposals as well as Kogiken. The Kogiken Plan I Type A High Speed Heavy Bomber was similar to the Plan IV Heavy Bomber but was larger. Instead of a conventional empennage, the Plan I Type A used a horizontal stabiliser ending in rounded vertical stabilisers. The glazing for the four man crew was longer and the fuse­lage was more streamlined. The same engine and engine arrangement was used but the nacelles had a slightly improved shape. For defence, two 7.7mm Type 89 machine guns and one 12.7mm Ho-103 machine gun were fitted and a maximum bomb load of 1,500kg (3,3061b) could be carried. The Kogiken Plan I Type В High Speed Heavy Bomber was basi­cally identical save it was larger and had a longer range. The final design from Kogiken, the Plan II High Speed Heavy Bomber, was slightly smaller and lighter than the Type В but added a fifth crew member and beefed up the defensive armament to three Ho-103 machine guns and one Type 89 machine gun.

The Kawasaki High Speed Heavy Bomber was the smallest of all the designs in the class. Consequently, its performance was less and carried a lighter bomb load and defensive armament. Instead of the Ha-211-II engines it used two Ha-140 24-cylinder, inverted V inline engines, which again were two Ha-40 engines placed in tandem. It was also unique in using the 7.92mm Type 98 machine gun in its defensive armament fit. Tachikawa’s designs, the Plan 1, Plan II and Plan III High Speed Heavy Bombers, were all variations on the same theme with minor differences

Tachikawa Plan I – data
Type	High Speed Heavy Bomber
Crew	Six
Powerplant	Four Nakajima Ha-14518-cylinder, air-cooled radial
engines, each developing 2,000hp driving a four-bladed metal propeller
Dimensions
Span	24.47m	80.3ft
Length	17.67m	58ft
Height	4.45m	14.6ft
Wing area	85.00m2	914.9ft2
Wing loading	223.61kg/m2	45.8 lb/ft2
Power loading	3.49kg/hp	7.7 lb/hp
Weights
Empty	9,540kg	21,0321b
Loaded	19,000kg	41,8871b
Useful load	9,460kg	20,8551b
Performance
Max speed	684km/h	425mph
	at 9,300m	at 30,511ft
Cruise speed	480km/h	298mph
	at 9,300m	at 30,511ft
Climb	N/A
Max range	4,899km	3,044 miles

Armament Two 7.7mm Type 89 machine guns, one 20mm Ho-5 cannon and up to 1,500kg (3,3061b) of bombs

Tachikawa Plan II – data

Type High Speed Heavy Bomber

Crew N/A

Powerplant Four Nakajima Ha-14518-cylinder, air-cooled radial engines, each developing 2,000hp driving a four-bladed metal propeller Dimensions Span 28.49m 93.5ft Length N/A Height N/A Wing area 80.00m2 861.1ft2 Wing loading 223.61kg/m2 45.8 lb/ft2 Power loading 3.31kg/hp 7.3 lb/hp Weights Empty N/A Loaded 17,900kg 39,4621b Useful load N/A Performance Max speed 694km/h 431mph at 9,300m at 30,511ft Cruise speed 490km/h 304mph at 9,300m at 30,511ft Climb N/A Max range 5,049km 3,137 miles Armament Up to 1,000kg (2,2041b) of bombs

between them. The key changes from the Kogiken plans were the engines used. The Plan I and Plan II bombers used four Ha-145 radials while the Plan III used only two of the Mitsubishi Ha-211MB 18-cylinder, air-cooled radial engines. Of all the designs, the Tachikawa Plan I had the largest crew com­pliment at six men.

In the reconnaissance class, three primary designs emerged, all by Kogiken. Each of them simply followed trends set in the fighter and bomber classes. The Kogiken Plan IV

Reconnaissance Plane was essentially the Kogiken Plan III Revised Light Bomber adapted for the reconnaissance role. Not sur­prisingly, the Kogiken Plan IV Revised Recon­naissance Plane was derived from the Kogiken Plan V Revised Light Bomber. The Kogiken Plan VIII High Speed Reconnais­sance Plane was based on the Kogiken Plan VI Heavy Bomber but had a highly stream­lined fuselage with nearly flush glazing over the crew compartment. As was typical of early Japanese reconnaissance aircraft the

defensive armament was extremely light for all of these planes.

None of the Kogiken aircraft would be con­structed. In part, this was due to the designs using technology that was either in develop­ment or not yet available. Another factor was the unorthodox nature of many of the aircraft drafted – one might liken the Kogiken aircraft to the results of a brainstorming with minimal restrictions on what might be deemed possi­ble. Nevertheless, the study was not a wasted effort and it is certainly reasonable to pre­

sume that the information provided valuable data and worthwhile methods for subse­quent IJA aircraft. For example, the Kawasaki Ki-64 would use the Ha-201 coupled engine with a surface evaporation cooling system. Another example was the Kawasaki Ki-88 which was to use a fuselage-buried Ha-140 engine that drove the propeller via an exten­sion shaft. The Mitsubishi Ki-46-III (code – named Dinah by the Allies) may have also benefitted from some of the aerodynamic streamlining studies done by Kogiken.

In 1939, a specification was drawn up that called for an aircraft capable of conducting long range reconnaissance and it was Tachikawa that answered the call to provide such a plane. However, the resulting Ki-74 would find itself both a victim of development delays and the changing fortunes of war.

In the spring of 1939, the Koku Hombu issued a specification for a long range reconnais­sance aircraft that could muster a range of 5,000km (3,107 miles) and a cmise speed of at least 280mph. The reason for this request was to provide a plane capable of operating from bases in Manchuria and flying to the west of Lake Baikal. The lake, the deepest in the world, is located north of Mongolia, near the southern Siberian city of Irkutsk. Certainly the intent was to monitor Russian and their allied Mongolian forces, especially in the face of Japanese defeats at the Battle of Lake Khasan in 1938 and the Battle of Khalkhin Gol in 1939, both at the hands of the Soviets. Tachikawa submitted a proposal to meet the

Koku Hombu’s specifications, drawn up by the design team led by Dr. H. Kimura. The ini­tial design for the Ki-74 was drafted in 1939. To achieve the required performance, Kimura selected two Mitsubishi Ha-214M radial engines. Each engine developed 2,400hp and would drive a six-bladed pro­peller. It was the pressure cabin for the Ki-74 that would be the stumbling block to finalis­ing the design.

Even before the Ki-74 was conceived, work on developing a pressure cabin for use in high-altitude aircraft was being conducted by Tachikawa. The purpose of such a cabin was to maintain air pressure for the crew when operating at altitudes in which the outside air pressure is much lower and the air thinner. Cabin pressurisation is desired for aircraft fly­ing higher than 3,048m (10,000ft) and doing so provided the crew with a much more com­fortable working environment that did not require the use of oxygen and flight gear to protect against the cold. It also prevented
conditions like hypoxia, barotrauma and alti – tude/decompression sickness. Two designs were built that would test pressure cabin con­cepts. The first was the Tachikawa Ki-77. Conceived as a plane to make a non-stop flight from Tokyo to New York, work on the Ki-77 began in 1940. For the Ki-77, Dr. Kimura utilised a sealed crew cabin but one which was not pressurised. The belief was that the cabin would keep in the oxygen but in testing it failed to meet expectations and the crew had to wear their oxygen masks constantly. With the poor showing of the Ki-77 cabin, Tachikawa tested a fully pressurised cabin in the Tachikawa SS-1. The SS-1 was a modifi­cation of the Army Type LO transport which itself was a licence built version of the Lock­heed Model 14 Super Electra (codenamed Thelma by the Allies). Work on the SS-1 also began in 1940 and the one and only example was completed in May 1943 with subsequent testing providing excellent data on pres­surised crew cabins.

The research into pressure cabins and the construction of the Ki-77 and SS-1 delayed the Ki-74 project so badly that work on it was halted; once it became obvious that the cabin for the new plane would not be ready the entire project was shelved. No prototype was produced.

However, towards the close of 1941, the Ki-74 project was resurrected in order to investigate the possibility of adapting the design to suit the role of a long range, high alti­tude bomber and reconnaissance platform. One such bombing mission envisioned was against the United States. To meet such a requirement, adjustments had to be made to the initial reconnaissance-only Ki-74 design. Armour was incorporated along with self­sealing fuel tanks. In addition, the appropriate apparatus for bombing was introduced. Finally, the initial Ha-214M radial engines were replaced by two Mitsubishi Ha-211-І radial engines, each producing 2,200hp. Once the redesign was completed it was pre­sented to the Koku Hombu who approved it in September 1942 ordering three prototypes.

It was not until March 1944 that the first Ki-74 prototype was completed, but the other two aircraft were ready soon afterwards. The latter two aircraft differed from the first Ki-74 only in the fact that they used the Mitsubishi Ha-211-І Ru engines that incorporated turbo­superchargers. With the completion of the authorised batch of three aircraft, flight testing of the Ki-74 began. Handling was considered acceptable but the Ha-211-І and the Ha-211-І Ru engines were proving to be temperamen­tal and prone to mechanical problems. A fur­ther thirteen pre-production aircraft were ordered, but due to the severe problems with the engines it was decided to replace them with Mitsubishi Ha-104 Ru radials. While the Ha-104 Ru was more reliable it also developed less horsepower, in fact only 2,000hp.

Tachikawa Ki-74 (FE-2207)

This example was at MAMA in storage as listed on the 1 August 1946 manifest. It was later slated for transfer to the Park Ridge storage facility in September 1946 but no further trace of FE-2207 remains and was most likely scrapped,

Tachikawa Ki-74 (FE-2208)

Like FE-2206, this Ki-74 was housed at AOAMC on 1 August 1946 and met the same fate.

Tachikawa Ki-74 (FE-2209)

FE-2209 was the third Ki-74 kept at AOAMC and joined the previous two aircraft on the scrapheap.

The Ki-74 as built was a mid-wing mono­plane. The pressure cabin made up the majority of the front of the aircraft with the bomb bay underneath. The use of the pres­sure cabin necessitated smaller window arrangements (as opposed to more conven­tional glazing) and the flight deck was offset to the port side of the fuselage. The aircraft had a crew of five which consisted of the bombardier, pilot, co-pilot, navigator/radio operator and gunner. All were housed within the cabin with the bombardier in the nose, the pilot and co-pilot on the flight deck and the navigator/radio operator and gunner in stations behind the flight deck. Because the Ki-74 was expected to operate at high – altitude where interception would be diffi­cult, the plane carried a very minimal arma­ment consisting of a tail mounted 12.7mm Ho-103 machine gun that was fired by the gunner via remote control. Although the Ki-74 was not a dedicated bomber, it carried a payload of 1,000kg (2,205 lb) of bombs which was comparable to IJA bombers then in service.

As construction commenced on the pre – production Ki-74s, plans were formulated to put them to use. When a number of Ki-74s had been built, they were to be assembled into shotai (a flight comprised of three air­craft) and massed to conduct bombing mis­sions against the US airbases in Saipan from which B-29 Superfortresses operated.

While the bulk of the Ki-74s were con­structed as bombers and reconnaissance platforms, another task was proposed. With much of the communication between Japan and Germany severed by the Allies, especially by sea, a plan was made to use a Ki-74 for non-stop flights to and from Germany. In 1944, the fourth pre-production Ki-74 was removed from the line and underwent modi­fications to allow it to accomplish such a feat. Higher powered На-211-I-Ru engines were utilised and fuel was carried to enable the air­craft to fly up to 12,000km (7,456 miles) – suf­
ficient to fly from Tokyo to Berlin. In addition, all non-essential equipment was removed and the flight deck was reallocated to the middle of the fuselage and lengthened. The modified Ki-74 would never make such a flight as Germany surrendered to the Allies before it could make the first attempt. The fif­teen Ki-74s were never to see combat, in part because the flight testing of the twelve remaining pre-production aircraft was not completed before the end of Japan’s part in World War 2.

Prior to the end of hostilities, two further variants of the Ki-74 were proposed. The first adapted the Ki-74 to a transport role but this was soon discarded. The second was the Ki-74-II which would have been a dedicated bombing platform. As such, the Ki-74-II was a redesign which showed some big differences to the Ki-74. The foremost alteration was the pressure cabin which was smaller and kept forward of the wings within the fuselage. This allowed for a deeper bomb bay that was needed to carry the planned 2,000kg (4,4101b) bomb load. Due to the heavier weight, the operating range was estimated to be 7,144km (4,439 miles) (in comparison to the 8,000km/4,971 miles of the Ki-74). Because of the heavier bomb load, the Ki-74-II was to be supported on a twin tyred front landing gear. The wings for the Ki-74-II were to be more slender than the Ki-74 for high-altitude operation and instead of the sin­gle tail mounted machine gun, two machine guns or cannons were to be used. Two Mit­subishi На-104-Ru engines would power the bomber, but like the transport concept, the Ki-74-II was abandoned and did not advance beyond the design stage.

Thanks to its long development history the US was aware of the Ki-74. The main thing they did not know was the role. Thinking that the Ki-74 was a fighter it was assigned the codename Pat. It was not until May 1945 that the true role of the Ki-74 was discovered and so the codename was changed to Patsy.

In the summer of 1942, the Koku Hombu was formulating specifications for a fighter that supported a heavy armament and could operate at high altitude. After settling on the specifications, the Koku Hombu approached Tachikawa and Nakajima and asked each firm to produce a design to meet these requirements.

The specifications for the fighter included a maximum speed of 800km/h (497mph) and a range of 3,000km (1,864 miles). The Koku Hombu knew the demands were high, per­haps even impossible to obtain, and so asked Tachikawa and Nakajima to put forward pro­posals to meet the demands. But they handi­capped Tachikawa by allowing Nakajima to ignore the range requirement. As such, Naka­jima could concern themselves with making their design fast without worrying about how far it could operate. Undeterred, Tachikawa’s designers set about the task of coming up with a concept that would achieve what the Koku Hombu asked for. What resulted was a departure from the conventional.

It was decided that two Mitsubishi Ha-211 Ru (Ha-43 Ru), 18-cylinder, air-cooled radial engines should be used placed in the fuse­
lage in a push-pull configuration. The key advantage this offered was a reduction in drag over a more conventional, wing mounted engine arrangement. Secondly, the centreline thrust symmetry of the aircraft would be maintained in case of engine failure which, in turn, allowed for nearly no loss of control. Each engine was to drive a four – bladed propeller. A twin-boom arrangement was mated to the low mounted wings. For weapons, a 30mm Ho-155 cannon was fitted
into each wing while a 37mm Ho-2044 can­non was situated directly below the Ho-155, installed in the tail boom. If required, the КІ-94-І would be capable of carrying up to 500kg (1,1021b) of bombs. The Ki-94-1 was to use a pressurised cockpit for the pilot and fea­tured a tricycle landing gear.

Once the Ki-94-1 was finalised, construction began on a wooden mock-up to be com­pleted in October 1943. Tachikawa then invited representatives from the Koku

Hombu to visit and inspect the Ki-94-I. On inspection and review, Tachikawa was to be disappointed when the design was rejected outright. The Koku Hombu inspectors found the Ki-94-l to be too unorthodox, too complex to build and that Tachikawa’s performance estimates were optimistic.

Tachikawa, however, did not give up on the Ki-94-I and reworked the aircraft into a heavy fighter that was designated the Riku-

gun Kogiken Ki-104. To boost the armament, two 57mm Ho-401 cannons were added. Unfortunately, this design was also rejected. With the rejection of the high altitude fighter and the subsequent heavy fighter revision, Tachikawa finally abandoned the Ki-94-1. Tachikawa did not wish to let Nakajima’s design against the high altitude fighter speci­fications, the Ki-87, go unchallenged. The result was the Ki-94-II.

MUNEO HOSAKA

Contemporaries

Focke-Wulf Fw 190 VI8/Ш (Germany), Focke-WulfTal52H (Germany), Mikoyan-Gurevich MiG-3D (Russia), Mikoyan-Gurevich 1-220 and 1-230 series (Russia),Yakovlev 1-28 (Russia), Poiikarpov ITP(M-2) (Russia), Yakovlev Yak-3PD and Yak-ЗТК (Russia)

Because the КІ-94-ІІ was never flown, the specifications are based on Tachikawa’s estimated performance.

Type High-Altitude Fighter

Crew One

Powerplant One Nakajima [Ha-44] 13 (Ha-219), 18-cylinder radial engine, developing 2,450hp for take-off, fitted with a Ru-204 turbosupercharger, driving a constant speed, four-bladed metal propeller Dimensions Span 13.99m 45.9ft Length 11.97m 39.311 Height 4.60m 15.1ft Wing area 27,99m! 301.3ft2 Wing loading 230.45kg/m2 47.21b/ft! Power loading 2.63kg/hp 5.8 lb/hp Weights Empty 4,690kg 10,3401b Loaded 6,450kg 14,2201b Performance Max speed 720km/h 447mph at 10,000m at 32,808ft Range 2,200km 1,367 miles Climb 17 min 38 sec to 10,000m (32,808ft) Service ceiling 14,250m 46,751ft Armament Two 30mm Ho-155 cannons, two 20mm Ho-5 cannons and either two 30kg (661b) air-to-air rockets or one 500kg (1,1021b) bomb

Deployment

None. One prototype was completed with a second under construction when the war ended.

In October 1943, the Koku Hombu rejected Tachikawa’s radical, twin engine, twin – boom, push-pull fighter, the company’s answer to the Koku Hombu’s request for a high-altitude fighter. Tachikawa was told the Ki-94-I was unconventional, complex and its estimated performance specifications were optimistic. The rejection left Nakajima’s Ki-87 the sole contender for the specification, something Tachikawa was not going to let happen.

Soon after the rejection Tachikawa utilised the same specifications given to Nakajima to plan a revised design. Whereas Tachikawa had to meet the Koku Hombu’s 3,000m (1,864 mile) range requirement and a 800km/h (497mph) maximum speed, Nakajima only had to contend with meeting the speed max­imum. Unbridled by the range issue, Tachikawa engineers went about the task of producing a design capable of matching and exceeding the Ki-87.

Knowing that the Koku Hombu would likely reject anything out of the ordinary in concept, a more conventional approach was taken. The man behind the revised aircraft was Tatsuo Hasegawa. Retained from the Ki-94-I was the pressurised cockpit for the pilot but everything else was redesigned. The new project used a standard configuration for a single-engine, all-metal fighter to ensure acceptance by the Koku Hombu. The power – plant selected for the plane was the Nakajima [Ha-44] 13 (Ha-219), 18-cylinder radial engine that was rated at 2,450hp. The engine was equipped with a fan cooled, exhaust driven Ru-204 turbosupercharger that was situated
on the underside of the fuselage. Originally, it was planned that a six-bladed propeller should be used. However, testing showed that when in operation a blur was created by the spinning prop, obscuring the pilot’s for­ward vision. Therefore, a four-bladed pro­peller was selected. For weapons the aircraft had a similar cannon armament as the Ki-94-I, but this was downgraded to two Ho-155 30mm cannons and two Ho-5 20mm cannons with one of each calibre cannon fit­ted into each wing. The wings were a typical laminar flow-type with the cockpit situated behind the trailing edges of the wings. As the dimensions show, the new design was fairly large by Japanese standards, even supersed­ing Nakajima’s Ki-87 in size.

With the drafts completed, Tachikawa presented them to the Koku Hombu. After review, the design was accepted as the Ki-94-II and Tachikawa received the order to produce a static test airframe, three proto­types and 18 pre-production aircraft. As soon as approval was received for the Ki-94-II, work began on the construction of the first two prototypes with the first to be completed by 20 July 1945. However, this date would not be met as delays in production caused the program to fall behind schedule which, in turn, delayed the final completion of the first Ki-94-II.

Tachikawa scheduled the first flight for 18 August 1945. However, on 15 August 1945, the war ended for Japan and the Ki-94-II was pre­vented from making any flights. The end of the war meant that the second prototype was never completed.

MUNEO HOSAKA

MUNEO HOSAKA

It was only after January 1945 that the Japan­ese were given access to the very latest Ger­man jet technology. Prior to that, access came only after German equipment had achieved operational status. Thus, in the beginning of 1944, the Japanese were made aware of the Messerschmitt Me 262 jet fighter and Me 163 rocket-powered interceptor long after they were flying. Consequently, it was not long before official requests for data came from Japanese representatives in Berlin. In the subsequent negotiations the Germans were told that only the IJA would be building the Japanese version of the Me 262, the Nakajima Ki-201 Karyu, the development of which began in January 1945. But even before this, the IJA began to formulate jet designs of its own, spurred by the release of technical information by the Germans.

In late 1944, the IJA initiated a study for a sin­gle engine jet fighter and the task was given to the Tachikawa Dai-Ichi Rikugun Kokusho.

The IJA’s Captain Hayashi and Captain Yasuda assembled and led two teams to research the concept and begin design. The one restriction imposed was the requirememt for at least a half hour’s endurance. At this time, only the Ne 12 series of turbojets was available. The Nel2, a development of an earlier project called the Ne 10, was found to be too heavy. A lighter model, the Ne 12B, was produced in limited numbers until the Ne 20 turbojet was first tested in March 1945. This engine proved to be superior to the Ne 12B.

The problem facing both Hayashi and Yasuda was that performance and endurance on a par with a twin engine design had to be achieved using only a single power unit. With the Nel2B unacceptable, both of these looked to the projected developments of the Ne20. These included the Ishikawajima Nel30, Nakajima Ne230 and the Mitsubishi Ne 330 turbojets because they were expected to produce improved thrust over the Ne 20.

With at least the basic dimensions of the tur­bojet in mind, each team got to work drafting their designs for the jet fighter. Two concepts emerged from both teams towards the mid­dle of 1945.

Hayashi’s team took the turbojet and placed it inside the fuselage near the tail. The fuselage was to be fairly slender in shape with the cockpit forward of the low mounted wings which were to be placed about mid-fuselage. The aircraft was to have a nose intake with the turbojet’s exhaust being vented out through the tailpipe or rear of the fuselage. Yasuda’s group took the turbojet and placed it on top of the fuselage. As opposed to Hayashi’s more slender aircraft, the Yasuda design had a shorter and wider fuselage. As a result of the engine being on top, this eliminated the pos­sibility of a conventional tail stabiliser arrange­ment and thus each tailplane ended in a vertical stabiliser. Yasuda felt that with the engine outside the fuselage, the nose could then be used to carry armament allowing for improved and concentrated accuracy. Yasuda’s design was very reminiscent of the Heinkel He 162 Volksjager.

At this juncture, the Volksjager will be dis­cussed briefly. The He 162 was designed as a fighter that could be built quickly with semi­skilled or unskilled labour, using few war crit­ical materials and only a single turbojet. This enabled the He 162 to be turned out more quickly than the more complex Me 262 then in service. The He 162 began with the Volk­sjager competition, but as Heinkel had the inside track with Deputy of the Reich Ministry of Armament and War Production, Karl-Otto Saur, who also happened to be the managing director for Heinkel, the study for the He 162 was already underway. By the time the other competing designs were submitted for the competition, the mock-up of the He 162 was already under construction. Little surprise the contract for the Volksjager went to Heinkel in September 1944. On 6 December 1944, the He 162 VI flew for the first time.

The He 162 used a light metal monocoque fuselage with a moulded plywood nose. The high-mounted wing was one piece, made of wood and plywood skinning with metal wing tips. The two tailplanes sported vertical sta­bilisers on their ends. Only four bolts secured the wings to the fuselage. A single BMW 003A-1 Sturm turbojet sat atop the fuselage just behind the cockpit and to help him aban­don the aircraft in an emergency, the pilot was provided with an ejection seat. For weapons, two MG 151 20mm cannons were fitted with 120 rounds per gun. The top speed of the He 162 was 905km/h (562mph) at 6,000m (19,690ft) with a 438km (272 mile) radius at full power.

In January 1945, Erprobungskommando 162 was created to field test the He 162 and on February 6 I/JG 1 was ordered to convert to the jet fighter. The He 162 was an unforgiving aircraft but in the hands of a skilled pilot it was an exceptional dogfighter. Pilots were told to avoid combat with Allied aircraft, however in late April and early May, I/JG 1 scored a hand­ful of aerial victories. This was tempered by the loss of 13 aircraft and 10 pilots, mostly due to accidents. The only other unit activated, the l.(Volkssturm)/JG 1 at Sagan-Kupper, never received their He 162 fighters and this was fortunate. The pilots of this unit were to only receive training in the He 162S, a glider version of the He 162 that had no engine, non- retractable landing gear and a rudimentary second cockpit for the instructor. After a few gliding flights, the untrained pilot was expected to fly the jet powered He 162 and the results would have been disastrous. A fly – able two-seat He 162 known as the Doppel – sitzer, fitted with a second cockpit for the instmctor at the expense of the cannons and ammunition, oxygen system and fuel capac­ity, was not completed by the end of the war in Europe.

On 15 April 1945, the Oberkommando der Luftwaffe approved the release of specifica­tions and production data for the He 162 to the Japanese. A delegation of UN officials studied the He 162 and visited Heinkel’s He 162 production line in Rostock, Germany. Impressed with the aircraft, the Japanese quickly requested technical data on the fighter. Of course, by this stage of the war for Germany there was no way that physical blueprints, production tools, jigs or a sample He 162 could be shipped to Japan. Instead, the only means available to rapidly send infor­mation on the jet was via wireless transmis­sion – i. e., radio. To help facilitate the transmission of the data, Commander Yoshio Nagamori used a datum line (a fixed, mea­surable line, used as a reference from which angular or linear measurements are taken) to measure the He 162 and transmitted the resulting dimensions to Japan. Only a portion of the data Nagamori sent was received in Japan.

Even though parts of the measurements for the He 162 made it to the Japanese mainland, enough was received to begin making use of the information, filling in the gaps, revising the design to suit Japanese production capa­bility and compiling the drafts needed to realise the aircraft. Even though the 1JN was the branch that obtained the He 162 data, it appeared that it would be the IJA who would produce it. In addition to developing the air­craft from the data, plans were made to begin production.

Whether Captain Yasuda and his team used the He 162 as their influence or arrived at a similar design by coincidence may never be known. But the IJA would reject Yasuda’s fighter and instead selected Captain Hayashi’s design for continued work. Per­haps it was felt that with the acquisition of the He 162, Yasuda’s design was redundant. With Hayashi’s aircraft approved, he and his team moved forward with refining the design and constructing a prototype. However, by August 1945 when hostilities ceased, none of the IJA’s jet programs were ready to fly. Neither Hayashi’s jet nor the Japanese version of the He 162 would progress past the initial design stage. Only the Nakajima Ki-201 ever made it to the construction phase which, by the end of the war, amounted to a single incomplete fuselage.

As a note, ‘Ki-162’ has been used by some as the designation for the Japanese produced He 162. There is no historical evidence to sup­port this although it is not without precedent, such as the case with the proposed Mitsubishi Ki-90 that was to be the Japanese version of the Junkers Ju 90. In addition, one may see the full name as the ‘Tachikawa Ki-162’. It is not unreasonable to believe that Tachikawa may have played a part in assessing the He 162 data given that the IJA had the Tachikawa Dai-Ichi Rikugun Kokusho and the Rikagun Kokugijutsu Kenkytijo (also at Tachikawa) at their disposal. Whether Tachikawa would have actually built the pro­duction Japanese He 162 is not known.

Tachikawa Ki-162 – data

Contemporaries

Blohm und Voss P.221/01 (Germany), Republic F-84 Thunderjet (US), Heinkel He 162 (Germany), Arado E.580 (Germany), BMW Strahljager I (Germany), Heinkel PJ073 (Germany), Henschel Hs 132 (Germany), Antonov SKh (Russia)

Specifications

Very little is known of the jet designs created by Yasuda or Hayashi and thus no specification information has surfaced. Likewise, since there was little time to act on the He 162 data, there is no information on what the specifications would have been for the Japanese version though it would not be unreasonable to conclude the dimensions and performance would have been similar to the German jet.

Deployment

None. None of the jet fighters got past the design stage.

While the UN put its focus on SAMs, the IJA’s resources went into developing Air-to-Sur – face missiles (ASMs). The culmination of these developments, begun in 1942 by the Koku Hombu, was the І-Go series of missiles. The majority of the research on the І-Go was carried out by Rikugun Kokugijutsu Kenkyujo located in Tachikawa. Once the preliminary work for the missiles was completed, the Koku Hombu reached out to Mitsubishi, Kawasaki and the Aeronautical Research Institute of Tokyo University to commence final development of the І-Go as they saw fit, using the initial data assembled by Rikugun. Sumitomo Communication Industry Co. Ltd. was the provider of the autopilot and the transmitter/receiver system for the first two I – Go missiles with T. Hayashi designing the for­mer and K. Nagamori the latter.

The I-Go-l-A (Ki-147) was the Mitsubishi version of the І-Go. The final design of the Ki-147 was completed by the end of 1943. Work began on the missile using a basic air­plane configuration and its construction was made of wood and metal. It was propelled by a rocket engine built by Nissan Jidosha KK which produced 240kg (529 lb) of thrust with a burn time of 75 seconds, providing a top speed of 550kg (342mph). The warhead was substantial using 800kg (1,764 lb) of explosive triggered by an impact fuse. Guidance was by radio from the carrying aircraft. The first Ki-147 missiles were completed in 1944 and by mid-year unguided test drops had com­menced at Ajigaura, Atami and Shiruishi. The carrier aircraft was a modified Mitsubishi Ki-67-I Hiryu bomber. By October 1944, guided test drops of the Ki-147 had begun. Despite the testing, the Ki-147 did not enter production and only fifteen were built. The Ki-147 had a length of 5.8m (18.9ft), a span of 3.6m (11.8ft) and a launch weight of 1,400kg (3,0861b).

The I-Go-l-B (Ki-148) was the Kawasaki I – Go. Smaller than the Ki-147, the Ki-148 used a HTP rocket motor that developed 150kg (331 lb) of thrust with an 80 second burn time. The wings were constructed of wood while the body and fins were made from tin. As a consequence of the smaller size, the war­head comprised only 300kg (661 lb) of explo­sive and it used a direct-action fuse. For guidance, the Ki-148 used the same radio sys­tem as the Ki-147. Following wind tunnel test­ing with full – and half-size models, Kawasaki produced a number of missiles at their Gifu factory for testing to begin in late 1944. Ki-148 test launches were made from four modified Kawasaki Ki-48-II Otsu bombers at Ajigaura in Ibaraki Prefecture. By December 1944, up to 20 Ki-148 missiles were being launched per week from the bombers. Despite the rela­tively successful testing, the Ki-148 was never put into production and total deliveries of the pre-production/test Ki-148 missiles amounted to 180. Had the Ki-148 gone into service, the Kawasaki Ki-102 Otsu was to be the designated carrier aircraft.

Ki-148 had a length of 4.1m (13.4ft), a span of 2.6m (8.5ft) and a launch weight of 680kg (1,4991b).

The I-Go-l-C would be the Anal І-Go pro­ject. The Aeronautical Research Institute of Tokyo University decided to take a com­pletely different approach to guidance. Deciding that anti-shipping would be the main use of the I-Go-l-C, the missile dis­pensed with the radio guidance method and instead employed a novel system that used the shockwaves produced by naval cannons as the means to direct the missile. In essence, the missile would guide itself to the target by sensing the shockwaves developed in the air by large naval cannons during firing. Since shockwaves travel outwards from the can­non, the missile could determine direction and adjust its flight path accordingly to bring it onto the target. The main benefit of the sys­tem was that the missile was a fire-and-forget weapon. As long as naval ships engaged in bombardment, the I-Go-l-C would be able to track and attack them on its own. Testing of the system got under way in 1945 and the ini­tial results showed promise. However, the missile body was never built as the war ended before testing of the guidance hard­ware was complete. The proposed I-Go-l-C was to be 3.5m (11.4ft) long with a diameter of 1.6ft. Other specifications for the missile, such as its warhead size, rocket motor, per­formance and weight are still unknown. The I-Go-l-C is sometimes called the Ki-149 but there is no evidence to support the use of this name.

Since the Ki-147 and the Ki-148 achieved flight testing and both used the same radio guidance system, the procedures to launch and control the missiles were basically the same. The Ki-67 and Ki-48 bombers used in the testing were modified to accommodate the missile operator as well as the equipment needed to guide the weapon. Operationally, the missiles would be dropped at an altitude of 1,500m (4,922ft), 11km (6.84 miles) from the intended target. By the time the missile was 5km (3.11 miles) from the target, the alti­tude varied between 30m to 150m (98ft to 492ft) depending on the preset of the altime­ter. The operator would guide the missile via a joystick and just before it passed over the target, the missile would be put into a dive, bringing it down onto its target. The launching aircraft had to remain within sight of the mis­sile and in most cases would be 4km (2.5 miles) from the target when the missile hit. While the handling characteristics of the weapons were found to be good, analysis showed that the missiles tended to fall either 300m (984ft) short of the target or 100m (328ft) past the target. The reason for was that the operator had to rely on his own vision and clear conditions in order to guide the missile. He was not provided with any form of special optics nor did the missile carry a means to mark itself in flight such as using burning flares or smoke which the operator could use to maintain sight of the weapon. The only measure of this kind ever employed was a tail light which was used at night so the operator could track the missile. Had the Japanese given further consideration to the operator’s needs, accuracy may have been improved. A factor against the use of the Ki-147 and Ki-148 was that the launch aircraft had to be within 11km (7 miles) of the target and had to remain in the area to proceed with the attack. With the heavy Allied air presence, getting to the launch range would have been a formi­dable task and this may have been a factor in the Ki-147 and Ki-148 failing to enter service.

The Japanese purchased the He 119 V7 and V8 in 1940. See the chapter on the Kugisho R2Y Keiun for more information.

Heinkel He 162 jet fighter

See the Tachikawa Ki-162 chapter for more information concerning the Japanese acqui­sition of this fighter in April of 1945.

Heinkel He 177A-7 bomber

The UN were interested in the He 177 and negotiated to produce the bomber in Japan, with Hitachi building it under licence in Chiba in 1942. The major change was that the Japan­ese version would use four separate engines to avoid the plethora of problems the Ger­mans encountered with the original coupled engine design. Sample tools were delivered to Japan by submarine but Heinkel was unable to ship the remainder of the machining appa­ratus and jigs and production was dropped. One He 177A-7 was to be flown to Japan in 1944 to serve as a manufacturing pattern air­frame and evaluation aircraft but the bomber lacked the range, even after modification, to make the flight via the route demanded by the Japanese running through Persia and India. Some sources list the proposed plane as the Hitachi ‘He-Type’ heavy bomber.

Heinkel He 219 Uhu night fighter

The Uhu, meaning ‘owl’ in German, was per­haps the most advanced night fighter to see operational service in World War 2. The Japanese are believed to have been aware of the He 219 with full access to the relevant design data by July 1944. If this was the case, it is not known what, if anything, the Japanese did with the information.

Heinkel He 277 heavy bomber

The He 277 was, essentially, the He 177 with four separate engines instead of the coupled engines which caused so many problems for Heinkel and maintenance crews. Unlike the He 177, the He 277 would never enter pro­duction, being cancelled in July 1944 in favour of more fighters. It was believed that full details of the He 277 were provided to the Japanese in March 1944. One could assume that since the proposed Japanese version of the He 177 would use four separate engines, information on the He 277 would have been of value.

Kawanishi Baika

The invasion of the Japanese home islands was a genuine threat to Japanese military planners. Operation Downfall was the Allied plan to launch the final blow against Japan. This consisted of the capture of Kyushu (Operation Olympic) that would provide the jump-off point for the invasion of Honshu, near Tokyo (Operation Coronet). Given the geography of Japan, Japanese military lead­ership was able to narrow the likely avenues of attack. To that end, Operation Ketsugo was formulated. A critical component of the oper­ation was special attack units and they needed aircraft in mass numbers to succeed in repelling the invasion. This provided the spark for the Kawanishi Baika.

On 2 July 1944, the Kaigun Koku Hombu issued a directive to Kawanishi Kokuki K. K. to produce a special attack aircraft. The design was to be a replacement for the Kugisho Oka Model 11 and Model 22 as well as the special attack version of the Nakajima Kitsuka. The new aircraft, called the Baika (meaning Plum Blossom), needed to be constructed from as
much non-critical war materials as possible and be of simple design to allow for produc­tion by unskilled or semi-skilled labour in small, scattered workshops. These demands were a result of the relentless Allied bombing of Japanese industry and that Allied naval forces had a stranglehold on imports of raw materials needed to sustain the Japanese mil­itary. To meet this directive, Professors Ichiro Tani and Taichiro Ogawa, both of the Aero­nautical Institute of the Tokyo Imperial Uni­versity, began to study a means to achieve the requirements of the task before them, sup­ported by Kawanishi.

The engine for the Baika, the Mam Ka-10 pulsejet, was derived from the German Argus As 109-014 pulsejet, the technical plans for it having been delivered to Japan via subma­rine in 1944. The Aeronautical Institute of the Tokyo Imperial University studied the design and in time developed the Ka-10. A pulsejet is a simplistic engine that operates by mixing air that is taken into the engine via a shuttered or valve intake with fuel that is then ignited in the combustion chamber. The force of the explosion closes the intake and thus the
resulting gas can only be expelled through the exhaust and forward thrust is generated. This cycle, or pulse, is repeated over and over up to 45 times per second in the case of the Argus Ar 109-014.

A pulsejet has four main benefits. Firstly, due to the simple nature of the engine it can be easily built. Secondly, it can use low grade fuels. Third, pulsejets offer reduced mainte­nance. Finally, they have a lower cost per unit when compared to other engines. However, the pulsejet does have three major flaws – it is not fuel efficient and, due to the operating nature of the engine, it is noisy and generates significant vibration.

The choice in using the pulsejet for the Baika was clear. With the situation for Japan being what it was in late 1944 and into 1945, the Ka-10 offered a far less complex engine than a turbojet or piston engine. This meant it could be built in greater numbers by unskilled or semi-skilled labourers. Because it could use low grade gasoline it put less of a strain on the supply chain struggling to provide more refined aviation fuel. Tani and Ogawa did find that the Ka-10 suffered from having a short

service life in regard to its fuel valve. They also had concerns that the high noise of the engine would provide enough advance warn­ing that countermeasures could be set or sent up to combat the Baika. Finally, it was realised that the vibration caused by the engine would put a strain on the aircraft, per­haps causing failures in the aircraft’s struc­ture. The benefits, however, outweighed the disadvantages and work on the Baika design proceeded.

A meeting was called on 5 August 1945 to be held at the Aeronautical Institute of the Tokyo Imperial University. It was attended by Admiral Wata and Admiral Katahira from the Kaigun Koku Hombu, professors Naganishi, Ogawa and Kihara of the Aeronautical Insti­tute, and Chairman Katachiro of Kawanishi. In the discussions, the Baika was selected over the rival Kugisho Oka Model 43B, the lat­ter being seen as too complex to build in numbers quickly, especially since it used the Ne 20 turbojet. Some revisions, specifically in simplifying the design, resulted in two ver­sions of the Baika being discussed. As the Baika was to be used to defend the home island, launch rails were to be constructed that would use a solid fuel rocket to hurl the Baika into the air. The second version incor­porated a simple landing gear and it was decided that the Baika with the landing gear would be used for training pilots before they converted to the rail launched Baika. After all, given the mission of shimpfl attacks on Allied invasion ships, the pilot would not be return­ing and would have no need of landing gear. At the conclusion of the meeting, Kawanishi was given an order for one Baika prototype and ten two-seat trainers. The company was given a deadline of September to have the finalised design completed as well as a pro­duction plan finished. Mass production was to begin in October 1945.

Kawanishi was given the following specifi­cations for the Baika:

– length of no more than 8.5m (27.8ft)

– height of no more than 4m (13.1 ft)

– width, with folded wings, of no more than 3.6m (11.8ft)

– speed, with the Ka-10, must be at least 463km/h (287mph) at sea level

– a ceiling of 2,000m (6,561ft)

– range of at least 130km (80 miles)

– 100kg (2201b) explosive payload

As the Baika was developed, three versions of the aircraft emerged. Two were similar except for the cockpit placement. Despite the initial direction that the Baika would be rail launched, all versions used landing gear. The first version, or Type I, had the Ka-10 pulsejet directly above and behind the cockpit – this resulted in a fairing that enveloped a portion of the front support strut for the engine. The second version, the Type II, moved the Ka-10 further back, eliminating the need for the fair­ing. The final version, or Type III, placed the Ka-10 below the fuselage instead of above it. With the first two, the adjustment of the pulsejet may be due to maintain the centre of gravity on the aircraft. Facilitating pilot egress was likely not the reason for the move. The need for landing gear suggests that rail launching was not the only means to get the Baika airborne. Towing or using rocket boost­ers may have been considered or the use of the landing gear may have simply been for training use only. It is probable that the land­ing gear could be jettisoned to improve aero­dynamics. The Type III, with the underslung engine, would suggest that it was to be car­ried by a parent aircraft much in the manner of the Oka in addition to rail launching. It is unknown what the two-seat trainer version would have looked like. It is not unreason­able to assume that the warhead would have been removed and a second cockpit installed with ballast simulating the warhead, much like the Kugisho Oka Model 43 K-l Kai, the two-seat trainer for the Oka.

Initially, the Baika featured 8mm of armour protection for the pilot and although this only protected his back, it was a means to allow for some modicum of defence against inter­ceptors firing from behind rather than ground fire. However, this was changed and the armour was removed, allowing for an increase in the warhead size up to 250kg (551 lb). While this did result in a reduction of range, it was not seen as a detriment given that the likely engagement distances would be rather less than 130km (80 miles).

On 6 August 1945, another meeting on the Baika was called. Masayama Takeuchi of the Kaigun Koku Hombu had concerns in regard to its construction and sought to have the Baika built from as little war-critical material as possible, meaning that wood would be used wherever possible. The Baika also had to have passable handling characteristics in the air to give the pilot the best opportunity to strike his target. Beginning on 8 August 1945, a team of 60 men was assembled at Kawan­ishi to oversee development and production of the Baika to be led by engineer Tamenobu. It all came too late for on 15 August hostilities came to a close and the Baika project came to an end before it had left the drawing board.

As a note, some sources make the case that the German Fieseler Fil03R Reichenberg, the manned version of the Fi 103 (V-l), was an influence for the Baika. There are US intel­ligence reports which indicate that the Japan­ese were well aware of the Fi 103 by October 1943 and that one was obtained in November 1944. These reports also suggest that the Japanese were very interested in the air launching techniques for the weapon. Another report indicates that the Japanese also knew of the Reichenberg project. A 1946 USAAF report shows the Baika as a copy of the Fi 103R. Finally, a manifest of cargo on the Japanese submarine 1-29 (the same that car­ried data on the Messerschmitt Me 163B and Me 262; see the Mitsubishi J8M SyOsui chapter for more information) listed a single Fi 103 fuselage as being onboard. The contempo­rary illustrations of the Baika today (including the one here) are derived from the drawings of the aircraft made by Technical Comman­der Eiichi Iwaya in the 1953 Japanese book Koku Cijutsu No Zenbo. Whether the Baika was truly inspired by the Fi 103R or was sim­ply an independent design may never be known for certain.

Kawanishi Baika – data

Contemporaries

Fieseler Fi 103R Reichenberg (Germany)

Type Special Attack Aircraft

Crew One

Powerplant One Maru Ka-10 pulse jet; rated at 360kg (7941b) of thrust Dimensions Span 6.58m 21.6ft Length 6.97m 22.9ft Height, unknown up to 3.99m/13.1ft by requirements Wing area 7.58m! 81.6ft1 Weights Empty 750kg 1,6531b Loaded 1,430kg 3,1521b Armament One 250kg (551 lb) warhead Performance Max speed 648km/h 402mph at 2,000m at 6,561ft Cruise speed 485km/h 301 mph at 6,000m at 19,685ft Range 278km 172 miles Climb 3 min 55 sec to 2,000m/6,561ft Ceiling 2,000m 6,561ft Fuel capacity 600 litres 158 gallons Deployment None. Did not advance past the drawing board.

By 1944, Japan was hard pressed to fuel her war machine with the raw materials it des­perately needed. Being an island, only two means were available for Japan to receive ore, fuel and other vital materials from what holdings Japan had left. The first was by sea and the second was by air. The sea route was fraught with risk due to the US Navy and Allied submarine and warship presence in the Pacific. Thus, delivering cargo by air, while also not without risk, appeared a better option, despite the lower tonnage capacity in comparison to sea-going freighters. There­fore, the Kaigun Koku Hombu asked Kawan­ishi to design what would be one of only a handful of dedicated transport seaplanes of the war.

The UN knew full well the impact the US Navy’s unrestricted submarine warfare doc­trine was having, which made merchant ships the primary target. By the end of the war, 1,200 Japanese merchant ships had been sent to the bottom along with five mil­lion tons of cargo. In part this was due to poor convoy methods and protection by the UN, but also because the US had broken the Japanese merchant marine cipher (the ‘mam code’). Hence, moving cargo by sea would more often than not result in the shipping being located and sunk. In 1944, shipping losses were at their highest and by 1945, while they did decline, it was because fewer ships were moving on the open ocean.

The desperation for fuel and other war materials was illustrated by the IJA’s Kokusai Ki-105 Otori (meaning Phoenix), the twin- engine version of the Kokusai Ku-7 Manazuru (Crane) transport glider. The IJA planned to use the Ki-105 as a fuel tanker which would fly from Japan to the Sumatra oil fields in Indonesia, load up with fuel and then return. However, to make the return trip the Ki-105 would consume some 80 per cent of the fuel by the time the aircraft returned to Japan. The UN looked for a better solution with a large transport capable of carrying a significant cargo load. Because a large expanse of ocean had to be crossed in order to reach what few territories the Japanese still held, the UN desired to have a seaplane to do the job. In January 1944, the IJN asked Kawanishi to develop such an aircraft.

Kawanishi was a leader in flying boat development and had gained most of its experience in designing large sea going air­craft. Two of their most successful designs were the Kawanishi H6K (codenamed Mavis by the Allies) and the H8K (Emily), with the latter arguably the best flying boat of World

War 2. The company was also not lacking in cargo flying boat design having modified the H6K to serve as a transport as the H6K2-L and H6K4-L. Even the H8K was adapted as a trans­port, the H8K2-L Seiku (or Clear Sky). Kawan­ishi had also been working on the design of the K-60, a long-range transport flying boat. With these credentials, Kawanishi was able to capitalise on their knowledge to begin the design of the HI IK Soku (Blue Sky) for the IJN.

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

Kawanishi presented the KX-8 to the IJN and the design was accepted. Authorisation was given to construct a full scale wooden mock-up of the Soku now designated the HI 1K1 for inspection before Kawanishi could proceed with the actual prototype. Construc­tion of the mock-up commenced at the port of Komatsujima in the city of Komatsushima on the island of Shikoku (the smallest of the four main islands making up Japan). This area was selected by Kawanishi because it had access to the Seto Inland Sea which, once the prototype was built, would be needed to undertake sea and flight trials. Unfortunately for the Soku, the deteriorating

war picture saw delay after delay affect the construction of the mock-up. To add to the problem, Kawanishi was instructed by the UN in 1945 to reduce production of the H8K and instead, concentrate on building the Kawan­ishi N1K2-J Shiden-Kai fighter. Together, these factors would see the mock-up approaching its completion in April 1945, well over a year after the design had been initiated.

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

Kurai Aerial Torpedo No.6/No.7

In April 1944, the UN initiated a design for an air dropped, anti-submarine torpedo. While not a tme guided weapon, what made the design unique was that the torpedo was winged and once in the water, entered a cir­cular pattern as it dived down. Work on the torpedo was carried out by the First Technical Arsenal Branch at Kanazawa under Com­mander Fukuba. The torpedo body was made of wood with the exception of the metal nose. The torpedo had no means of propulsion, either for flight or in the water. The wooden wings, each 1.5m (4.9ft) in length, were glued to the main torpedo body at a 20° upward angle. The wing span was approximately.9m (2.6ft) and the nose car­ried a 100kg (2201b) warhead and the total weight was 271kg (597 lb). The wood rudders were fixed at an 8° angle which, once in the water, imparted the counter-clockwise circu­lar path. The rudder was covered with a wood fairing to stop it affecting the freefall glide of the torpedo. Once the torpedo entered the water, the aluminium pin holding the fairing on sheared off and the fairing came free.

The first tests were carried out to evaluate the gliding properties of the torpedo. In all, forty drops were made of which fifteen were complete failures, the torpedo tumbling or spinning out of control. The wings were mod­ified according to the specifications given above, resulting in the Kurai No.6 which improved the gliding ability but not to a satis­factory level. Underwater testing was con­ducted by releasing the torpedo from a boat and the results showed a 17° dive angle at a speed of 5-6 knots. Colour dye released from the nose of the torpedo assisted the evalua­tors in determining how the weapon worked underwater. The maximum depth the tor­pedo could reach before the pressure over­came it was 100m (327ft). From the tests, it was determined that a form of gyrostabilisa – tion would be required.

The designated carrier plane for the Kurai was the Nakajima B6N1 and B6N2 Tenzan (known as Jill to the Allies). No modification of the plane’s torpedo rack was required. In operation, the pilot had to visually sight the target and release the torpedo from a height of 100m (327ft). An air spun vane would arm the weapon after it was released and the tor­pedo would go into a 20° downward glide. Once in the water, it would enter its circular dive with a diameter of 79m (260ft), making one revolution through a depth of 79m (260ft) after which it would continue to circle and dive until it was crushed under pressure or had struck the submarine before reaching 100m (327ft). A magnetic proximity fuse was to be used on the torpedo.

In all, 100 of the Kurai No.6 were built with many of them expended in testing. Kugisho constructed the rudders and the metal com­ponents (nose and wing braces) while the Marunimoko Company (located in Fut – sukaishi, Hiroshima Prefecture) produced the torpedo body and wings.

The poor results of the KQrai No.6 resulted in slight modifications to the design. The wing span was increased and the rudders made taller and set at 6° rather than 8°, and the nose was thickened to enhance the ability of the torpedo to penetrate a submarine hull. This new model was designated the Kurai No.7 and in January 1945, eleven test drops were made, but the weapon showed little improve­ment over the Kurai No.6. The end of the war brought the entire project to a close, the engi­neers having run out of time to solve the poor gliding performance and finalise the special fuse.

Two Kurai No.6 mock-ups were captured and shipped to the US for delivery to TAIC. What their fate was is unknown.