Category JAPANESE SECRET PROJECTS

In June 1944, the first Boeing B-29 Super­fortresses appeared over Japan. It was the start of a bombing campaign that would see key Japanese cities, infrastructure and indus­tries reduced to ashes through conventional and firebombing raids. With the aircraft industry being a priority target, the Kaigun Koku Hombu looked to ways to combat the B-29 menace. One concept was a point defence interceptor that could quickly rise to meet the bombers and so the Mizuno Shinryu II was born. However, the development of the Shinryu II (Shinryu meaning ‘Divine Dragon’) began with designs for a far more conven­tional craft.

In November 1944, the Kaigun Koku Hombu looked into the possibilities of an air­craft to undertake shimpu missions. While the mission was not unique, the fact that the
aircraft being investigated would be a glider was. The Kaigun Koku Hombu envisioned that gliders would be launched with rocket boosters from caves or shore positions and pilots would guide the aircraft and the 100kg (220 lb) explosive payload inside it into Allied ships or tanks should the Japanese home islands be invaded.

The Kaigun Koku Hombu assigned the Dai – Ichi Kaigun Koku Gijutsu-sho at Yokosuka the task of turning the glider into reality. The pro­ject was led by Shigeki Sakakibara who staffed a number of teams that would each be responsible for one part of the glider. The dif­ferent sections were the wings, the fuselage, control surfaces, aerodynamic testing and test flights once the prototype was complete. The Kaigun Koku Hombu gave instructions that the glider must be built from as much

wood as possible. This restriction was imposed for two reasons. The first was that in using wood and keeping the use of metal to an absolute minimum, the glider could be manufactured in any small shop using only wood working tools, and secondly, as a con­sequence, what metals were available would be conserved for other military uses.

Much of the glider’s design was conceived by Yoshio Akita. A number of concepts were discussed and sketched and after much deliberation among Akita and his teams the design was complete by May 1945, and Mizuno, a small aircraft manufacturer, had almost finished the prototype. The glider was very simple and used a high-wing monoplane form. The straight and flat wings were wide but had a short span and were designed to ensure that the glider was easy to handle given that inexperienced pilots would be at the controls. Also, the planform would be able to accommodate the rocket engines that were to be used to boost the glider into the air. The pilot sat in an open cockpit.

The design was sent to the Kaigun Koku Hombu for review. Sakakibara studied the plans and projections and after his analysis it was felt the glider was flawed and changes were necessary. After these had been made the design was approved. Work began on the revised JinryQ as the glider was now called by the middle of June 1945. To hasten the con­struction, the finalised blueprints and work plans for the Jinryti were drawn up even as the components for the first prototype were being built. Construction of the JinryQ was again given to Mizuno. Working around the clock, the company completed two proto­types with such speed that wind tunnel test­ing of the design was still underway. In fact, the first flight of the Jinryti occurred even before the results of the testing had been pro­vided to Tonsho and Sakakibara.

Tashiichi Narabayashi was the pilot who flew the maiden flight in mid-July 1945 at the airfield in Ishioka, a city located in Ibaraki pre­fecture, about 90km (56 miles) northeast of Tokyo. The Jinryti was towed into the air by a Tachikawa Ki-9 (known to the Allies as Spruce) piloted by SaburO Fujikura, a man known for his skill in flying gliders prior to the beginning of the war.

For the first test, Narabayashi assessed the Jinryti’s handling. On landing, his opinion was that the glider was stable and possessed good handling characteristics. For the second flight Narabayashi would investigate the Jinryti’s diving capability and after a few bounces on the ground the Ki-9 and the Jinryti took off. At a height of 2,300m (7,545ft), Narabayashi went to cast off from the Ki-9 but found that the tow rope release had stuck; however, he was able to cut the rope and proceed with the test flight. When Narabayashi put the Jinryti into a dive and had reached 300km/h (186mph), the glider began to vibrate to such a degree that he was unable to read the gauges. Pulling the nose up to bleed off speed, Narabayashi discovered that the vibra­tions ceased. During his descent Narabayashi examined the vibrations and after landing the issue was reviewed. The conclusion was that the tail was not sufficiently reinforced and the vertical stabiliser was too small. The JinryQ was modified by adding some strengthening in the tail and the fitting a second stabiliser. The changes were later validated both in the air and in the wind tunnel testing of the mod­ified JinryQ model. Interestingly, before flying the JinryQ, Narabayashi had suspected that the aircraft would have stability problems which, as was seen, proved to be the case.

With the handling and flight characteristics of the JinryQ proven, the testing moved to the next phase – that of powered flight. The glider was relocated to an airfield in Kasumigaura, about 19km (12 miles) north of Ishioka. Here, the JinryQ was modified to accept a group of three Toku-Ro 1 Type 1 rocket engines that together would produce 661 lb of thrust dur­ing a 10 second burn. Testing of the rocket array showed two serious flaws. The first was the quality of the rockets that resulted in a number of failures. The second was the inconsistency of the burn times. Narabayashi noted his concerns and forwarded them to Major Suganuma who had been placed in charge of the JinryQ project. In addition to expressing his doubts about the rocket engines, he also stated that the JinryQ would be unsuited for shimpQ missions because, despite the changes made to the glider to improve the flight characteristics, it was a challenging aircraft to fly. Narabayashi sug­gested that instead of being used for shimpQ operations the glider should be modified to take six rocket engines each with a 30 second burn time. He estimated that at maximum burn the JinryQ could attain a speed of 750km/h (466mph), and for weapons he envi­sioned that it could carry ten explosive charges adapted from artillery shells used by the IJA in their 100mm guns (likely the Type 92). Not only did Narabayashi agree that the JinryQ could be used against tank and ships but added that it could also be used to attack US B-29 bombers. Despite the issues with the rockets work continued on preparing the Jin­ryQ for powered flight.

Major Suganuma, however, would become the catalyst for the ShinryQ II’s continued development. Taking Narabayashi’s concerns onboard, Suganuma formed a team to revise the JinryQ and produce a design for an inter­ceptor rather than a glider; Suganuma was especially interested in this idea since he had access to rocket engines that promised 32 sec­ond burn times. Two people were retained from the JinryQ project: Sakakibara, the lead designer, and Yoshio Tonsho who would over­see the construction of the prototype. YQjiro Murakami was tasked with the aerodynamic testing of the ShinryQ II. All of those assigned to develop the ShinryQ II were ordered by Sug­anuma to maintain the utmost secrecy.

Unlike the JinryQ, the ShinryQ II was to be built from the outset as an interceptor. Sakak­ibara would use a canard design that made this the second Japanese aircraft to be devel­oped during the war with such a feature (the first was the KyQshQ J7W Shinden on page 84). In addition, the main wings had a plan – form similar to a cropped delta. These design features were included as a means of ensur­ing stability in flight as well as good handling characteristics. Since the average Japanese pilot had little experience with canard equipped aircraft, the ShinryQ II had spoilers fitted into the top of each main wing. Each spoiler was able to rotate between 60° and 90° and if the mechanism for controlling the spoilers was damaged, they would automati­cally return to the closed position. The pilot was provided with a canopy covered cockpit.

For power, the ShinryQ II was to use four Toku-Ro 1 Type 2 rocket engines located in the rear of the fuselage. Each engine provided a 30 second burn time and all together up to 600kg (1,3221b) of thrust could be delivered. Two rockets would be used to get the ShinryQ II airborne while the other two engines would be used when making the attack. There was a concern regarding the operating tempera­tures of the Toku Ro rockets and two meth­ods of cooling the engines were considered. The first would have utilised an air-cooled combustion chamber that would have required an air inlet using a bayonet mecha­nism in order to maintain air flow across the chamber. It also would have required specific positioning of the fuel injectors so as not to have the air flow disrupt the injection process. The second method would use injectors which sprayed a water and alcohol mixture onto the rocket nozzle, cooling it. In reviewing the two solutions for cooling, it was determined that the water/alcohol system would be the simplest to implement.

No provision was made for a wheeled land­ing gear system and design skids were used. A nose skid was provided with a basic spring suspension to absorb the landing forces. Under each wing was a non-sprung skid arrangement supported by two struts. For take-off the ShinryQ II was to use a two­wheeled dolly similar to the one used by the

Mitsubishi J8M SvOsui. Once airborne the pilot could jettison the dolly. In addition to con­ventional runway take-off procedures, other methods for launching the Shinryd II were considered but what exactly these were is not known. It can be speculated that towing the Shinryu II aloft was one consideration. Another may have been air dropping the Shin – гуй II in the same manner as the Kugisho MXY7 Oka. In both cases this may have pre­served two of the rocket engines which would have been used up had the Shinryu II taken off from the ground.

In order to combat the B-29, which could operate at altitudes up to 10,241m (33,600ft), the Shinryu II was to be equipped with a pres­surised cockpit or, if such a cockpit proved problematic, the pilot would wear a pressure suit. For weapons, the Shinryu II was to be armed with eight rockets. Attached to the inside of the rear landing skid arrangement were four tubes, one on top of the other and angled downwards, which contained the rockets.

There has been some conjecture as to the mission objective of the Shinryu II. Some sources make the case that the Shinryu II was to be used like the Oka while others come to the conclusion that the Shinryu II was to attack armoured ground targets such as tanks. In both cases these sources state that the nose of the Shinryu II contained an impact fused explosive warhead and once the rocket arma­ment was expended, the pilot would crash the aircraft into his final target using the war­head to deliver the coup de grace. However, analysis of the Shinryu II shows that neither mission was likely. The aircraft would have been far more complex to build than the Showa Тока or Oka and the Shinryu II was constructed for manoeuvrability, high altitude operation and the means to land. In addition, using the Shinryu II for shimpfr missions against tanks makes little sense when there were other simpler and more effective means (both already in service and under develop­ment) to eliminate armour. Perhaps this is a case of the Jinryu glider’s role being applied to the ShinryCi II, or an assumption based on the fact that, like the UN’s other special attack air­craft such as the Nakajima Kitsuka, Kawanishi Baika and Showa Тока, the Shinryti II pos­sessed no letter/numerical designation. So, by extension, the Shinryu II must also have been a special attack weapon. This, of course, is not to say that the pilot could not choose to use the Shinryti II as a shimpti aircraft.

As an interceptor, the Shinryu II had a simi­lar role to the Mitsubishi J8M Syusui and the German Bachem Ba349 Natter for which the Japanese were aware of and obtained data on (although the plans never made it to

Japan). Like the J8M and Ba349 and due to the limited range afforded by the rocket engines, the Shinryu II would have to be posi­tioned close to targets that were likely to be bombed. And like the J8M, the Shinryti II would have used a jettisonable wheeled dolly to take-off while firing a pair of its rocket engines. Unlike the J8M which burned up all of its fuel at once, the Shinryti II had a second set of rocket engines which could be used to sustain flight endurance or to increase speed during the attack. In the same way as the Ba349, the Shinryti II would be armed with rocket projectiles, likely fired as a group to affect a spread pattern, to bring down the bomber target. Finally, akin to the J8M, once the fuel and ammunition were expended, the Shinryu II would glide back to its base to be recovered, refuelled and rearmed.

The Shinryti II would never be built because the end of the hostilities in August 1945 terminated any further work on the design. Likewise, the Jinryu glider would never fly under power. After the failure of the rocket motors during ground tests, the war came to a close before more suitable and reli­able motors could be acquired and tested. Mizuno completed a total of five Jinryu glid­ers. As a note, Jinryu is the known name for the first Mizuno glider. For the purposes of this text, the author used Shinryti II to differentiate the interceptor from the glider. The kanji is the same for both spellings but is pronounced differently. Both translations of Jinryu and Shinryti mean ‘Divine Dragon’. Shinryti II is also used in contemporary texts and as such, is used here for recognition purposes. Whether the interceptor would have carried the same name as the glider is unknown.

Japan shared a fundamental flaw with Ger­many in regards to not developing a bomber capable of long range missions. The lack of this capability is considered by some to be a pivotal nail in the coffins of each country dur­ing the war. In both cases, efforts to develop such a bomber came too late to affect the out­come of the conflict. Although the Japanese had considered the need for such a bomber at the outset of hostilities – as had the Ger­mans with the disastrous Heinkel He 177 Greif – very little happened until the need was dire, and by then the noose was tight, chok­ing any hope for putting a long range bomber into service.

The main cause of this apathy was the early success in the Pacific theatre where the short and medium range bombers then in use by the Japanese were adequate to fulfil the needs of the IJA and UN. With the entry of the United States into the war a formidable prob­lem arose. Geography put the military machine of the US far out of reach of Japan.

When the tide of war turned against the Japanese, it was soon realised that some means to attack the US mainland had to be acquired, not only to destroy the war industry of America but to ravage the civilian popula­tion centres to reduce morale and bring the war to the US doorstep. In consequence, the US would have to allocate or divert resources to increase the defence of the homeland which would affect the war on other fronts. As history was to show, the Japanese did suc­ceed in launching attacks against America, but only in the form of the Fu-Go balloon bombs and isolated attacks on the west coast from submarine-launched float planes. None had much of an effect.

There were some early attempts to pro­duce a long range bomber – for example, the Mitsubishi G7M1 Taizan (a 16-shi project) – plus designs that were actually built such as the Nakajima G5N Shinzan and Nakajima G8N Renzan. The Shinzan was not a success and the Renzan failed to reach operational
service as a combat aircraft, let alone reach America and return.

It was to be Nakajima who would attempt to provide a strategic long range bomber capable of bringing the war to America. The man behind the project was Chikuhei Nakajima, chairman and engineer of Nakajima Hikoki K. K. Motivated by his fears over the inability of the Japanese to reach and destroy US indus­trial capacity, Chikuhei tried to convince the UN and the IJA of the need for a strategic bomber. However, officials from both services refused to consider his ideas. Thus, without official sanction or request, Chikuhei invested a portion of Nakajima’s resources to draft designs for a bomber that could take-off from Japanese bases, cross the Pacific, attack tar­gets on the West Coast of America and return to either their original bases or elsewhere in Japanese or Axis held territory. Nakajima gave the design work the name ‘Project Z’.

On 29 January 1943, Nakajima began the task of assembling drafts and studies for the

design of the bomber, along with reports which studied the feasibility and problems of production. On the completion of this stage in April 1943, he again pitched the concept to both the IJA and the UN. This time, neither service turned Nakajima away. However, despite the information Nakajima had assem­bled for the proposed bomber, and despite both services now accepting the need for such an aircraft, the IJA and the UN also pro­duced their own ideas. Not surprisingly, the two services had differing opinions on the requirements for the bomber. The IJA desired a type that could operate at 9,998m (32,800ft) and carry a heavy defensive armament. By contrast, the UN wanted a bomber capable of flying at a height of 14,996m (49,200ft), an alti­tude where interception would be minimal and thereby allowed a lighter defensive weapon load to be carried. Furthermore, the IJN wanted the bomber to take-off from Japan, bomb any target within the US, then utilise bases in Germany or German held ter­ritory to land, as opposed to making a round trip.

Though there were a number of variations of the aircraft during the Project Z develop­ment, three basic designs of what became the Fugaku emerged. The project presented by the IJA used a ‘tail sitter’ undercarriage, featured dual vertical stabilisers and bore some resemblance to German designs. It also had a rounded off nose similar to the Boeing B-29 Superfortress and Messerschmitt Me 264 ‘Amerika’ bomber. The UN’s proposed design used a tricycle landing gear arrange­ment and rounded nose but utilised a single vertical stabiliser. Nakajima’s proposal kept the single vertical stabiliser but had a stepped nose much like that used on the G5N Shinzan which the company had previously worked on.

By June 1943, Nakajima had received plans from the IJA and IJN, reviewed them and begun work on drafting a final design. To con­tinue the research and further development and study the Project Z aircraft, the Army and Navy Aviation Technical Committee was formed on 9 August 1943. The IJA delegation was headed by Captain Ando. Later in August, Chikuhei Nakajima prepared a thesis entitled ‘Strategy for Ultimate Victory’. Chikuhei used his personal clout to make sure his document reached not only IJA and IJN officials, but also politicians and even Prime Minister Hideki Tojo. His thesis was laid out in six chapters and contained Chikuhei’s plan for defeating the US as well as defending Japan. The key component was the Project Z bomber which he proposed could be used to destroy US air­fields as a means to deny the US the ability to launch raids against Japan. This suggestion was in part due to his belief that Japanese air forces were not strong enough to repel a bombing raid. Another facet of the thesis was the use of the bomber to attack the US war industry. Without materials and oil, the US could not produce aircraft, tanks and other weapons. More importantly, he added, the Japanese should use the bomber to destroy the Soviet military industry as a means to sup­port Germany. This implied that Nakajima could provide Germany with such long range bombers.

The Project Z bomber would employ an all metal stmcture with the wings mounted in the mid-fuselage position. The plane was envisioned to be powered by the Nakajima Ha-54, 36-cylinder radial engine, also known as the D. BH. The Ha-54 was, in fact, two Ha-44 18-cylinder radials paired together. It was pro­jected that the Ha-54 engine could produce up to 5,000hp and that six of these would be sufficient to propel the bomber to a generous maximum speed of 679km/h (422mph). Each engine would drive two contra-rotating, three-bladed propellers with a 4.5m (14.7ft) diameter. The Ha-54 engine, however, would not be ready for some time (and as events turned out, by war’s end it was still only a pro­totype engine and problems with cooling the power unit through the use of a ducted cowl­ing were never solved). Therefore, Nakajima had to settle for the experimental NK11A (Ha-53) which, while also in development, was expected to be ready for trials. The draw­back was that the NKUA was expected to muster only 2,500hp and this would certainly have lowered the performance estimates. The introduction of the NK11A meant that a revision of the Project Z airframe became necessary.

The bomber’s ceiling was estimated to be 15,000m (49,212ft) and it was believed that a heavy defensive armament was not neces­sary as the high altitude would offer protec­tion from fighter opposition. To a lesser extent the projected speed would also reduce vul­nerability. Consequently, the bomber would carry at least four Type 99 20mm cannons, but contemporary illustrations of the bomber often show a much heavier armament. This may be a result of having to settle for the less powerful NK11A and any speed/altitude advantage would have been lost, so an increased weapon load would have been necessary to protect the aircraft. Typically, illustrations show two cannon mounted in the tail, two in the nose, two twin-cannon tur­rets placed in the front and rear of the fuse­lage top and at least one belly turret. Variations included waist gunner stations. For a normal bomb load, the bomber was expected to carry up to 20,000kg (44,092 lb) of

Contemporaries

Convair B-36 Peacemaker (US), Convair XC-99 (US), Messerschmitt Me 264 and Me 264B (Germany), Junkers Ju 390 (Germany), Junkers EF100 (Germany), Messerschmitt Me P 08.01 (Germany), Tupolev Tu-4 (NATO codename Bull) (Russia), Tupolev Tu-85 (NATO codename Barge) (Russia), Tupolev Tu-70 (Russia), Vickers-Armstrong Victory Bomber (UK)

Specifications in parentheses refer to the Fugaku specifically. All other specifications refer to the primary Nakajima Project Z design.

Type Long range strategic bomber

Crew Six to ten (seven to eight)

Powerplant Six Nakajima Ha-54 36-cylinder, air-cooled radials developing 5,000hp at engine start, each driving two alternating stroke, contra-rotating three bladed propellers of 4.5m (14.7ft) diameter/Six Nakajima NK11A [Ha-53] 18-cylinder, air-cooled radials developing 2,500hp at engine start and each driving a alternating stroke, four-bladed propeller of 4.8m (15.7ft) diameter

Deployment

None. The ‘Project T and Fugaku aircraft existed only as paper designs.

bombs, but in the case of anti-shipping mis­sions, torpedoes could be carried (see below). For attacks on the United States, the bomber would carry only up to 5,000kg (11,023 lb) of bombs.

As work continued on the Project Z, plans were made to assemble and house the bomber’s production line. By the fall of 1943, these plans had been completed and con­struction of the new facility had begun. By January 1944, the Project Z moniker was dropped and changed to the Fugaku which means ‘Mount Fuji’.

As it was, more pressing demands on Nakajima resulted in less and less work being done on the Fugaku. To compound the prob­lem, by the time the design was nearing com­pletion, Japan was on the defensive and chances of producing the Fugaku, let alone using it to attack America, were about nil. The IJA believed that there was no probability of the Fugaku being built and therefore aban­doned the project, leaving the UN as the sole remaining party involved. Even the Gunjusho (the Ministry of Munitions) felt the Fugaku was impossible to realise and ordered Kawanishi to design a new long range bomber. Unfortunately, the Gunjusho failed to inform the IJA, UN and Nakajima about the Kawanishi bomber, which was known as the ТВ. When the new bomber project was dis­covered, a hail of protests and arguments erupted that hampered not only the develop­ment of the Fugaku but all long range bomber projects including the ТВ which was soon cancelled.

However, it was the fall of Saipan in 1944 that sealed the Fugaku’s fate. The Japanese air forces no longer had need of a super long range bomber and demanded more perti­nent aircraft to protect the mainland. As such, all work on the Fugaku was stopped and the plans, calculations and drafts were shelved. Work on the production facility was halted prior to completion and left unfinished. With the Japanese surrender, all documentation
for the Fugaku was to be destroyed to prevent the information being handed over to the Allies. Papers on the Fugaku that survive to this day, including a number of drafts for var­ious Project Z/Fugaku proposals, were mis­laid or kept for safe-keeping by individuals. Since the war it has been claimed that the Misawa Air Base would have been used by Fugaku bombers to launch raids against the US. While Misawa was used by the IJA and operational IJA bombers flew from this facil­ity, there has been no definitive evidence to support or refute Misawa being considered as a Fugaku base.

Bombing was not the only mission that was envisioned for the Fugaku and during the Pro­ject Z brainstorming three other concepts arose and later formed part of Chikuhei’s the­sis. The first was an attack design that had 400 Type 97 7.7mm machine guns crammed into the aircraft. The front and the back of the bomber would accommodate 40 machine guns arranged in ten rows. The intention was to rain thousands of rounds of bullets down on to enemy ships with the theory that a swath of destruction 45m (148ft) wide and 10km (6.2 miles) long could be achieved by 15 Fugaku aircraft. Once the decks of these ships were swept of personnel, nine Fugaku bombers, each with twenty 907kg (2,0001b) bombs or torpedoes, would deliver the coup de grace, covering a path 200m (656ft) wide and 1km (0.62 miles) in length with high explosive.

Another version had the Fugaku loaded with 96 Type 99 20mm cannons. The front and the back of the aircraft would contain 12 cannons arranged in eight rows while another 36 cannons were fitted on each side of the aircraft. This particular variant was to target enemy bombers flying missions against Japan and would use hidden bases untouched by the Japanese airfield bombing campaign. By flying over the enemy bomber formation and unleashing a withering fusil­lade of cannon fire, it was speculated that ten
of the cannon equipped Fugaku could bring down 100 bombers, the area covered by the cannons from one plane being 2.5m (8.2ft) and 3km (1.86 miles) long. A system of ground radar stations would give advance warning of the incoming enemy bomber force, allowing time for the Fugaku to inter­cept and destroy the bombers before they reached Japan. This was all very impressive on paper but had it been put into practice the results were likely to have been less than stel­lar, especially when considering the failure of the Mitsubishi G6M1 heavy escort fighter (a G4M converted into a gunship to provide cover for bomber formations). Finally, the Fugaku was considered as a transport which would have provided a significant heavy lift capability. It was estimated that one Fugaku transport would be able to carry 300 soldiers with full equipment, about equal to one infantry rifle company with a heavy weapon platoon. Chikuhei envisioned a grand scheme of a raid against America where four hundred transports would deposit 120,000 men (equivalent to a Japanese Army, which equates to a US and British Corps) on US soil to take over the Seattle-Tacoma airport located in Washington. After landing the troops would move overland to attack and destroy Boeing’s B-29 producing Renton Fac­tory in Renton before returning to Japan.

There is no evidence to suggest any of these concepts made it to the final Fugaku designs. However, if any of the three ideas were supported, a transport may have topped the list for possible consideration given the late war need for aircraft capable of bringing raw materials into Japan to feed the war industry that was slowly being starved. As a note, although the designations G10N and G1 ON 1 have been used in print for this aircraft for many years, there has been no confirma­tion in historical sources that confirms this was the case.

In the spring of 1938, the UN issued a 13-shi specification for a long range fighter. This came about as a result of combat experience in China that showed that Japanese fighters did not have the range to escort bombers on missions deep into Chinese territory, the result of which were high losses. What Naka­jima produced to answer the specification would have been a complete failure had it not been for one redeeming feature.

The 13-shi specification was a very strict one with a number of very demanding crite­ria. Nakajima’s Katsuji Nakamura would pro­duce the initial prototype. It was an aerodynamically clean З-seat monoplane with low mounted wings. Each wing housed a Nakajima Sakae radial, developing 1,130hp. However, one wing was fitted with a Sakae 21 engine, the other with the Sakae 22, and their propellers rotated in opposite directions to reduce torque. To complement the nose armament, twin remote controlled barbettes, each with two 7.7mm Type 97 machine guns, were placed behind the pilot’s cockpit. Des­ignated the J1N1, the first two prototypes were delivered and put under test. A myriad of problems were noted – the plane was over­weight, the novel propeller arrangement caused numerous difficulties, the hydraulic system was too complex, the barbettes were too difficult to aim and the entire arrange­ment was too heavy. To top it all off, manoeu­vrability was poor and all the J1N1 had going for it was its range.

Rejected as a heavy fighter, the JIN was given new lease of life as a reconnaissance aircraft. Nakajima stripped the aeroplane of its weapons and the barbettes, cut the fuel capacity (which, in part, was made up by using drop tanks) and replaced the Sakae 22 engine with another Sakae 21 powerplant. The armament was a single, rear firing 12.7mm Type 2 machine gun to be was used by the radio operator. Now called the J1 Nl-C, following successful trials the aircraft received approval and entered service with reconnaissance units from August 1942. On encountering it in combat, the Allies code – named the plane Irving, thinking it was a fighter. The 1JN renamed the plane J1N1-R, equipping some examples with a turret mounting a 20mm Type 99 Model 1 cannon.

In early 1943, Commander Yasuna Kozono, who led the 251st Koktttai operating from Vunakanau Airfield in Rabaul, Papua New Guinea, believed that the J1N1 – C would make an excellent night fighter. Mechanics replaced the observer’s station and installed two 20mm Type 99 cannons that fired upward and forward at a 30° angle and two additional cannons firing downward and for­ward at a similar angle. Called the J1N1 – C Kai, the field modification proved a success and with that success, the UN became interested.

In short order, Nakajima was instructed by the UN to produce a dedicated night fighter version of the J1 N. By August 1943, the assem­bly of the first model, the J1N1-S Gekko (meaning ‘Moonlight’), had begun at Naka­jima’s Koizumi plant. The main changes saw the glazing over the crew compartment reduced and the step removed. The ring exhaust collector was also removed and the engines used individual exhaust stacks. In addition, it was realised that the downward firing cannons were ineffective and in the JINl-Sa were removed. Both the J1N1-S and JINl-Sa were sometimes fitted with a centi- metric radar in the front of the aircraft, the external antenna for the set being situated on the tip of the nose. Others had a searchlight in the nose while a number lacked the radar and searchlight to be replaced by a single for­ward-firing 20mm Type 99 cannon.

In combat, the Gekko proved satisfactory against the Consolidated B-24 Liberator, but against the faster Boeing B-29 Superfortress was hard pressed to make a single attack. Therefore, it should not be surprising that the JIN was considered as a candidate to be equipped with two turbojets. Successful as a reconnaissance platform as well as a night fighter, replacing the radial engines with tur­bojets would have provided the JIN with a superior speed that would have served it well in either role. A contemporary illustration of the turbojet equipped J1N shows the fuselage of a J1N1 – Sa. The illustration lacks the upward firing cannon and radar which suggests it was equipped with the nose mounted cannon as its armament. Perhaps it may have worked in conjunction with radar and/or searchlight equipped J1N1 -S and J1N1 – Sa during combat missions, or it may have been considered as a fast special attacker fitted with two 551 lb bombs (as surviving JIN aircraft were at the end of the war). The wings seem to have been unaltered outside of the required mod­ifications to fit the nacelles for the turbojets. As to what jet engines were to be introduced is not known. The Kugisho Ne20 was cer­tainly a candidate as was the Nakajima Ne 230. The adaptation of the J1N to jet power would likely have been an easier task than that faced by Kugisho in adapting the P1Y1 Ginga into the turbojet bomber Tenga.

Exactly when the proposal to modify the JIN to a turbojet aircraft was made is unknown. What is known is that it did not progress past the drafting board.

Even though the genesis of the turbojet began long before World War 2, it would take the war to accelerate the development of this new powerplant to the point that by the close of hos­tilities jet aircraft had been blooded in battle. Germany can, by some, be considered the leader in turbojet technology during the war, but the US and Britain were not far behind. Japan, too, was not idle in producing its own turbojet but it would take German knowledge to give their industries a boost. One such results was was an historic aircraft in the annals of Japanese aviation history: the Naka­jima Kitsuka.

Because the Kitsuka (which in Japanese means ‘Wild Orange Blossom’) was probably the most important Japanese aircraft to use a jet engine as its powerplant, it seems apt to provide a general overview of Japanese turbo­jet development in this section. The first axial – flow turbojet was patented in 1921 by Frenchman Maxime Guillaume. However, the technology of his day was not enough to realise a working model, in 1930, Englishman Frank Whittle designed a turbojet using a centrifugal
compressor and, despite relatively little inter­est being shown in it, he patented his concept. In 1933, German Hans von Ohain designed a turbojet similar to Whittle’s but it would not be until 1936 that Ernst Heinkel took an interest in the engine and hired von Ohain to continue his work. By March 1937, this resulted in the Heinkel HeS 1, the first German jet engine although in fact a hydrogen demonstrator. The following month Whittle tested his first jet engine, the WU or Whittle Unit.

Around this time, Rear Admiral Koichi Hana – jima became aware of Whittle’s work as well as that of Secondo Campini, an Italian who began work on a thermojet and an aircraft to use it: the Campini Caproni N. l in 1934. This rekindled his interest in jet propulsion and using his position as head of the engine division of the Dai-Ichi Kai – gun Koku Gijutsu-sho, saw to it that studies were conducted in such engines. Hanajima reached out to the Tokyo Imperial University and Mit­subishi Jukogyo K. K. and together all manner of rocket and jet engines were investigated such as ramjets. To Hanajima’s disappointment, little official interest was generated from the results.

1938 saw German firm BMW begin their research into turbojets and the Heinkel He 178 VI prototype was built to test the HeS 3 turbo­jet that was being developed from the earlier HeS 1. In late 1938, Messerschmitt started work on what would become the world’s first jet fighter to enter squadron service, the Me 262. In Japan, and despite the lack of interest being shown in jet propulsion, Captain Tokiyasu Tanegashima was appointed as the head of the Engine Test and Field Support Shop of KQgisho. He was issued with a meager sum to fund jet engine research although, with the assistance of Professor Fukusaburo Numachi, he would initially focus his efforts on turboprops. Both men were able to source the Ishikawajima – Shibaura Turbine Company and Ebara Seizo K. K. to help build a number of test engines that used compressors and gas turbines, but these labours did not bear fruit.

By 1939, BMW had tested its first axial-flow turbojet design and on 27 August of that year the He 178 VI made its first flight, the first tur­bojet powered aircraft to fly. In February 1940, the British Air Ministry ordered two examples

of the E.28/39 research aircraft from the Gloster Aircraft Company to serve as testbed aircraft for Whittle’s engines. 1940 also saw the Italian N. 1 fly for the first time and Heinkel began glid­ing tests of the He 280 jet fighter prototype as it waited for its two HeS 8 turbojets now under development (the He 280 did not enter pro­duction). November would see Junkers test the Jumo 004 turbojet and Gloster’s jet fighter proposal, the Meteor, was ordered in February

1941. Also in November, Lockheed com­menced work on the L-1000 axial-flow turbo­jet, the first American jet. Finally, in December, Whittle’s W.1X turbojet, a flight ready engine, was tested for the first time.

Japan though, was not idle in 1940. Early in the year, Tanegashima, with the help of the Mit­sui Seiki Kogyo K. K., created a free piston com­pressor for a gas turbine based on a Junkers design, but it was not a success as a means for aircraft propulsion. Another attempt was tried by a different department. Under the leader­ship of Lieutenant Commander Osamu Nagano, head of the Kugisho aircraft engine division, and Masanori Miyata, who led the Kugisho electric parts section, built a tiny free piston compressor gas turbine, generating one tenth of a horsepower at 12,000rpm that drove a magneto that lit a lamp. Despite this measure of success, apathy on the part of the UN con­tinued to stymie progress. Tanegashima soon realised that the Japanese industry was not capable of constructing a free piston engine and switched his studies to axial flow jets.

On 15 May 1941, the Gloster E.28/39 flew for the first time, but previously in April, Heinkel’s He 280 VI had flown under jet power on its maiden flight, the first jet fighter to fly. 1942 saw the Junkers Jumo 004 under test while BMW focused efforts on the BMW 003 Sturm. Heinkel was instructed to concentrate on developing the HeS 011, a turbojet that was to power the second generation of German jets. On 18 July, the Messerschmitt Me 262 flew under turbojet power, becoming the second jet fighter to fly, and on 2 October, the American Bell XP-59 Airacomet jet fighter made its maiden flight. By this time, Japanese engineers and scientists had learned of the flight of the He 178 as proof that an aircraft powered by a jet engine was feasible. This was just the boost the flagging Japanese jet engine research desperately needed.

As a result two different paths were taken with renewed vigour. The first employed the principle of the thermojet (as used by Secondo Campini) and was called the Tsu-11. While this engine was to be selected for use in the Kugisho Oka Model 22, it was found to be unsuited as a powerplant for a jet aircraft. The second route, that of a pure jet engine, was pursued further. Kugisho’s Vice Admiral Misao

Wada was the man who oversaw the develop­ment of a turbojet and the first result was the TR-10. This had a single stage, centrifugal com­pressor with a single stage turbine and was, in essence, built by adapting a turbosuper­charger. The engine was constructed by Ebara Seizo K. K. When the TR-10 was first tested in the summer of 1943 its performance did not meet expectations. The TR-10 was renamed the NelO and the engine was further devel­oped by adding four axial stages in front of the engine inlet. This reduced the load on the cen­trifugal compressor, lowered the engine RPM and produced more thrust. The revised jet engine was designated the Ne 12. The problem with the Ne 12, however, was its great weight and so steps were taken to lighten the engine, which resulted in the Ne 12B.

1944 was an ominous year for Japan. When the Mariana Islands of Saipan and Tinian were wrestled from the Japanese by US forces in July and August, Japan found herself well within striking distance of the Boeing B-29 Super­fortresses. Prior to this, B-29 raids had to fly from remote bases in China and India and so the bombing of Japanese targets was relatively rare. Staging from Saipan and Tinian, B-29s were far closer, could be more active and the Japanese were only too aware of this. In addi­tion, it was surmised that it would only be a matter of time before the main Japanese islands were targeted for invasion. In August 1944, the Kaigun Koku Hombu called for a meeting to discuss changes in air strategy to combat the air and land threat as well as to consider the aircraft that would be used. The Kaigun Koku Hombu invited aircraft designers from both Nakajima and Kawanishi to attend and the outcome of this meeting was the pro­posal for three classes of aircraft termed Kokoku Heiki (one literal translation being ‘Empire Weapon’). The first class, or Kokoku Heiki No. l, was the adaptation of current air­craft to accept a 800kg (1,7601b) bomb with which their pilots would undertake shimpQ missions and target enemy invasion ships. If the bomb overloaded the carrying capacity of the aircraft, then RATO (Rocket Assisted Take – Off) units would be used to get them airborne. Kokoku Heiki No.3 was to be a conventional, radial engine aircraft designed by Kawanishi as the TokkO-ki, which would be used for shimpii missions, but this project was soon abandoned (perhaps because the UN was to build the sim­ilar Nakajima Ki-115 as the Showa Тока). It would be Kokoku Heiki No.2 which provided the seed for the Nakajima Kitsuka. This ‘Empire Weapon’ was to be an aircraft that used the Tsu-11 and, when available, the Ne 12 turbojet.

However, three months prior to the meeting, efforts were underway to obtain the Me 262 from Germany. In May 1944, the Japanese negotiated for the manufacturing rights to the Me 262 and the Germans initially agreed to the release. However, the deal was not concluded due to the large number of modifications that the design was found to require after its flight testing. It was not until July 1944 that orders were given to provide the Japanese with blue­prints of the Me 262 fighter and the Junkers Jumo 004 and BMW 003 turbojets.

On 22 July 1944, Reichsmarschall Hermann Goring authorised the licensing of the Me 262 to Japan and the delivery of one sample air­craft. However, the Japanese submarine 1-29 had left Lorient, France, on 16 April with a sam­ple Junkers Jumo 004 turbojet and plans for the Me 262 and BMW 003 turbojet among its cargo. Also aboard the submarine was Technical Commander Eiichi Iwaya who carried on his person a portion of the documentation on the German fighter and turbojets. By 14 July, the 1-29 had arrived in Singapore. Iwaya, seeking to reach Japan as soon as possible, disembarked from 1-29 and took only a portion of the German documentation. From Singapore, Iwaya flew to Tokyo. On 26 July, Allied code intercepts pin­pointed the location of 1-29 and the USS Saw­fish sent her to the bottom near the Balintang Channel in the Luzon Strait, taking the precious cargo with her.

When Iwaya arrived in Japan, all he pos­sessed of the German files with regards to the Me 262 and turbojets was a single copy of a cross-section of the BMW 003A turbojet. The subsequent news of the loss of 1-29 was a crushing blow, but not a fatal one by any means. In studying the BMW 003A document, the Japanese found it to be of a similar design to the Ne 12 but instead of the centrifugal com­pressor the German engine used an eight stage axial-flow compressor. It was adjudged that this method was superior to the Ne 12 and as such, efforts should be concentrated on build­ing the Japanese equivalent to the BMW 003A. Despite the decision against it, work on the Ne 12B continued. Four companies were involved in the development of the new turbo­jet. Each was to be provided with a copy of the BMW 003A cross-section and other available data and to build their own versions. Ishikawa – jima-Shibaura Turbine Company was to develop the Ne 130, Nakajima Hikoki K. K. the Ne 230, Mitsubishi Jukogyo K. K. the Ne 330, and Kugisho would move forwards with the Ne 20.

Following the August conference with the Kaigun Koku Hombu, Ken’ichi Matsumura, chief designer for Nakajima and with the assis­tance of Kazuo Ono, produced a number of concept drawings for the Kokoku Heiki No.2. Within Nakajima, the new aircraft was given the codename Maru-Ten. On 14 September 1944, UN representatives met with Nakajima at their Koizumi plant to discuss the concepts which had been put forward. The design that stood out was based on a description of the Me 262 as provided by Technical Commander Eiichi Iwaya who, while in Germany, was able to view and study the German jet. Thus, Mat – sumura’s drawing bore an outward resem­blance to the Me 262. After reviewing the concept, the design was approved as the Kokoku Heiki No.2. In keeping with the shimpu mission of the aircraft, the initial design had no landing gear and was to be launched from cat­apult ramps, boosted with RATO units. The cal­culated range was a mere 204km (127 miles) due to the designated engine, the Ne 12, which burned fuel at a rapid rate. At sea level the esti­mated speed was 639km/h (397mph). A single bomb fixed to the aircraft was the only arma­ment. Another feature was the inclusion of folding wings to allow the aircraft to be hidden in caves and tunnels and protected from bombing attacks.

On 8 October, Kugisho ordered Kazuo Yoshida, plant director for Nakajima, to have a wooden mock-up of the aircraft completed and ready for inspection by the end of the month. In addition Nakajima was told to have the initial structural plans finished by the same date. This was ordered so that production of the aircraft could begin without delay. Unfortu­nately, delays would be a major problem. The UN promised that the Ne 12 would be ready for testing by November 1944 and in short order thereafter, production engines would be avail­able. Based on this assumption, Nakajima was to construct thirty aeroplanes by the end of December 1944. Because of the rush to pro­duce the aircraft, a myriad of problems arose with the design which necessitated changes. A major issue was the lack of critical war materi­als which required the use of substitutes and brought additional delays. To compound the problem, Nakajima was concerned that the Ne 12B would not be ready despite the UN’s promises.

Meanwhile, Kugisho proceeded with the Ne 20. The engineers were forced to use alloys which were not to the standards of the German engine and would be a source of problems dur­ing testing. The design of the Ne 20 was smaller than the BMW 003A but it retained the com­bustion chamber shape of the German engine. While it used the same size of burner as the BMW 003A, it only used twelve instead of six­teen due to the smaller size. Kugisho would draft and refine the design of the Ne 20 through December.

On 9 December 1944, the UN called a meet­ing to discuss the progress and outlook of the Kokoku Heiki No.2. Based on the problems Nakajima were having with the aircraft, not to mention the doubts about the Ne 12, the pro­duction schedule was revised. Nakajima were requested to produce the first prototype by February 1945 for use in static testing. It was also during this meeting that the aircraft’s spec­ifications underwent a revision. Instead of a fixed bomb, the bomb could now be released by the pilot. The role of the aircraft was also changed. No longer was it to be used for a shimpu mission but instead for close air sup­port, the aircraft acting as a fast attack bomber. As a consequence of these changes, the design had to incorporate a landing gear. The UN issued its specifications for the new jet, which was now called the Kitsuka, and the docu­ments requested:

Span: no more than 5.3m (17.3ft) with the wings folded

Length: no more than 9.5m (31.1ft)

Height: no more than 3.1m (10.1ft)

Powerplant: Two Ne 12 jet engines Maximum Speed: 513km/h (319mph) with 500kg (1,102 lb) bomb Range: 204km (127 miles) with a 500kg (1,1021b) bomb or 278km (173 miles) with a 250kg (551 lb) bomb Landing Speed: 148km/h (92mph)

Take-off Run: 350m (1,148ft) using two 450kg (992 lb) RATO bottles

Manoeuvrability: The aircraft had to be highly manoeuvrable, have a short turn radius and be stable at speed to facilitate target tracking Protection: Shatter proof glass for the canopy. Front windscreen to have 70mm of bullet proof glass. 12mm of steel armour plate below and behind the pilot. Fuel tanks to be 22mm sandwich types

Basic Instrumentation: Tachometer, altimeter, artificial horizon, airspeed indicator, Model 0 Type 1 flux gate compass, fuel pressure gauge, oil pressure gauge, oil temperature gauge, tail pipe temperature gauge and a pitot tube electric heater

Basic Equipment: Type 0 parachute, automatic fire extinguisher, Type 3 dry battery, Type 3 radio receiver, Type 1 life raft and a reserve weight of 30kg (66.1 lb)

1945 would open with more misfortune for the Japanese war machine. Japanese troops were pushed out of Burma from 5 January and B-29s would bomb Tokyo the next day. Two days ear­lier, Matsumura and Ono, along with others involved in the Kitsuka project, discussed the possibility of using the Ne 20 turbojet in place of the Ne 12. In the debate, some suggested that the Ne 20 was not as far in development than the Ne 12 and would delay progress if used. On the other hand, some argued that the Nel2 was not achieving significant results. In the end, the consensus was that the Ne 12 should remain as the powerplant only because it was projected to be ready before the Ne 20.

On 28 January 1945, the wooden mock-up of the Kitsuka was finally ready for inspection at Nakajima’s Koizumi plant. Vice Admiral Misao Wada and his staff visited the plant and inspected the mock-up with both Matsumura and Ono in attendance. It was made clear to the Kugisho inspectors that the Kitsuka was a very simple aircraft that could be constructed in 7,500 man-hours. By comparison, it took 15,000 man-hours to build a Mitsubishi A6M Reisen. Following the inspection, Nakajima was told to make two slight adjustments to the Kitsuka. The first involved the windscreen. Originally, the front windscreen was rounded but now it was desired that it should be flat panelled. This change may have been sug­gested to allow for the future installation of a reflector gun sight because such a sight requires flat panels to avoid sighting problems due to canopy distortion. The second alteration was to make the canopy slide to the rear instead of opening to the side. At the conclu­sion of the meeting, Nakajima was told to cease all work on the Nakajima J5N1 Tenrai and the company was also informed that they could expect the Nakajima G8N1 Renzan to be terminated as well. These changes in produc­tion and development were done to speed the coming production of the Kitsuka. The close of January also saw the final design draft of the Ne20 completed and almost immediately work began to build the first engine. Kugisho’s Aero Engine Division provided 400 machine tools and engineers and labourers began to toil day and night to realise the Ne 20.

February 1945 opened with the Japanese naval docks in Singapore targeted and destroyed by B-29 bombers along with contin­ued fighting in the Philippines. A second inspection of the Kitsuka was called for on 10 February. Present at the inspection, among the other engineers and Kugisho personnel, were Technical Commander Iwaya and the man who was destined to fly the Kitsuka, Lieutenant Commander Susumu Takaoka. The Kitsuka was given final approval and production was to commence at once, even before the Kitsuka had been flight tested. The first five Kitsuka air­craft, No. l through No.5, were to serve as pro­totypes and none would be fitted with armour plating or self-sealing fuel tanks. In addition the first two aircraft would not to be equipped with the bomb carrying apparatus. February would also see the Ne 12B tested for the first time.

Unfortunately for the Kitsuka, US bombing ensured that production did not go smoothly. Due to the ever increasing number of strikes against the industrial centres of Japan, it was felt that it was only a matter of time before the Nakajima Koizumi plant would attract the attention of US bombers. Therefore, on 17 Feb­ruary, engineering staff for the Kitsuka was moved to Sano in Tochigi Prefecture. Despite the move, a sizable portion of the Kitsuka com­ponent construction remained at Koizumi while the wings, tail assembly and the centre and aft portion of the fuselage were con­structed by Kugisho in Yokosuka. In the face of further bombing attacks, production was dis­persed among silkworm factories and build­ings in Gunma Prefecture (northwest of Tokyo).

March arrived in a blaze of smoke and fire as the US ramped up their incendiary bomb cam­paign against Japan’s cities. Tokyo and Nagoya were particular targets, the burning cities light­ing the night sky. On March 26, the first Ne 20 engine was successfully test run from a cave set into a cliff in Yokosuka. With the success of the Ne 20, the Kitsuka engineering team began to seriously consider replacing the Ne 12B with the Ne 20. It was clear that the Ne 20 outper­formed the Ne 12B and, based on the higher thrust potential, it was decided that the Kitsuka should use the Ne 20 even if it meant a longer delay while the engine became available. Although the current Kitsuka production did not yet involve the engine mountings, a revi­sion of the aircraft design plans was required to accommodate the Ne20. By March 31, these revisions were complete and the Kitsuka pro­gram entered a stage of finality.

With the revised Kitsuka, some of the speci­fications were adjusted as follows:

Maximum Speed: 620km/h (385mph) with a 500kg (1,1021b) bomb at sea level Range: 351km (218 miles), at sea level, at full power

Take-off Run: 500m (1,640ft) with two 450kg (992 lb) RATO bottles Landing Speed: 92km/h (57mph)

Bomb Load: 500kg (1,102 lb) as normal with the ability to carry a 800kg (1,763 lb) bomb; a Type 3 rack would be used for the larger bomb Protection: Reduce the bullet proof glass thickness to 50mm and add 12mm of armour to the front of the cockpit, while the fuel tanks would incorporate an automatic fire suppression system

Engineers working on the Ne20 found that, although the initial test of the engine was a suc­cess, there were many issues to solve. At first, the blades were prone to cracking but this was soon overcome. An electric starter was fitted into the compressor spinner that could spin the engine at 2,250rpm; the engine would reach maximum RPM within 10-15 seconds of engine start. Gasoline was used to start the engine and once running the fuel was switched to a pine root distillate using 20-30 per cent gasoline. What was becoming a problem was how to position the tail cone. Lieutenant Commander Osamu Nagano and his team, along with Cap­tain Tokiyasu Tanegashima, laboured to refine the Ne 20. The worsening bombing situation saw the Ne 20 team moving to Hadano in Kanagawa Prefecture, a three hour drive from Yokosuka.

Set up in warehouses belonging to a tobacco factory, the Ne 20 group comprised 10 officers and 200 men. Here, two bench testing stations were created and Ne 20 devel­opment and testing continued. The process revealed numerous flaws. At one stage the pressure of the axial-flow compressor was found to be too low. Nagano came to the con­clusion that the camber of the stators was not correct and so he took them out, bent them on an anvil and then reinstalled them. These were tested in the second Ne 20 to be built. Yet another difficulty arose with the thrust bearings on the compressor which was burn­ing out very quickly. Nagano solved the prob­lem by revising the bearings and bearing rings. One problem that reappeared was blade cracking. The blades were made from manganese-chromium-vanadium steel and not the more suitable nickel alloy. These blades were then welded to the disk and, as such, the blades did not have the strength to withstand the operating stresses of the motor. After one to two hours of operation, cracks would appeare on the blade roots at the point where they connected to the disk. The solu­tion was to thicken the blades but this low­ered the efficiency of the engine. However, the Ne 20 was able to run for four or five hours before cracks appeared and while the engine could have run longer, there was no guaran­tee when blade failure would occur. With these improved results, work began to pro­duce a small number of engines.

25 April 1945 would see the first Kitsuka fuse­lage completed. This was then subjected to stress and load testing which began on 20 May, but with the stipulation that the fuselage was not to be damaged during tests. Nakajima was scheduled to produce 24 Kitsuka aircraft by June 1945 and with the availability of six Ne 20 engines. On the surface, the Kitsuka project looked to be moving along. The reality was a far different story.

On 13 June, Vice Admiral Wada held a meet­ing to discuss the Kitsuka. Wada addressed a number of issues that were becoming prob­lematic. Nakajima’s G8N1 Renzen program had to be stopped in order to free up produc­tion capacity for the Kitsuka as both a special attack aircraft and an interceptor. More trou­bling was that unless the stock of aluminium was conserved the supply would be exhausted by September 1945. At best, even with conser­vation, by the close of 1945 there would be no more aluminium available. As a result, only steel and wood would be left and to use such materials would, again, have caused a revision to the Kitsuka design. The final blow was that high grade aviation fuels would only be avail­able for the Homare series of radial engines. All other engines, including the Ne 20, would have to make do with poorer quality fuel. This, cou­pled with defeat after defeat for the Japanese military, cast a very serious cloud over the Kit­suka project and some no longer saw value in continuing with the aircraft. Others however, had a strong desire to see the Kitsuka taken to completion because it would put Japan into the jet age.

On 25 June 1945, the first Kitsuka was com­pleted but without its engines. Although exter­nally the Kitsuka bore a resemblance to the Me 262, that was as far as it went. The wings of the Kitsuka had a total of 13° sweepback, the centreline of the wings being at 9°. Wing tip slots eliminated the tip stall discovered during wind tunnel testing and split flaps and droop ailerons were fitted to compensate for the heavy wing loading. Nakajima К series airfoils were used – а К 125 airfoil at the wing root and a К 309 airfoil at the wing tip. The wings were

of double spar construction with nine main support ribs, all covered with steel and duralu­min skinning. Mitsubishi A6M Reisen flap hinges were used on the trailing edge flaps and the wing tips were fabricated from wood and steel sheeting. The outer wing folded upwards. The Kitsuka had a slight gull wing form thanks to 5° dihedral of the centre span and 2° dihedral of the outer wing. All control surfaces were fab­ric covered. The fuselage had a slight triangu­lar shape, being composed of three sections (nose, centre section and aft). The centre sec­tion had the centre wing span built into it and much of this and the other two sections were constructed from sheet steel due to the unavailability of duralumin in quantity. Twenty – four bulkheads were contained within the complete fuselage with two bulkheads coming together where each section met, which were then bolted together to complete the fuselage. Two fuel tanks were fitted, one in front of and the other behind the cockpit. The tail of the Kit­suka was fairly conventional and the aft fuse­lage line was kept high so that the stabiliser would not be effected by the jet efflux. For the tricycle landing gear, the main gear (to include the brake system) from a Mitsubishi A6M Reisen was modified to suit the Kitsuka and the 600mm x 172mm-sized wheels retracted into the wing. The 400mm x 140mm-sized nose wheel was taken from the tail wheel of a Kugishd P1Y Gingaand it retracted into the rear of the nose.

After being assembled the Kitsuka was then broken down, loaded into trucks, and moved to Nakajima’s Koizumi plant where two Ne 20 engines awaited it. By 27 June, the Kitsuka had been put back together and the engines installed, and two days later weight and bal­ance checks had been completed. The Kitsuka was then declared ready for flight testing. On 30 June 30 1945, both Ne 20 engines on the Kit­suka were started and run for a short time. Flight testing could not be conducted at the air­field at Koizumi because the runway was too short and had many approach restrictions. Mis – awa Air Base (Misawa Hikojo), in Aomori Pre­fecture 684km (425 miles) north of Tokyo, was also considered since it had open approaches and was rarely visited by Allied long range fight­ers. However, because of the great distance it was ruled out. Finally, it was settled that the air­field at Kisarazu Air Base (Kisarazu Hikojo) would be the location for the first flight because it was far closer to Yokosuka than Mis­awa. Once more the Kitsuka was disassem­bled, loaded into trucks, and moved to the Kisarazu airfield, adjacent to Tokyo Bay.

On arrival, the Kitsuka was reassembled and made ready for its first flight. Unfortunately, on 14 July, during engine testing, a loose nut was ingested which completely shattered the blades in one of the compressors. The damage to the engine was so extensive that repairs were simply not possible and replacement the only option. This delayed the flight for many days. As the Kitsuka was being repaired, the personnel for the 724 Kokutai, which had been designated a special attack unit and which would fly the Kitsuka in service, had been assembled at Yokosuka after its formation on 1 July 1945. On 15 July, the new unit moved to Misawa Air Base where it began training using Aichi D3A1 and D3A2 carrier bombers (known as Val to the Allies), which had been relegated to the training role.

On 27 July, Lieutenant Wada conducted some successful taxi tests with the Kitsuka. High speed taxi tests, however, were prepared by appointed Kitsuka test pilot Lieutenant Commander Susumu Takaoka. Two days after the initial taxi tests, Takaoka ran the Kitsuka up to 129km/h (80mph) and then applied the brakes to test their effectiveness. He found that their stopping power was not adequate, though he felt the problem was not so severe that flight testing had to be stopped. Ground testing was finally completed on 6 August, the same date that Hiroshima was devastated by the ‘Little Boy’ atomic bomb dropped from the B-29 ‘Enola Gay’. News of this strike soon reached the Kitsuka crews, technicians and engineers.

7 August 1945 would see excellent flying conditions and the Kitsuka was made ready for flight. Weather reports stated a 24km/h (15mph) southwest wind and a crosswind blowing from the right across the 1,692m (5,550ft) length of Runway 20 that pointed towards Tokyo Bay. The Kitsuka was only given a partial fuel load to keep the weight to 3,150kg (6,9451b); this allowed for approximately 16 minutes of flight time. No RATO bottles were fitted so that the take-off characteristics of the aircraft could be assessed. Takaoka climbed into the cockpit and made ready to take-off. On his signal the Ne 20 turbojets were started and he was soon taxiing out to the start of the run­way. Once there, he extended the flaps to 20° and kept the brakes set. So as not to cause a compressor stall, Takaoka slowly eased the engine throttles forward and when both had reached ll. OOOrpm, he released the brakes and the Kitsuka began to roll. Twenty-five sec­onds later and after a run of 725m (2,378ft), the Kitsuka was airborne and went into the history books as the first Japanese jet to fly.

At 610m (2,000ft), Takaoka levelled off. He was instructed to not retract the landing gear nor exceed 314km/h (195mph). As a test pilot he was used to hearing the roar of a conven­tional aircraft engine and used such noise as a means to detect problems. However, Takaoka was not prepared for the whine of the turbojets

that told him almost nothing outside of what his instruments reported. He circled Kisarazu airfield, keeping it in sight in case of a failure and because the airspeed kept rising, Takaoka had to constantly throttle back to keep from exceeding the gear down speed limit. A brief test of the control sensitivity showed that the rudder was stiff, the ailerons were heavy but were working and the elevators were overly responsive. When his flight time was up, Takaoka was wary of how he would land. He did not want to drop the turbojets to below 6,000rpm since that risked a flameout from which he would likely not recover in time. Therefore, he chose a long, shallow drop, low­ered his flaps 40° and brought the turbojets down to 7,000rpm. On touchdown, he only needed moderate braking to bring the Kitsuka to a stop using only a little under 61 Om (2,000ft) of runway. Takaoka brought the Kitsuka back to the ramp amid throngs of cheering men. The total flight time was 11 minutes. In his immedi­ate report on the flight, Takaoka stated he had experienced no problems with the engines and had no recommendations for improving the aircraft. During his debriefing, technicians had removed the cowlings to the Ne 20 turbo­jets and examined each engine. They found no faults and so gave the Kitsuka clearance for another flight, scheduled for 10 August 1945.

For the second flight, more fuel was to be stored and RATO bottles used; this would allow for a longer flight and test the RATO units as boosters. Takaoka would again pilot the Kit­suka. Prior to the flight Takaoka examined the RATO bottles which were fitted to the under­side of the fuselage and found fault with the angle at which they were set. However, to adjust them would have taken too much time and so instead of 800kg (1,7631b) of thrust, the bottles were reduced to 400kg (881 lb) each.

On the day of the second flight, Allied air power was highly active and any flight attempt was bound to be spotted putting the Kitsuka at risk. Consequently, it was decided to wait until the following day on 10 August. However, it would be remembered for the drafting of the Imperial Rescript on the Termination of the War by the Japanese cabinet at the behest of Emperor Hirohito, though the populace had no knowledge of this.

11 August 1945 shared a similar weather pat­tern to the day the Kitsuka had first flown. The difference was that several UN and IJA officials of high rank had arrived to witness the second flight. Once more Takaoka climbed into the cockpit, signalled for engine start and taxied out to the runway. As before he extended the flaps 20°, and after receiving the signal to take­off, he slowly opened the throttles until the engines had reached 11,000rpm before releas­ing the brakes and the Kitsuka rolled forwards.

At four seconds into the take-off roll, Takaoka activated the RATO units. Immediately, the acceleration caused the nose of the Kitsuka to pop up, the tail slamming onto the runway. Takaoka fought to get the nose down by jam­ming the stick forwards but he received no response from the aircraft’s elevators. The two RATO units burned for a total of nine seconds and during eight of those seconds Takaoka was helpless and unable to correct the nose up condition. One second prior to the units burn­ing out, the elevators finally took effect and the nose came down so hard Takaoka was sure the front tyre had blown when it contacted the runway. Takaoka felt a sense of deceleration as the Kitsuka reached the halfway point on the runway – his speed at that point was 166km/h/l 03mph. A second later, with the feel­ing of deceleration still present, Takaoka decided to abort the take-off and he cut the power to the engines. Unfortunately, the brake issue Takaoka had discovered during high­speed taxi tests now came back to haunt him.

Despite maximum application of the brakes, the Kitsuka showed no signs of slowing and Takaoka was rapidly running out of runway. As he neared one of the taxiways, Takaoka held the left brake in an attempt to make the Kitsuka bring its left wing down into the ground to bleed off speed (known as a ground loop). The Kitsuka’s nose turned slightly but this then put the aircraft on a crash course with a group of hangars and buildings. Takaoka reversed the braking, holding the right brake. The Kitsuka came back around onto the runway and despite Takaoka working the brakes, it was to no avail. The aircraft ran out of tarmac and crossed the 100m (328ft) of grass overrun before the landing gear caught in a drainage ditch and collapsed. The Kitsuka slid along its belly until finally coming to a halt by the edge of the water of Tokyo Bay. The damage to the Kitsuka was extensive. In addition to the man­gled landing gear, the two Ne 20 engines were badly damaged, having been jarred from their mounts but still remaining attached to the wings. Initial assessments suggested that the damage was so severe the Kitsuka could not be repaired. On the positive side, the aircraft did not catch fire and causes of the accident were swiftly looked into. UN Captain Ito, who was present for the flight, was thankful that the Kitsuka did not become airborne with the nose high attitude during the RATO burn. Had that happened and once the RATO bottles cut out, the Kitsuka would have most likely crashed into the ground. A motion picture camera cap­tured the flight and the film developed to see if it could shed any light on the crash.

On 15 August, the film of the ill-fated flight was studied but proved inconclusive as to whether or not the Kitsuka was airborne once

the RATO bottles were exhauasted, as was suspected. This would have explained the heavy impact of the front landing gear on the runway and the sense of deceleration experi­enced by Takaoka. In any case, the Kitsuka would never fly again for at 12.00pm the Impe­rial Rescript on the Termination of the War was broadcast on the radio bringing World War 2 to a conclusion.

The end of the war would see none of the Kitsuka production plans realised. Nakajima, by the close of December 1945, was to have produced 200 Kitsukas. In reality, Nakajima completed only one with a further 22 under construction. The Kyushu Hikoki K. K. was, also by the end of the year, to have turned out 135 Kitsuka aircraft but was only able to begin con­struction of two aircraft, started in July 1945, which remained unfinished by the close of hostilities. A third producer, the Sasebo Naval Arsenal (Sasebo Kaigun Kosho), was sched­uled to have begun production of the Kitsuka in September 1945 with 115 completed by the close of December. The fourth production line was to be at the Kasumigaura Naval Air Arsenal with the commencement of Kitsuka construc­tion scheduled for October 1945; 80 aircraft were to have been completed by the end of December.

A number of variants of the Kitsuka were planned, none of which would see completion come the capitulation. One of these was a two – seat trainer. Given the nature of the Kitsuka, it was appreciated that a trainer would be required to help the conversion of pilots used to conventional piston engined aircraft to the peculiarities of a turbojet powered aircraft. Five of the Kitsuka airframes under production by Nakajima were modified by including a sec­ond cockpit for the instructor. Outside of the inclusion of the additional cockpit, it is unknown exactly what other changes were made in the Kitsuka to accommodate it. If there were a parallel to the German Me 262B-la two-seat trainer, the rear fuel tank would have been removed to make room for the instructor’s cockpit. The German solution to the loss of fuel was to utilise the two front bomb racks for drop tanks. Whether Nakajima considered the use of drop tanks (as the Kit­suka could use them) or simply accepted the reduced endurance for the sake of expediency is not known. The two-seat trainer would be the only variant of the Kitsuka to reach the pro­duction phase.

It was planned that some of the two-seaters were to be modified for reconnaissance roles. The instructor’s cockpit was to be removed and replaced with a crew position for an observer. He was to have a Type 96 Model 3 radio set at his disposal for use in relaying tar­get information to other aircraft. It is unknown

Contemporaries Messerschmitt Me 262A-1 a/U3 and Me 262A-5a (Germany), Messerschmitt Me 262A-2a/U2 (Germany), Messerschmitt Me 262B-la (Germany), Messerschmitt Me 262C-la, Me 262C-2b, and Me262C-3 (Germany)

Deployment

None. One finished aircraft was built by Nakajima (two if one counts the airframe completed for load testing) with a further 24 in various stages of construction by war’s end.

Survivors

Nakajima Kitsuka (tail number A-103)

With the loss of the only completed Kitsuka following its crash on 11 August 1945, examples captured by the US following the war were from the stocks of incomplete Kitsuka aircraft found in Nakajima and KyQshu’s plants. This particular Kitsuka arrived at NAS Patuxent River and on 18 October 1946 was shipped to San Diego, California. The aircraft eventually found its way back to the Paul. E. Garber facility where it is believed to be the second Kitsuka held in storage there.

Some sources have the serial for this Kitsuka as 7337.

Nakajima Kitsuka (tail number A-104)

Also at NAS Patuxent River with A-103, it was later shipped to NAS Willow Grove in Willow Grove, Pennsylvania on 23 October 1946. Following its arrival, no further trace of the Kitsuka is known.

Nakajima Kitsuka (no tail number assigned)

This Kitsuka was received in the US and appeared on a storage manifest in 1950 being housed at NAS Norfolk in Norfolk, Virginia. In 1960, it was shipped to the Paul E. Garber facility. From 1972 until the facility closed to the public, it was on display hanging from the ceiling (see page 118).

if any cameras were to be fitted but it would not be unreasonable to conclude that the observer would at least have had a hand-held camera.

An interceptor version of the Kitsuka was discussed, as previously mentioned, and a number of general arrangements for it were considered. One of these was the inclusion of a single Type 5 30mm cannon with 50 rounds of ammunition installed in the nose. A second design was to feature enlarged and extended wings incorporating flaps and double-edged leading slots. A more definitive interceptor was to replace the Ne 20 engines with either Ne 130 or Ne 330 turbojets. A second cannon was to be added in the nose. Interestingly, it appears that if the IJA had used the Kitsuka, the Type 5 can­nons would be replaced with two Ho-155 30mm cannons. This may have been a stopgap or fallback if the IJA’s own Ki-201 Karyti failed to materialise. With the heavier weight the structure of the Kitsuka, including the landing gear, would have been strengthened. A fighter – bomber model was envisioned for the defini­tive interceptor by including a fitting for a single 500kg (1,1021b) or 800kg (1,7631b) bomb.

As originally planned, a model of the Kitsuka was proposed for shimpti missions. Similar to the Kitsuka as constructed, this version was to carry either a 500kg (1,1021b) bomb, a 250kg (551 lb) bomb or two Type 99 20mm cannons. With the latter, it could be assumed the can­nons would be used for self-defence and for fir­ing at the target before ramming the aircraft into the victim using any remaining fuel and ammunition as the secondary explosive ele­ment. A variant of this Kitsuka was to utilise a 200m (656ft) launch rail that Kugisho had been designing and which they expected to have ready for testing by September 1945. Using a rocket booster, the Kitsuka would leave the launch rail at 220km/h (137mph) at an acceler­ation of between three to four ‘g’.

In regards to the 724 Kokutai, with the end of the war they would never see their Kitsuka air­craft. It was planned that by November 1945 the unit would have been based near Yokosuka at a site along the Miura Peninsula, west of Tokyo Bay. It was expected that by then the unit would have received sixteen Kitsukas. In addition, the unit was to use one of the handfuls of Kawan – ishi El 5K1 Shiun (meaning ‘Violet Cloud’; code – named Norm by the Allies) reconnaissance floatplanes, which were removed from active service following their disastrous combat debut in 1944. The Shiun, operating from a nearby har­bour, would locate the shipping targets, mark them and then loiter in the area to broadcast radio signals. The Kitsukas would then be rapidly launched and, by means of the radio sig­nals received through the Kuruku system, attack the ships at low level with bombs and ramming tactics. Had the reconnaissance ver­sion of the Kitsuka gone into production, the 724 KokQtai was to receive it as a replacement for the far more vulnerable Shiun.

Finally, with the close of the war, none of the projected turbojet successors to the Ne20 would enter production. One prototype of the Ishikawajima Ne 130 had been completed by June 1945 but testing was unfinished by the time the war ended. Nakajima started devel­opment of the Ne230 in May 1945 and had three under construction by August 1945. How­ever, none of the engines were completed or tested. Mitsubishi was unable to construct a Ne 330 and so it remained on the design board.

A note about the use of the name Kitsuka as opposed to the more commonly used Kikka. Kitsuka is the proper translation of the kanji characters. However, it is pronounced ‘kikka’. Kikka was used in post-war reports as phonet­ically it approximated to Kitsuka and thus has become the accepted name of the aircraft. Neither name is incorrect. Also, some sources use the J9Y1 (or sometimes J9N1) designation for the Kitsuka. While logical for the intercep­tor version of the Kitsuka, there is no evidence in wartime Japanese sources to support the designation. One may also find the designation J8N1 used but this is not supported.

In 1926, Aichi contracted Heinkel to design a carrier fighter for entry into a Navy competi­tion to replace the Mitsubishi Type 10 fighter then in service. Called the HD 23 by Heinkel, it was known as the Aichi Type-H Carrier Fighter in Japan. Two were built by 1927 and much emphasis was placed on the capability of the plane to ditch at sea, including jettison – able landing gear and the ability for the engine to stop the propeller in the horizontal position. However, performance-wise, the Aichi Type-H Carrier Fighter showed up poorly and lost the competition to Nakajima.

Heinkel HD 25 two-seat float plane

Licence-built in Japan as the Aichi Navy Type 2, this aircraft saw service on a number of heavy cruisers from 1926 onwards, though their service life was short due to the advent of catapult launched seaplanes. The few Aichi Navy Type 2 aircraft were then sold to the civilian market. Later, in 1930, three Type 2 aircraft were converted to transports for civilian use.

Heinkel HD 25 transport

Built as the AB-1, Aichi used the Heinkel HD 25 as the basis for their entry into a ‘made in Japan’ passenger/transport contest operated by the Aviation Bureau of the Department of Communications. The AB-1 could be con­verted to a seaplane if required and proved its worth going on to win the contest and seeing several years’ service in private hands.

Heinkel HD 26 single-seat float plane

A single example was built by Aichi (also as the Aichi Navy Type 2) while the Navy also acquired a Heinkel constructed HD 26. Both were tested in 1926, but like the two-seater, the model was made obsolete by catapults. Both aircraft were turned over for civilian use.

Heinkel HD 28 three-seat float plane

The Navy purchased one HD 28 from Heinkel in 1926. Tested by the Navy, problems with the Lorraine-Dietrich engine saw the HD 28 failing to meet expectations and in 1928 the Navy withdrew their interest in the design.

Heinkel HD 56 seaplane

To meet a 1929 Navy need for a catapult launched seaplane, Aichi once more turned to Heinkel and imported the HD 56. Meeting the needs of the Navy after modification, it was accepted into service in 1931 as the Aichi E3A1 beginning with the first deliveries out of an eventual total of 12 aircraft. The E3A1 saw combat during the Sino-Japanese conflict, operating from Jintsu-class cruisers. It did not, however, remain in service long, being replaced with superior aircraft. Some E3A1 seaplanes were retained by the Navy as train­ers with the remainder released to the civilian market.

In 1986, Ted Nomura self-published his comic Tigers of Terra: Families of Altered Wars under his Mind Visions label. In 2006, his work celebrated 20 years of alternative military history in visual form. Antarctic Press assumed the printing duties for Nomura’s comics, not only continuing Tigers of Terra but with spin-offs including the popular Luftwaffe: 1946, Kamikaze: 1946, and many others, to include several x-plane technical manuals. The latter publications were done with the assistance of Justo Miranda. Nomura’s profile artwork in this book come from his many comics and where available, the alternate history he has given them is provided.

Tachikawa Ki-229 as operated by the IJA. This was the Japanese version of the Horten Ho 229. Horten VII trainers were used by the IJA as the Ki-226.

Ted S. Nomura/Mind Visions and Antarctic Press

Nakajima Kitsuka (code named Linda), flown by an unidentified Tokkotai unit. Ted S. Nomura/ Mind Visions and Antarctic Press

Kawasaki Ki-88 (code named Bonnie) as briefly operated by the IJA. Ted S. Nomura/Mind Visions and Antarctic Press

Tachikawa Ki-94-I.

Ted S. Nomura/Mind Visions and Antarctic Press

Tachikawa Ki-162 (code named Jan), flown by the Fussa/Tachikawa IJA Test Squadron, November 14, 1945. Ted S. Nomura/Mind Visions and Antarctic Press

Messerschmitt Me 262A-2 (code named Marsha) flown by the 58th Tokkbtai, December 1, 1945.

Ted S. Nomura/Mind Visions and Antarctic Press

Heinkel Неї 11 (code named Bess) with Fieseler Fi 103R-IV (code named Cindy) as operated by the 47th Tokkbtai, December 7, 1945. Ted S. Nomura/ Mind Visions and Antarctic Press

Nakajima Ki-87 (code named Jeff) as flown by Major Saburo Kurusu, Fussa/Tachikawa IJA Test Squadron, November 14, 1945. Ted S. Nomura/ Mind Visions and Antarctic Press

Rikugun Ki-93 (code named Dora) flown by Hauptmann Dora Oberlicht of J/KG 200, operating at the Fussa/ Tachikawa IJA Test Center, November 14, 1945. Ted S. Nomura/ Mind Visions and Antarctic Press

Tachikawa Ki-94-II (code named Ted) flown by Lieutenant Colonel Ichiro Mikasa, Fussa/Tachikawa IJA Test Squadron, November 14, 1945. Ted S.

Nomura/Mind Visions and Antarctic Press

Kawasaki Ki-64

Designers at times relish the freedom to let their visions develop and flow from the drafting board to the tarmac, ready to take to the skies. Takeo Doi, working for Kawasaki, was just such a designer. Despite the very real work developing, testing and producing combat air­craft for the IJA, Doi had a concept that he, on his own, brought to the fore. Initially, the IJA would not hear of the design but later, when the Ki-64 took shape, their mind would change.

In 1939, Doi was involved with two Kawasaki programs: the Ki-45 Toryu and the

КІ-60/КІ-61 Hein. The Ki-45 was proving to be a horribly troublesome aircraft. Problems with the landing gear, concerns with drag, engine difficulties and more were proving a thorn in Kawasaki’s side. It was Doi who stepped in to solve the issues plaguing the initial Ki-45 design. In addition to working to fix the floundering Ki-45, by 1940, Doi was involved with the preliminary develop­ment of the Ki-60 heavy fighter and the Ki-61 Hein.

Even with such responsibilities, Doi had a design of his own for a high-speed fighter. His concept incorporated a number of novel fea­
tures which were perceived as rather unorthodox in comparison to other more conventional types. Since Koi’s aircraft was purely his own and not created to meet any sort of specification, Koi would be disap­pointed when the IJA forbade Kawasaki giv­ing any further time to the design.

Doi’s disappointment then turned to joy when, in October 1940, the IJA authorised Kawasaki to proceed with developing the Ki-64 to meet a requirement for a fighter capable of a maximum speed of 700km/h at 5,000m (435mph at 16,405ft) and a 5 minute climb to that height.

To power the Ki-64, Doi would enlist the help of fellow engineers employed by the Akashi engine plant. The decision was made to use the Kawasaki Ha-201 ([Ha-72] 11) engine. This was actually a combination of two Ha-40 engines, the Ha-40 being the licence-built version of the Daimler-Benz DB601A. Each Ha-40 was a 12-cylinder, liq­uid-cooled powerplant and the Ha-201 was formed through having one engine in front of the cockpit and the second behind it. The rear engine drove the first of the contra-rotating propellers and it had a variable pitch. The front engine drove the second propeller, which was of a fixed pitch. Both propellers were three-bladed. All told, the Ha-201 was expected to produce 2,350hp.

The use of the Ha-201 was not the most novel feature of the Ki-64. It was the means of cooling the engine that was notable. The Ha-201 was to be cooled by a steam con­densing system. A tank of 15.4 gallons of water was fitted into each wing and the outer wings and flaps served as the cooling surface, totalling 23.99m2 (258.3ft2). The port wing ser­viced the front engine while the starboard wing provided coolant to the rear engine. As the water coolant turned to steam, it was pumped out into the wings where the steam would condense back into water which in turn was pumped back into the engine. The main benefit of this system was lower drag on the airframe as the need for air inlets was removed or minimised. Each laminar flow wing housed the fuel tanks and one 20mm Ho-5 cannon while two more were fitted in the fuselage deck. One drawback to the wings being packed with the cooling system apparatus was that it left little room for the fuel tanks and consequently the Ki-64’s oper­ational range suffered. The majority of the fuel was carried in the fuselage, the tanks being placed in and around the space left available by the Ha-201 engine. The main fuel tank was situated in front of the cockpit, hold­ing 306.7 litres (81 gallons). Under it was the oil reservoir, holding 79.5 litres (21 gallons) of oil for the engines. Behind the cockpit were
two coolant tanks holding 83.3 litres (22 gal­lons) and 117.4 litres (31 gallons) respec­tively. The smaller serviced the front engine, the larger the rear engine.

Doi tested the Ha-201 and the cooling sys­tem to a considerable degree. In 1942, one of the Ki-61 Hein fighters was specially modified to test the cooling method and its trial flights began in October 1942 and ran through to the end of 1943. Because of this thorough testing, the construction of the Ki-64 was delayed and so did not reach completion until December

1943. Nevertheless, Doi was satisfied that the cooling system would grant an additional 41 km/h (25mph) to the Ki-64 and battle dam­age would not significantly reduce the effec­tiveness of it and as such the exhaustive testing was worth the effort.

With the Ki-64 complete, flight testing com­menced in December 1943. Four test flights were successfully made without mishap. However, on the fifth, the rear engine caught fire. The test pilot was able to land the aircraft and the fire was quenched. Mechanics stripped the engine out of the Ki-64 and returned it to the Akashi plant for a full repair. The Ki-64 itself was returned to the city of Gifu which, at the time of World War 2, was a major industrial centre.

Plans were made to improve the Ki-64 by replacing the 2,350hp Ha-201 with an enhanced model that could generate up to 2,800hp. The propellers would be replaced with two, constant-speed contra-rotating pro­pellers that were electrically operated. It was envisioned that with these modifications, the Ki-64 Kai would be able to attain a top speed of 800km/h (497mph).

Unfortunately for the Ki-64, repair work lan­guished, especially in the face of more press­ing needs for the Japanese arms industry and the production of more conventional aircraft. As a result, both the Ki-64 and the Ki-64 Kai were cancelled. After Japan’s surrender, the Ha-201 was still at Akashi, its repairs incom­plete. When US forces arrived in Gifu, the Ki-64 was found and technical teams gutted the airplane of its cooling system. The system
was then crated and shipped to the United States for study at Wright Field in Dayton, Ohio.

Given the relatively long development time of the Ki-64, US intelligence had already become aware of the design. Thus, expecting the Ki-64 would see service, the airplane was assigned the codename Rob.

The Rammer

The practice of tai-atari, which literally means ‘body crashing’, was not unique to Japan. The deliberate ramming of one aircraft by another aircraft has happened as far back as World War 1 when Imperial Russian Air Force pilot Pyotr Nesterov used his 1912 Morane – Saulnier monoplane to ram an Austrian Alba­tross B. II on 26 August 1914. In World War 2, the first ramming attack went to Lt. Col. Leopold Pamula who used his stricken PZL P. llc to down a Messerschmitt ВИ09 on 1 September 1939. It would be the Russians, Germans and Japanese who would make ramming a part of their war doctrine.

Whereas the Japanese would simply use available aircraft to conduct ramming or tai-atari attacks, the Germans took it a step further by producing and designing aircraft specific to the task. One operational example was the Focke-Wulf Fw 190A-8/R7. To enable the fighter to penetrate bomber formations the Rammjager (or Sturmbocke) was Fitted with armour plating to enable it to weather defensive fire as well as possibly surviving a successful ram. Sturmstaffel 1 was the first Luftwaffe unit to operate the fighter. As the war went on and US bombers filled the skies, and the Luftwaffe was more and more hard pressed to stem the tide, a number of dedicated rammer aircraft designs

The aircraft depicted here sports the colours and markings of the 53rd Sentai operating in defence of the Japanese homeland.

appeared. One of them was the Zeppelin Rammer.

The Rammer was a small, single seat air­craft that was towed into the air. As it was designed for ramming, the constant cord main wings were strengthened by the use of three tubular spars along the forward edge of the wings. The remainder of the aircraft was bolstered to allow it to withstand impact forces. A single Schmidding 109-533 solid fuel rocket developing 1,000kg (2,205 lb) of thrust was fitted into the tail and the motor provided
a total of twelve seconds of thrust. In the nose were fourteen R4M rockets or a single SG 118 battery. The cockpit was within an armoured tub providing 28mm of armour plate in the front and sides with 20mm in the rear. The glazing was 80mm of bulletproof glass in the front and 40mm thick on the sides. The method of attack was to tow the Rammer within.48km (0.3 of a mile) from the target and release it. The pilot would ignite the rocket motor to boost speed and fire off the nose weapon at the first target before making a ram attack on a second (or the same) tar­get. After engaging in the ram attack, the pilot would glide back down to earth. The Ram­mer was test flown, without power, in Janu­ary 1945 and a pre-production batch of sixteen aircraft was ordered. However, Zep­pelin’s production facilities were destroyed by US bombing before their construction could commence.

The Japanese would use aircraft already in operational service for ramming attacks such as that Kawasaki Ki-45 and even stripped down Kawasaki Ki-61 Hein fighters. It was long thought that Japan never developed a dedicated rammer aircraft of its own but this is no longer the case. Recently discovered in the archives of the Japanese National Insti­tute for Defence Studies is just such a project.

The aircraft was a joint venture between the IJA and the UN, something that occurred with more regularity towards the close of the war. The design was based on the Sytisui – shiki Kayaku Rocketto (meaning ‘Autumn Water’-type ram attack rocket), a project started in March 1945 for a unmanned, remote controlled anti-bomber missile. The plan was to ground launch the missile, guide it remotely towards the target, engage the tar­get via ramming, and then recover the missile (if it survived the collision) for reuse. Design work was carried out by the Kokukyoko (the Aeronautical Bureau) and, although a mock – up was completed, the war ended before finalised production plans could be com­pleted, let alone the missile ever being tested. The missile’s design borrowed heavily from the Mitsubishi J8M Syusui in terms of its shape. Interestingly, the Messerschmitt Enz – ian anti-aircraft missile had a shape influ­enced by the company’s Me 163 rocket interceptor, of which the J8M was the Japan­ese version (see page 96).

The piloted version used much the same design as the missile and was a small, tailless aircraft featuring low mounted 45° swept wings. The fuselage was bullet shaped with a large vertical stabiliser into which the cockpit was blended. Located in the back of the fuse­lage were four Type 4 Mark 1 Model 20 rock­ets, the same as those used on the Kugisho

MXY7 Oka which on such a small aircraft pushed the maximum speed to an estimated 1.125km/h (699mph or just over Mach 0.91) — i. e. a transonic speed. With a speed in the transonic range, this aircraft would have pre­sented a formidable challenge to the Japan­ese given that even the Germans had only just started investigating the problems of high­speed flight when their jet and rocket aircraft began to push into such speeds with the resultant issues of compressibility. It is unknown if the Japanese rammer had swept wings because the designers understood the principles in relation to overcoming com­pressibility problems at transonic speeds, or if the shape was chosen as a means to provide an angled cutting surface to facilitate ram­ming attacks, or as a drag reducing planform. The wings were strengthened to withstand the high impact forces experienced when striking the enemy bomber. Even though the rammer could rely on speed as a defence when under power, it still had to contend with the defensive armament of the B-29 and thought the pilot had some measure of armour plating and bulletproof glass to pro­tect him. The aircraft was certainly capable of gliding back to base to be refuelled and relaunched once it had conducted its attacks. Given the small size of the plane, no landing gear was fitted. As such, it is likely the under­side of the fuselage was reinforced or had a skid installed. How it was to be launched is unknown – it could have been towed aloft, catapult launched or perhaps even vertically launched.

In a ram attack, typically the tail would be targeted because the loss of the tail assembly would send the bomber out of control. Strik­ing the wings and engines was another focus of ramming attacks. Finally, the aircraft fuse­lage was the other key area to strike. The probable mission profile of the rammer flying from a ground base would include being positioned within very close proximity of likely bombing targets. With the short burn time of the rockets (8-10 seconds) the air­craft’s operational radius would have been very limited. After launching, as bombers came into range the pilot would attempt to ram into either the tail or wing of the target with the objective of severing it from the fuse­lage. If enough speed momentum remained after the initial hit, another ram attack would be made. Should the aircraft remain in flyable condition and if the pilot did not elect to ram his entire plane into a target, he would return to base where the rockets would be replaced. If the bombers were still close by, he could fly another sortie. If the rammer was towed into the air, the rockets would most likely have been fired on approach and again after hitting a target. This would provide enough power to grant a second pass with sufficient speed to allow for significant damage to be inflicted on the bomber when it struck.

However, the Japanese rammer would remain a paper project only. It is unclear if the design was to be the definitive rammer model or simply a proposed concept.

Aichi turned to Heinkel to produce a long – range reconnaissance float plane to meet a

1931 request by the Navy for just such a craft. Called the Aichi AB-5, testing showed the design to be sound but with room for further refinement. This would result in the AB-6 of

1932 which, despite being successful, was not accepted into service having been beaten by a Kawasaki design.

Heinkel He 50/He 66

In 1933, the Navy issued requests for a carrier dive bomber. Aichi elected to utilise Heinkel’s He 50 which was then entering service with clandestine military air force training units. Called the He 66 for export reasons, Heinkel delivered a single He 66 to Aichi who, after some modifications, submitted it to the Navy. Winning the Navy’s competition, the modified He 66 was then licence built in Japan, entering service with the Navy in 1935 as the Aichi DIAL The D1A1 would see action in China in 1937. The Allies, thinking the D1A1 would be met in battle, assigned it the codename Susie. As it was, the D1A1 remained in Japanese ser­vice only as a trainer, having long since been withdrawn from frontline service.

Contemporaries

Republic XP-69 (US), Heinkel P.1076 (Germany), Caproni CA.183bis (Italy)

Type Fighter

Crew One

Deployment

None. Only one Ki-64 was completed and flown before the end of the war.

In August of 1942, the IJA saw a need for a air­craft that, in its primary role, would serve as an interceptor flying sorties to defend instal­lations, airfields and other assets that were considered important and therefore subject to enemy attack. Design specifications were drafted by the IJA for the aircraft and it was Kawasaki who put forth what they felt was the answer: the Ki-88.

Prior to drafting their design specifications, the IJA had sifted through a number of ideas before settling on a plane that had to have a heavy armament to ensure it could inflict sig­nificant damage to enemy aircraft, especially bombers, and also good handling character­istics to make it not only a stable gun plat­form, but also to avoid a steep learning curve for new pilots.

To this end, Tsuchii Takeo, a designer for Kawasaki, began work on what would become the Ki-88. Takeo selected a 37mm cannon as the primary weapon, supported by two 20mm cannons. It is probable that the 37mm Ho-203 cannon and two Ho-5 20mm cannons would serve as the armament fit with all three weapons fitted in the nose. Given the size of the Ho-203 (which was a lit­tle over 1.53m (5ft) in length, weighing 88.9kg (196 lb)), this presented a problem in squeez­ing them, along with the engine, into the
nose. To get around this, Takeo placed the l,500hp Ha-140 liquid-cooled, turbo- (or super-) charged engine in the fuselage, behind the cockpit. The three-bladed pro­peller was driven using an extension shaft that ran from the engine to a gearbox con­nected to the propeller. In essence, Takeo built the aircraft around the Ho-203.

The main advantage of placing the engine in the fuselage was that it allowed the cannon to fire through the propeller hub, producing a more stable firing platform that resulted in improved accuracy. Another advantage was that it allowed a skilful designer to make the nose more streamlined, enhancing speed performance.

A good number of references infer that Takeo’s design was inspired by the Bell P-39 Airacobra. While there is no evidence that specifically states that Takeo simply copied the American fighter, the P-39 was in limited operational use by the time design work began on the Ki-88 in 1942, notably seeing action in the Battle of Guadalcanal. Thus, the Japanese were aware of the design. Whether an example was ever captured for analysis is unknown but certainly intelligence was avail­able on the plane. Or, it may be that Takeo arrived at the same conclusion as did H. M. Poyer, designer of the P-39, when looking at
how best to accommodate a large calibre cannon in a single engine aircraft.

In June of 1943, Takeo finalised his design for the Ki-88. Apart from the use of a 37mm cannon and the engine placement, the Ki-88 bore no further resemblance to the P-39. The Ki-88 had a deep fuselage to accommodate the Ha-140 engine that was situated below and to the rear of the cockpit. The air scoop for the Ha-140’s radiator was mounted on the bottom of the fuselage, just forward of the wing roots. The radiator itself was positioned back from the scoop on the bottom interior of the fuselage, almost directly underneath the pilot’s seat. Jutting out on the left side of the fuselage, just above the trailing edge of the wing, was the scoop to provide air to the turbo – or super-charger of the Ha-140. The landing gear was conventional and the main gear retracted into the wings, while the tail wheel was fixed. A fuel tank was provided in each wing, mounted behind the wheel wells. On either side and to the bottom of the Ho-203 cannon were the Ho-5 cannons.

With the final design complete, work began on a full scale mock-up of the Ki-88 and this was completed sometime in 1943. In addition, work had already begun on con­struction of the fuselage and wings for a pro­totype and it was expected that by October
1943 the Ki-88 would be nearing completion. The IJA, however, had other plans for the Ki-88. After inspecting the mock-up and in reviewing the projected performance data of the plane, it was seen that it offered no real advantage over other designs then in opera­tional use, notably the Kawasaki Ki-61 Hien. Thus, Kawasaki was ordered to terminate all work on the Ki-88.

Kamikaze, which in Japanese means ‘divine wind’, was not a term used by the Japanese to reference their special attack units but came into common use in the West. Instead, shimpu and shimbu were more often used by both the UN and the IJA respectively. May 1944 would signal the beginning of dedicated suicide attack missions against the US and her allies. The effect of being on the receiving end of such attacks was horrific and would take its toll on US sailors.

A post-war report by the US Strategic Bombing Survey bluntly stated that kamikaze attacks were effective and given the situation for the Japanese, very practical. Statistics of sunk and damaged US ships during the Philippines campaign (October 1944 to Janu­ary 1945) showed that kamikaze attacks were far more effectual. Of course, being subjected to such attacks wreaked havoc on morale as well as a surge in mental illness. The US Navy, the focus of the majority of kamikaze attacks, saw such illness rise by 50 per cent in 1944 when compared to 1941. So bad was the problem that during the Okinawa campaign, the US Navy stopped warning crews that kamikaze attacks were to be expected as they only added to the sailor’s stress levels. General George C. Marshall wrote in a 1945 report to the US Secretary of War that, ‘The American soldier has a very active imagina­tion… and is inclined to endow the death­dealing weapons of the enemy with extraordinary qualities…’ And thus the ‘Kamikaze Airplane’ appears on the scene.

Following the close of World War 2, an illus­tration of an aircraft appeared in either Popu­lar Mechanics or Popular Science magazine. The aircraft, labelled a kamikaze plane, was a curious mixture of what appeared to be the tail of a Mitsubishi A6M Reisen, a fuselage not too unlike the Nakajima Kitsuka and a canopy similar to aircraft such as the Kawanishi NIKI Kyofu (meaning ‘Mighty Wind’ but known as Rex to the Allies) or the Nakajima Ki-84 Hay – ate (meaning ‘Gale’; Frank to the Allies). Even more curious was the fact that the aircraft used air-cooled radial engines, one in each wing, but in a pusher configuration.

The Kamikaze Airplane was said to have been sighted by some US Navy crew mem­bers as it flew over their ships. It was from

The Kamikaze Airplane – data

No specifications were provided for the aircraft. Deployment

None. The Kamikaze Aircraft was strictly fictional.

their descriptions that the illustration of the aircraft was created. The result was certainly unlike any plane then in the theatre but there is some precedent in terms of genuine air­craft being misidentified. One example was the ‘Kawasaki Type 97 Medium Bomber’ that was given the codename Julia. Because of very inaccurate illustrations of the plane that were derived from a written description, Julia was in fact the Kawasaki Ki-48 (Lily). It may very well be that the Kamikaze Airplane was actually a US Grumman F7F-2N Tigercat of which two US Marine Corps squadrons equipped with the plane began operating from Okinawa in September 1945. One was

VMF(N) 531 while the second was a photo reconnaissance unit. With the Tigercat being new to the Pacific Theatre, it can be surmised that some sailors and crew mistook the twin – engine Fighter for a Japanese plane and sub­sequently described something other than what was actually seen. However, the Kamikaze Airplane was written off as a spec­tre of the imaginations of sailors who had borne the brunt of kamikaze attacks.

In the late 1930s, a He 70 was imported to Japan. Few details are available but the wing form of the He 70 would later provide the influence for the wing design of the Aichi D3A1 carrier bomber, known to the Allies as Val.

Heinkel He 112B-0 fighter

In 1937, the UN was seeking new fighters to combat the increasingly modern aircraft being encountered in China. Heinkel was at the time looking to export the He 112, a design which was ultimately rejected by the Luftwaffe. The UN placed an order for 30 HE 112B-0 fighters, known in Japan as the A7Hel Type He Air Defence Fighter. 12 of the 30 were delivered though Japanese pilots disliked the performance of the plane and mechanics had difficulties maintaining the liquid-cooled engines. As Japanese fighters of improved capability were entering service, the He 112B-0 never saw combat and the Japan­ese cancelled the remaining 18 aircraft. Ser­viceable He 112B-0 were used as instructional aircraft and as means to study German manufacturing techniques. Figuring the He 112B-0 was in active service, the Allies codenamed the aircraft Jerry although it was never encountered.

Heinkel He 118 dive bomber

With the Luftwaffe uninterested in the He 118, Heinkel found the Japanese receptive to the plane. The UN placed an order for a sin­gle He 118 to be delivered by February 1937 along with the licence to manufacture the He 118 in Japan. The IJA also purchased a sin­gle He 118 for delivery by October 1937. Known in Japan as the DXHel, Hitachi Seisakusho was to be the company that would produce the licensed aircraft. The He 118 V4 was shipped to Japan and assem­bled at Yokosuka for the UN, but during a test flight it broke up in the air and the UN aban­doned the plane. The IJA received the He 118 V5 months later but it too lost interest and Heinkel received no further orders.

Junkers G 38/K 51 heavy bomber

The Army sought to have their own version of the Junkers massive G 38 airliner and in September 1928, Mitsubishi entered into a contract with Junkers for the design specifi­cations, blueprints, manufacturing data and licence to build the aircraft as a bomber, known as the К 51, the export version of the G 38. Mitsubishi sent designers to Germany in 1928 to study the G 38 and production tech­niques, and by 1930, the necessary tools, jigs and material were imported and in place. Junkers sent a team of engineers to Japan to assist with the production. The first bomber, the Ki-20, was completed in 1931. A total of six were built from 1931 to 1935. Kept in secret, the general public was not made aware of the Ki-20 until 1940 when three Ki-20s partici­pated in a parade fly-over. The Ki-20 did not see action.

Junkers К 37 bomber

A single К 37 bomber was imported through Sweden and was donated to the Army as Aikoku-1. Used during the Manchurian Inci­dent, the Army was impressed with the К 37 and in 1932 asked Mitsubishi to make a simi­lar bomber. Using the К 37 as a basis and cap­italising on experience from the Ki-20, the prototype Ki-1 heavy bomber was completed in March 1933. Despite problems with the engines, the Ki-1 was adopted to replace the old Type 87. The Ki-1-II soon appeared in an attempt to fix issues with the Ki-1 but it was not liked by the crews that flew it. Another air­craft, the Ki-2 light bomber, was also built using the К 37 as a basis. The Ki-2 and later Ki-2-ІІ (both being built from 1933 to 1938) proved very successful, seeing action in China and later as trainers into the late 1930s. The Allies thought the КІ-2-ІІ was still in ser­vice when the war began and assigned it the codename Louise.

Performance (specifications are estimations by Kawasaki)

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

Range 1,198km 745 miles

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

Ceiling 11,000m 36,089ft

Armament

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

Deployment

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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