Deployment

None. A wooden mock-up was built before the Taizan project was cancelled.

was rounded and fully glazed, a style unlike any Japanese bomber then in service. The wings were mounted mid-fuselage, each wing sporting the Nu engine in a well-stream – lined nacelle. On top of the fuselage, fore and aft of the wings, was a turret for a portion of the defensive armament. A fairly spacious tail gunner position was fitted beneath the verti­cal stabiliser on the underside of the fuselage with a rear facing ventral gun station. A rela­tive rarity in Japanese bomber design was the tricycle landing gear. Takahashi’s perfor­mance estimates put the normal operational range at 6,412km (3,984 miles) which, with a lighter payload, could meet the 16-shi specifi­cation. The maximum speed would have been 555km/h (345mph) with a relatively light defensive weapon armament of two Type 99 20mm cannons and two Type 97 7.7mm machine guns.

Unfortunately for Takahashi, Operation Barbarossa, the German invasion of the Soviet Union on 22 June 1941, would prevent the required machine tools and equipment to produce the Nu engine from being exported to Japan. Without the powerplant, the design was doomed. With Takahashi’s proposal hav­ing fallen by the wayside, Kiro Honjo resumed control of the M-60 project. This time, instead of a four-engine bomber, Honjo would utilise two engines and base his design heavily on the G4M.

The G7M Taizan (meaning ‘Great Mountain’) as the design was later designated was to use two 18-cylinder, air-cooled radial engines, the Mitsubishi MK10A (Ha-42-11), developing 2,000hp each. The wings were mounted mid­way on the fuselage and the aircraft was to be constructed of metal with fabric covering the ailerons and rudders. It was anticipated that the Taizan would carry the same 800kg (1,7641b) bomb load as the G4M1 but unlike the Hamaki, the Taizan would have a far more potent defensive armament as the bomber would operate far from fighter protection. This step also took into account the shortcomings in the G4Ml’s protection. Of course, using less powerful engines and a heavier weapon fit caused a revision in performance when com­pared to Takahashi’s design. A 31 October 1942 performance estimate gave the G7M1 a range of 5,559km (3,454 miles) at a speed of 518km/h (322mph) at 5,000m (16,404ft) with a weapon fit of two Type 99 20mm cannons, two Type 2 13mm machine guns and two Type 1 7.9mm machine guns. However, as work on the G7M1 proceeded and the design underwent further testing, these estimates would continue to be revised. Unfortunately for Mitsubishi, the revised estimates did not see any expected improvements to the performance but rather some deterioration.

By 1942, Mitsubishi had completed the bomber’s design and were ready to construct a full size wooden mock-up of the G7M1 Taizan, which was in due course completed. Unfortunately, the Kaigun Koku Hombu had now issued a 17-shi specification for a bomber that Kawanishi was developing as the K-100 (which some sources designate as the G9K Gunzan, meaning ‘Mountain Group’, but this has never been verified; other sources have the G9K as a 1944 19-shi bomber project). Mitsubishi was instructed to halt all further work on the G7M1 until the K-100 could be evaluated.

Kawanishi completed the initial design of the K-100 bomber and the Kaigun Koku Hombu reviewed it along with the G7M1 in the summer of 1943. By this time, the G7M1 had suffered further range performance reductions, dropping from a proposed nor­mal range of 3,705km to 2,778km (2,302 miles to 1,726 miles). This was caused in part by the heavier armament compared to the initial fit, removing the two Type 1 machine guns and adding three more Type 2 machine guns to make a total of six Type 2s. This was, to a degree, tempered by a higher speed of 544km/h (344mph) at 5,000m (16,404ft).

Based on the projected performances of both aircraft, it was felt that neither design would be suitable either for the 16-shi or the

17- shi specifications. The Kaigun Koku Hombu was critical of the G7Ml’s design for concen­trating much of the defensive weaponry in the frontal arc of the bomber, thereby reducing the aircraft’s defences in the side and rear arcs. In addition, it was considered that the actual per­formance of the G7M1 would likely have been little, if at all, better than the operational G4M1. Another nail in the coffin for the G7M1 was the fact that the Kaigun Koku Hombu was looking to four-engine bombers as the real means to achieve the necessary range (at least 8,816km/5,478 miles, allowing for a one way trip from Tokyo to Los Angeles). In fact as early as 1938 the UN had asked Nakajima to produce a four-engine bomber, the G5N Shinzan (‘Mountain Recess’) which was based on an imported Douglas DC-4E.

With the Kaigun Koku Hombu showing no interest in the G7M, Mitsubishi shelved all fur­ther work on the bomber. Ironically, the G5N Shinzan would prove a failure and had a worse range than the G4M. Only with the con­struction of the four-engine Nakajima G8N1 Renzan (‘Mountain Range’) which first flew in October 1944 would the original 16-shi range specification be met. By then, the need for such bombers had passed as attention had turned to defending Japan and fighters/inter – ceptors were required.

The concept of the J4M Senden (‘Flashing Lightning’) was bom of the need for a high performance interceptor that could operate at high altitude. The main catalyst for this was the American Boeing B-17 Flying Fortress. The bomber, in action in the Pacific Theatre from 1941 to 1943, proved to be difficult to intercept since it normally flew at heights that operational Japanese fighters could not reach or attain with difficulty. Even if an interception was achieved, the B-17 carried a formidable defensive armament with which to protect itself. To a lesser extent, the Consolidated B-24 Liberator was also a factor when it began to replace the B-17s still remaining in the Pacific. In 1942, two companies, Mit­subishi and Kawanishi, were given a 17-shi Otsu specification by the Kaigun Koku Hombu to develop an aircraft to meet the need for a high altitude, high performance aircraft.

Mitsubishi Jukogyo K. K.’s response to the 17-shi Otsu directive was anything but con­
ventional when compared to Kawanishi’s design, the J3K1. The proposed plane, known within the company as the M-70, was a mono­plane pusher design that featured twin booms connected to vertical stabilisers by a low mounted horizontal stabiliser. The booms were slung under the low, fuselage mounted wings. The heart of the aircraft was to be the Mitsubishi [Ha-43] 12 MK9D tur­bocharged, radial engine. Rated at 1,650hp at 8,000m (26,246ft), it was projected that this engine would push the Senden to a top speed of 704km/h (437mph) via its six bladed pro­peller. For weapons, there was a Type 5 30mm cannon and two Type 99 20mm can­nons. All three were arranged in the fuselage nose with the Type 5 being centrally mounted and the two Type 99 cannons on either side of the fuselage. If required, the aircraft could carry a small bomb load of up to 120kg (2641b). Mounted across the top of the fuse­lage behind the cockpit were inlets to feed air to the turbocharger and engine. The purpose
of the turbocharger was to boost the manifold pressure on the engine over and above oper­ating pressures at sea level as a means to maintain and improve performance at alti­tude. For landing gear, the Senden had a tri­cycle arrangement with the nose gear retracting into the fuselage and the main wheels being housed in the booms. The pilot sat in the glazed nose of the aircraft in a cock­pit that was blended into the fuselage. The majority of the Senden was constructed of metal with fabric being used on the rudders and ailerons.

The Senden came in two versions. The first was the project described above while the second variation replaced the blended cock­pit with a bubble canopy to improve the pilot’s radius of vision. It also removed the protruding inlets and replaced them with two bands of flush inlets that wrapped around the fuselage, the first being directly behind the cockpit and the second around the engine area just past the wings. Finally, the horizon-

tal stabiliser was moved to the top of the ver­tical stabilisers. The remainder of the aircraft was basically the same between the two ver­sions. The blended cockpit version is credited as the J4M1 Project 1 while the second, with the bubble canopy and modified inlets, is sometimes referred to as the J4M4 Project 2.

After analysing the two designs, Mitsubishi selected the original configuration, the J4M1, to develop further. To confirm their initial pro­jections, a full scale model was constructed in 1943 and put to the test in a wind tunnel. Unfortunately for Mitsubishi, the tests proved to be a disappointment. Performance projec­tions based on the testing were below the ini­tial calculations and problems with the MK9D in terms of not reaching its horsepower rating only added to the concerns.

However, the Kaigun Koku Hombu and the UN ensured that Mitsubishi would not have to concern themselves further with the Senden. In 1943 as Mitsubishi was working on the Senden, the Kaigun Koku Hombu issued an

18- shi Otsu specification. From it, the Kyushu J7W Shinden resulted (page 84 for details). With the 18-shi Otsu requirements being simi­lar to the 17-shi Otsu specifications and with the J7W showing far more promise and having
the support of the UN, Mitsubishi were told to cease work on the Senden and instead further develop the Mitsubishi A7M ReppQ (‘Hurri­cane’) to meet the 17-shi Otsu standards. The result was the A7M3-J Model 34 Rifuku (Land Wind) that had not advanced beyond the design phase before the war ended.

Despite the fact that the J4M Senden did not progress past a wind tunnel model, US air intelligence was aware of the design mainly through captured documentation. In the Jan­uary 1945 issue of the US Recognition Journal, the J4M Senden was announced as a possible adversary in the coming weeks of the war. No artist renderings of the Senden were included in the article. The J4M was given the codename Luke in anticipation of Allied pilots encountering the aircraft in combat, something which was never to occur.

As a note, although there are artist impres­sions of a jet-powered Senden (as shown here) there is no evidence to support the notion the J4M was ever revived or consid­ered for turbojet power as there were other designs being considered (for example, the J7W2 and the Ki-201) which offered better prospects and capability.

In 1943, the Japanese were only too well aware of a threat looming on the horizon. That threat was the Boeing B-29 Super­fortress. With the development of the B-29 starting in 1939, the Japanese were in no doubt that once the bomber entered produc­tion it would eventually appear over Japan. The problem for the Japanese was that they did not have an effective countermeasure against the B-29 and feared they would not be able to have one ready in time for its antici­pated arrival. Fortunately, the answer was found in one of the most radical fighters ever to achieve operational status.

Towards the middle of 1943, representa­tives of the Japanese military in Berlin were notified of the development and progress of the Messerschmitt Me 163, a point defence interceptor powered by a rocket engine. Interest was expressed immediately. In short order Japanese attaches from the UN and the IJA visited Bad Zwischenahn in Germany where Erprobungskommando 16 was sta­tioned. This unit had been created earlier in 1943 to develop Me 163 combat tactics,
deployment and training as well as the coor­dination of the various contractors and test centres involved in development and pro­duction of the Me 163. During the tour EKdo 16 personnel explained to the Japanese the temperamental nature of the Walther HWK 509A rocket motor and the dangerous and explosive properties of the two fuels the motor used. This did nothing to dissuade the Japanese who saw the answer to their needs right before their eyes. To them, the benefits of an interceptor able to climb rapidly and possessing a very high speed overrode any concerns about the fuels or the engine. The Japanese wasted no time in entering negoti­ations to obtain the Me 163B.

However, not everyone was in agreement about the value of the Me 163. Detailed reports had been sent to Japan from Germany regard­ing the findings of the attaches which overall were positive; nevertheless, some argued that it would not be possible to produce the fuels the aircraft required in sufficient quantity to support operational requirements. Others criticised the unorthodox nature of the Me 163
and that developing such a plane and its engine would consume much needed resources. Despite these objections, the sup­porters for the Me 163 won out.

The Japanese swiftly and successfully negotiated the licences to manufacture both the Me 163B as well as its HWK 509A rocket motor. The motor licence alone cost the Japanese 20 million Reichsmarks. In addition to the two licences, Germany was to provide complete blueprints for the Me 163B and the HWK 509A, manufacturing data for the air­craft and engine, one complete МеІбЗВ, three HWK 509A motors, and two sets of sub – assemblies and components by no later than 1 March 1944. Also, Japanese military attaches in Berlin were to be notified of any improvements to the Me 163 design so changes could be incorporated into the Japanese version. The Japanese also requested to oversee the manufacturing processes for the Me 163B and the rocket motor as well as being allowed to study and review Luftwaffe operational procedures for the fighter. Three submarines were tasked
with shipping the materials to Japan – the RO-500, RO-501 and 1-29.

RO-500 was still named U-511 when it departed from Lorient in France on 10 May 1943 bound for Penang, Malaysia. Aboard were four Japanese including Vice Admiral Naokuni Nomura and Major Tam Otsu Sugita of the IJA medical service. Also aboard was the data for the Me 163B. During the transit, U-511 was named Satsuki 1 (‘satsuki’ mean­ing the month of May). On 16 July, U-511 reached Penang where Nomura, Sugita and the other Japanese passengers disembarked and returned to Japan by air. U-511 departed Penang for Kure, Japan, on 24 July 1943 and arrived in Kure on 7 August 1943 where the submarine was presented to the UN as the RO-500.

RO-501, a Type IXC/40 submarine, was for­mally U-1224. On 15 February 1944, U-1224 was handed over to the UN who gave it the name Satsuki 2, and on February 28, it was commissioned into the Imperial Navy as RO-501 with Lieutenant Commander Norita as captain. On 30 March 1944, RO-501 departed from Kiel, Germany, with the man­ufacturing data and blueprints for the Me 163B among other cargo. At 7.00pm on 13 May 1944, north west of the Cape Verde Islands, the USS Francis M. Robinson, a Buck – ley class destroyer escort, reported a sonar contact 755m (825 yards) from the ship. The Francis M. Robinson immediately initiated an attack, launching 24 Mark 10 Hedgehog bombs and five salvos of Mark 8 depth charges. Sonar reported four explosions sig­nifying the death of the RO-501.

1-29 of the Imperial Japanese Navy departed from Lorient, France, on 16 April 1944. She carried on board a HWK 509A rocket motor, the fuselage of a Fieseler Fi 103 and a Junkers Jumo 004A turbojet, again with other cargo. Technical Commander Eiichi Iwaya, a passenger, carried with him the plans for the МеІбЗВ and Me 262 while another passenger, Captain Matsui, had plans for accelerators used for rocket launching. Between the two of them, they also had plans for a glider bomb and radar equipment. On 14 July 1944, the 1-29 arrived safely in Singapore. Here, Iwaya and Matsui disembarked, along with a portion of their documents, and con­tinued on to Tokyo by air. On 15 July, Allied code breakers intercepted a message from Berlin to Tokyo regarding the cargo that the 1-29 carried and on 26 July 1944 at 5:00pm near the western entrance of the Balintang Channel, Luzon Strait, the USS Sawfish spot­ted the 1-29 on the surface. She fired four tor­pedoes and three struck the Japanese submarine. 1-29 sank almost immediately and only one sailor survived who swam to a nearby Philippine island and reported the loss.

Technical Commander Eiichi Iwaya, upon leaving the 1-29, did not take all of the docu­mentation he had for the Me 163B (or the Me 262) and the loss of the 1-29, along with that of the RO-501, delivered a major blow to the development program. However, the information Iwaya had preserved, combined with what was received from the RO-500, was enough to keep the project alive and in July 1944 the UN issued a 19-shi specification fora rocket powered interceptor. This decision was based on the analysis of the documenta­tion on hand for the Me 163B and the current construction capacity and capability of the air industry, and also down to the drive of Vice Admiral Misao Wada who supported the development of the rocket aircraft.

Upon issuing their 19-shi specification, the Kaigun Koku Hombu assigned the project to Mitsubishi. Mitsubishi were initially reluctant to accept the design, but further considera­tion and the need to adapt the Me 163B design to Japanese production capability saw the manufacturer agree. Even though the UN was behind the aircraft, the IJA would also be involved in the development of both the air­craft and rocket motor. The Japanese rocket interceptor was to be called the J8M1 Syusui (which means ‘Autumn Water’) and in IJA service the Syusui was to be designated Ki-200.

On 27 July 27 1944, all personnel involved met to discuss the Sytisui and it was agreed to follow the design plan of the Me 163B as much as possible. The key reason was that the design was proven and worked and thus critical time could be saved. The same applied to the rocket motor. A second reason for adhering to the Me 163B design was that Japanese fabricators had almost no experi­ence with the type of aircraft that the Me 163B was. But not everyone was in full agreement.

The IJA saw flaws in the Me 163B and felt that Japanese industry could not fully pro­duce the Syusui to the specifications of the German aircraft. Modifications to meet the current capabilities of the Japanese aviation industry would be required to both the rocket motor and the aircraft which, as a conse­quence, would force changes to the design. As such the IJA argued that in the end a new design would be required anyway. The UN, however, would hear none of it and was adamant that the Me 163B design would be followed.

Mitsubishi forged ahead with assembling a team to develop the J8M1. The project was led by Mijiro Takahashi at Mitsubishi’s Nagoya plant. Under Takahashi was Tetsuo Hikita who would be the lead designer for the air­frame. In addition to the Mitsubishi men, rep­resentatives of the Yokosuka Kokutai were involved, namely Captain Kumamoto and Commander One, who was tasked with test flying the J8M1 upon completion. Technical Commander Eiichi Iwaya was also a part of the overall development team given his famil­iarity with the МеІбЗВ acquired during his time in Germany. One last meeting was held on 7 August 1944 to finalise the development of the Syusui and then work began.

The first stage was the wooden mock-ups. On 8 September 1944, the full scale mock-up of the cockpit was completed and on 26 Sep­tember 1944, the mock-up of the Syusui was completed. Both the UN and the IJA inspected them and suggestions were made for possible alterations to the design. These changes were incorporated and Takahashi’s team laboured day and night to produce the detailed blueprints for the J8M1. Three proto­types were to be built; the first would be for load testing while the remaining two would be used for the flight test program. As the rocket motor was not yet available, two of the prototypes would be weighted to simulate the motor and fuel. To hasten construction, when one portion of the aircraft was drafted and Finalised, a copy was sent to the assem­bly shop assigned to construct the compo­nent so work could begin without delay.

Externally, the J8M1 was unmistakable in its lineage but Takahashi and his group had to make modifications as they adapted the МеІбЗВ design. For example, the МеІбЗВ used two MK 108 30mm cannons which were heavier and shorter than the 30mm cannons the Japanese were to use. Fuel capacity was similar to the German aircraft and so were the dimensions, although the J8M1 was slightly longer due its more pointed nose and had a wider span and smaller wing area. (The Syusui unlike the Me 163B did not use a nose – installed generator, the space being used for radio equipment.) The wing thickness was also increased. The main difference, how­ever, was the weight: the Sytisui was 363 to 408kg (800-900lb) lighter than the МеІбЗВ. This was not due to any effort to purposely lighten the Sytisui as it lacked armour protec­tion for the pilot and carried less ammunition for its cannons than the German interceptor. For weapons, the J8M1 was to be equipped with two Type 5 30mm cannons in the wings while the IJA’s Ki-200 would use two Ho-155 30mm cannons or two Ho-5 20mm cannons.

Because the Japanese lacked the experi­ence in flying tailless aircraft, Kugisho was tasked with creating a glider version of the Syusui. In part, the glider would provide per­formance data, findings from which could be incorporated into the Syusui, but would also serve as a trainer for rocket aircraft pilots. Therefore, the MXY8 Akigusa and MXY9 Shuka were developed, as described else­where in this book on page 77.

While work was underway on the first three prototypes, a production plan for the fighter was put together and was completed by October 1944. By March 1945, 155 SyQsui were to be produced with another 1,145 built by September 1945. Ultimately, by March 1946 at least 3,600 SyQsui were anticipated to be in service.

In addition to developing the Syusui, Mit­subishi was also assigned the task of creating the Japanese version of the Walther HWK 509A rocket motor and both the UN and the IJA were involved in the motor program. To assist the engineers in Mitsubishi’s engine department, personnel from the IJA’s First Army Air Arsenal engine section were assigned to the firm. The resulting motor was called the KR10 but was also known as the Toku-Ro.2. Components for the KR10 were constructed by four companies: Hitachi, Ishikawajima, Mitsubishi and Washimo. Washimo, for example, was responsible for the fuel flow control mechanisms and the relief valve for the Ко fuel tank.

Mitsubishi faced several problems in build­ing the KR10, the main issue being that the HWK 509A used a nickel-chromium alloy in the fuel injector atomiser, regulating valves and relief valves. Since the Japanese did not have access to this alloy they had to use plain chromium steel. It was expected that the KR10 would be ready for testing by October 1944, but the first prototype exploded imme­diately when it was started for the first time, partly believed to have been caused by the metal used. A deviation was made from the original HWK 509A plan in that the KR10 motor used wider supports and included a bearing in the middle for the Ко fuel com­pressor. This revision in the KR10 resulted in the KR12 but the addition of a second version of the motor risked compounding any pro­duction problems. Indeed, testing of the KR12 also resulted in an explosion. Mitsubishi engi­neers discovered that a bearing seal had failed that allowed the Ко fuel to leak into the motor and then come into contact with the bearing lubricant with catastrophic results. Given that it offered no real advantage, the KR12 was shelved and work focused solely on the KR10. These accidents, their subse­quent investigations and the resulting revi­sions put the KR10’s development further and further behind.

For fuel, the Syusui used two ingredients which, when combined, provided the com­bustion and resultant thrust. The First, Ко, was the Japanese version of the German fuel

T-Stoff formed from eighty per cent hydrogen peroxide with the remainder Oxyquinoline and pyrophosphates to act as stabilisers. Ко was the oxidising fuel. The second, Otsu, was the Japanese equivalent of C-Stoff. Otsu was the reductant fuel and was composed of thirty per cent hydrazine hydrate with the remainder being methanol, water and potas­sium-copper cyanides. Together, Ко and Otsu were a hypergolic fuel combination, which meant that when the two fuels were combined they spontaneously ignited. The problem with Ко and Otsu was that they were colourless and, of course, when they came together, the result was explosive. This required strict handling procedures and con­tainment methods. Both fuels were stored in special ceramic pots. To produce both fuels, three chemical companies were contracted. They were the UN’s First Fuel Arsenal, Mit­subishi Kasei and Edogawa Kagaku. In the Syusui, the fuels were stored in wing and fuselage mounted tanks. The pilot sat between two 91 litres (24 gallons) tanks of Ко while behind him in the fuselage was a 961 litres (254 gallons) tank and a 8 litre (2 gallon) tank of Ко. Each wing housed two tanks of Otsu, the capacity of each tank in each wing being 64 and 197 litres (17 and 52 gallons) in the two tanks respectively.

By December 1944, the second and third J8M1 s had been completed but as no engines were ready for installation, ballast was used to simulate the weight of the KR10 with full fuel tanks. Earlier, the first J8M1 had been completed and load tested on 1 December 1944. However, the 7.9 magnitude Tonankai earthquake that struck the Tokai region of Japan at 1.30pm on 7 December 1944 destroyed the aircraft and the testing facility that housed it. The remaining J8M1 aircraft were transferred to the UN’s First Naval Air Technical Arsenal. From there, the aircraft were shipped to Hyakurigahara, located about 79km (49 miles) northeast of Tokyo. December would also see delays due to the increasing B-29 bomber raids. Attacks against Mitsubishi’s Nagoya facility resulted in the KR10 program being moved to the Dai-Juichi Kaigun Kokusho complex at the Hiro Naval Arsenal in Kure, Hiroshima. Here, work con­tinued on the motor supervised by Professor Kasai of the Kyushu University (although another source states the entire engine devel­opment group was moved to an underground facility in Natsushima in Yokosuka prefec­ture, overseen by the Dai-Juichi Kaigun Kokusho).

During testing, the KR10 delivered less thrust than the HWK 509A. Although the SyQsui was lighter than the Me 163B, when Takahashi and Hikita completed perfor­mance calculations for the SyQsui based on the thrust rating of the KR10, they found that the lighter weight did not totally offset the lower thrust. Regardless, the estimated speed and climb rate was considered exceptional.

On 8 January 1945, a Nakajima B6N1 (known as Jill to the Allies) towed the SyQsui into the air from the Hyakurigahara airfield and after a successful flight the design was vali­dated. Work quickly proceeded on further production of the SyQsui, this time with the KR10. However, the motor program was at least three months behind schedule and it was not until 11 April 1945 that the KR10 was suffi­ciently developed to enable it to function with some measure of reliability. With the possibil­ity of powered flight, Captain Shibata, com­mander of the 312 KokQtai due to be equipped with the J8M1, sought to speed up the process for testing. In discussions with the SyQsui development team it was decided that if the KR10 could produce thrust for at least two minutes without mishap, the motor should be Fitted to the SyQsui so that powered flight test­ing could commence. 22 April 1945 was set as the deadline for the first powered flight.

Meanwhile, Germany made another attempt to send more material to Japan including documents and parts for the Me 163. These items and other cargo were loaded onboard U-864 that departed from the Bruno U-boat pen located in Bergen, Norway, on 5 February 1945. However, having past Fedje the submarine developed a misfire in one of her two MAN diesel engines and it was necessary to return to Bergen to effect repairs. The British submarine HMS Venturer, dispatched to deal with U-864, spotted the German submarine’s periscope on 9 Febru­ary 1945. Korvettenkapitan Ralf-Reimar Wol­fram realised he was being followed and began to take evasive action, moving in a zig­zag fashion. James S. Launders, Venturer’s captain, decided to press home the attack and fired all four of his loaded torpedoes in a spread pattern. U-864 crash dived, dodged three of the torpedoes but turned into the fourth which struck the submarine. The resulting explosion split U-864 into two.

Unfortunately for the SyQsui, the deadline for the KR 10 would not be met. In exhaustive testing, another motor detonated after having achieved two minutes of burn time. In addi­tion, fears of B-29 raids saw the KR10 team being moved to the Yamakita factory com­plex in Hakome prefecture while the Mit­subishi SyQsui development group was relocated to the IJA research and develop­ment centre in Matsumoto in Nagano Prefec­ture. These moves consumed precious research time throughout April and May 1945. Both groups were eventually able to continue

work on the KR10 in an attempt to enhance its reliability and, in June, success was achieved. A KR10 from the Yamakita group functioned for four minutes while the Mit­subishi group in Matsumoto managed three minutes. With these motors now meeting the

two minute requirement, plans were swiftly prepared to install the Yamakita KR10 into a J8M1 while the Matsumoto motor was to be placed into another airframe that would be completed as a Ki-200.

The J8Ml’s installation was completed first

in the second week of June 1945 at Mit­subishi’s Number One Plant in Nagoya. The Syusui lacked much of its operational equip­ment including weapons and was trans­ported to Yokoku airfield. This site was favoured because it was situated along a shoreline, which meant that if the pilot had to ditch the aircraft he could do so into the ocean, offering a better chance for survival as well as possibly lessening the damage to the Syusui. The Syusui arrived at Yokoku at the beginning of July and ground testing began immediately. Secured to the tarmac, the tail of the Syusui was removed exposing the KR10 and motor running tests commenced. It was found that the motor did not burn fuel evenly, generating plumes of light red smoke from the combustion chamber as it ran. By 5 July 1945, technicians and engineers had cor­rected the burn problem to the point that the KR10 was deemed ready and the Syusui’s first powered flight was scheduled for 7 July 1945.

In front of a crowd of onlookers, the Syusui was moved to the start of the 1,200m (3,937ft) runway, the longer of the two at Yokoku. It was then fuelled with 568 litres (150 gallons) of Ко into the fuselage tanks and 159 litres (42 gallons) of Otsu into the wing tanks as the mixture ratio was approximately 10 to 3.6. At 4:55pm, the pilot, Lieutenant-Commander Toyohiko Inuzuka, fired the engine and within 11 seconds and after only 320m (1,049ft) of runway, the Syusui lifted off the ground and into the air, Inuzuka releasing the dolly and raising the nose to provide a 45° angle climb. Then, at 350m (1,148ft), a puff of black smoke issued from the motor, sput­tered and went out. The speed that had been built up carried the Syusui up to 500m (1,640ft) where Inuzuka levelled off and banked to the right ready to return to the run­way and land. As Inuzuka continued his right hand bank, the Syusui began to drift and air­speed rapidly dropped off. As he approached the runway, Inuzuka raised the nose of the Syusui to try and avoid colliding with a build­ing but it was too late. A wing clipped the side of the building, putting the Syusui into a crash so forceful that it broke apart, scattering pieces across the south-west edge of the air­field. Both wings were ripped away and the front of the aircraft was completely destroyed. Inuzuka survived the impact and was extracted from the wreckage. However, the extent of his injuries was so severe that he died the following day.

No time was wasted in trying to find the cause of the motor failure. Mechanical issues were ruled out and it was surmised that the puff of smoke and the subsequent loss of power from the KR10 was due to fuel being cut off from the motor. Miraculously, the fuel

tanks did not explode on impact and it was found that at least half of the fuel loaded prior to take-off remained. It was determined that the culprit was the fuel line from the Ко tank. Due to poor design, when the Sytisui went into its climb the fuel in the tank shifted away from the line which starved the motor of the needed oxidiser and thus the KR10 cut out. While the investigation was being carried out, bench tests of two additional KR10 motors (one each at Matsumoto and Yamakita) resulted in both exploding. This left a single KR10, the one slated for the Ki-200.

Flight testing of the Sytisui was suspended until the problem with the fuel system could be resolved. A further four Sytisui aircraft had been completed by Mitsubishi by the time a solution was found. These changes were incorporated into the KR10 engines then under development and flight testing was scheduled to resume in late August 1945. However, on 15 August 1945, Japan surren­dered. All further work on the Sytisui ceased and no further flights were made. At the end of the war the Ki-200 remained engineless, its KR10 never having been installed. Aside from the seven J8M1 aircraft built – including the one to be finished as the Ki-200 – another six were in various stages of completion. A fur­ther four KR10 motors had been completed with another two nearly finished. Enough components had been constructed to assem­ble a further twenty motors.

Another variant of the J8M had been planned which was called the J8M2 Syusui – Kai. The J8M2 lost one of the Type 5 30mm cannons/ammunition to be replaced by addi­tional fuel tankage. It was hoped that this would increase the endurance of the aircraft. The end of hostilities would see the J8M2 remain only a preliminary design though pro­duction of the J8M2 was a certainty had it been completed. As mentioned earlier, the IJA was not pleased with the Ki-200 and it would undertake development of its own ver­sion of the J8M, the Ki-202 Syusui-Kai, to right the wrongs it felt were evident in the Sytisui. For more details, please see the chapter on the Ki-202 (page 40).

A note regarding the use of Sytisui as the name for the J8M. The kanji for the aircraft (SyO and Sui) translate as ‘Autumn Water’. However, Shtisui has been used in many sources with translations ranging from ‘Sword Stroke’ or ‘Swinging Sword’ to ‘Rigor­ous Sword’, but the name Shtisui is not cor­rect. The use of Shiisui evolved from the metaphor that Sytisui represents – the wavy pattern on the metal blade of a highly sharp­ened sword as well as the brightness of the polished metal which reminds one of the waves on a body of clear water.

Contemporaries

Messerschmitt Me 163B Komet (Germany)

Specifications in parenthesis pertain to the J8M2 only and are based on Mitsubishi’s estimated data.

Type Interceptor/Fighter

Crew One

Powerplant

One Toku-Ro.2 (KR10) bi-fuel rocket motor developing 1,500kg (3,307 lb) of thrust

Dimensions Span Length Height Wing area Wing loading	(J8M2)	9.47m 6.03m 2.68m 17.72m2 219.22kg/m2 219.70kg/m!	31.1ft 19.8ft 8.8ft 190.8ft2 44.9 lb/ft2 45 lb/fl2
Weights
Empty		1,445kg	3,1851b
	(J8M2)	1,510kg	3,3281b
Loaded		3,000kg	6,6131b
	(J8M2)	3,650kg	8,0461b
Maximum		3,870kg	8,5311b
	(J8M2)	3,900kg	8,5981b
Useful load		1,545kg	3,4061b
	(J8M2)	2,140kg	4,7171b
Performance
Max speed		900km/h at 10,000m	559mph at 32,810ft
Cruise speed		699km/h	434mph
Landing speed		150km/h	93mph
Range		3 min 6 sec of powered flight at 599km/h 372mph
Max range		5 min 30 sec of powered flight
Climb		40 sec to 2,000m (6,561ft)

2 min 8 sec to 4,000m (13,123ft) 3 min 8 sec to 8,000m (26,246ft) 3 min 50 sec to 10,000m (32,808ft)

Ceiling 12,000m 39,370ft

Fuel capacity 1,181 litres (312 gallons) of Ко and

522 litres (138 gallons) of Otsu

Armament

Two Type 5 30mm cannons with 53 rounds of ammunition per gun (one Type 5 cannon with 53 rounds of ammunition)

Deployment

None. A total of seven J8M1 aircraft were completed with one to be finished as a Ki-200. The 312 Kokutai were to receive the J8M1 had it entered production. No J8M2 was ever built nor were any Ki-200 aircraft.

Survivors

Mitsubishi J8M1 Sytisui (FE-300)

One of three brought from Yokosuka on 3 November 1945, this Sytisui is aircraft No.403 and is thought to have been captured at Mitsubishi’s No. l plant in Nagoya. Appearing on the 10 March 1946 report for aircraft releasable to the aviation industry, the Sytisui would be made available for display purposes on 1 August 1946 appearing to the public in Hollywood, California. The aircraft was later obtained and restored by Edward Maloney for display at the Planes of Fame Museum in Chino, California, where it remains to this day.

Mitsubishi J8M1 Sytisui (tail number 24)

After being received at NAS Patuxent River, the aircraft was moved to NAS Glenview in Glenview, Illinois (a suburb of Chicago, Illinois), where it was on display by 3 October 1946. This Sytisui eventually reached a derelict state and was scrapped.

Mitsubishi J8M1 Sytisui (tail number A-25)

Nothing is known about this particular Sytisui other than it likely ended up as scrap.

Mitsubishi J8M1 Sytisui

Mitsubishi has recently restored a J8M1 and it is currently on display at the company’s Komaki Plant Museum. A portion of the restoration contains components from a badly damaged J8M1 fuselage found in a cave but it still required significant custom fabrication of new parts to finish the project. Prior to Mitsubishi obtaining the fuselage, the remains had been on display on the grounds of the Japanese Air Self-Defence Force’s Gifu Air Base.

Ki-200 – data (estimated)

Type	Interceptor/Fighter
Crew	One
Powerplant	One Toku-Ro.2 (KR10) bi-fuel rocket motor
developing 1,500kg (3,3071b) of thrust
Dimensions
Span	9.47m	31.1ft
Length	5.88m	19.3ft
Height	2.68m	8.8ft
Wing area	17.69m2	190.5ft"
Weights
Empty	1,505kg	3,3171b
Maximum	3,870kg	8,5311b
Performance
Max speed	800-900km/h	497-559mph
	at 10,000m	at 32,808ft
Cruise speed	351 km/h	218mph
Range	2 min 30 sec of powered flight
Max range	7 min of powered flight
Climb	3 min 40 sec to 10,000m (32,808ft)
Fuel capacity	1,181 litres (312 gallons) of Ко

and 522 litres (138 gallons) of Otsu

Armament

Two Ho-155 30mm cannons (or two Ho-5 20mm cannons)