Mitsubishi T. K.4 Type 0

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

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

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

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

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

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

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

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

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

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

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

DANIEL UHR

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

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

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

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

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

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

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

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

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

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

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

S-31 Kurowashi – data Contemporaries Daimler-Benz Schnellbomber mit DB P83 Gruppenmotor (Germany) Type Heavy Bomber Crew Five

Powerplant Four 24-cylinder, liquid-cooled X-engines, each developing 2,500hp, each pair driving two, metal 3-bladed contra­rotating propellers Dimensions Span Length Height Wing area 32.82m 21.09m 5.88m 1.33.00m2 107.7ft 69.2ft 19.3ft 1,431.6ft2 Weights Loaded 17,850kg 39,3521b Performance Max speed 690km/h 429mph Cruise speed 589km/h 366mph Landing speed 145km/h 90mph Range 5,900km 3,666 miles Ceiling 15,100m 49,540ft Fuel Weight 8,000kg 17,6361b Armament Eight 7.7mm machine guns and four 23mm cannons (see text for arrangement); up to 8,000kg (17,6361b) of bombs

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