Kyushu J7W "Shinden" pt. 3

After the war concluded, certain outer surfaces of the initial prototype were damaged and were later fixed for delivery to the US forces that occupied the area.

As per Japanese reports, the second prototype (of which no images have emerged, to my knowledge) was nearing completion when the war concluded.

The attached photos feature the first prototype following its repairs, prior to being painted, awaiting delivery to the US military.

Here's what the Japanese Wikipedia say about the Kyushu "Shinden-kai" J7W2 equipped with a jet engine:

There is a theory that there was a plan to eventually convert the Shinden into a jet aircraft, known as the "Shinden-kai" (designation J7W2). The basis for this theory regarding the Shinden's jet conversion plan is a contribution to an aviation magazine by Kiyohara Kunitake, former Deputy Chief of the First Design Section in the Kyushu Aircraft Design Department.

In his article, Kiyohara wrote: “On June 5, 1944, either during the ‘Study Group on the Prototype "Shinden" Project Requirements’ held at the Air Technical Arsenal or following subsequent instructions, a member of the Air Technical Arsenal’s Engine Division stated, ‘Proceed with the design with the use of a gas turbine in mind.’ The engine to be installed on the "Shinden" would have a static ground thrust of 900 kg, equivalent to roughly 3,000 HP, and would likely achieve a speed of about 420 kt (780 km/h). However, a takeoff booster rocket would be necessary, and the plan was to treat this as an overload. It appears this was the Ne-130 jet engine then under development at Ishikawajima-Shibaura Turbine. Given the engine layout of the "Shinden," converting it to jet engines did not seem particularly difficult. I remember feeling excited and hoping it would be realized as soon as possible. Ultimately, this did not come to fruition, but the prototype of the twin-engine jet attack aircraft "Kikka," designed by Nakajima Aircraft, was also built at Kyushu Aircraft, and the war ended just as the first prototype was nearly complete.” he testified. 

However, no other specific records have been found indicating that the "Shinden" was designed with jet conversion in mind. Furthermore, while Nishimura Mitsuo, who served as the chief engineer for the "Shinden’s" powerplant installation, acknowledges that there was talk of jet conversion, he also testified that “no concrete progress had been made” toward its realization. The development of the Ne-130 jet engine—which was under prototyping at the time and slated for installation—had only just reached the stage of full-power testing near the end of the war and was not yet in a condition suitable for actual operation.

The reason for this was that its predecessor, the Ne 20, suffered from various fatal defects. As a result of these defects, its endurance was extremely short, with a maximum operational life of only 15 hours during design-phase full-power operation. These defects were also exposed during test flights of the "Kikka," which was being developed in parallel with the "Shinden" at the time, and no progress was being made toward resolving them. These defects were present not only in the Ne-20 but also in the Ne-130, which was under development at the time, and naturally, the "Shinden" was not in a condition to be equipped with them.

Furthermore, by the end of the war, Japan had virtually exhausted its supply of rare metals (such as nickel and chromium) necessary for manufacturing the heat-resistant metals essential for jet engines; the development of high-heat-resistant alternative metals to address this resource shortage was a major obstacle even for the exhaust turbine, as is often noted. Consequently, it is believed that even if a prototype engine had been completed, mass production would have been virtually impossible.

Allow me to conclude this series of posts on the "Shinden" by sharing my thoughts on the aircraft. Although undoubtedly distinctive, highly intriguing, and in simple terms, truly impressive, I think the "Shinden" ought to be regarded not as a "miracle weapon" but rather in a more realistic and pragmatic light.

The aircraft was primarily designed as an interceptor for the B-29. U.S. bombers flying at very high altitudes would necessitate the development and installation of a pressurized cabin in the "Shinden," something I have not read anywhere that was taken into consideration. The IJAAF was experimenting with pressurized cabins (Kawasaki Ki-108), but the Navy?

Bombers flying at lower altitudes would afford the protection of escort fighters, and the "Shinden" was not intended to engage in aerial battles with them. Even if that became feasible, by the second half of 1945, the Japanese military did not have enough highly trained fighter pilots to stand a chance. Training new pilots to fly this new high-performance interceptor would require many months. Given that Japan had nearly depleted its supply of high-quality aviation fuel, it is very difficult to see how new pilots would have been trained to reach a level of proficiency sufficient to make a difference. 

Most Allied sources mention that by the summer of 1945, the bombing campaign against Japan was nearly complete and the B-29s were mostly out of targets. Furthermore, during the invasion of the Japanese mainland, medium and low-altitude bombers would be deployed to support the ground forces, so again, not many B-29s would be in the sky for the "Shinden" to intercept. All in all, I see the "Shinden" as a design that could have made some impact if it had been completed, produced, and delivered to combat units by the end of 1944, to be thrown into combat at the beginning of 1945, rather than as a 1946 design. I can imagine in 1945 the 302 Kokutai having a bunch of "Shindens" led by Akamatsu and perhaps a night fighter version, a J7W1-S with a couple of cannons right behind the pilot's seat but in 1946...unlikely.

But hey, it went against Godzilla, didn't it?