Nakajima Army Type Ko Model 4 Fighter / Nieuport-Delage NiD 29 - video

An extremely rare but short video today features Nakajima Army Type Ko Model 4 Fighters.

Here's what the English Wiki has to say about the type:

"The Japanese company Nakajima bought a pattern aircraft and built 608 for the Imperial Japanese Army as the Ko-4."

And here's what the Japanese Wiki has on the type:

In Japan, after importing 110 completed “NiD 29 C.1” aircraft, Nakajima Aircraft acquired the license to produce the aircraft. The first domestically produced aircraft made its maiden flight in December 1923, and 608 units were produced for the Imperial Japanese Army as the Type Ko Model 4 Fighter. In addition, the Army Artillery Arsenal produced 46 aircraft. Japan was the country that adopted the “NiD 29” (referred to in Japan at the time as the “Type ニ Model 29 Fighter”; “ニ” is the katakana initial of 「ニューポール」 (Nieuport)) in the greatest numbers worldwide.

The “Ko” type was manufactured by Nieuport, the “Otsu” type by Salmson, the “Hei” type by Spad, the “Tei” type by Farman, the “Bo” type by Cordonnier, and the “Ki” type by Henriot. The designation “Model 4” indicates that three other Nieuport models had already been adopted by the Imperial Japanese Army. "Model 3" was the Nieuport 24C.1 Trainer/Fighter, "Model 2" was the Nieuport 83 E.2 Trainer and, "Model 1" was the Nieuport 81 E.2 Trainer.

The engine installed in this aircraft was the “Mitsubishi Hispano-Suiza 300-horsepower engine,” a domestic version of the “Hispano-Suiza HS-8Fb water-cooled V-8 gasoline engine, 300 hp” produced at the “Mitsubishi Internal Combustion Engine Co., Ltd., Nagoya Works.” (The abbreviation for “Hispano-Suiza-type” was “I-type” in the Army and “Hi-type” in the Navy.) 

It employed a Lamblin radiator, which offered low air resistance, and was mounted at the base of the main landing gear.

This aircraft was the first fighter to be mass-produced by the Imperial Japanese Army. It was the first Imperial Japanese Army aircraft to be equipped with two 7.7 mm machine guns (the Imperial Japanese Navy’s Mitsubishi 1MF Fighter was the first to adopt them), which were mounted above the engine and in front of the pilot’s windscreen.

Although it served as the Imperial Japanese Army’s main fighter during the Manchurian Incident, it saw almost no actual combat and was later sold off to the civilian sector for use as training aircraft and other purposes. Its successor was the Type 91 Fighter.

Messerschmitt Me 210 in Japan

According to Akimoto:

The Messerschmitt Me 210A twin-engine, two-seat fighter-bomber (serial number 2350), imported by the Army along with the Fw 190, began assembly at Kawasaki's Akashi factory in January 1943, and its maiden flight was conducted in May of the same year by pilot "シューテア" (the name is given in katakana. Google reads this as "Schuteer" or "Schulter". Leave a comment if you know the correct spelling of the German test pilot). During military testing, it made an emergency landing, damaging the landing gear struts, engine mount, and propeller, and was subsequently sold to Kawasaki for use as research equipment.

A key feature of this aircraft was its remotely controlled turrets, each equipped with a 13mm autocannon on one side of the fuselage, in addition to the fixed armament in the nose. Its bomb load could reach a maximum of 1,000 kg. While the innovative remote control mechanism for the turrets and the dive brakes attracted attention, the former was not highly regarded for its practicality, and the latter was deemed too precise to be domestically produced. Furthermore, its performance did not meet expectations.

The Japanese Wiki says it was a "Me 210 A-1", the English Wiki disagrees and says it was a "Me 210A-2" and adds:

"received one aircraft bought in Germany for tests and delivered by blockade runner. It was operated by the Testing unit of the First Tachikawa Air Army Arsenal."

An on-line source also mentions:

"The Japanese army and the Kawasaki plant in 1942 were interested in a new German heavy fighter/bomber due to the fact that the Japanese did not have any similar design. The Japanese commission, which was sent to Germany to bring the Me 210 A-1 aircraft, was impressed by this aircraft. Therefore, this aircraft was purchased and in January 1943 it was sent to Japan, probably on board the U-180 submarine.... Due to the lack of spare parts and the inability to deliver the appropriate parts from Germany, the aircraft was scrapped. However, Japanese designers used the technologies used in the Me 210 to develop the Ki-93 aircraft, and it was planned to use similar automatic cannons in the planned modernization of the Ki-74."

I could not find any reference to the Japanese using Me210 technologies on the development of the Ki-93 and the Ki-74. Furthermore, the Ki-74 was a bomber and there was no planned version equipped with "automatic cannons". The Ki-93 did have a big cannon, so, perhaps the author mixed the aircraft types.

Marcus Z left the following comment:

Hello George, according to Edwin M. Dyers' "Japanese Secret Projects" it was a Messerschmitt Me 210 A2, Werksnummer 2350 which was modified to the standard of the Me 410 (with the exception that it retained the original Daimler-Benz DB601F engines). It was sent to Japan in 1942 for evaluation. Cheers Marcus Z

Thank you Marcus.

Photos Tanaka Shoichi via Jun Oizumi

Fiat BR.20 "Cicogna" in Japanese service

I was recently going through the Japanese propaganda videos dubed in Indonesian found in the Dutch archives. One video showcasing the "power of the Japanese Air Force" features a collection of short clips. Among them there is some really short footage of a Fiat BR.20 "Cicogna" operated by an IJAAF "jubakutai" (heavy bomber unit).

Although really very short, this is the only footage of a BR.20 in Japanese service I know of. Obviously the original would have included additional material, but regrettably, I believe it's unlikely it will ever surface.

According to the Japanese Wikipedia:

In 1938, 85 units of the late-model BR.20 were exported to the Imperial Japanese Army and deployed in the Second Sino-Japanese War under the designation "I-shiki" (Type I) Heavy Bomber. The aircraft served as an interim measure pending the introduction of the Type 97 Heavy Bomber [Mitsubishi Ki-21 "Sally"]; by the time the Type 97 was deployed to the front lines, stocks of Italian-standard bombs and spare parts had been exhausted, leading to the aircraft's withdrawal from frontline service. Nevertheless, the Breda-SAFAT 12.7mm machine guns with which the aircraft was equipped proved invaluable to the Army's development of its own aircraft machine gun, the Ho-103.

Type I Heavy Bomber (Fiat BR.20) flown by the 1st Chutai of the 98th Sentai.

Type I Heavy Bomber (Fiat BR.20) flown by the 1st Chutai of the 12th Sentai. 

(Photo Tanaka Shoichi via Jun Oizumi)

In case you didn't know, the best and immediately available (not ancient, out-of-print or inaccurate) reference for the "Sally" and the Fiat BR.20 in Japanese service, is the 3rd release in our Eagle Eye series.

Available from our online store: HERE

The Mindset Behind the Development Process of the Imperial Japanese Army Fighter Aircraft: Kawasaki Ki-60 & Ki-61 "Hien"

Let's begin with what Francillon has to say about the Kawasaki Ki-60 & the Ki-61 "Hien"

Ki-60:

"While negotiating with Daimler-Benz A.G. for the manufacturing rights for the German DB 601A inverted-vee liquid-cooled engine, Kawasaki were successful in impressing upon members of the Koku Hombu that most contemporary foreign high-performance fighters were powered by liquid-cooled engines. Consequently, in February 1940, Kawasaki were instructed to design around the German engine, or its Japanese version, two fighter aircraft: the Ki-60 heavy interceptor and the Ki-61, a lighter all-purpose fighter. "

Ki-61:

"While negotiating with Daimler-Benz, Kawasaki had approached the Army with initial design studies for various fighter aircraft making use of this engine. As reports from the air war in Europe were showing the apparent superiority of aircraft powered by liquid-cooled engines, the Koku Hombu instructed Kawasaki in February 1940 to proceed with two aircraft of this type: the Ki-60, a heavy interceptor, and the Ki-61, a lighter all-purpose fighter, priority being given to the heavier aircraft".

The Japanese Wikipedia and virtually all Japanese sources see things differently:

"In the summer of 1939, when the Nakajima Ki-43 "Hayabusa" [Oscar], was still undergoing evaluation, the Army began preparations for the development of a new fighter aircraft, exchanging opinions and conducting inspections with various companies. While air-cooled radial engines manufactured by Nakajima and Mitsubishi dominated the Japanese aviation engine landscape, Kawasaki had—since acquiring the manufacturing rights for the German BMW liquid-cooled V-type engine in 1924—developed, produced, and installed that engine (and its improved variants) in its own aircraft. However, the engine series culminating in the Ha-9 model had reached its performance limits, necessitating a shift to a new type. Meanwhile, liquid-cooled engines remained highly valued overseas for high-speed military aircraft; unable to abandon this technology, the Japanese military decided to domesticate the German Daimler-Benz DB601 engine. In 1937, the Navy assigned the acquisition of manufacturing rights to Aichi, while the Army assigned them to Kawasaki—both companies having prior experience in liquid-cooled engine production. Kawasaki, slightly lagging behind Aichi, dispatched a team of engineers to Germany in 1939 and invited technicians from Daimler to assist, ultimately completing the first domestically produced DB601A in December 1940. After further research, Kawasaki submitted plans for the light fighter KDA-21 and the heavy fighter KDA-22 in January 1940. 

Under the Japanese Army's "Research Policy" and "Research Schedule for Next-Generation Aircraft" dated 1940, the goal was to  first complete a "Type 1" interim model—equipped with two 20mm cannons and capable of a top speed in the 550 km/h range—by December 1940, followed by the completion of evaluations for this interim model by September 1941, with the development of the final operational version to proceed based on those results.

As this was essentially Japan's first attempt at a dedicated heavy fighter, the research schedule for future aircraft outlined a phased approach: first, an interim model armed with two 20mm cannons would be completed by December 1940 and undergo evaluation by September 1941; subsequently, a production-ready model would be developed based on those results. The target maximum speed for the final operational version was envisioned to be in the 640 km/h range.

In February 1940, acting on this policy, directives were issued for the development of the Ki-60 heavy single-seat fighter powered by the DB601A and the Ki-61 light single-seat fighter powered by the Ha-40 (the domestic version of the DB601A) as the next generation of fighters. The chief engineer for both was engineer Takeo Doi.

The first Kawasaki Ki-60 prototype.

The type incorporated various new technologies, such as a sliding canopy designed for improved rearward visibility, a retractable tailwheel, and—for the first time in Japan—retractable main landing gear that shortened in length during the retraction process. This shortening-retraction mechanism was adopted despite the resulting mechanical complexity and increased weight in order to narrow the spacing between the wing-mounted cannons.

The English Wikipedia has this about the Ki-60:

"From the start of flight testing, it became apparent that the design was seriously flawed in several key areas. The take-off run was unacceptably long, while, in flight, the aircraft displayed some lateral instability, excessively heavy controls, and poor control response. The spinning characteristics were described as "dangerous", and the stalling speed was extremely high. Although a top speed of 600 kilometres per hour (370 mph) had been projected the Ki-60 was only able to achieve 548 kilometres per hour (341 mph)."

The source is mentioned as "Green, William; Swanborough, Gordon (1976). JWW2 Aircraft Fact Files: Japanese Army Fighters, Part 1."

Curiously, absolutely no Japanese source mentions anything even remotely close to the above statements.

On the contrary, Japanese sources mention that:

"Test results confirmed that the aircraft achieved a maximum speed of 560 km/h at an altitude of 4500 m, a climb time of 6 minutes to 5000 m, and a service ceiling of 10000 m. This was about 15 km/h faster in maximum speed and 30 seconds faster in climb time compared to the Nakajima Ki-44 "Shoki", which had been completed and was undergoing testing earlier."

"In June 1941, during the height of the evaluation process, a comparative test was held in Kakamigahara between a Messerschmitt Bf 109E imported from Germany and Japanese fighter planes. The Ki-60 also participated in this test, and it was found that it could engage in aerial combat on equal or slightly superior terms with the Bf 109E.

Compared to its rival, the Nakajima Ki-44 "Shoki", the Ki-60 had superior turning performance as long as the Ki-44 didn't use its combat flaps, making it easier to pilot and take off/land than the Ki-44. The pilot of the Ki-60 at that time was Captain Kuroe Yasuhiko, who became captivated by the Ki-60's charm and a fan of it ever since."

Other Ki-60 details missing from all non-Japanese sources:

a. "the Ki-60 was armed with 20mm cannons and designed strictly for "hit-and-run" tactics."

b. "The engines installed in the Ki-60 were units imported from Germany to serve as samples for domestic production."

dc. "A total of three prototype aircraft were produced. Two of these were deployed to the 47th Independent Air Squadron alongside pre-production models of the Ki-44, but both were lost in accidents before they could see combat. The remaining aircraft survived until the end of the war."

Finally, completely contrary to what all non-Japanese sources say about the type, all Japanese sources agree that: 

"Although the aircraft was ultimately not adopted for service, flight test results indicated it was an excellent machine that fully met its design objectives."

The main reason for the Army rejecting the Ki-60 is that the Ki-61 "Hien", demonstrated unexpectedly outstanding performance. 

The second Kawasaki Ki-61 "Hien" (Tony) prototype (c/n 6102). The vision panels forward of the windscreen have been increased to two. Aiming for aerodynamic cleanliness and light weight, the Ki-61 achieved performance levels far exceeding those anticipated. In comparative trials against the Bf 109E, the Ki-61 was found to be superior in speed, climb rate, endurance and handling qualities.

As for the "Hien", here's a piece from the Japanese Wikipedia, that includes details largely absent from non-Japanese references:

"The design concept for the Ki-61 was that of a versatile fighter—sometimes referred to as a "medium fighter"—that did not strictly adhere to the "heavy fighter" or "light fighter" categories defined in the "Aviation Weaponry Research Policy." It is said that internal Army debate inevitably arose because the requirements for light single-seat fighters demanded not only maneuverability and climbing ability but also the installation of 12.7 mm cannons. Deputy Chief Engineer Owada stated that "a fighter aircraft must surpass the enemy in overall performance; categorizing them into 'light' and 'heavy' fighters is irrational", a view that was shared by the entire Kawasaki development team. Some sources even indicate that the development team referred to the concept as a "medium fighter", suggesting the idea originated with Kawasaki.

Doi himself stated that he sought to craft the Ki-61 into an ideal fighter, without being bound by the Army's "light fighter" doctrine. Detailed design work began around September 1940. 

Additionally, Watanabe Yoji in his "The Liquid-Cooled Fighter “Hien”: The Silver Wings of a Japanese-German Collaboration" notes that as early as May 1940—during the initial development phase—Doi had already discussed the possibility of equipping the Ki-61 with an air-cooled engine.

The wooden mockup review took place in June 1941 [23], and the prototype was completed and made its maiden flight in December 1941. Although some sources suggest that the Army had low expectations for the Ki-61—given that it utilized an engine of the same family as the Ki-60—it achieved a top speed of 590 km/h during testing, surpassing both the Ki-60 and the Bf 109E by 30 km/h. This level of performance was entirely unexpected, even by its designer, Doi. For context, other Army fighters of the era had lower top speeds: the "Hayabusa" (a "light fighter") ranged from 495 km/h to 515 km/h, while the "Shoki" (a "heavy fighter", prior to official adoption) topped out at 580 km/h. Consequently, Doi and Owada were awarded the Mainichi Aviation Prize in October 1942 and the Army Technical Merit Award in December 1943.

The Mindset Behind the Development Process of the Imperial Japanese Army Fighter Aircraft: Part #1 "Hayabusa" & "Shoki"

Let's begin with what Francillon has to say about the "Hayabusa":

"Design work on the Hayabusa began in December 1937 when the Army, giving up their long-standing policy of awarding competitive contracts to Japanese manufacturers, instructed Nakajima Hikoki K.K. to design a single-seat fighter to supersede the Army Type 97 Fighter (Nakajima Ki-27)."

And about the "Shoki":

"Shortly after instructing Nakajima to proceed with the design of the Ki-43, the Koku Hombu gave them their specification for an interceptor fighter. In a pronounced departure from previous Japanese standards, speed and climb rate were emphasized at the expense of manoeuvrability. The Ki-44, as the project became known,..."

The English Wikipedia entries heavily rely on Francillon and basically repeat the above.

But let's see what the Japanese Wikipedia has to say about the mindset behind the development of these two fighters and the "Army Aviation Weapons Research Policies":

The Nakajima-built Type 97 Fighter (Ki-27 "Nate"), officially adopted in December 1937, featured an ambitious design—the Army's first all-metal, low-wing monoplane—despite its conservative fixed landing gear. It was an excellent dogfighter with superior climb rates and maneuverability. However, by the time the Type 97 appeared, the Bf 109 (Germany) and Spitfire (UK)—both featuring retractable landing gear—had already emerged in Europe, prompting the Army to explore the development of new fighters.

In the "Army Aviation Weapons Research Policy" for the 1937 fiscal year—formulated by the Army Aviation Headquarters while the Ki-27 was under development—single-seat fighters were defined in two categories: "machine-gun equipped" and "autocannon equipped." The aircraft developed in accordance with these specifications were the Ki-43 (for the former category) and the Ki-44 (for the latter). 

The "Army Aviation Weapons Research Policy" for the 1938 fiscal year further refined these categories into "Light Single-Seat Fighter" and "Heavy Single-Seat Fighter" and added a third: the long-range two-seat fighter based on the concept of a twin-engine multi-role fighter. 

Based on this, instructions for the research and development of both "light" and "heavy" fighters were issued to Nakajima, Kawasaki, and Mitsubishi; Nakajima’s responses were the Ki-43 (Type 1 Fighter "Hayabusa") for the light fighter category and the Ki-44 (Type 2 Fighter "Shoki") for the heavy fighter category (Chief Engineer Koyama Yasushi led the design teams for both). Aoki Kunio, an engineer on the Ki-43 design team, stated that while the "Hayabusa" was also intended to be a heavy fighter (modeled after the Bf 109), the team's lack of experience in heavy fighter development resulted in it becoming a light fighter instead. 

Although proponents of light fighters argued that the Ki-44 was unnecessary, the development process—which had previously stalled—was revitalized following lessons learned during the Nomonhan Incident in 1939. Combat experience showed that Soviet Red Air Force fighters were effectively employing "hit-and-run" tactics, creating a recognized need for a cutting-edge fighter capable of executing such attacks and pursuing high-speed aircraft like the I-16.

According to FAOW #65 the attached photo features:

"the third (aircraft number 4303) of the three Nakajima Ki-43 "Hayabusa" (Oscar) prototypes built in 1939. Its shape differs considerably from that seen in full-scale models and drawings due to modifications and upgrades made to the prototype aircraft from late autumn of 1940 to early 1941. The rear fuselage, canopy, and the position of the slightly longer antenna mast, among other things, became almost identical to the production model. However, the flaps were still of the split type, and the armament covers and muzzles remained for 7.7mm guns. The reason why only two fuselage stripes were painted on the third prototype is unknown."

But note the very unusual yellow (?) band starting from the canopy side and continuing on the wing.

Unlike the Ki-43, the Ki-44 faced delays; the Army and the manufacturers lacked experience with heavy fighters, making it difficult even to finalize basic specifications, and consequently, its development schedule was prioritized below that of the Ki-43. Before the Army had even issued its formal performance requirements, Nakajima proceeded with development by setting the Bf 109 as a benchmark. According to Aoki, the "Shoki" was intended as an insurance measure in case the "Hayabusa" was not adopted, and it possessed strong characteristics of an experimental aircraft. This nature allowed Nakajima to incorporate new technologies and concepts into the "Shoki".

Drawing on lessons from the Nomonhan Incident and research into Western aircraft trends, the Army recognized the importance of protective measures. Consequently, the Ki-44 was equipped not only with fire-resistant fuel tanks (self-sealing tanks featuring a multi-layered rubber casing to prevent leakage and ignition upon impact—a feature the Army had previously ordered Nakajima to install starting with the Ki-43 prototype) but also, for the first time on a Japanese fighter, a 13 mm thick armor plate behind the pilot's seat for protection. This armor plating covered the headrest and backrest areas, with a total weight of 60 kg.

At the initial development stage, the armament requirements called for one fixed cannon and two fixed machine guns. The configuration consisted of two 12.7 mm cannons (Ho-103 Type 1 Fixed 12.7 mm Cannon)—utilizing newly developed high-explosive ammunition—mounted in the wings, and two conventional 7.7 mm machine guns (Type 89 Fixed Machine Gun) in the nose. It also featured a retractable tailwheel, a rarity among Army aircraft.

The prototype made its maiden flight on June 4, 1940. However, due to insufficient engine performance and numerous technical issues, various improvements were implemented. However, compared to conventional fighters, it was inferior in turning performance; the large-diameter engine resulted in poor forward visibility; and its high stall speed necessitated high-speed landings. On the other hand, it demonstrated excellent accuracy in firing tests, and in mock dogfights held in the summer of 1941 against a Bf 109 E-7 imported from Germany, the Ki-44's overall performance surpassed that of the Bf 109 E. Consequently, it was deemed a valuable asset capable of countering the latest Western fighters, though it remained unpopular among many veteran pilots who favored agile dogfighting capabilities.

According to FAOW #16 the attached photo features:

"the first prototype Nakajima Ki-44 "Shoki", serial number 4401, completed in August 1940. The photograph was taken in December of the same year at Tachikawa Airfield during operational testing, and the tail section of what appears to be the second prototype is visible on the far right of the frame. Due to the lack of a suitable high-powered engine, it was equipped with the Nakajima "Ha-41" (1,250 hp), a large-diameter bomber engine, resulting in an extremely wide nose. Only the first prototype differs from the second and subsequent prototypes in its cowling shape, cowl flaps, the air outlet immediately behind them, and exhaust pipes. The paint scheme is the Army's basic gray-green, and the stripe on the rear of the fuselage indicates that it is the first prototype."

In the "Army Aviation Weapons Research Policy" for the 1940 fiscal year, the "heavy" versus "light" fighter distinctions were explicitly codified. The "Heavy Fighter" evolved into the primary, all-purpose fighter—featuring high speed, heavy armament, superior range, and robust armor protection—capable of engaging both enemy fighters and bombers. Conversely, the "Light Fighter" was relegated to the role of an auxiliary fighter, prioritizing dogfighting but accepting compromises in performance and equipment to focus primarily on combat against other fighters. 

In December 1941, Nakajima received a preliminary directive for the Ki-84 as an advanced iteration of the "Heavy Fighter"; this aircraft was later officially adopted as the Type 4 Fighter "Hayate". This aircraft emerged as the definitive, all-purpose fighter, excelling in speed, armament, armor protection, range, maneuverability, handling, and ease of production. 

In the subsequent "Army Aviation Weapons Research Policy" for the 1943 fiscal year, the distinction between "light fighters" and "heavy fighters" was abolished; the "light fighter"—already an obsolete compromise—was absorbed into the "heavy fighter" category and redesignated as the "short-range fighter" (or "Kinsen"). That same policy introduced additional categories: "long-range fighter" ("Ensen"), "high-altitude fighter" ("Kohsen"), and "night fighter" ("Yasen").

P.S. This piece should teach a lesson to those who rely only on English sources, especially antiquated ones, and completely ignore the work of Japanese aviation historians!