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!

"KAIGUN SENTO DAI 812 HIKOTAI"

Title: "Kaigun Sento Dai 812 Hikotai - Nihon Kaigun Yakan Sentoki-tai "Fuyo Butai" Ibun"

(The Legend of I.J.N Night Fighter SQ "Sen-To 812" with photo & illustrated)

Authors: Yoshino Yasutaka

Pages: 244

Photos: 118 b/w, 20 in-colour

Size: 21X26cm

Art: 22 colour profiles by Nishikawa Yoshinobu, 4 pages of illustrations by Sato Shigeo & Kunihiko

Published by: Dai Nippon Kaiga, Nov. 2012, p/b

Comments: PERFECT coverage of the unit, mostly equipped with Yokosuka D4Y2-S "Suisei" Night Fighters, but also Nakajima J1N "Gekko". Plenty of maps explain the various combat missions of the unit and pilot biographies. In short, everything you want to know about the unit. The color-detailed illustrations of the "Suisei" by Sato-sama are particularly interesting since they show the cockpit of the aircraft and the various bombs used. Although it's all in Japanese, this publication, for which Yoshino-san and DNK should be commended for all the effort they put in, is HIGHLY RECOMMENDED to all Japanese aviation history fans. DO NOT MISS IT!

The publication is in print and available.

Price: $US 33.00 (Postage NOT included)

Send over an email if interested with your name and delivery address (to calculate postage): arawasiorder@gmail.com

Kawanishi E7K "Alf" in Action! - video

When the Battle of Hong Kong began on December 8, 1941, the bulk of the attacking force was the Japanese Army's 38th Division. However, the Imperial Japanese Navy played an integral supporting role.

Today’s video showcases the Kawanishi E7K2 "Alf" from the light cruiser Isuzu being launched to assist a naval landing party raised from Isuzu herself. Isuzu landed a company of 85 men on December 20 1941 which helped occupy Kowloon, as "Austin" explained.

Combinedfleet.com also mentions: On 9 December 1941, after 0900, the Kawanishi E7K2 "Alf" reconnaissance floatplane from ISUZU strikes the river gunboat CICALA, which is patrolling near Brothers Point, releasing two 60-kg bombs; both fail to hit. 

While not seen in the video, Akimoto states that Isuzu's "Alf" seaplane displayed a blue tail marking of "UI-" during that time.

Print Scale (not famous for their accuracy) has released a decal set dedicated to the "Alf". It includes decals for the seaplane seen in the video but unfortunately the artwork shows an E7K1 with the liquid-cooled inline engine, whereas the seaplane in the video is a E7K2 with a Mitsubishi Zuisei 11 radial engine. Bummer! But I guess the decals ares still useful. What do you think of the camouflage? Does it look in the video to be a two-tone brown/green as depicted in the decal set or a solid green?

Questions!

Wooden Propeller Blades

I had a question regarding the use of wooden propellers in the IJAAF/IJNAF.

The standard painting methods seem to not apply to them, yet at the same time, a consistent color is also not clear...

I have not seen one with any warning strips either.

The use of them in trainers is clear, but also on early seaplanes. They range from a dark color, possibly stained wood, or perhaps even painted in the brownish color late war metal propellers were... But then at the same time, lighter colors exist, such as the K5Y with a grey looking one! In all cases, the metal leading edge is still clear, either lighter, or darker, but always distinct from the propeller color.

If painted, what colors would they be? Were there any standards for wooden propellers, and was the leading edge made from metal, or brass, like earlier aircraft propellers?

It's an interesting thought that I've not seen brought up before... Most modellers simply paint them the "standard" look, but I have seen some in nice wood, to simply black overall.

Any insight on this would be great, thank you for your time! -NJ

Answer:

From the Taisho era through the early Showa era, Japanese wooden aircraft propellers were crafted by laminating and gluing high-quality lumber—such as mahogany, walnut, and cherry—and then shaping the resulting blocks using tools like hand planes. Prominent manufacturers included companies like Yamaha, known for musical instrument production, established on October 12, 1897 as Nippon Gakki Seizo Co., Ltd. In 1921, at the request of the Imperial Japanese Army, began manufacturing wooden propellers for military aircraft, and in 1931, began manufacturing metal propellers.

The wooden propellers were covered with "urushi"*, and had metal tipping to protect them from damage from rain, pebbles, and runway debris. 

The attached photograph shows the scene of propeller manufacturing at the factory of Nippon Gakki Seizo K.K. (now Yamaha Corporation) in Hamamatsu City, Shizuoka Prefecture, around 1921. On the left, workbenches are lined up, and one can see artisans carving propeller shapes out of stacked wooden boards. In the background on the right, men in business suits and Army personnel are observing the work.

Nippon Gakki began manufacturing propellers in March 1921. Why did a company that made musical instruments come to produce equipment for military aircraft? The answer lies in the propeller manufacturing methods of that era. Propellers at the time were made of wood; creating them required artisanal skill to glue together hard, difficult-to-work boards—stacked at an angle to match the propeller's shape and then carve them down using a hand plane. Consequently, Nippon Gakki, which possessed advanced woodworking expertise gained from manufacturing wooden organs and pianos, was ideally suited to produce aircraft propellers.

A propeller manufactured by "Nippon Gakki" from Yamaha's official site.

An inscription on the side reads: "Manufactured by Nippon Gakki Co., Ltd., November 1925." Serial No. 155; Material: Walnut.

The propeller of a Type 13 training seaplane or Yokosuka K1Y.

A propeller attached to an Army engine used for training purposes.

A wooden propeller for the Navy's Type 90 Crew Trainer or Mitsubishi K3M "Pine". It measures 2,750 mm in total length and weighing 17.04 kg.

IJNAF propellers and struts from the collection of Kojima-san.

The propellers of the trainers.

Initially the propellers of the Tachikawa Ki-9 "Spruce" and the Yokosuka/Kawanishi K5Y "Willow" were made from wood with metal tipping. Note the interesting and quite unusual propeller on this "Willow".

The propeller of this K5Y2 seaplane is closer to the standard dark brown seen in the previous photos.

The propeller and the skeleton remains of a K5Y at the "Tsukuba Kaigun Kokutai Kinenkan"

The propeller of the sole complete "Willow" survivor in Indonesia. I'm not sure if the propeller is original though.

Initially the propellers of the Tachikawa Ki-9 "Spruce" and the Tachikawa Ki-17 "Cedar" were made of wood with metal tipping similar to the propeller of the "Willow". But very soon they were treated to the "case hardening" or "encapsulated" method. This was devised by the German company Schwarz during the late Taisho and early Showa periods; to prevent damage from pebbles, ice, and the like, the propeller surface is encased in a celluloid coating reinforced with wire mesh. The wire mesh consists of 0.2mm-diameter brass wire, and the coating is a cellulose nitrate-based finish approximately 1mm thick. Additionally, a 0.5mm-thick brass strip—known as a "tipping"—is attached to the leading edge of the blade using wood screws or nails.

The propeller of this Ki-9 Koh in the attached photo could be an early wooden example without the "case hardening".

On the other hand, the propeller of this Tachikawa Ki-9 Otsu has been most probably "case hardened". Note the single white band on the edge of each tip.

Another "Spruce" propeller, this time with two white bands.

As can be seen in this "Spruce" photo, at some point, the metal tipping was discarded.

A photo of a Tachikawa Ki-17 "Cedar" with the propeller lacking tipping.

In this color (not colorized) photo of a "Spruce" that served with the Korean Air Force after the end of WWII, the propeller has most probably been repainted with the same paint used for the top surface camouflage. Note the lack of tipping.

A "Spruce" propeller still exists and is displayed in Japan, but some sources indicate it has been repainted, so the color seen in the photo is not the original one.

Some Japanese sources mention that the color of the "Spruce" propeller was either beige or light green depending on the celluloid coating.

HTH

*"Urushi" refers to the sap collected from the deciduous tall tree of the Anacardiaceae family, Toxicodendron vernicifluum (Urushi, scientific name: Toxicodendron vernicifluum), found in Japan, China, and the Korean Peninsula is a natural resin paint and adhesive primarily composed of urushiol. In addition, in Southeast Asia such as Vietnam, Myanmar, and Bhutan, there are natural resins commonly called lacquer, though their compositions and uses differ. Crafts made from lacquer are called lacquerware, and especially Japanese lacquerware, due to its high quality.

The traditional colors of lacquer as a paint are black and vermilion; black is used as pigments such as iron oxide powder and soot, while vermilion lacquer uses pigments such as bendo and cinnabar. It is also sometimes done using black and vermilion lacquer to distinguish the coat.

Nakajima J1N "Gekko" (Irving), 153 Kokutai

A set of photos feature Nakajima J1N "Gekko" (Irving) flown by the 153 Kokutai as indicated by the numbers "153-" and "53-" on the aircraft tails.

A late-model Nakajima J1N "Gekko" (Irving) Model 11 (J1N1-S) with the step on the dorsal fuselage removed. This particular aircraft has had its downward-facing guns removed.

The same Nakajima J1N "Gekko" (Irving) Model 11 (J1N1-S) seen in the previous photo. On January 5, 1945, this "Gekko" of the 153rd Kokutai, Sento 851 Hikotai, made an emergency landing at Taisho Army Airfield in Osaka due to engine trouble. The drop tanks under the wings were the same type as those used on the Zero fighter (300 liters capacity) and were painted light gray. The crew, consisting of Chief Petty Officer Takano and LTJG Hayashi, and others received eight aircraft, including this one, at Atsugi Air Base. Two of the aircraft, including Hayashi's, landed at Taisho on their way to Kanoya. They departed the following day, the 6th, and headed to Taiwan via Kanoya to rendezvous with the main force. Because all the aircraft stationed at Clark Air Base in the Philippines, where they were scheduled to deploy, had been withdrawn, the 851 remained in Taiwan.

A Nakajima J1N1-Sa "Gekko" (Irving) captured by US forces at Clark Air Base. The inspection/maintenance hatch is open, and the hole through which the barrel of the Type 99 Model 2 cannon protrudes is clearly visible. The photograph was taken on February 12, 1945, one month after the defeat in the air battles over the Philippines. It is believed to be an aircraft of Sento 812 Hikotai, the last "Gekko" unit to advance under the command of the 153rd Kokutai.

The same Nakajima J1N1-Sa "Gekko" (Irving) captured by US forces at Clark Air Base.

Sometimes the aircraft in this photo is identified in various sites and FB pages as a Kawasaki Ki-45 "Toryu" (Nick).  

One more photo of the same Nakajima J1N1-Sa "Gekko" (Irving) captured by US forces at Clark Air Base. 

Artwork by Kuroki Hitomi, of the previously seen Nakajima J1N1-Sa "Gekko" (Irving) captured by US forces at Clark Air Base, featured in FAOW #57. 

Below is a set of photos featuring another 153 Kokutai "Gekko", tail code "153-71" captured by US forces at Clark Air Base. 

Note the "H-6" (officially the Type 3 Airborne Radio No. 6) radar antennae protruding from the fuselage sides. The H-6 was the most widely deployed radar for Japanese Navy aircraft, seeing extensive use in maritime search and patrol missions from 1944 onwards. It operated on a wavelength of 2 meters (150 MHz); specifications indicated a detection range of 95 km for large ships and 55 km for a single large aircraft.

Approximately 2,000 units of the H-6—which utilized a maximum-sensitivity detection method—were manufactured by Japan Radio Co. and Kawanishi.

Unit history from the Japanese Wikipedia:

As land battles in New Guinea intensified and a counteroffensive by the U.S. Army—which had been rebuilding its forces in Australia—loomed, there arose a need for long-range reconnaissance units operating on the front lines stretching from western New Guinea to eastern Dutch East Indies. The 753rd Kokutai, which had long been based at the Kendari airfield on Celebes Island and was responsible for bombing missions toward the strategic stronghold of Darwin, had also been performing long-range reconnaissance duties; however, it was being severely depleted without ever being able to return to the home islands. Consequently, the 153rd Kokutai was formed as a new unit dedicated exclusively to reconnaissance. However, initially, they were unable to procure reconnaissance aircraft. Consequently, even though they had a full complement of personnel, they could not conduct reconnaissance missions and could do little more than analyze and relay reconnaissance information obtained from Army air units. 

January 1, 1944: Established at Kendari Airfield with Hsinchu Airfield as its home base (authorized strength: 12 land-based reconnaissance aircraft; however, no aircraft were available initially).

Directly under the command of the Southwest Area Fleet and the 13th Air Fleet.

By March, reconnaissance operations began using Mitsubishi Ki-46 "Dinah" transferred from the Army. In early March, Yokosuka D4Y "Suisei" (Judy) arrived from the mainland.

March 5, 1944: Reconnaissance of southern New Guinea conducted with two "Suisei".

March 10, 1944: Reconnaissance of New Guinea commenced every 10 days using "Dinah".

March 30, 1944: Engaged in patrol and search operations over the waters north of New Guinea following the Palau Air Raid. Operations continued until the alert was lifted on April 8.

April 9, 1944: Ordered to advance into New Guinea; moved to Wakde Island Airfield off the coast of Biak Island. Began patrols on the 13th.

April 22, 1944: Ground operations began in Hollandia.

May 4, 1944: Reconnaissance of Hollandia after its fall; reported on the status of airfield repairs.　　　　　

Around this time, the Sento 311 Hikotai was incorporated, forming a mixed fighter-reconnaissance unit. 

Early May 1944: Withdrew to Sorong (Jefman) Airfield, the westernmost point of New Guinea. Avoided the ground battle on Wakde Island that began on the 18th.

May 25, 1944: Incorporated 12 aircraft from the 201st Kokutai, which was undergoing training in Davao.

May 27, 1944: The "First Operation Kon" was launched (Operation Kon was a three-stage Japanese military operation designed to support the Battle of Biak Island). Engaged in air patrol until the order to cease operations on June 3.

Dispatched two fighters from the main force to escort the 24th Sentai bombing enemy positions on Biak Island.

June 5, 1944: "Operation Kon II" launched. Resumed patrol duties along shipping lanes.

June 7, 1944: Ordered the entire unit to withdraw to Kendari. Abandoned equipment and withdrew from "Operation Kon".

Thereafter, engaged in reorganization efforts.

July 10, 1944: A major reorganization of the kokutai was carried out. Placed under the direct command of the First Air Fleet and withdrew to Davao.

Transferred the Sento 311 Hikotai to the 201st Kokutai and incorporated the disbanded 251st Kokutai as Sento 901 Hikotai.

July 25, 1944: As the first batch of procured aircraft, four "Suisei" and nine "Gekko" arrived in Manila.

Throughout August, patrol operations were impossible due to a shortage of aircraft, so the unit focused solely on analyzing intelligence from the Army’s 15th Sentai.

September 1, 1944: Air raids on Davao began.

September 2, 1944: Another air raid on Davao. Four "Gekko" engaged the enemy. Three "Suisei" began patrolling for enemy task forces.

September 9, 1944: During the air raid on Davao, the "Gekko" used Type 3 cluster bombs but failed to shoot down any enemy aircraft, resulting in the loss of all aircraft.

Mid-September 1944: Two "Suisei" and eight "Gekko" aircraft advanced to Nichols Airfield on Luzon Island.

Upon arrival, both the "Suisei" and six of the "Gekko" aircraft were unable to conduct patrols due to mechanical failures. Patrols were carried out with the remaining "Gekko".

September 21, 1944: During a pursuit following the air raid on Manila, the enemy fleet was discovered; one aircraft was lost.

September 22, 1944: The remaining one aircraft guided the Zero Fighter Squadron of the 201st Kokutai.

October 27, 1944: The Davao detachment began supporting "Operation Tago" (a joint operation by the Japanese Army and Navy to transport reinforcements to Leyte Island during the Battle of the Philippines).

Late November 1944: Ran out of aircraft.

January 9, 1945: The First Air Fleet was ordered to withdraw to Taiwan.

The vast majority of the 153rd Kokutai personnel were unable to evacuate to Taiwan during the rescue operations that continued until February 10th, and were left behind in the Philippines. The 15,000 aircrew members of all the air units that could not evacuate formed the "Clark Area Defense Unit" under the command of General Sugimoto Ushio, commander of the 26th Air Fleet, and were deployed to ground combat under the 2nd Tank Division of the Army. Commander Wada Tetsujiro, who was in command of the 153rd Kokutai personnel on the ground, died of illness on October 29th after the surrender and did not survive to return home.

Questions!

Hi,

I’ve attached a scan of a photo that was in an album of a member of 11 Squadron of the RAF who was stationed at Miho in 1946. The photo would not have been taken at that airfield, I was wondering if any of the readers of your website blog might recognise the location from the hangar to the rear of what looks to me like a B6N Tenzan aircraft.

Thanks,

Simon Gifford

"Combat History of the 96 Rikko"

The absolutely best history book on the Mitsubishi G3M "Nell" is entitled "96 Rikko Senshi" (Combat History of the 96 Rikko), authored by Kobayashi Noboru. Kobayashi-san's exhaustive research and personal interviews with surviving veterans make this book an essential gem in the library of Japanese aviation history buffs. It's a Japanese publication, so naturally it's all in Japanese.

Title: "96 Rikko Senshi" (Combat History of the 96 Rikko)

Author: Kobayashi Noboru

Pages: 628

Photos: 385 b/w

Size: 14X20cm

Published by: Kojinsha 2022, h/b

The publication is in print and available.

Price: $US 27.00 (Postage NOT included)

Send over an email if interested with your name and delivery address (to calculate postage): arawasiorder@gmail.com

The Experimental 9-Shi Medium Attack-Bomber (Ka-15)

There is a peculiar aircraft that makes its appearance in the video of the previous post. It has a bump on its nose.

This is an extremely rare footage of the very little known Experimental 9-Shi Medium Attack-Bomber (Ka-15), the intermediary type between the  8-Shi Special Reconnaissance Aircraft or Mitsubishi G1M and the Mitsubishi G3M "Nell".

Experimental 9-Shi Medium Land Attack Aircraft (Ka-15) with Kisarazu Kokutai crews just before takeoff heading for Omura. 

The commander of the Kisarazu Kokutai at that time was Captain Takenaka Ryuzo, seen here briefing the crews wearing a white Type 2 military uniform. We can see that the Experimental 9-Shi Medium Land Attack Aircraft (Ka-15) behind him has no tail markings. 

The aircraft was piloted by Flight Leader Lieutenant Commander Soga Yoshiharu (one rank higher when the video was shot), who led the attack force toward Omura; however, this aircraft did not actually participate in the transoceanic bombing mission. The Type 9 Medium Bomber was the aircraft on which Major Soga conducted tests; he was very fond of it and apparently flew it himself for a while, even using it for official flights. The figure in flight gear saluting in front of the Type 9 Medium Bomber is LCDR Soga. (Special thanks to Sato Nobuhiko for the aditional information)

One of the Hei Type Experimental 9-Shi Medium Land Attack Aircraft (Ka-15)

Encyclopedia has the following about the type:

In February 1934, the Navy instructed Mitsubishi to develop a prototype of the 9-Shi Medium Attack-Bomber to advance and put into practical use the previous 8-Shi Special Reconnaissance Aircraft. Mitsubishi assigned Engineer Honjo Kiro as the chief engineer, as with the 8-Shi Special Reconnaissance Aircraft, and the first prototype was completed in June 1935. The following month, flight tests were conducted at Kakamigahara by Pilot Kajima, yielding excellent results. Subsequently, Lieutenant Soga of the Navy took primary responsibility for flight testing. 

The main differences from the Type 8 Experimental Reconnaissance Aircraft were: (1) The engine was replaced with a Hiro Type 91 600 HP engine (2) The seat arrangement was changed to a side-by-side configuration for the pilot and co-pilot, with the commander’s seat and radio operator’s seat behind them, and a seat for the engineer and upper gunner between the front and rear spars. (3) Armament was reinforced, with 7.7mm machine guns mounted forward-upper, rear-upper, and rear-lower; the upper guns were fitted with retractable windshields, and the lower guns utilized a section of the fuselage underside that could be opened and closed. (4) A torpedo or bomb suspension device was placed on the underside of the fuselage, allowing for the carriage of one 800 kg torpedo or one 500 kg bomb, or two 250 kg bombs. (5) The main landing gear was changed to a single-leg configuration.

Aircraft Nos. 1, 2, 5, and 6 were equipped with two Type 91 water-cooled 600 HP engines, had wooden four-bladed propellers, and lacked flaps and a drop-down turret; the lower machine gun was designed to be fired from a prone position by opening a hatch. Aircraft No. 3 was equipped with two Type 2 Kinsei air-cooled 680 HP engines, had a wooden four-bladed propeller, and increased tail surface area.

Aircraft No. 4 was equipped with two Type 3 Kinsei air-cooled 790 HP engines, had a metal Hamilton Standard three-bladed variable-pitch propeller, and was fitted with cowl flaps. 

While the first six aircraft all featured the Type Ko seating configuration, aircraft Nos. 7–21 were of the Type Hei design, featuring an observation tower (leave a comment if you know a better word that can describe it) on the nose. They were equipped with two Kinsei Type 2 680-HP engines, had wooden four-bladed propellers, were fitted with flaps, and featured a retractable upper gun turret and a drop-down lower gun turret. Additionally, only No. 8 had its outer wing dihedral angle increased on a trial basis, and only No. 11 was equipped with two Kinsei Type 3 790 HP engines and Hamilton Standard metal three-bladed variable-pitch propellers. 

[Number of Aircraft Produced] From June 1935 onward

Type Ko (Type 91 600 HP x 2) 4 aircraft

Type Ko (2 x Kinsei Type 2 680 HP engines): 1 aircraft

Type Ko (2 x Kinsei Type 3 790 HP engines): 1 aircraft

Type Hei (2 x Kinsei Type 2 680 HP engines): 14 aircraft

Type Hei (2 x Kinsei Type 3 790 HP engines): 1 aircraft

Total: 21 aircraft

Developed from the 8th Experimental Special Reconnaissance Aircraft, which demonstrated excellent performance, this aircraft exhibited outstanding high performance as a twin-engine long-range aircraft, and the decision on the production model was urgently sought. There were two seating configurations: the Type Ko (Aircraft Nos. 1–6) and the Type Hei (Aircraft Nos. 7–21). A decision on which to adopt proved difficult to reach, and further delays were caused by engine and propeller testing, as well as other modifications. It was not until June 1911 that it was finally officially adopted as the Type 96 Land Attack Aircraft. In May 1936, Aircraft Nos. 2 and 5 were used to conduct a round-trip flight from Tateyama to Northern Manchuria. On the return leg, No. 2 encountered severe weather near Mingyuegou in Jilin Province, broke apart in mid-air, and crashed, resulting in the deaths of all five crew members. It was later determined that engine failure was the cause of the accident. Additionally, accidents sometimes occurred due to a drop in fuel pressure during takeoff and landing or when the engine was at low RPM, or due to landing gear malfunctions.

Mitsubishi G3M "Nell" + In Action - video

Today's video warrants two posts; thus, this one will focus on the historical context and the ensuing events. In the upcoming post tomorrow, we will explore the different details, including an extremely rare IJNAF X bomber.

On July 11, 1937, immediately after the start of the Sino-Japanese War, in preparation for the expansion of hostilities, the Japanese Navy General Staff issued an Immediate Readiness Order and formed the First Combined Air Fleet (Rengo Koku Kantai) with the main medium bomber forces from Kisarazu and Kanoya Kokutai. As of August 1, the Kisarazu main force incorporated medium bombers from the Tateyama Kokutai, totaling 20 medium bombers while the Kanoya Kokutai consisted of 18 medium bombers. On August 8, the main Kisarazu force completed its deployment to Omura Air Base, while the headquarters and the KanoyaKu completed their deployment to Matsuyama Air Base in Taipei.

The attached video features the departure of Kisarazu Ku bombers on August 8, 1937, en route to Omura.

Then, with the aim of preemptively destroying the Chinese Air Force, on August 14, orders were issued for KisarazuKu to attack Nanjing Airfield and its associated facilities, and for KanoyaKu to attack the same targets in Nanchang. However, shortly after, orders were issued to cancel the attack due to bad weather caused by a typhoon. At 11:40, KanoyaKu received orders to sortie, while KisarazuKu was placed on standby. KanoyaKu changed its targets to Hangzhou and Guangde Airfields, bombing and damaging hangars at each airfield and destroying more than ten Chinese aircraft (two Japanese aircraft did not return). 

On August 15, an unprecedented trans-oceanic bombing campaign began.

The main Kisarazu force departed from Omura Airfield, advanced toward the mainland at extremely low altitude, and carried out a bombing run at an altitude of 500 meters near Nanjing. The Chinese side counterattacked with ground artillery fire, and after engaging in aerial combat with interceptor fighters, the Kisarazu bombers returned to Jeju Island Airfield. With four aircraft lost in crashes and 30 casualties—including two killed in action—the KisarazuKu suffered significant losses, as many aircraft were also hit. Since the only precedent for transoceanic bombing was Germany’s raid on London during World War I, the Japanese Navy Ministry’s description of this as an “unprecedented transoceanic bombing” was not entirely untrue. However, the newspapers did not report in detail on these friendly casualties; instead, only the damage inflicted on the Chinese side was emphasized, and the mission was touted as a “brave and daring air raid by the Navy and Air Force.” 

Meanwhile, the KanoyaKu set out for Nanchang with 14 operational aircraft, but was hampered by heavy rain, resulting in few achievements or casualties.

Håkans Aviation page has the following more detailed description focusing on the Chinese side:

At 13:30 on the same day [August 15, 1937] the Nanking Air Defence Command received a report that 16 Japanese aircraft had flown past Soochow towards Nanking. The alarm was sounded, and Chinese Air Force fighters took off to meet them. The Japanese aircraft were 20 G3Ms from the Kisarazu Kokutai. The Japanese aircraft had flown in directly from Ohmura in Japan and landed back at Cheju-Do. 

From Chu Yung, squadrons of the 3rd PG scrambled their aircraft. Wong Pan-Yang led eight Boeing 281s from the 17th PS. Chen Yau-Wei, Commander of the 8th PS, led five Fiat CR.32 fighters. Scrambled were also seven Hawk IIs from the 28th PS, 5th PG, and one Hawk III and five Hawk II from the 34th Provisional PS. 

In the ensuing melee, four G3Ms were shot down and six damaged. Claims were confused but it is generally acknowledged that Captain Wong Sun-Shui (in no. 1703) downed the first G3M to fall in the Battle of Nanking when the eight Boeings from the 17th PS attacked a flight of six Mitsubishi G3M bombers over Nanking and claimed to have shot them all down without losses. This was the No.4 aircraft in a Shotai that bombed the Ta Hsiao-Chang Airfield, most likely the no. 5 Shotai led by Lieutenant Yoshida. 17th PS’ Wong Pan-Yang and Su Ying-Hsien shared one victory at Chu-Yung while Chun Chia-Chu claimed another which crashed south-east of Nanking. Chin Shui-Tin also took part in this interception but didn't claim any aircraft. 

The Japanese aircraft fled and the 8th PS went after them. Chen Yau-Wei and Huang Chu-Ku shared a victory near Chu-Yung while Shen Tse-Liu and Liu Chi-Wei together shot down an enemy plane west of Lui Shui. 

Captain Chow Ting-Fong, commander of the 34th PS led six Hawks from Chia Hsiang and followed eight Japanese aircraft to Nanking. Captain Chow attacked one of these and shot it down over Fang Shan. 

4th PG’s Captain Lee Kuei-Tan led three Hawk IIIs of the 21st PS and Captain Huang Kuang-Han, C.O. of the 22nd PS, led eight Hawk IIIs from Hangchou to Nanking to help in this interception and they also attacked the bombers. Lee Kuei-Tan claimed a shared bomber together with three other pilots. Tan Won and Yuan Chin-Han shared a victory. Cheng Hsiao-Yu, Pa Ching-Cheng and Wu Ting-Chun each claimed one shot down. Wu Ting-Chun’s aircraft was damaged in this combat and he was forced to make an emergency landing. Liang Tian-Cheng claimed two victories. Huang Kuang-Han claimed a Japanese G3M halfway between Nanking and Lui Shui. 

Because of low clouds, each group fought on it’s own with little co-ordination. A total of 14 Japanese aircraft were claimed shot down. Five Chinese aircraft were damaged.