Military Review

"Nakadzima" Ki-115 "Tsurugi": a plane for kamikazes

In the fall of 1944, the Japanese Empire, faced with a host of problems on all fronts, was forced to resort to desperate measures. In October, the first unit of the kamikaze pilots was formed, and in the future the number of such units only grew. Until a certain time, suicide bombers flew only on re-equipped serial aircraft, but then a proposal appeared to develop specialized equipment. It resulted in several new designs, including the Nakajima Ki-115 Tsurugi aircraft.

Initially, kamikazes flew only on production aircraft of existing types, which underwent some revision. However, this approach did not justify itself from an economic and tactical point of view. January 20, 1945 army command aviation placed an order to create a new aircraft, originally adapted for a single flight to a target without the possibility of return. At the request of the customer, the aircraft should have been characterized by extreme simplicity of production and the lowest possible cost. In the future, it was planned to assemble it even in small workshops with disabilities.

Serial aircraft "Nakajima" Ki-115 "Tsurugi". Photo San Diego Air & Space Museum /

From the aircraft did not require high flight performance, but he had to have a chance to break through the enemy's air defense. For this, the cruising speed had to be at the level of 340-350 km / h, the maximum at the dive in front of the target - more than 500 km / h. The armament was to consist of one medium-caliber aerial bomb carried under the fuselage.

An order to create a kamikaze aircraft was received by the Nakajima company, one of the leaders of the Japanese aviation industry. The development of the project was transferred to the subsidiary Ota Seisakusho. To carry out some work to the project attracted Mitaka Research Institute. The main designer of the project was Aori Kunihara.

In accordance with the Japanese nomenclature of aircraft designations, the new aircraft received the designation Ki-115. In addition, he was given the name "Tsurugi" - in honor of one of the types of the Japanese direct sword.

Scheme of the Ki-115 aircraft after finishing. Photo

According to the project, the plane Ki-115 was supposed to be a cantilever nizkoplan with a three-point chassis, equipped with a tail crutch. In the nose of the fuselage provided for the installation of engines of several models, which was initially taken into account in the project. To obtain optimal characteristics, it was proposed to use the simplest discharged chassis, to abandon the developed wing mechanization and introduce several other ideas.

The plane was supposed to be simple and cheap, which affected the materials used. The fuselage power set was proposed to be made of steel pipes, the covering - of sheet metal, duralumin and canvas. The whole wing should be made of dural, tail - from wood. The plumage was also supposed to get plywood trim. At the same time, the finished airframe, at least, outwardly resembled the aggregates of many other Japanese and foreign aircraft.

One of the Japanese drawings. Photo by National Air and Space Museum / smithsonian

For most of its length, the aircraft fuselage had a circular cross section. Behind the cockpit, the diameter of the fuselage decreased, forming a tail boom. In the forward part of the fuselage there was a metal motorama, initially compatible with various Japanese engines. Due to this, serial aircraft could be equipped with any available air-cooled motors with sufficient characteristics. The engine was covered with a tin hood.

Directly behind the engine were placed the fuel and oil tank, as well as some other devices. They placed a single cabin. The tail boom was empty, inside it there was only a wiring control rudder.

Design of drop landing gear. "A" and "B" - the design of the locks. Photo by National Air and Space Museum / smithsonian

The aircraft received a duralumin wing with a straight leading edge. The trailing edge of the planes had a negative sweep. Rounded tips were used. The wing planes were installed with a noticeable transverse V. An interesting feature of the wing, associated with the need to simplify the design, was the lack of developed mechanization. On the outer part of the trailing edge, a pair of ailerons with cable wiring was placed. The flaps were initially absent.

The tail fin included a keel with a small sweep of the leading edge and a relatively large rudder. The stabilizer was made straight and also equipped with a large wheel area. It is curious that, despite the desire to simplify the design, the engineers of Nakajima still equipped the rudders with trimmers.

"Nakadzima" Ki-115 "Tsurugi": a plane for kamikazes
General view of the Ki-115. Photo

In accordance with the technical specifications, the kamikaze airplane Ki-115 should have been completed with any available engines with a capacity of at least 800 hp. Taking into account the designs of different motors of the time, a universal motor mount was created. However, such opportunities in practice were not useful. All serial "Tsurugi" were completed only with 14-cylinder star-shaped engines Xa-35 Py 23 of Nakajima, which developed the power of 1130 hp. A metal screw of constant pitch with a diameter of 2,9 m was mounted on the motor shaft.

Cooling of the cylinder block was carried out due to the oncoming flow of air entering under the hood. The oil system of the power plant included a radiator located in the root of the right half wing. Above the center section was a fuel tank with a capacity of 450 l.

Front view. Photo

Over the rear of the center section placed single cockpit. She had not very developed equipment, but fully complied with the requirements. On the dashboard fit all the necessary devices for monitoring systems and piloting. There was a traditional set of controls based on knobs and pedals.

The cabin was closed with a canopy visor consisting of three glass panels. Behind it was a gargrotta with a pair of side windows. The lantern did not have a central section and did not close.

Ki-115 got the simplest chassis. Under the wing was placed a pair of main racks. These devices were assembled from metal pipes and had a frame structure. The rack was equipped with a relatively large diameter wheel and did not have a shock absorber. On the wing of the rack were fastened with the help of locks: after takeoff, they were asked to drop. In the tail of the fuselage there was a metal crutch, also without a shock absorber.

"Tsurugi" in the assembly shop. The machine has an improved wing and updated mechanization. Photo by National Air and Space Museum / smithsonian

Under the center section in the fuselage there was a recess for the suspension of bombs, in which there were locks. According to the project, the plane "Tsurugi" could fly into the air one bomb in caliber from 250 to 800 kg. It was assumed that this would be enough to defeat various ships or enemy ground targets. In connection with the alleged specificity of combat use, the pilot should not have dropped the bomb: he was asked to crash into the target along with it. For an exact exit on the appointed purpose it was offered to use the elementary telescopic sight fixed on a peak of a lamp.

Ki-115 was not supposed to fight with the enemy's aircraft, and therefore did not receive cannon or machine-gun weapons. It was assumed that on the way to the target the kamikaze aircraft would cover their fighters. In addition, the presence of barreled weapons could significantly increase the cost of the machine.

Dashboard aircraft. Photo

The finished aircraft "Tsurugi" was supposed to have a length of 8,55 m with a wingspan of 8,57 m. The wing area is 12,2 sq.m. Parking height - 3,3 m. Own weight of the structure was only 1640 kg. Normal take-off weight was determined at the level of 2630 kg, the maximum - at 300 kg more. According to calculations, the plane was supposed to develop cruising speed in 300 km / h, maximum - 500 km / h. Flight range - to 1200 km.

The first prototype of the Nakajima Ki-115 Tsurugi aircraft was built in March of the 1945 of the year, and was immediately put to the test. Checking the car on the ground ended in failure and showed the need for many improvements. The chassis without springs and brakes significantly hampered taxiing on the ground and run. An attempt to lift the plane into the air was also unsuccessful. He was too heavy for his wing, and therefore the run was different in unacceptable length.

Handle control aircraft. Photo by National Air and Space Museum / smithsonian

The next few weeks, the designers headed by A. Kukhinara spent on refining the various elements of the design. First of all, improved wing. The rear edge had to be strengthened and equipped with new flaps of a small area. Also it was necessary to develop a new control system for the release of these planes. Despite the noticeable complication of the design of the aircraft, this made it possible to lift it into the air and carry out comprehensive tests.

Also in the course of refining engineers redesigned the chassis several times. At first, only brakes appeared on the racks of a simplified design. This had some effect, but the lack of depreciation did not eliminate all the problems. Soon a new version of the main rack with rubber shock absorbers appeared. A simple crutch received a simplest spring.

Engine control knob. Photo by National Air and Space Museum / smithsonian

During the tests and refinement, new original ideas were worked out. So, for additional acceleration at the time of the attack it was proposed to use solid fuel boosters. This idea was tested during the tests, but the results of these tests, unfortunately, are unknown.

According to the results of the first tests of the Ki-115 in the base configuration, it was proposed to develop an improved version of the project. Airplane Ki-115 Otsu first of all had to be different from the existing “Tsurugi” wooden wing of increased size. Metal remained only aileron framework and flaps. It was proposed to move the cockpit slightly forward to improve visibility on takeoff

From a certain point, the command of the Japanese became interested in the Ki-115 project fleet. They proposed the development of a special deck modification of this aircraft, which had characteristic differences. This project started in the spring of 1945, but did not manage to give real results. Design work continued until the very end of the war, because of which the decked version of the Tsuruga did not reach the test stage.

Serial Ki-115 after removing some units. Probably a post-war snapshot. Photo

By the beginning of the summer of 1945, Nakajima had completed the tests and received permission to start mass production. The main site for production was to be the company's plant number XXUMX in the city of Ota. A little later, the plant in Ivata was attracted to the project. According to the original plans of the customer, the new kamikaze planes could be made even in various small workshops, but this proposal was never implemented, and all the serial "Tsurugi" were assembled by a pair of full-fledged plants.

Before the end of the war and the surrender, Japan managed to build X-NUMX planes such as the Ts-105 Tsurugi. The bulk of this technology - the 115 prototype and the 1 serial machines - was assembled in Ote. Another 82 aircraft built a factory in Iwate. According to various sources, at least a part of this equipment was transferred to the customer and entered service.

Trophy "Tsurugi" at the entrance to the air base in Yokot, 1948 year. Photo of US Air Force

Apparently, the end of spring and the summer of 1945, the year went to the development of a new aircraft and the preparation of future suicide pilots. Despite all the efforts of the designers, the simplified and cheap aircraft was not very easy to fly, and therefore the kamikaze pilots had to spend time and effort on their studies. Apparently, this fact led to the fact that the serial Ki-115 could not take part in the battles.

Until the very end of the war in the Pacific, Tsurugi aircraft remained far from the front. They have never been used for its intended purpose. As a result, the opponents in the person of the United States, and then the Soviet Union, did not even realize what a severe surprise for them Japan is preparing in an atmosphere of strict secrecy. Moreover, the foreign military learned about the existence of a new kamikaze aircraft only after victory. The commission of the victorious countries inspected the Japanese military factories, and during such trips found several previously unknown samples of aircraft.

The Ki-115 aircraft at the Pima Air & Space Museum (USA, Tucson). Photo Wikimedia Commons

Planes found were carefully studied on the ground and tested in the air. According to the results of such tests, experts made one or other conclusions. In particular, a search was conducted for ideas and solutions suitable for use in their own projects. The project of a simplified aircraft intended for a single flight to a target, as expected, did not arouse much interest. However, information about the Ki-115 allowed to supplement the existing picture and expand the available data on the Japanese aircraft industry.

After the defeat of the Japanese Empire, special aircraft had no prospects. Constructed serial "Tsurugi" turned out to be useless, which determined their further fate. Unusual aircraft sent for recycling. In the shortest possible time, almost all of the built machines were dismantled at Japanese enterprises. Only a few of these aircraft survived. In particular, one of them is part of the exposition of the National Museum of Aeronautics and Aeronautics of the USA (Washington, DC), the other is stored in one of the Japanese museums. The “Japanese” model from the late forties stood at the gate of one of the air bases. Later it was restored and became a museum exhibit. Also known other instances in varying degrees of preservation.

The main goal of the Nakajima Ki-115 Tsurugi project was to create a promising aircraft of the simplest design possible to perform a single sortie and at the cost of its own life to destroy the designated target. The task of simplifying and reducing the cost of construction, with certain reservations, was solved. However, this led to several significant technical and operational problems that could hinder combat use. As a result, the finished equipment did not hit the front and had no influence on the course of the war.

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  1. The comment was deleted.
  2. Proxima
    Proxima 3 July 2018 15: 31
    Before the war and surrender, Japan managed to build 105 aircraft type Ki-115 “Tsurugi” (from the text)
    How much" belay fellow So, for reference, only in Kuibyshev (plant No. 1 and 18) produced more 20 IL-2 per day! fellow And was it worth such crumbs to devote an entire article? It is clear that this cruel and useless toy had no effect on the course of hostilities.
    And about the hinged chassis, Japanese designers gave a blunder. It often happened that the kamikaze, not finding a worthy goal, were returning to their airfield, and in this case, stupid and useless death of both man and aircraft. hi
    1. MPN
      MPN 3 July 2018 17: 01
      Quote: Proxima
      And was it worth such crumbs to devote an entire article?

      Worth it. Many interesting things have been released even in one copy. Then someone like that. Thanks to the author for the work! hi Another thing I have not seen any real meaning in this product. Of all the kamikaze aircraft, only Oka could be more or less effective. hi (in my opinion)
    2. 2329 Carpenter
      2329 Carpenter 3 July 2018 18: 30
      Yes, the article is not about the number of aircraft released. The article is simply about an unusual airplane for its intended purpose and structural elements.
      As for the "stupid and useless" death of a person - they hardly thought so, and the Japanese think.
      They have a different mentality, a different mindset. They are generally different.
      And we do not understand them in many ways.
      Like them - us.
      1. RaptorF22
        RaptorF22 3 July 2018 19: 31
        Meanwhile, a resident of the Russian Federation tried to sail away to Japan on a makeshift raft wink Islands on which you want to howl lol
  3. dDYHA
    dDYHA 3 July 2018 16: 56
    I think the planes were preparing to repel the last US strike on Japan itself. One hundred percent would be there. I wouldn’t have to come back.
  4. Gnefredov
    Gnefredov 3 July 2018 17: 55
    Thanks so much for the article. I read it in one go :)
  5. cariperpaint
    cariperpaint 3 July 2018 19: 02
    I remember in the book the wind of the gods read about some kind of jet Japanese aircraft that they did for kamikazes ... It has long been ...
    1. RaptorF22
      RaptorF22 3 July 2018 19: 32
      We have our own kamikaze laughing On a raft I wanted to swim to Japan
      1. cariperpaint
        cariperpaint 3 July 2018 19: 50
        Do not care for everyone) pay attention to each moron) planes do not fly) only rafts can be reached)
    2. Mikhail Matyugin
      Mikhail Matyugin 4 July 2018 22: 52
      Quote: cariperpaint
      I remember in the book the wind of the gods read about some sort of jet type Japanese aircraft that they made for kamikazes ... It has long been ..

      "Eye" = "tank bomb" it. A very dangerous thing, by the way, was.

      And again, dear Cyril, thanks again for such wonderful material!
    3. DimerVladimer
      DimerVladimer 5 July 2018 09: 56
      Quote: cariperpaint
      I remember in the book the wind of the gods read about some kind of jet Japanese aircraft that they did for kamikazes ... It has long been ...

      The Americans called the Tank Bomb (Fool's Bomb). Not quite reactive - rather a solid-fuel accelerator glider - a very effective solution.
      To fight effectively is only to intercept its carrier on approach (used from a bomber), after uncoupling, interception was impossible, to shoot down MZSA was practically impossible.

      Here is a photo in the Museum of the living Oka-II

      and her training option

      the production of Oka aircraft (Yokosuka MXY7 Ohka) did not last long - from September 1944 to August 1945, the Japanese managed to build 854 units.
      1. DimerVladimer
        DimerVladimer 5 July 2018 14: 15
        Oka with carrier
      2. VictorZhivilov
        VictorZhivilov 24 July 2018 11: 53
        Little Alaverdi: I must also add that the Japanese were not pioneers in creating such weapons. Earlier in Germany was created Fi. 103 Reichenberg
        Another noteworthy fact:
        “After Field Marshal Milch’s categorical demand to take measures to save the pilot, the designers were obliged to equip the projectile with an ejection seat. It was not so easy to carry out this decision - the cockpit was very cramped and it was simply impossible to“ push ”any additional equipment there. In addition "the chair itself was yet to be created, and its development promised to drag out indefinitely. In general, time was lost, and this requirement was never fulfilled." Source:
  6. Mikhail Matyugin
    Mikhail Matyugin 5 July 2018 20: 44
    In general, it’s probably worth recognizing that in the current conditions by the end of 1944, kamikaze tactics were quite relevant for the Japanese their pilot training level fell worse than ever, American submarines interrupted the supply of fuel and supplies from the captured colonies, and in air battles they had losses 20: 1 in favor of the Americans ... And so was the chance of 1 plane - 1 ship ...
  7. Redfox3k
    Redfox3k 6 July 2018 09: 55
    One thing is surprising, the Japanese did not even give the pilot a chance to return. By the way, instead of a specially machined control knob, a shovel from a shovel could be put.
  8. Ivan Vasev
    Ivan Vasev 11 July 2018 19: 09
    Very similar to the Yak-18, -50.
  9. VictorZhivilov
    VictorZhivilov 24 July 2018 11: 27
    Thank you for expanding your horizons. Not suspected of existence Nakajima Ki-115 "Tsurugi"
    Particularly noteworthy in this aircraft engine.
    All serial "Tsurugi" were equipped with only 14-cylinder star-shaped engines Ha-35 Ru 23 firm "Nakajima", developing a power of 1130 hp

    Read more about the engine here:
    It should also be noted that in time, this engine was used on such aircraft as Mitsubishi A6M "Zero" и Nakajima Ki-43 "Hayabusa"

    And, it is also noteworthy that the handle was handled skillfully and this despite the fact that the aircraft was used once because of its specificity.