Nakajima Ki-115 Tsurugi (Sabre) Kamikaze

By the beginning of 1945 the Japanese Army had begun preparations for the anticipated American and Allied invasion of the Home Islands. Aircraft of all kinds were being set aside for use for Kamikaze missions, including obsolescent types and trainers. Fearing even this would not be enough, Nakajima was directed to design an aircraft specifically built for use as a Kamikaze. This became the Ki-115 Tsurugi (Sabre).

The Tsurugi was designed to be constructed using semi-skilled labor and non-strategic materials. The fuselage structure was made from steel tubing. The cowling was tin with sheet steel used to cover the rest of the fuselage, tail surfaces were wooden with fabric coverings, wings were of all-metal construction.

From the outset the Tsurugi was designed to accept any surplus engine in the 800 to 1,300 horsepower range. In the event, all Ki-115 actually constructed were powered by 1,150 horsepower Nakajima Ha-35 radial engines. Bomb load was a single 500 – 1,764 pound (250 to 800 kg) bomb semi-recessed into the fuselage.

The aircraft never saw combat, and was unknown to Allied intelligence until after the Japanese surrender. Four were taken to America after the war for evaluation but there is no known record of any U.S. test flight. Here is an example serving as a “gate guard” at an unknown facility after the war. The lack of shock absorbers on the wheel struts made ground handling difficult, the pilot was intended to jettison the gear once he became airborne.

Construction number 1002 was preserved for the U.S. National Air and Space Museum. It was cataloged as FE-156 / T2-156 for evaluation purposes.

Here is a series of souvenir photos taken by American service personnel inside the Nakajima Aircraft Company factory at Ota, Japan in September 1945. The G.I.s are exploring the Ki-115 production line.

A wider view of the previous photo. The factory was damaged during a USAAF raid on 10FEB45 and never repaired, the factory was essentially functioning as an open-air facility for the remainder of the war.

Another view of the Ki-115 production line. Of the 105 Tsurugi produced, 82 were constructed at Ota. There are photos of these aircraft up on their landing gear, presumably these were collapsed by the U.S. forces to prevent any chance of the aircraft being used.

A very interesting view of the Nakajima production lines at Ota, Ki-115 Tsurugi on the left and Ki-84 Hayate (Frank) fighters on the right. The Tsurugi in the center has had its Hinomaru and anti-glare panel applied but the camouflage is incomplete, unlike the examples at the end of the line at the left. The topside colors of these aircraft are generally interpreted as a dark green, although each production facility utilized their own mixes as supplies allowed and various browns and olive drabs have also been documented.

Not the best quality of photo but it does show the Ki-115 line up on their gear. Especially interesting is documentation of the painting process in progress – the aircraft in the foreground has her dark uppersurface camo in place, the next has the white surround to the Hinomaru and dark camo outline applied, while the third has Hinomaru without the white outline.

Another variation in overall appearance is seen on this example. The mottling effect is either surface corrosion of the steel skin or a very thin application of a camouflage paint. Note the tin cowling panels appear pristine. I favor the rust interpretation myself but still have some doubts.

A color cockpit photo of Tsurugi construction number 1002 preserved at NASM. Note the basic instrument panel and wooden construction – the joystick, throttle quadrant, foot troughs, canopy frame, and even the seat are made of wood.