Engineering:Nakajima Ki-115

Short description: Japanese suicide attack aircraft

Ki-115 Tsurugi
Role	Kamikaze aircraft
Manufacturer	Nakajima Aircraft Company
First flight	March 1945
Retired	15 August 1945 (end of war)
Status	Retired
Primary users	Imperial Japanese Army Air Force Imperial Japanese Navy Air Service
Produced	104 or 105

The Nakajima Ki-115 Tsurugi (剣, "sabre") is a one-man kamikaze aircraft that was developed by the Imperial Japanese Army Air Force during the closing stages of World War II in 1945. The Imperial Japanese Navy called this aircraft Tōka (藤花, "Wisteria Blossom").

Historical context

The aircraft's intended purpose was to be used in kamikaze attacks on Allied shipping and the invasion fleet expected to be involved in the invasion of Japan, Operation Downfall, which in the end did not take place.

Because the Japanese High Command thought that Japan did not have enough obsolete aircraft to use for kamikaze attacks, it was decided that huge numbers of cheap, simple suicide planes should be constructed quickly in anticipation of the invasion of Japan.

Construction

The aircraft was very simple, being made from "non-strategic" materials (mainly wood and steel). To save weight, it was to use a jettisonable undercarriage (there was to be no landing), so a simple welded steel tube undercarriage was attached to the aircraft. This, however, was found to give unmanageable ground-handling characteristics, so a simple shock absorber was then incorporated. The cross section of the fuselage was circular and not elliptical as were most planes of this size and type; such a fuselage was easier to make.

Tsurugi had an instrument panel with some flight instruments, rudder pedals, a joystick type control column and a place for a radio. Flight controls included both ailerons and elevators and (in production versions) flaps.

The Ki-115 was designed to be able to use any engine that was in storage for ease of construction and supply, and to absorb Japan's stocks of obsolete engines from the 1920s and 1930s. The initial aircraft (Ki-115a) were powered by 858-kilowatt (1,151 hp) Nakajima Ha-35 radial engines. It is not known if any other engine was ever actually fitted.

After testing, the first production aircraft were fitted with the improved undercarriage and two rocket units. These may have assisted with take-off or may have been designed for the final acceleration towards the target.

Performance

A Ki-115 shortly after the war. Propellers were removed to prevent flight.

The aircraft had a top speed of 550 km/h (342 mph) and could carry a bomb weighing as much as 800 kg (1,760 lb), large enough to split a warship in two. However, as it was otherwise unarmed and heavily laden with its bomb, it would have made an easy target for enemy fighter aircraft.

The controls were crude, the visibility terrible, and the performance abysmal. Tsurugi had very poor take-off and landing performance and could not be safely flown by anyone other than experienced pilots. There were fatal crashes during testing and training. However new, better versions with improved controls and better visibility were under intensive development. The Japanese High Command had plans to construct some 8,000 per month in workshops all across Japan.

The war ended before any flew in combat. Individually, they would have been rather inefficient weapons, but used in waves of hundreds or thousands they could have been quite destructive.

Variants

• Ki-115 Prototype: Single-seat suicide attack aircraft. prototype version, tested during early 1945.
• Ki-115 Tsurugi: Single-seat suicide attack aircraft, production version.
• Ki-115b Tsurugi: Single-seat suicide attack aircraft. proposed version using larger wooden wing, none built.
• Ki-230: Single-seat suicide attack aircraft. projected version, none built.

Surviving aircraft

Ki-115 in USAF markings at Yokota Air Base

Of the 105 examples produced, two airframes are known to exist.

• Ki-115 1002 is on display at the Pima Air & Space Museum in Tucson, Arizona, and is on loan from the National Air and Space Museum.
• Another, once displayed as a gate guardian at Yokota Air Base, was since 1952 turned over to Japanese authorities and is reportedly at a Japanese museum.

Specifications (Ki-115a)

Data from Japanese Aircraft of the Pacific War

General characteristics

• Crew: 1
• Length: 8.55 m (28 ft 1 in)
• Wingspan: 8.6 m (28 ft 3 in)
• Height: 3.3 m (10 ft 10 in)
• Wing area: 12.4 m² (133 sq ft)
• Empty weight: 1,640 kg (3,616 lb)
• Gross weight: 2,580 kg (5,688 lb)
• Max takeoff weight: 2,880 kg (6,349 lb) with 800 kg (1,764 lb) bomb
• Powerplant: 1 × Nakajima Ha-35 Model 23 14-cylinder air-cooled radial piston engine, 840 kW (1,130 hp) for take-off

980 hp (730 kW) at 6,000 m (20,000 ft)

• Powerplant: 2 × solid rocket attack boosters (optional)
• Propellers: 3-bladed fixed-pitch metal propeller

Performance

• Maximum speed: 550 km/h (340 mph, 300 kn) at 2,800 m (9,200 ft) with undercarriage jettisoned
• Cruise speed: 300 km/h (190 mph, 160 kn)
• Range: 1,200 km (750 mi, 650 nmi)
• Wing loading: 208 kg/m² (43 lb/sq ft)
• Power/mass: 0.322 kW/kg (0.196 hp/lb)

Armament

• Bombs: 1 × 250 kg (550 lb), 500 kg (1,100 lb), or 800 kg (1,800 lb) bomb

See also

Aircraft of comparable role, configuration and era

• Mitsubishi A6M7
• Nakajima Ki-43-IIIa
• Yokosuka MXY-7 Ohka

Related lists

• List of aircraft of Japan during World War II
• List of military aircraft of Japan

References

Notes

Bibliography

• Francillon, René J. (1979). Japanese aircraft of the Pacific War. London: Putnam. ISBN 0-370-30251-6. OCLC 6124909. https://www.worldcat.org/oclc/6124909.  (new edition 1987 by Putnam Aeronautical Books, ISBN:0-85177-801-1.)
• Gunston, Bill. The Illustrated Encyclopedia of Combat Aircraft of World War II London: Salamander Books, Ltd., 1978. ISBN:0-89673-000-X.