(Wikipedia !!!)
The aircraft's intended purpose was to be used in kamikaze attacks on United States 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 for the invasion of Japan
The aircraft was very simple, being made from "non-strategic" materials (mainly wood and steel). To save weight, it was to use a droppable take-off gear (there was to be no landing), so a simple welded steel tube undercarriage was attached to the aircraft.[2] 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 the instrument panel with some flight instruments; rudder pedals in addition to the rudder lever and also a place for a radio. Flight controls included both ailerons 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 obsolete stocks of engines from the 1920s and 1930s. The initial aircraft (Ki-115a) were powered by 858 kW (1,150 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[2] or may have been designed for the final acceleration towards the target.[3][4]
