In 1939 Imperial Army imported Kellett KD-1A to learn about autogyros. Damaged in crash, this was transferred to Kayaba Seisakusho KK, Sendai, to assist development of Japanese 2-seat observation autogyro. Ka-1 (240-hp Argus) flew 26 May 1941; outstanding machine, about 240 built. Ka-1 KAI had tip rockets to boost capability; single Ka-2 had 240-hp Jacobs.