In early 1925, Eiji Sekiguchi, chief designer of the aircraft department of
Kawanishi Kikai Setsakuho (Kawanishi Machinery Manufacturing Works), started work on a long-range
floatplane for use by
Nippon Koku K.K. the airline subsidiary of Kawanishi on airmail services. The resulting design, the
Kawanishi K-8A, was a single-engined
monoplane with a fabric covered wooden structure. It was powered by a
Maybach Mb.IVa water-cooled inline-engine, as used in Kawanishi's successful
K-7 biplane, but was larger and heavier than the K-7. The aircraft was fitted with a twin-float undercarriage, while the crew of two sat in open cockpits. The first prototype was completed in January 1926 with a
shoulder-wing layout, but following aircraft had the wing raised to a
parasol wing arrangement. The aircraft demonstrated relatively poor performance, but showed good stability, making it popular for long-distance flights. A total of 5 K-8As were completed in 1926, all going to
Nippon Koku K.K.. The design attracted the attention of the
Teiko Kaibo Gitai, (the Imperial Maritime Defence Volunteer Association), a patriotic organization, who placed an order for two modified aircraft, the
Kawanishi K-8B, with reduced span wings, a slimmer fuselage and the crew cockpits moved rearwards. These two aircraft were completed in 1927, demonstrating improved performance. ==Operational history==