The Kawanishi H3K was a long range reconnaissance seaplane designed by Shorts and produced under licence in Japan by Kawanishi. In 1929 Kawanishi's chief engineer, Yoshio Hashiguchi, travelled to Britain to look for a suitable design for a long range patrol flying boat. Shorts demonstrated the Singapore I and the Calcutta. Hashiguchi preferred the Calcutta, but wanted to use different engines to avoid having to cooperate with Nakajima, which had the licence to build its Bristol Jupiter engines (Nakajima and Kawanishi had originally worked together, but the two men had argued and their companies became rivals).
Shorts produced a new aircraft based on the Rangoon (the military version of the Calcutta), but with Rolls Royce Buzzard engines. The new S.15 was a three-engined biplane, with the engines mounted between the wings. The lower wing was attached to the top of the hull, with the upper wing attached by five pairs of struts. The tail had a single main vertical control surface and two smaller outer vertical surfaces. The S.15 used modern construction techniques, and would give Kawanishi valuable experience of working on all-metal aircraft.
The S.15 had two open side-by-side cockpits, engineering and wireless positions and internal accommodation that included a ward room and galley. The first aircraft was built in Britain, where it made its maiden flight on 10 October 1930. The aircraft was then shipped out to Japan, where it was re-assembled with the help of a team from Shorts. Its first flight in Japan came on 8 April, and after a period of tests was accepted for production as the Navy Type 90 Model 2 Flying Boat. Four aircraft were built in Japan in 1932-33, and were similar to the first aircraft, but with enclosed cockpits. The aircraft were used for reconnaissance flights and training. One was lost in a accident but the surviving four aircraft remained in service until 1936.
The H3K was rather similar to the much larger Shorts Sarafand, but was actually the older aircraft, making its maiden flight in 1930, the year before work began on the Sarafand.
Engine: Three Rolls-Royce Buzzard engines
Power: 820-825hp each
Wing span: 102ft 0in
Maximum take-off Weight: 37,920lb
Max Speed: 138mph
Armament: Six 0.3in machine guns