In 1939 the Imperial Japanese Navy instructed the Kawanishi Aircraft Company to develop a two-seat high-speed reconnaissance floatplane, which was required to have sufficient performance to escape interception by land based fighters. It was planned to equip a new class of cruisers, intended to act as a flagship for groups of submarines, operating six of the new floatplanes to find targets. The first of the new cruisers, Ōyodo was also ordered in 1939. Kawanishi designed a single-engined low-wing monoplane, powered by a 1,460 hp Mitsubishi MK4D Kasei 14 14-cylinder radial driving two Contra-rotating two-bladed propellers, the first installation of contra-rotating propellers produced in Japan, while a laminar flow airfoil section was chosen to reduce drag. It had a single main float under the fuselage and two stabilising floats under the wing. The stabilising floats were designed to retract into the wing, while the central float was designed to be jettisoned in case of emergency, giving a sufficient increase in speed to escape enemy fighters. The first prototype of Kawanishi's design, designated E15K1 in the Navy's short designation system made its maiden flight on 5 December 1941. Five more prototypes followed during 1941–42. Problems were encountered with the retractable stabilising floats, resulting in several accidents when the floats could not be lowered for landing, and the system was eventually abandoned, with the stabilising floats being fixed, and a more powerful Mitsubishi MK4S Kasei 24 engine fitted to compensate for the increased drag.
Operational history
Despite these problems, the E15K1 was ordered into limited production as the Navy Type 2 High-speed Reconnaissance SeaplaneShiun Model 11. Six were sent to Palau in the South Pacific, but these were quickly shot down by Allied fighters, as the jettisonable float failed to separate on demand. This resulted in the cancellation of production in February 1944, with only 15 Shiuns completed, including the six prototypes. According to the 61st Air Flotilla, 12th Reconnaissance Squadron wartime report No. 4..
April 30, 1944, five Shiun received by 61st Air Flotilla, 12th Recon Sqn.
May 15, 1944, three aircraft completed preparation.
June 12, 1944, two aircraft completed preparation.
According to 61st Air Flotilla, 12th Recon Sqn wartime reports.
1500 June 1, 1944, one Shiun arrived at Palau.
1230 June 3, 1944, one Shiun arrived at Palau.
June 3, 1944, one Shiun flew an anti-submarine flight. No enemy force found.
June 15, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
June 15, 1944, two Shiun were destroyed by US Navy task force at the Bonin Islands.
June 17, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
June 23, 1944, one Shiun flew an anti-submarine flight. No enemy force found.
June 25, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
June 26, 1944, two Shiun flew reconnaissance flights. No enemy force found.
June 28, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
June 30, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
July 9, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
July 10, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
July 11, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
July 12, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
July 14, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
July 15, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
July 16, 1944, one Shiun flew a reconnaissance flight. Another Shiun flew an anti-submarine flight. No enemy force found.
July 19, 1944, one Shiun flew a reconnaissance flight. No enemy force found.
July 21, 1944, two Shiun flew anti-submarine flights. No enemy force found.
July 25, 1944, two Shiun flew anti-submarine flights. Met enemy fighter. One Shiun was destroyed.
August 10, 1944, one Shiun flew an anti-submarine flight. No enemy force found.
August 12, 1944, one Shiun flew an anti-submarine flight. No enemy force found.
August 12, 1944, 12th Reconnaissance Squadron was disbanded.
The commander of the squadron, Lt. Kiyoshi Aikawa wrote "..Never make again such an aircraft as the Shiun...". He reported that the reliability of the aircraft was poor, and it needed high amounts of maintenance.
Variants
E15K1 : Single-engined reconnaissance floatplane. Production version.
