Yokosuka built two prototypes, powered by 90 hp (67 kW) Hatakaze four-cylinder air-cooled inline engines in 1930, flying in 1930, and after successful testing, a version powered by a 130 hp Gasuden Jimpu[2] radial engine was ordered into production as the Navy Type 90 Seaplane trainer, with the short designation K4Y1.[2]
Operational history
Production began at Watanabe in May 1933, Watanabe building 156 by 1939, with production then transferring to Nippon Hikoki who built a further 53 in 1939–40.[3]
The K4Y1 started to replace the K1Y from 1933, remaining the Imperial Japanese Navy Air Service's principal basic seaplane trainer throughout the Pacific war. A few aircraft were released for civilian use.[2][3]
1 X as second letter is for experimental aircraft or imported technology demonstrators not intended for service,
2 Hyphenated trailing letter (-J, -K, -L, -N or -S) denotes design modified for secondary role, 3 Possibly incorrect designation, but used in many sources