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Role Floatplane trainer
National origin Japan
Manufacturer Yokosuka Naval Air Technical Arsenal
First flight 1930
Introduced 1933
Primary user Imperial Japanese Navy
Number built 211

The Yokosuka K4Y (or Navy Type 90 Seaplane Trainer) was a Japanese floatplane trainer of the 1930s. A single engined two-seat biplane, 211 K4Ys were built between 1933 and 1940, serving as the Imperial Japanese Navy's basic floatplane trainer throughout the Second World War.


Development and design

In 1930, the Imperial Japanese Navy Air Service's basic seaplane trainer was the Yokosuka K1Y or Type 13 Seaplane Trainer, which had been in use from 1925, and it instructed the First Naval Air Technical Arsenal based at Yokosuka to design a replacement.[1] The design team, lead by Jiro Saha and Tamefumi Suzuki designed a single-bay biplane with a welded steel-tube fuselage and wooden wings, it being the first Japanese designed aircraft with such a fuselage.[2]

Yokosuka built two prototypes, powered by 90 hp (67 kW) Hatakaze four-cylinder inline engines in 1930, flying in 1930, and after sucessful testing, a version powered by a 160 hp Gasuden Jimpu 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 srtarted to replace the K1Y from 1933, remaining the Imperial Japanese Navy Air Service's prinicpal basic trainer throughout the Pacific war. A few aircraft were released for civilian use.[2][3]

Units using this aircraft


Specifications (K4Y1 seaplane)

Data from Japanese Aircraft 1910-1941 [4]

General characteristics

  • Crew: 2
  • Length: 9.05 m (29 ft 8 in)
  • Wingspan: 10.90 m (35 ft 9 in)
  • Height: 3.51 m (11 ft 6 in)
  • Wing area: 29.5 m2 (318 sq ft)
  • Empty weight: 740 kg (1,631 lb)
  • Gross weight: 990 kg (2,183 lb)
  • Powerplant: 1 × Gasuden Jimpu 2 seven-cylinder air-cooled radial engine, 120 kW (160 hp)


  • Maximum speed: 163 km/h; 101 mph (88 kn) at sea level
  • Cruise speed: 93 km/h; 58 mph (50 kn)
  • Range: 315 km; 196 mi (170 nmi)
  • Endurance: 3½ hours
  • Service ceiling: 3,460 m (11,352 ft)
  • Time to altitude: 3,000 m (9,843 ft) in 29 min 20 sec


  1. ^ Mikesh and Abe 1990, pp. 273, 277.
  2. ^ a b c Mikesh and Abe 1990, p.277.
  3. ^ a b Francillon 1970, p.494.
  4. ^ Mikesh and Abe 1990, pp. 277–278.


  • Francillon, R.J. Japanese Aircraft of the Pacific War. London:Putnam, 1970. ISBN 0 370 00033 1.
  • Mikesh, Robert C. and Shorzoe Abe. Japanese Aircraft 1910-1941. London:Putnam, 1990. ISBN 0 85177 840 2.


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