Aviation of World War II

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Yokosuka K5Y1 in flight
  • Training aircraft
  • First flight: 1934
  • Yokosuka

K5Y. The main training machine of the Imperial Japanese Navy was the Yokosuka K5Y aircraft. It was produced from 1933 to 1945 and became the most massive Japanese aircraft in its class. A total of 5591 aircraft were manufactured.

And work began on the K5Y in 1932, when Kaigun Koku Hombu instructed the specialists of the 1st Aviation Arsenal of the Fleet in Yokosuka, with the help of designers from Kawanishi, to bring to mind the Type 91 training aircraft, first flown in 1931. The aircraft had good characteristics, but had insufficient flight stability intended for pilot training. Therefore, its design was significantly redesigned, as a result of which a biplane machine, the K5Y1, was created.

The new aircraft differed from its predecessor by a new upper wing with an increased transverse angle V and greater sweep, as well as a larger tail area. In addition, the fairings characteristic of the Type 91 aircraft were not installed on the fixed landing gear. The K5Y1 was powered by a Hitachi Amakaze 11 air-cooled radial engine with a capacity of 340 hp with covered with a hood in the form of a Townend ring. The armament was represented by a Type 89 7.7 mm machine gun placed above the engine. The second machine gun, movable, Type 2 caliber 7.92 mm could be mounted in the rear cockpit. Under the wing, the K5Y1 had the ability to carry two 30 kg training bombs or ten 10 kg bombs.

The first experimental aircraft took off in December 1933. After the completion of the reduced test program, it was accepted into service with the fleet as the Type 93 Model 1 Transitional Trainer Fleet (K5Y1 Model 1) and was sent into serial production in January 1934. Initially, it was carried out at the Kawanishi plant, but later it was transferred to the factories of a number of other aircraft manufacturing companies that were less loaded with the production of combat aircraft: Nippon Hikoki KK (2719 K5Y aircraft were manufactured here), Hitachi Kokuki KK (1393 pcs) , Fuji Hikoki KK (869 pcs) and Watanabe Tekkoso KK (556 pcs). A small number of aircraft were built by Nakajima and Mitsubishi.

In parallel with the wheeled version, the K5Y float version was produced, designated K5Y2 Model 2. A total of 872 of these aircraft were produced.

Further development of the design of a successful training aircraft was entrusted to Nippon. The company's designers developed variants of the K5Y3 Model 12, K5Y4 Model 13 and K5Y5 Model 14 with more powerful engines of the Amakaze series, but only the float K5Y3 of them was flown. Projects K5Y4 and K5Y5 (both on wheeled chassis) remained on paper.

K5Y aircraft were used until the last days of the war and played a huge role in the training of the flight personnel of the aviation of the Japanese Navy. The Allies gave them the code name "Willow".

Yokosuka K5Y1
Crew 2
Wing span, m 11
Wing area, m² 27.70
Length, m 8.05
Height, m 3.20
1 × PE Hitachi Amakaze 11
power, hp 1 × 340
Weights, kg
Empty weight 1,000
Loaded weight 1,500
Maximum speed, km/h 209
Cruise speed, km/h 136
Maximun rate of climb, m/min 222
Service ceiling, m 5,700
Service range, km 1,000

Armament. Usually absent. Sometimes 1 × 7.7mm Type 97 synchronous and 1 × 7.7mm Type 92 on turret. Bombs - 2 × 30 kg or 10 × 10 kg. In a single version for kamikaze 1 × 250-kg bomb.

Photo Description
 Drawing Yokosuka K5Y1

Drawing Yokosuka K5Y1

Drawing Yokosuka K5Y2

Drawing Yokosuka K5Y2

Design. The upper wing of the K5Y1, unlike the lower one, was characterized by a small sweep. The design of the biplane box is metal with linen lining. Under the lower wing of the K5Y, knots for training bombs could be attached.

The fuselage of the K5Y had a metal frame and a mixed metal-linen covering. A fixed 7.7 mm Type 89 machine gun was mounted in front of it. Another 7.7 mm Type 92 machine gun was mounted in the rear cockpit.

The power plant. Hitachi GK2B Amakase 11 air-cooled 9-cylinder radial engine with 340 hp. Wooden two-blade fixed-pitch propeller with a diameter of 2.75 m.


  • "Encyclopedia of military engineering " /Aerospace Publising/
  • "Japan Warplanes of World War II" /Oleg Doroshkevich/