Yokosuka K5Y ‘Willow’ Type 93 Intermediate Trainer

The Yokosuka K5Y 'Willow' Type 93 Intermediate Trainer was the most widely produced training aircraft produced in Japan, and remained in production from 1933 to 1945.

The K5Y was developed from the Type 91 Primary Trainer. This had been produced in 1930-31 in order to fill a gap between the current 500hp front line aircraft and 100hp training aircraft, but tests in 1931 showed that it was too close in performance to the front line aircraft, and lacked stability. 

The Type 91 was a single bay biplane with N struts, cowled main wheels, a radial engine with ring cowling, a welded steel tube structure for the fuselage and wooden framework for the wings and a fabric covering.

Work on improving the Type 91 began in 1933. It retained many features from the Type 91, and as a result was very similar in size and weight. The work was split between Kawanishi and the First Naval Air Technical Arsenal at Yokosuka (Dai-Ichi Kaigun Koku Gijitsusho). This arsenal was known by a variety of names during its existence, but it kept the short designation code Y and most of its aircraft are known as Yokosuka models.

The aircraft was given a new upper wing with more dihedral and sweep-back than on the type 91. It was also moved closer to the fuselage. The tail surfaces were also redesigned. It was powered by a 340hp Hitachi Amakaze 11 radial engine, equipped with a Townend ring. This replaced a slightly lower powered Gasuden Tempu 11 radial engine. The new aircraft was slightly faster and had a slightly better rate of climb than the Type 91. Otherwise it was very similar, with the same N struts, single bay wings and construction methods. 

The prototype was completed by December 1933 and was very quickly accepted by the Japanese Navy. It entered production at Kawanishi in January 1934 as the Navy Type 93 Intermediate Trainer K5Y and was produced in two versions - the K5Y1 land plane and K5Y2 twin-float floatplane.

The K5Y was produced in small numbers by Kawanishi, with sixty K5Y1s and K5Y2s appearing in 1933-36. Production then sped up greatly, and eventually 5,770 were built.

Nakajima entered production in 1935-36, building 24 K5Y1s.

Watanabe then took over, building 393 K5Y1s in 1936-39 and 163 K5Y2s in 1937-39.

In 1940 production switched to Hitachi and Nippon. Hitachi produced 1,393 of both models in 1940-44. Nippon produced 2,025 K5Y1s and 706 K5Y2s in 1940-45.

Fuji joined the production team in 1942, building 869 between then and 1945.

Sixty were built by Mitsubishi at an uncertain date.

Finally the Dai-Ichi Kaigun Kokusho at Kasumigaura produced 75 K5Y1s in 1944.

Variants

K5Y1

The K5Y1 was the land-plane version of the trainer

K5Y2

The K5Y2 was the floatplane version of the trainer. It was produced by most of the companies involved in K5Y production, but in most cases the numbers produced are unclear. Watanabe produced 163 in 1937-99 and Nippon produced 706 in 1940-45.

K5Y3

The K5Y3 was a floatplane powered by a 515hp Amakaze 21 radial engine. Two prototypes were built by Nippon Hikoki K.K, but it didn't enter full production.

K5Y4

The K5Y4 would have had a 480hp Amakaze 21A radial engine and a smooth engine cowling. None were built.

K5Y5

The K5Y5 would have been similar to the K5Y4, but with a 515hp Amakaze 15 engine. Again none were built.

Stats

K5Y1

Engine: Hitachi Amakaze 11 9-cylinder radial
Power: 340hp
Crew: 2
Span: 36ft 1in
Length: 26ft 5in
Height: 10ft 6in
Empty weight: 2,205lb
Maximum take-off weight: 3,307lb
Max speed: 132mph
Climb Rate: 13min 32sec to 9,845ft
Service ceiling: 18,700ft
Range: 633 miles
Armament: One fixed forward firing 7.7mm machine gun, one flexibly mounted rear firing 7.7mm machine gun
Bomb load: Two 66lb or ten 22lb bombs

K5Y2
Seaplane
Engine: Hitachi Amakaze 11 9-cylinder radial
Power: 340hp
Crew: 2
Span: 36ft 1in
Length: 28ft 10in
Height: 10ft 6in
Empty weight: 2,535lb
Maximum take-off weight: 3,638lb
Max speed: 123mph
Climb Rate: 19min 35sec to 3,280ft
Service ceiling: 18,700ft
Range: 436 miles
Armament: One fixed forward firing 7.7mm machine gun, one flexibly mounted rear firing 7.7mm machine gun
Bomb load: Two 66lb or ten 22lb bombs

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How to cite this article: Rickard, J (7 July 2015), Yokosuka K5Y ‘Willow’ Type 93 Intermediate Trainer , http://www.historyofwar.org/articles/weapons_yokosuka_K5Y_willow.html

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