Kawanishi Kokuki K.K. H3K1

Suggestions Aircraft
1

Navy Type 90-2 Flyingboat (H3K1)
(Company designation Type F)

Long but very intersting history

Spoiler

The Army’ introduction of the very large junkers G 38 into japan in 1928 strongly influenced the Navy to manufacture a very large fIying-boat. Planning began in 1929, and the Navy contracted with Kawanishi to work with Short Brothers in the United Kingdom, regarded as the world authority on large flying-boats.

Representing Kawanishi, Yoshio Hashiguchi was sent to Shons to assist in the design of a new three-engined biplane fIying-boat that was based on the Short Singapore and Calcutta. The new aeroplane was powered by three 825hp Rolls-Royce Buzzard engines, strut mounted between the two wings.The entire project, known as the KF Flying-boat, was kept very confidential during design and manufacture.

When completed, it was sent by ship to japan in the spring of 1930 where it was assembled at the Experimental Department of the Yokosuka Kokutai, then assigned to Tateyama Kokutai for operational testing. Flight tests revealed that it had good performance and good endurance, an essential for an
aircraft of this type.

While service testing was under way, licence manufacturing rights were secured by Kawanishi, and
production began with the use of drawings, documents and imported
components from Shorts. Under the continued supervision of Yoshio Hashiguchi, the first Kawanishi built flying-boat was completed in March 1931 and a second aircraft one-year later.

Tests were delayed because of unfamiliarity with the imported engines, but in October 1932, the Navy completed its evaluation of the one imported and two Kawanishi-built aircraft in service with the Tateyama Kokutai.

They were then accepted for Navy service as the Type 90-2 Flyingboat, with the short designation
H3K1. Two more examples followed in November 1932 and February 1933.

The four aircraft built by Kawanishi had distinctive features of their own, but all had the same type
engines and performance. Significant features of the design of these large metal flying-boats were that
the lower part of the hull was made of sheet stainless steel which formed a monocoque structure, a servo-rudder to reduce manual control forces, and the addition of a tail gun turret, the first in Japan.

These were recognized as the largest flying-boats in the Pacific.

One H3K1 commanded by Lieut Sukemitsu Itoh made a 1,300nm (1,496sm) long-range demonstration flight between the Tateyama Naval Air Base, on Tokyo Bay, and Saipan in the summer of 1932.
Unfortunately, on 8 January 1933, one of these flying-boats crashed while alighting at night near Tate-yama on a training flight.

A slowreading altimeter was given as the cause of the accident that killedthe noted naval pilot Lieut-Cdr Shinzo Shin, and two more of the crew of nine.

These large flying-boats established Kawanishi as a manufacturer of flying-boats throughout the
Pacific War years and after.

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Statistics:

  • Three-engined biplane flying-boat.

  • All-metal two-step hull with stainless steel stressed-skin below water-line. Wings of metal structure covered with fabric.

  • Crew of six to nine.

  • Three 825-955hp Rolls-Royce H-IO Buzzard twelve-cylinder vee water-cooled engines, driving two-bladed wooden propellers.

  • One nose twin-flexible 7.7mm machine-gun, two dorsal twin-flexible
    7.7mm machine-guns, one tail twin-flexible 7.7mm machine-gun. Bomb
    load: two 500kg (1, 1021b) or four 250kg (551Ib) bombs.

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