HISTORY

Photo: Naval History and Heritage Command

Nakajima by February 1944. The gun armament

was improved and variants with magazines for

up to 150 rounds could be used on the Type 21.

Such a Zero may have been designated as Type

21a.

Here comes the Rufe

April 2023

Wildcats aboard the USS Wasp prepare for an air strike against Tulagi and adjacent islands in the early morning

hours of August 7, 1942.

Photo: Naval History and Heritage Command

Floatplanes are a very old idea. Fighters of this

design had already been deployed in combat

during the First World War. After the war, their

priority gradually declined as the performance

of these seaplanes fell gradually behind that

of fixed landing gear machines. The Imperial

Japanese Navy returned to the idea in 1933

during preparation for a new seaplane tender.

IJN came up with a specification for a machine

that was to protect a coastal base during its

construction and was to be capable of reaching

speeds of 200 knots. Kawanishi had been

preparing a study of such a seaplane since 1934.

It was to operate from a tender, or launch from

a catapult, and be able to counter fighter aircraft.

The prototype was not built, and preparations

were halted in 1936. Subsequently, the concept

of a two-seat machine was considered, but even

this idea was abandoned.

In the late 1930s, the US Navy prepared a plan to

build 2,000 flying boats. The Japanese decided to

respond to this threat. Therefore, in September

1940, the IJN commissioned Kawanishi with

the specification for the 15-Shi fast interceptor

seaplane. Kawanishi had already been working

on a fast floatplane reconnaissance aircraft

(later designated the E15K Shiun) for several

months, and the Navy hoped for synergy from

this decision. However, at the same time, it

feared certain delays because Kawanishi’s

aircraft carried a number of innovative features.

Therefore, the IJN decided to convert the

Mitsubishi A6M2, which was currently

undergoing combat test deployment in China,

to a fighter seaplane. Mitsubishi was fully

occupied with the production of Zeros and other

types of aircraft. Therefore, the IJN turned to

Nakajima, which began licensed production

of A6M2 fighters at its Koizumi plant in late

1941. The company had some free design and

production capacity and was therefore awarded

with works on the seaplane.

Shinobu Mitsutake was appointed chief

designer. His team tried to make the most of the

A6M2 design. Some authors state that standard

fighter seaplane was based on the A6M2 Type 11,

which did not have folding wingtips. In fact, at

least the first few dozen production machines

had folding wingtips. On captured Rufes, this

design feature is still documented on the 37th

aircraft produced.

The designers added a metal central float to the

fuselage. The pylon was mounted to the main

wing spar and attached to the rear wing spar by

a “V” shaped strut. The pylon, with incorporated

the oil cooling system, was located roughly

This picture taken from Dauntless on August 7, 1942, shows smoke rising from burning fuel supplies

on Tanambogo Island, where the Rufe seaplanes were based. To the right is Gavutu Island and to the left

is Gaomi Island. Florida Islands can be seen in the background.

where the Zero had the auxiliary tank attached.

The absence of the auxiliary tank was replaced

by tanks in the float. The stabilizing floats were

mounted on separate pylons. Hatches were

added to the wing´s skin to allow access to the

internal wing structure and pylons.

This elegant solution for mounting the central

float was already used on the F1M Pete biplane

and contributed to the high aerodynamic purity

of Mitsutake’s design. The central float and

its dynamic effects on the fuselage structure

during take-off, high-G maneuvers, and landing,

necessitated the need to reinforce the fuselage

structure in the cockpit area by additional metal

sheets.

On the first few dozen machines, a system for

purging the fuel tanks was installed on top of

the central float. The fittings of this system,

which protruded from the float at the top, were

protected by a hemispherical cover. The float

was also fitted with a rudder.

The last significant change from the Zero was

an increase in the vertical tail area for the

stability of the machine. Testing of the prototype

began on the day of the Japanese attack on

Hawaii and continued intensively during early

1942. The prototype was converted from the

land-based version of the Zero fighter, the A6M2

Type 11 c/n (6)69. The next nine A6M2-N aircraft

were to be produced at Nakajima by conversion

from Mitsubishi A6M2 Type 21 carrier fighters,

which were to undergo repairs due to damage

in combat. Among them were the machines c/n

(5)159 and (3)312, which took part in the attack

on Hawaii aboard the aircraft carrier Shōkaku.

However, the converted seaplanes suffered

INFO Eduard

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