N1K1 Kyofu (Mighty
Wind) Fighter Floatplane
In 1940, anticipating a
coming war in which Japan would be involved in far-ranging offensive
operations, the Japanese Navy issued a requirement for a floatplane
fighter which could be used for offensive operations in forward areas
were no airfields existed. In response to this requirement, the
Nakajima Hikoki K. K. concern at Koizumi offered a design based on a
modified Mitsubishi A6M2 Reisen carrier-based fighter. This eventually
emerged as the A6M2-N and was given the Allied code name Rufe when it
entered service. However, this aircraft was considered as only an
interim solution, and the Kawanishi Kokuki K. K. of Naruo was
instructed to begin work on a more-advanced aircraft specially designed
for the purpose. The Japanese Navy issued a 15-Shi specification (so
named for the 15th year of the Showa era, which was 1940) for this
aircraft in September of 1940.
A team of engineers at
the Kawanishi plant including Toshihara Baba, Shizuo Kikuhara, Hiroyuki
Inoue, and Elizaboro Adachi came up with a design for a compact
aircraft with mid mounted wings of laminar-flow section. A single large
float was to be installed underneath the fuselage, with auxiliary
floats being carried underneath each outer wing. The central float was
to be attached to the fuselage by a forward V-strut and an I-strut at
the rear. The initial design had the auxiliary floats being retractable
and with metal planing bottoms and inflatable rubberized-fabric tops.
However, these retractable floats were deemed to be too heavy and
complex, and were replaced by fixed cantilever floats prior to the
first flight of the prototype. The aircraft was to be powered by a 1460
hp Mitsubishi MK4D Kasei 14 air-cooled radial driving a pair of
contra-rotating two-bladed propellers. The contra-rotating propellers
were intended to offset the high propeller torque on takeoff expected
from such a powerful engine mounted in a relatively small airframe.
The first N1K1
prototype took off on its first flight on May 6, 1942. The
contra-rotating propellers of the prototype were later dropped as being
too complex, and the design was modified to accept a 1460 hp MK4C Kasei
13 (Ha.32/13) radial engine driving a single conventional three-bladed
propeller via an extension shaft. The single propeller installation was
simpler and less mechanically troublesome, but it did produce (as
expected) an extremely powerful torque on takeoff that required
considerable skill on the part of the pilot to counter.
Armament consisted of
two 20-mm Type 99 Model 1 cannon and two 7.7 mm (0.303 in) machine
guns.
Once in the air, the
N1K1 was found to be an extremely pleasant aircraft to fly and it had
remarkable manoeuvrability by virtue of its combat flaps. The Japanese
Navy accepted the design under the designation N1K1 Navy Fighter
Seaplane Kyofu (Mighty Wind) Model 11, and production began.
Service trials aircraft
were delivered to the Japanese Navy starting in August of 1942. Early
production aircraft were powered by 1460 hp MK4C Kasei 13 engines, but
later production aircraft were powered by 1530 hp MK4E Kasei 15 engines
which differed only in minor details.
The Kyofu entered
service with the Japanese Navy in July of 1943, and was assigned the
Allied code name "Rex". Production was slow in gearing up and by
December of 1943, it had reached only 15 aircraft per month.
However, by the time
that the Kyofu entered service, Japan had been thrown back onto the
defensive, and the Kyofu was never to serve in the offensive fighter
role for which it had been designed. Instead, the the N1K1 was assigned
as an interceptor based at Balikpapan in Borneo, a role for which it
had never been intended. Even though the Kyofu was a rugged and
efficient floatplane, it was no match for the single-seat Allied
fighters which opposed it. Consequently, production of the Kyofu was
terminated in March of 1944 after the delivery of only 89 production
aircraft. Also abandoned at the same time was the N1K2-I Kyofu-Kai
project, to have been powered by the improved 1900 hp Mitsubishi MK4R
Kasei 23 engine.
Later in the war, one
Kyofu unit was assigned as an interceptor with the Otsu Kokutai
operating from the inland Lake Biwa on the Japanese home island of
Honshu.
Specification of the
Kawanishi N1K1 Kyofu Floatplane
Powerplant: One
Mitsubishi MK4E Kasei 15 fourteen-cylinder air-cooled radial rated at
1530 hp for takeoff, 1400 hp at 8530 feet, 1280 hp at 19,685 feet.
Performance:
Maximum speed 302 mph at 18,700 feet, service ceiling 34,645 feet
cruising speed 230 mph at 6560 feet. Climb to 16,400 feet in 5 minutes
32 seconds. Normal range 660 miles, maximum range 1040 miles.
Weight: 6,067
pounds empty, 7,716 pounds loaded, 8,184 pounds with maximum loadout.
Dimensions:
wingspan 39 feet 4 7/16 in, length 34 feet 8 7/8 in, height 15 feet 7
in, wing area 252.95 square feet.
Armament: Two
7.7 mm (0.303 in) Type 97 machine guns in the fuselage and two 20-mm
Type 99 Model 1 cannon in the wings. Two 66 lbs bombs could be carried
externally.
N1K1-J Shiden
(Violet Lightning)
In December of 1941,
the Kawanishi engineering team proposed to their management that it
might be a good idea to produce a land-based version of the company's
N1K1 Kyofu seaplane fighter. Kawanishi management thought enough of the
idea that they decided to go ahead with the project as a private
venture.
Initially, few changes
over the N1K1 were planned other than the replacement of the floats
with retractable land undercarriage. However it was decided to replace
the 14-cylinder Kasei engine with an eighteen-cylinder Nakajima Homare
air-cooled radial which, it was hoped, would deliver 2000 hp. To take
advantage of the increased power, a new four-bladed propeller with a
diameter of 10 feet 10 inches was to be fitted. However, since the
original mid-wing configuration of the Kyofu was retained, a very
stalky undercarriage was required in order that the prop be able to
clear the ground. This in turn required a rather complex scheme of
double landing gear retraction, in which the legs contracted as they
folded into the wing wells. The aft portion of the fuselage was
deepened to give more vertical stabilizing area and included a
retractable tailwheel.
A unique feature of the
N1K1-J was its set of combat flaps. Whereas flap extension was manually
controlled on the Kyofu seaplane, the flaps on the landplane version
had the ability automatically to change their angle in response to
changes in g-forces during manoeuvres. This automatic operation freed
up the pilot from having to worry about his flaps during combat, and
eliminated the possibility of a stall at an inopportune time.
The land based fighter
made its maiden flight on December 27, 1942. Since the aircraft was a
private venture, it had no military designation, and was known as the
Model X-1 experimental land based fighter by the manufacturer. The
engine was the 1820 hp Nakajima Homare 11 radial. It was armed with two
7.7 mm Type 97 machine guns in the fuselage and two 20-mm Type 99 Model
2 cannon housed in underwing gondolas.
Since the Homare 11 had
been accepted for production before the completion of its final tests,
it was plagued with teething troubles. The early Homare engine failed
to develop its rated power, the propeller torque during takeoff was
excessive, and the visibility during taxiing was poor. However the
aircraft had pleasant flying characteristics and the automatic combat
flaps gave the aircraft exceptional manoeuvrability.
By July of 1943, four
prototypes had been built, and one was handed over to the Navy for
trials. The performance was disappointing, the maximum speed being only
357 mph (403 mph had been promised). However, it was faster than the
Mitsubishi A6M5 Reisen and was more manoeuvrable and longer-ranged than
the faster Mitsubishi J2M2 Raiden. By this time, the Japanese Navy was
in desperate need of fighters capable of countering the Vought F4U
Corsair and the Grumman F6F Hellcat, and gave authorization for
Kawanishi to proceed with further development of the land-based version
of the Kyofu under the designation N1K1-J Shiden (Violet Lightning)
Interceptor Fighter. The J indicated that it was a landplane
development of the original N1K1.
Further prototypes and
service trial aircraft were built during 1943. They were fitted with
the more powerful 1990 hp Nakajima NK9H Homare 21 radial. The cowling
was modified and featured an additional lower lip scoop. Individual
exhaust stacks were fitted, and an external oil cooler was mounted on
the port side of the cowling behind and below the cooling gills. Two
additional 20-mm Type 99 Model 2 cannon were installed in the wings
just outboard of the external underwing cannon gondolas.
Quantity production was
ordered by the Navy as the Navy Interceptor Fighter Shiden Model 11. By
the end of 1943, 70 aircraft had been built at the Naruo Works, and the
first aircraft had been delivered by the Kawanishi plant at Himeji.
The N1K1-J entered
service with land-based squadrons of the Japanese Navy early in 1944.
Armament consisted of 2 7.7-mm machine guns in the fuselage and four 20
mm cannon in the wings (2 in the wing, 2 in underwing gondolas). The
first large unit of Shidens to be deployed was the 341st Kokutai (Air
Corps), which was transferred to Luzon from Formosa on October 20,
1944. The N1K1-J was first encountered by American forces in combat
over Formosa and the Philippines. It was assigned the Allied code name
George. It quickly established itself as one of the toughest and most
troublesome Japanese fighters yet to be met in combat. It was a truly
exceptional combat aircraft in the hands of an experienced pilot. It
proved itself superior to most US shipboard fighters that it
encountered, and many experienced Shiden pilots regarded the
previously-formidable Grumman F6F Hellcat as a particularly easy
"kill".
The N1K1-J was,
however, not without its faults. Operations were plagued by frequent
undercarriage malfunctions, the complex double-retraction landing gear
causing lots of problems. Aircraft availability was frequently limited
by insufficient maintenance crews and by logistics problems. The Homare
engine was rather unreliable and was a maintenance headache. The wheel
brakes were so bad that most pilots chose to land their Shidens on the
grass alongside the runway in order to shorten the landing run.
The N1K1-Ja Model 11A
differed from the Model 11 in having all four of its 20-mm cannon
inside the wing, and it dispensed with the fuselage-mounted machine
guns. The N1K1-Jb Model 11B had four improved 20-mm cannon in the wing,
was fitted with two underwing racks for bombs of up to 550 pounds in
weight, and late production N1K1-Jb fighters had completely redesigned,
square-tipped vertical tail surfaces. The N1K1-Jc Shiden Model 11C was
a specialized fighter-bomber version similar to the Model 11B but with
four underwing bomb racks. At least one N1K1-J used in the Philippines
was captured by US forces. It was repaired and tested by American
Technical Air Intelligence Unit pilots at Clark Air Base. The respect
that American pilots had for the airplane was found to be fully
justifiable.
Following the fall of
the Philippines to US forces, the Shiden was met in large numbers
during the invasion of Okinawa. A Japanese military communique reported
an engagement in which a unit of 34 Shidens met a force of 70 Allied
fighters, destroying 20 of them against a loss of only twelve of their
number. Shidens also equipped the 343rd Kokutai the First Air Fleet
based at Tinian, and were later based at Shikoku in Japan in defense of
the home islands during the spring of 1945.
Late in 1944, a Shiden
was modified as the N1K1-J-Kai with a supplementary rocket unit to
increase power for short periods. The rear portion of the fuselage was
modified to house a rocket motor. Several aircraft received this
modification, but the conversion never achieved operational status.
The Shiden Special
Attack aircraft was a variant capable of carrying out suicide attacks.
In early 1945, four Shiden 11s were modified for this mission, but were
never expended.
A total of 9 prototype
and 520 N1K1-J production aircraft were built by the Naruo plant, and
468 N1K1-J production aircraft were built by the Himeji plant. This
brought total production of the Shiden to 1007 examples, including
prototypes. Production of the N1K1-J was phased out at the Narou plant
in December 1944 in favour of the improved N1K2-J. Production of the
N1K1-J at the Himjei plant was halted by the damage caused by B-29
raids.
Kawanishi N1K2-J Shiden of the 343rd Kokutai
N1K2-J Shiden Kai
(Violet Lightning Modified)
Although the N1K1-J was
an outstanding fighter, it did have some serious defects. Its Homare 21
engine was notoriously unreliable, and the complex doubly-retracting
landing gear was subject to frequent failures. Even before the N1J1-J
entered production, work had already begun at Kawanishi on correcting
some of its more glaring defects, in particular its long and complex
landing gear.
The result of these
changes was the Shiden-Kai (Violet Lightning--Modified). Given the
designation N1K2-J, the aircraft was completely redesigned so as to use
fewer components in order to simplify its construction. More
non-critical materials were to be used. Another step towards
simplification involved the use of pre-formed sheet construction.
Perhaps the most easily-noted innovation was the use of a low-mounted
wing in place of the original mid-mounted wing. This permitted a
shorter set of landing gear legs to be used, and the complex
double-retraction system which had caused so many problems could be
eliminated. In addition, the fuselage was lengthened and the tail
surfaces were redesigned. The result was a virtually new aircraft,
although the unreliable 1990 hp Homare 21 engine of the N1K1-J was
retained. Armament was four 20-mm cannon, all mounted internally to the
wing.
The first N1K2-J
prototype took off on its maiden flight on December 31, 1943. It was
handed over to the Japanese Navy for trials in April of 1944. Although
the Homare 21 engine was still mechanically unreliable, the Navy liked
the aircraft so much that they authorized quantity production of the
N1K2-J to be its standard land-based fighter and fighter-bomber even
before the service trials were completed. Production aircraft were
designated Navy Interceptor Fighter Shiden Kai (Violet Lightning
Modified) Model 21. In addition to the Kawanishi plant at Naruo, the
Shiden Kai was ordered into production at the Himeji works of Kawanishi.
Shiden Kai fighter aircraft were also ordered into production from the
Dai-Nana Kokuki Seisakusho (7th Airframe Works) of the Mitsubishi
Jukogyo K. K. at Tsurashima, from the Aichi Kokuki K. K. at Eitoku,
from the Showa Hikoki K. K. at Shinonoi, and from the Naval Air
Arsenals at Hiro, Omura, and Koza.
A further seven
prototypes had been completed by June of 1944, However, the prototypes
began to experience a long series of teething troubles, which proved
difficult to correct. The Shiden-Kai program began to slip its
schedules, and by the autumn of 1944 the N1K2-J production lines were
beginning to experience shortages of vital components due to B-29
attacks against the factories of Kawanishi's subcontractors. By the end
of 1944, only 60 Shiden Kais had been delivered by the Naruo factory,
and production at Himeji did not begin until March of 1945. The other
manufacturers in the Shiden Kai pool were never able to produce more
than a handful of aircraft.
The Shiden Kai was to
become perhaps the best all-round fighter to be operational in the
Pacific theatre. It was fast, powerful, and maneuverable, and was
well-armed and armoured. In the hands of an experienced pilot, the
Shiden-Kai was the equal of any Allied fighter, even the later models
of the P-51 Mustang which began to appear over Japan in the spring of
1945. In one notable action, on February 16 1945 over Yokohama, Warrant
Officer Kinsuke Muto of the 343rd Kokutai in an N1K2-J single-handedly
battled a dozen F6F Hellcats. He shot down four of them before the rest
were forced to break off combat and return to their carrier. However,
against the B-29, the N1K2-J was less successful, since its climbing
speed was insufficient and the power of the Homare 21 engine fell off
rather rapidly at higher altitudes.
A two-seat trainer
version, the N1K2-K Shiden Kai Rensen (Violet Lightning Modified
Fighter Trainer) was planned, but only a few examples were produced by
fitting a second seat behind the pilot's seat of some existing N1K2-J
airframes.
The Shiden Kai had its
centre of gravity too far aft, and to correct this problem the N1K3-J
Shiden Kai 1 Model 31 was built, which had the Homare 21 engine moved
forward six inches. This freed up enough space to permit two 13.2-mm
machine guns to be fitted in the engine cowling. Two prototypes were
built at Himeji, but this model was never put into production.
The N1K3-A Shiden Kai 2
Model 41 was a carrier-based variant of the N1K3-J. It too was never
put into production.
In an attempt to
overcome some of the operational problems caused by the still
unreliable Homare 21, the N1K4-J Shiden Kai 3 Model 32 and its
carrier-borne variant the N1K4-A Shiden Kai 4 Model 42 were developed.
These were powered by the 2000 hp NK9H-S Homare 23 fuel-injected
radial. Two prototypes of the N1K4-J and one of the N1K4-A were built
in the spring of 1945 at Naruo. The carrier-based aircraft was accepted
for production as the Shiden 41, but was later abandoned since by that
time Japan's carrier forces had been completely destroyed.
One of the weaknesses
of the Shiden Kai was its rather lacklustre high-altitude performance.
It had proven to be ineffective against the B-29 owing to its poor
climbing ability. In search of better high-altitude performance, the
N1K5-J Shiden Kai 5 Model 25 was planned, powered by a 2200-hp
Mitsubishi MK9A eighteen-cylinder air-cooled radial. However, the sole
prototype of the N1K5-J was destroyed prior to completion during a B-29
raid in June of 1945. Another high-altitude interceptor version of the
Shiden Kai was to be based on a Homare 44 engine equipped with a
three-speed mechanical supercharger. The end of the Pacific War brought
an end to all these projects.
Only 415 production
examples of the outstanding N1K2-J fighter were built, owing primarily
to construction snags and delays resulting from the continuous B-29
raids on the Japanese homeland in the last year of the war. With the
exception of Kawanishi's Naruo and Himeji plants, the other companies
involved in the production pool were late in getting started and
delivered only a token number of machines before the war ended. It is
fortunate for the Allies that this outstanding aircraft was not
available in greater quantity.
After the war in the
Pacific was over, several N1K2-J fighters were discovered intact at
Japanese airfields and were brought back to the United States for
study. Several of these are now on display in museums or are awaiting
restoration.
(Navy Interceptor
Fighter Shiden "Violet Lightning" - Kawanishi N1K2-J)
Allied Codename:
(Kawanishi N1K2-J) George - (N1K1 Kyofu) - Rex
Type: Single
Seat Land Based Fighter Interceptor
Powerplant: One
1,900 hp (1484 kw) Nakajima NK9H Homare 21 18-cylinder radial piston
engine.
Performance:
Maximum speed 370 mph (595 km/h) at 18,370 ft (5600 m); cruising speed
230 mph (370 km/h) at 9,845 ft (3000 m); service ceiling 35,300 ft
(10760 m).
Range: 1,451
miles (2335 km) with a single drop tank.
Weight: Empty
5,858 lbs (2657 kg) with a maximum take-off weight of 10,714 lbs (4860
kg).
Dimensions: Span
39 ft 4 1/2 in (12.00 m); length 30 ft 8 in (9.35 m); height 13 ft 0 in
(3.96 m); wing area 252.96 sq ft (23.50 sq m).
Armament: Four
wing mounted 20 mm Type 99 Model 2 cannon, plus two 551 lbs (250 kg)
bombs on underwing racks.
Variants: N1K1
Koyfu (naval floatplane), N1K1-J (land based prototype), N1K1-Ja
(revised armament), N1K1-Jb (modified wing with the intent to carry
cannon and rockets), N1K1-Jc (night fighter), N1K2-J (Navy Interceptor
Fighter Shiden KAI), N1K2-K (two seat trainer), N1K3-J (two
prototypes), N1K4-J (two prototypes), N1K4-A (carrier based), N1K5-J
(single prototype destroyed while under production).
Operators:
Japanese Navy.
