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Kawanishi N1K1 Kyofu (Rex)

Floatplane Fighter / Interceptor Aircraft

Imperial Japan | 1943

"The impressive Kawanishi N1K1 Kyofu fighting floatplane arrived to fulfill a wartime requirement that was no longer there."

Authored By: Staff Writer | Last Edited: 02/27/2020 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site; No A.I. was used in the generation of this content.
Early in World War 2 (1939-1945), Japanese authorities understood that their conquest of the Pacific would strain their carrier group's reach, limiting the effectiveness of fighters and bombers being launched from their decks. Expensive and complex airfield construction operations would also restrict forward-operating capability of the Empire and thus pressure fell to develop a system centered around use of floatplanes which did not require any fixed points on a map from which to operate from. The Empire of Japan became the only major player in the war to put an emphasis on dedicated "fighting floatplanes" (other powers simply relegated these types of aircraft for roles such as reconnaissance, gunnery spotting, and anti-ship warfare) as there was an understanding of their strategic limitations in the war going forwards.

Development on a dedicated fighting floatplane began in 1940 with the project hoping to capture an existing single-seat design with added floatplane capabilities that did not diminish fighter performance while retaining a suitable offensive punch. Kawanishi was eventually given the lead on the program while Nakajima was charged with developing a floatplane version of the famous Mitsubishi A6M "Zero" navy fighter to serve in the interim.

Kawanishi eventually returned with the N1K "Kyofu" which, unlike many floatplanes of the period, utilized a monoplane wing arrangement (as opposed to a biplane configuration). Its undercarriage showcased a large central float with smaller, retractable floats added under each wing. The fuselage was well-rounded and highly streamlined, tapering off at the empennage which fixed a single vertical tail fin and horizontal planes to either side. The single-seat cockpit was under a heavily framed canopy and offered generally decent vision about the aircraft - views naturally obstructed by the large main wing members and long nose. The engine was situated in the nose section and capped by two-bladed contra-propeller units, drive power coming from a Mitsubishi Kasei 14 radial engine of 1,460 horsepower output. Combat flaps were automatically adjustable in-flight based on the acceleration of the aircraft - a rather unique quality of this new aircraft. Armament was the same as on the A6M fighter, combining 2 x 20mm cannons with 2 x 7.7mm machine guns while a bomb load of up to 132 pounds (2 x 66 lb) could be held under the wings.

First flight of an N1K prototype was on May 6th, 1942 and testing unveiled generally poor results from the contra-propeller arrangement. As such, this feature was dropped in favor of a more conventional engine and gearbox driving a three-bladed propeller system. The move was also made to replace the engine from the Kasei 14 series radial to the Kasei 13 model of similar horsepower output. The retractable nature of the outboard, underwing floatplanes did not make it into the finalized form leaving these appendages fixed in place during flight. On the whole, however, IJN pilots evaluating the mount appreciated their new product - save for take-off characteristics which required additional attention at the controls. Once in the air, the fighting floatplane was a sound investment with excellent agility.

With the evaluation period over, the N1K was adopted as the N1K1 "Kyofu" and slated for introduction in 1943 as Japanese factories ramped up for the change. By this point in the war, the Japanese Navy was still betting their future on the success of its A6M Zero fighter to maintain air dominance in the theater and it appeared as if this was to be a reality until Allied tactics and warplanes caught up, and eventually surpassed, Japanese prowess in the skies. The changing face of war in 1943, coupled with a slow procurement scheme, meant that the N1K began arriving in useful numbers only after the Japanese had lost the initiative in the skies. As such, its intended role of forward-operating fighting floatplane was neutralized by the lack of forward-operating positions now having fallen to the Allied advance - essentially the N1K arrived to fulfill a battlefield role that was no longer there.

This led to production of N1K1 aircraft being ended rather quickly in March of 1944 with fewer than 100 having been delivered. While participating in some of the latter actions of the Pacific War, the series ended up as part of the homeland defense of Japan against mounting Allied bomber raids. At one point, the N1K1 was to see a successor with a larger engine built - this set to become the N1K2. However, only the designation was reserved and nothing came from this work. Earlier on, while development on the N1K floatplane was still ongoing, Kawanishi also managed to sell to Japanese authorities a version of its aircraft to serve as a land-based fighter - made faster and more streamlined by its lack of fixed float equipment. This became the N1K2-J "Shiden" ("George") fighter line which proved a worthy opponent to the vaunted American line-up of Grumman, Vought, and North American fighters in the Pacific skies. This aircraft went on to have a decidedly more impressive combat history despite being limited in available numbers.

The N1K1 was codenamed "Rex" by the Allies.

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Power & Performance
Those special qualities that separate one aircraft design from another. Performance specifications presented assume optimal operating conditions for the Kawanishi N1K1 Kyofu (Rex) Floatplane Fighter / Interceptor Aircraft.
1 x Mitsubishi MK4C Kasei 13 radial piston engine developing 1,460 horsepower and driving a three-bladed propeller unit at the nose.
304 mph
490 kph | 265 kts
Max Speed
34,777 ft
10,600 m | 7 miles
Service Ceiling
652 miles
1,050 km | 567 nm
Operational Range
2,980 ft/min
908 m/min
City-to-City Ranges
Operational range when compared to distances between major cities (in KM).
The nose-to-tail, wingtip-to-wingtip physical qualities of the Kawanishi N1K1 Kyofu (Rex) Floatplane Fighter / Interceptor Aircraft.
34.8 ft
10.60 m
O/A Length
39.4 ft
(12.00 m)
O/A Width
15.6 ft
(4.75 m)
O/A Height
6,063 lb
(2,750 kg)
Empty Weight
8,190 lb
(3,715 kg)
Design Balance
The three qualities reflected below are altitude, speed, and range. The more full the box, the more balanced the design.
Available supported armament and special-mission equipment featured in the design of the Kawanishi N1K1 Kyofu (Rex) Floatplane Fighter / Interceptor Aircraft .
2 x 20mm Type 99-1 cannons in wings.
2 x 7.7mm Type 97 machine guns in engine cowling.

2 x 66 lb conventional drop bombs held underwing.
Notable series variants as part of the Kawanishi N1K1 Kyofu (Rex) family line.
N1K "Kyofu" - Base Series Name
N1K1 - Initial production model of 1943; 89 examples completed.
N1K2 - Proposed variant with larger engine; not produced.
Global customers who have evaluated and/or operated the Kawanishi N1K1 Kyofu (Rex). Nations are displayed by flag, each linked to their respective national aircraft listing.

Total Production: 89 Units

Contractor(s): Kawanishi - Imperial Japan
National flag of modern Japan

[ Imperial Japan ]
Relative Max Speed
Hi: 400mph
Lo: 200mph
Aircraft Max Listed Speed (304mph).

Graph Average of 300 MPH.
Era Crossover
Pie graph section
Showcasing Aircraft Era Crossover (if any)
Max Alt Visualization
Small airplane graphic
Production Comparison
Entry compared against Ilyushin IL-2 (military) and Cessna 172 (civilian) total production.
MACH Regime (Sonic)
RANGES (MPH) Subsonic: <614mph | Transonic: 614-921 | Supersonic: 921-3836 | Hypersonic: 3836-7673 | Hi-Hypersonic: 7673-19180 | Reentry: >19030
Aviation Timeline
1 / 1
Image of the Kawanishi N1K1 Kyofu (Rex)
Image from the Public Domain.

Mission Roles
Some designs are single-minded in their approach while others offer a more versatile solution to airborne requirements.
Some designs stand the test of time while others are doomed to never advance beyond the drawing board; let history be their judge.
Going Further...
The Kawanishi N1K1 Kyofu (Rex) Floatplane Fighter / Interceptor Aircraft appears in the following collections:
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