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Ki-84s and Ki-43s photographed on a former JAAF base in Korea post-war. The Ki-84 in the foreground is from the 85th Hiko-Sentai, the next one in line belonged to the 22nd Hiko-Sentai HQ Chutai.

The Captured Nakajima Ki-84 models fitted with engines exceeding 1800 horsepower could surpass the top speeds of the P-47D Thunderbolt and the P-51D Mustang at 6,000 m.

The Nakajima Ki-84 "Hayate" (キ84 疾風"Gale"?) was a single-seat fighter used by the Imperial Japanese Army Air Force in World War II. The Allied reporting name was "Frank"; the Japanese Army designation was Army Type 4 Fighter (四式戦闘機 yon-shiki-sentō-ki?). Featuring excellent performance and high maneuverability, the Ki-84 was considered to be the best Japanese fighter to see large scale operations during World War II.[1] It was able to match any Allied fighter, and to intercept the high-flying B-29 Superfortresses.[2] Its powerful armament (that could include two 30 mm and two 20 mm cannon) increased its lethality.[3] Though hampered by poor production quality in later models, a high-maintenance engine, a landing gear prone to buckle,[2] and lack of experienced pilots above all else, Hayates proved to be fearsome opponents; a total of 3,514 were built.[1]

Design and development

Design of the Ki-84 commenced in early 1942 to meet an Imperial Japanese Army Air Service requirement for a replacement to Nakajima's own, earlier Ki-43 Oscar fighter, then just entering service. The specification recognized the need to combine the maneuverability of the Ki-43 with performance to match the best western fighters and heavy firepower.[4] The Ki-84 first flew in March 1943.[5] Although the design itself was solid, the shortage of fuel and construction materials, poor production quality, and lack of skilled pilots prevented the fighter from reaching its potential.

The Ki-84 addressed the most common complaints about the popular and highly maneuverable Ki-43: insufficient firepower, poor defensive armor, and lack of climbing power. The Ki-84 was a cantilever low-wing monoplane of all-metal construction, except for the fabric-covered control surfaces. It had retractable tailwheel landing gear.[6] Armament comprised two fuselage-mounted, synchronized 12.7 mm (.50 in) machine guns and two wing-mounted 20 mm cannon, a considerable improvement over the two 12.7 mm (.50 in) machine guns used in the Hayabusa. Defensive armor offered Hayate pilots better protection than the unsealed wing tanks and light-alloy airframe of the Ki-43. In addition, the Ki-84 used a 65 mm (2.56 in) armor-glass canopy, 13 mm (.51 in) of head and back armor, and multiple bulkheads in the fuselage, which protected both the methanol-water tank (used to increase the effectiveness of the supercharger) and the centrally located fuel tank.

It was the Nakajima Ha-45 radial powerplant that gave the Hayate its high speed and prowess in combat. Derived from the Homare engine common to many Japanese aircraft, the Hayate used a direct-injection version of the engine, using water injection to aid the supercharger in giving the Ki-84 a rated 1,491 kW (2,000 hp) at takeoff. This combination theoretically gave it a climb rate and top speed roughly competitive with the top Allied fighters. Initial Hayate testing at Tachikawa in early summer 1943 saw test pilot Lieutenant Funabashi reach a maximum level airspeed of 624 km/h (387 mph) in the second prototype. After the war, a late-production, captured example was tested in the US with high octane fuel, and achieved a speed of 687 km/h (426 mph). The complicated direct-injection engine required a great deal of care in construction and maintenance and, as the Allies advanced toward the Japanese homeland, it became increasingly difficult to support the type's designed performance. Compounding reliability problems were the Allied submarine blockade which prevented delivery of crucial components, such as the landing gear. Many further landing gear units were compromised by the poor-quality heat treatment of late-war Japanese steel. Many Hayates consequently suffered strut collapses on landing. Further damage was caused by inadequately trained late war pilots.

Operational service

The first major operational involvement was during the battle of Leyte at the end of 1944, and from that moment until the end of the Pacific war the Ki-84 was deployed wherever the action was intense.[6] The 22nd Sentai re-equipped with production Hayates. Though it lacked sufficient high-altitude performance, it performed well at medium and low levels. Seeing action against the USAAF 14th Air Force, it quickly gained a reputation as a fighter to be reckoned with. Fighter-bomber models also entered service. On April 15, 1945, 11 Hayates attacked US airfields on Okinawa, destroying many aircraft on the ground.

The IJAAF's Ki-84, Kawasaki Heavy Industries' Ki-100, and the Kawanishi Aircraft Company's N1K2-J IJNAF naval fighter were the three Japanese fighters best suited to combat the newer Allied fighters.

Camouflage and markings

The Ki-84 is known to have appeared in three Japanese Ministry of Munitions sanctioned camouflage schemes;

Type N: The entire airframe was left in its original natural metal. Because of the different grades of alloy used for various panels, the overall finish soon weathered or oxidized to a pale metallic grey, with variations in shade and texture, depending on the grade of duralumin used for each area of skin. A black "anti-glare" panel was painted on the top forward fuselage and engine cowling (see photo of 73 Hiko-Sentai aircraft).[7]

Type B: Irregular blotches or stripes of dark green on the basic natural metal scheme. This was applied once the aircraft reached its operational base. On occasion the edges of national (hinomaru) and Sentai markings were accidentally covered.[7]

Type S: Three variations were seen on Ki-84s; S1 – Dark green upper surfaces, with light gray/green lower surfaces. S2 – The light gray/green on the lower surfaces was replaced by a pale blue/gray. These colors were often applied on an unprimed airframe; because of this and the poor adhesion of Japanese paints in the later years of the war this scheme often weathered quickly, with large patches of natural metal being visible (see photo of 85 Hiko-Sentai Ki-84 on a Korean base). S10 – The upper surfaces were left in a red/brown primer with the under surfaces in natural metal. The black anti-glare panel was optional.[7]

Other schemes were applied, particularly by the Shinbu-Tai "Special Attack" units. For example, a Ki-84 of 57 Shinbu-Tai, flown by Corporal Takano, had very dark brown-green upper surfaces (some sources state black), with a large red "arrow" outlined in white painted along the entire length of the fuselage and engine cowling. White Kana characters "hitt-chin" (be sure to sink) were painted above the arrow on the rear fuselage. The under surfaces were light gray.[8]

Factory applied markings included six hinomaru (national insignia), outlined with a 75 mm (2.95 in) white border on camouflaged aircraft, on either side of the rear fuselage and on the upper and lower outer wings. Yellow/orange identification strips were applied to the leading edges of wings, extending from the roots to ⅓ of the wingspan.[7]

It was a general rule that Japanese planes in overseas territories had a narrow white line called the "border break through line" or "field identification mark" surrounding their hinomaru; planes belonging to interception forces in Japan proper placed the insignia inside a white square (colloquially known as the "Homeland Defense bandage"), so that anti-aircraft defense units could more easily distinguish them from enemy planes.

The inside of the fuselage and the wheel cover wells were painted in a dark opaque bluish gray, and the propeller spinner was painted with a variety of colors based on the unit it belonged to.


Evaluation model.
Pre-production model.
Ki-84-Ia Hayate
Fighter Type 4 of Army. Armed with 2 × 12.7 mm Ho-103 machine guns and 2 × 20mm Ho-5 cannon in wings (most widely produced version).
Version armed with 4 × 20 mm Ho-5 cannon. (very limited production run. May never have equipped a full Sentai)
Version against Bombers, with 2 × 20 mm Ho-5 cannon and 2 × 30 mm (1.18 in) Ho-155 cannon in wings.
Ki-84-Ia (Manshu Type)
Manufactured in Manchukuo for Mansyu by Nakajima License.
Similar to models mentioned above (Ki-84-Ia, -Ib, -Ic).
Ki-84 N/P/R
High altitude versions.
Prototype airframes constructed entirely out of wood. 10 examples were produced of this type.
Prototype similar at Ki-84-Ib in steel.
Evaluation model, equipped with Mitsubishi 62 (Ha-33), 1,120 kW (1,500 hp).
Redesigning of Ki-84 N.





 People's Republic of China
 Republic of China (1912–1949)
  • Indonesian Air Force - In 1945, Indonesian People's Security Force (IPSF) (Indonesian pro-independence guerrillas) captured a small number of aircraft at numerous Japanese air bases, including Bugis Air Base in Malang (repatriated 18 September 1945). Most aircraft were destroyed in military conflicts between the Netherlands and the newly proclaimed Republic of Indonesia during the Indonesian National Revolution of 1945–1949.


After the war a number of aircraft were tested by the allied forces, two at the Allied Technical Air Intelligence Unit - South-West Pacific Area (ATAIU-SWPA) as S10 and S17 and a further two in the United States as FE-301 and FE-302 (Later T2-301 and T2-302).

One aircraft was operated and flown by the Planes of Fame Museum in Chino, California, before being returned to Japan for display at the Arashiyama Museum in Kyoto.[10] This aircraft is now exhibited at the Tokko Heiwa Kinen-kan Museum at Chiran, Japan.[11][12] It is the only surviving Ki-84.

Japanese aircraft of the Pacific war[13]

Nakajima Ki-84.svg

General characteristics

  • Crew: One
  • Length: 9.92 m (32 ft 7 in)
  • Wingspan: 11.238 m (36 ft 11 in)
  • Height: 3.385 m (11 ft 1 in)
  • Wing area: 21 m² (226.041 ft²)
  • Empty weight: 2,660 kg (5,864 lb)
  • Loaded weight: 3,613 kg (7,955 lb)
  • Max. takeoff weight: 3,890 kg (8,576 lb)
  • Powerplant: 1 × Nakajima Ha-45-21 Homare 18-cylinder radial engine, 1,485 kW (1,990 hp)


  • Never exceed speed: 800 km/h (496 mph)
  • Maximum speed: 631 km/h (392 mph) at 6,120 m (20,080 ft)
  • Range: 2,168 km (1,347 mi)
  • Service ceiling: 10,500 m (34,450 ft)
  • Rate of climb: 14.12 m/s (2,780.51 ft/min)
  • Wing loading: 172 kg/m² (35.1 lb/ft²)
  • Power/mass: 1.8 kg/hp (4 lb/hp)


  • 2× 12.7 mm Ho-103 machine guns in nose, 350 rounds/gun
  • 2× 20 mm Ho-5 cannon in wings, 150 shells/cannon
  • 2× 100 kg (220 lb) bombs
  • 2× 250 kg (551 lb) bombs
  • 2× 200 L (53 US gal) drop tanks
  • See also

    * Nakajima Ki-43 


    1. 1.0 1.1 Glancey 2006, p. 174.
    2. 2.0 2.1 Ethell 1995, p. 102.
    3. Ethell 1995, p. 103.
    4. Air International Volume 10 No. 1, pp. 22–29, 43–46.
    5. Green 1961, p. 79.
    6. 6.0 6.1 Mondey 1996, p. 230.
    7. 7.0 7.1 7.2 7.3 Fearis 1996, p. 44.
    8. Caruana 2004, pp. 950–951.
    9. Bueschel 1971, p. 52.
    10. Wieliczko 2005, pp. 64–65.
    12. Wieliczko 2005, p. 75.
    13. Francillon 1970, p.237.
    • Aeronautical Staff of Aero Publishers Inc. Nakajima KI-84 (Aero Series 2). Fallbrook, CA: Aero Publishers, Inc., 1965. ISBN 0-8168-0504-0.
    • Bueschel, Richard M. Nakajima Ki.84a/b Hayate in Japanese Army Air Force Service. Reading, Berkshire, UK: Osprey Publishing Ltd., 1971. ISBN 0-85045-044-6.
    • Caruana, Richard J. "The Nakajima Ki-84 Hayate" Article and scale drawings. Scale Aviation Modeller International. Volume 10 Issue 10 October 2004. Bedford, UK.
    • Ethell, L. Jeffrey. Aircraft of World War II. Glasgow, HarperCollins Publishers, 1995. ISBN 0-00-470849-0.
    • Francillon, Ph.D., René J. The Nakajima Hayate (Aircraft in Profile number 70). Leatherhead, Surrey, UK: Profile Publications Ltd., 1966.
    • Francillon, Ph.D., René J. Japanese Aircraft of the Pacific War. London: Putnam & Company, 1970 (2nd edition 1979). ISBN 0-370-30251-6.
    • Fearis, P. "The Emperor's Wings; The Nakajima Ki-84 Hayate." Article and scale drawings. Scale Aviation Modeller. Volume 2 Issue 1 January 1996. Bedford, UK.
    • Glancey, Jonathan. Spitfire: The Biography. London: Atlantic Books, 2006. ISBN 978-1-84354-528-6.
    • Green, William. War Planes of the Second World War, Volume Three: Fighters. London: Macdonald & Co. (Publishers) Ltd., 1961 (seventh impression 1973). ISBN 0-356-01447-9.
    • Green, William and Swanborough, Gordon. WW2 Aircraft Fact Files: Japanese Army Fighters, Part 2. London: Macdonald and Jane's Publishers Ltd., 1977. ISBN 0-354-01068-9.
    • Mondey, David. The Concise Guide to Axis Aircraft of World War II. New York: Bounty Books, 1996. ISBN 1-85152-966-7.
    • Sakaida, Henry. Japanese Army Air Force Aces 1937–45. Botley, Oxford, UK: Osprey Publishing, 1997. ISBN 1-85532-529-2.
    • Sims, Edward H. Fighter Tactics and strategy 1914–1970. Fallbroock (Ca), Aero publisher Inc. 1980. ISBN 0-8168-8795-0.
    • Thorpe, Donald W. Japanese Army Air Force Camouflage and markings World War II. Fallbrook, CA: Aero Publishers, Inc., 1968. ISBN 0-8168-6579-5.
    • Wieliczko, Leszek A. Nakajima Ki-84 Hayate. Lublin, Poland: Kagero, 2005. ISBN 83-89088-76-2. (Bilingual Polish/English)
    • Unknown Author Review in "AIRVIEW".
    • Unknown Author "The High Wind From Ota". Air International. Volume 10 No. 1
    • Various Authors. Yon-Shiki Sentoki Hayate (Pacific War No.46). Tokyo, Japan: Gakken, 2004. ISBN 4-05-603574-1.

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