Nakajima Ki-84

Ki-84
Ki-84 Hayate (Frank) preserved in California in 1970. As of 2014, this aircraft is displayed at a war memorial in Japan.
Role Fighter
Manufacturer Nakajima Aircraft Company
First flight March 1943
Retired 1945 (Japan)
Primary user Imperial Japanese Army Air Service
Number built 3,514 [1]
Variants Nakajima Ki-116
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 1,800 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 Service 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.[2] It was able to match any Allied fighter, and to intercept the high-flying B-29 Superfortresses.[3] Its powerful armament (that could include two 30 mm and two 20 mm cannon) increased its lethality.[4] Though hampered by poor production quality in later models, a high-maintenance Nakajima Homare engine, landing gear prone to buckle,[3] inconsistent fuel quality, and a lack of experienced pilots above all else, Hayates proved to be fearsome opponents; a total of 3,514 were built.[2] The Ki-84 was the fastest fighter in the Imperial Japanese military if good fuel was used and the aircraft was in good shape.

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.[5] The Ki-84 first flew in March 1943 [6] and deliveries from Nakajima's Ota factory commenced in April 1943.[7] 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 speed. 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.[8] Armament comprised two fuselage-mounted, synchronized 12.7 mm (.50 in) machine guns — a potentially difficult challenge to synchronize properly, due to the Hayate's four-blade propeller — 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 firm's own-designed 35.8 litre displacement, Ha-45 Homare ("Praise or Honor") air-cooled eighteen-cylinder radial engine, first accepted for military use in 1941, that gave the Hayate its high speed and prowess in combat. Derived from the Nakajima Homare engines common to many Japanese aircraft, the Hayate used the 'omare 21 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 captured late-production example was tested in the US and achieved a speed of 680 km/h (422 mph)[9] using 92 octane AvGas, plus methanol injection.[10]

The complicated direct-injection engine, partly from its already basically compact design (no more than 3 cm/1¼ inches larger in diameter than the Ki-43's 14-cylinder Nakajima Sakae radial) 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, who sometimes found it difficult to transition to the relatively "hot" Ki-84 from the comparatively docile Ki-43 Hayabusa, which had a significantly lower landing speed.

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.[8] 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).[11]

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.[11]

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.[11]

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.[12]

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.[11]

Variants

Production

Ki-84 Production: Ota and Utsunomiya, Nakajima Hikoki K.K. [13]
Year
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Annual
1943 1 1 3 11 8 24
1944 9 25 25 97 86 138 145 121 261 301 323 373 1,904
1945 357 129 216 185 198 168 194 48 1,485
Total 3,413

Not included:

Total Production:
According to USSBS Report: 3,413 [13] Figure includes: 3,413 Ki 84-I and Ki-84 II builds.
According to Francillon: 3,514 [1] Figure includes: 3,509 Ki 84-I and Ki-84 II builds, with 1 Ki-106, 1 Ki-113, 3 Ki-106 prototypes.

Operators

Wartime

 Japan

Post-war

 People's Republic of China
 China
 Indonesia

Survivors

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 which was captured at Clark Field during 1945, was transported aboard the USS Long Island (CVE-1) carrier to the United States. In 1952 it was sold off as surplus to Edward Maloney, owner of the Ontario Air Museum (Planes of Fame Museum) and restored to flying condition before being returned to Japan for display at the Arashiyama Museum in Kyoto. The aircraft is now displayed at Tokko Heiwa Kinen-kan Museum, Kagoshima Prefecture. It is the only surviving Ki-84.[9][15]

Specifications

Data from Report on Frank 1 [10]

General characteristics

Performance

Armament

See also

Related development
Aircraft of comparable role, configuration and era
Related lists

References

Notes
    1. 1 2 3 4 Francillon, 1979, p. 238
    2. 1 2 Glancey 2006, p. 174.
    3. 1 2 Ethell 1995, p. 102.
    4. ↑ Ethell 1995, p. 103.
    5. ↑ Air International & Volume 10 No. 1, pp. 22–29, 43–46.
    6. ↑ Green 1961, p. 79.
    7. ↑ USSBS, 1947, p.78
    8. 1 2 Mondey 1996, p. 230.
    9. 1 2 Chiran Peace Museum, Hayate Exhibition Room
    10. 1 2 Archives of M. Williams, TAIC 156A-1, Report on Frank 1
    11. 1 2 3 4 Fearis 1996, p. 44.
    12. ↑ Caruana 2004, pp. 950–951.
    13. 1 2 USSBS, Appendix M., p. 40–42
    14. ↑ Bueschel 1971, p. 52.
    15. ↑ Pacific Wrecks, JAAF Unknown Sentai, Ki-84-I Ko
    Bibliography
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