Aviation of World War II
A conventional low-wing cantilever monoplane, the Ki.84 had a flush-riveted semi-monocoque light alloy fuselage structure of oval section and a single-spar wing with light alloy stressed skinning. The structural design followed the common Japanese practice of building the wing integral with the centre fuselage in order to save the weight of heavy attachment points, hut the Ki.84 was very much sturdier than any of its predecessors. Of particular interest was the heavy mainspar built up of half-inch extruded AI angles into an I-beam design. The wing carried metal-framed fabric-covered ailerons and hidraulically-operated Fowler-type flaps with a maximum deflection of 35 deg. The fuselage centre section embodied two firewals between which was mounted a 35 Imp gal (160 l) water-methanol tank, and 162 Imp gal (737 l) of fuel was distributed between the main tank aft of the cockpit, a pair of wing tanks in board of the main undercarriage members and two outboard wing leading edge tanks. The windscreen incorporated 65-mm armourglass, the pilot was provided with 13-mm head and back armour, and the paired synchronized Ho-103 machine guns m the forward fuselage had 350 rpg while the two wing-mounted Ho-5 cannon each had 150 rounds. From the outset provision was made for underwing racks capable of lifting two bombs of up to 551 lb (250 kg) weight or 44 Imp gal (200 l) drop tanks. The initial Army version of the Homare installed in the prototypes, the Ha-45-11. offered a take-off rating of 1.800 hp at sea level and drove an electrically-operated four-blade constant-speed Pe-32 propeller.
A batch of no fewer than 83 service trials aircraft was initiated in the early summer of 1943. immediately upon confirmation by Army test pilots at the Tachikawa Air Arsenal of the Nakajima test pilot's enthusiastic report on the capabilities of the Ki.84. the first of these pre-production lighters following closely on the heels of the second Ki.84 prototype from the Ota plani in August 1943. Allhough in some respects performance fell short of that requested by the specification, the capabilities of Nakajima's new warplane were undoubtedly impressive, and one of the Army lest pilots at Tachikawa. Li Funabashi, attained a maximum level speed of 394 mph (634 km h) at 21.800 ft (6.645 m) in me second pre-production example which embodied the various minor modifications resulting from the prototype test programme. During diving trials, the aircraft attained a speed of 496 mph (798 km h). at which point the test pilot experienced difficulty with his oxygen supply, necessitating termination of the test.
The pre-production aircraft were largely hand-built, despite the quantity involved, and differed one from another in minor details, these including various detail changes to the vertical tail surfaces, the application of different types of ejector exhausts and the provision of a centreline rack for a drop tank. Individual aircraft were tested with longer-span wings and at least two of the pre-production examples were evaluated with retractable skis in Hokkaido during the winter of 1943-44, A total of 24 pre-production fighters had left the Ota line by the end of 1943, a service trials Chutai being formed with a number of these in October of that year, but the primary factor governing deliveries was at this time, availability of Ha-45 engine.
Ki-84. Combat Use.
The first battle of Hayate took place in the skies of China at the end of March 1944. By this time, a special squadron equipped with Ki-84 joined the 22nd Aviation Regiment under the command of Major Iwahashi. This unit was transferred to Hankow, and its Ki-44 and Ki-84 aircraft took part in supporting the next offensive of the Japanese troops. In the first air battle, which broke out on March 28, the Japanese were opposed by P-40N fighters from the 23rd mixed US-Chinese air group. In the aforementioned battle, Major Iwahashi won one victory. In total, the 22nd regiment fought in China for five weeks, and during this period the pilots were able to appreciate the fighting qualities of the Ki-84. In May, the personnel of the regiment, along with aircraft equipment, departed for the Philippines, where a major Allied offensive was expected.
For the first time, Ki-84 aircraft participated en masse in battles during the battle for the Philippines, which began on October 20, 1944. In total, 11 regiments opposed the allies in this region (1.11, 22, 29, 50, 51, 52, 71, 72 , 73 and 200th), armed with Hayate fighters. Although the pilots of these air units fiercely resisted in the air, they could not significantly change the situation in the face of a large numerical superiority of the enemy. In addition, the operation of the Ki-84 was complicated by many problems. Aircraft engines did not produce the necessary power and often failed due to a pressure drop in the unfinished fuel system. The hydraulics were also junk, and during landing, landing gear made of low-grade steel sometimes broke. In addition, "Hayate" began to be used as dive bombers, as a result of which they suffered significant losses from anti-aircraft fire. By the time the Philippines surrendered, the regiments equipped with the Ki-84 were badly battered and practically lost their combat effectiveness, having lost most of their aircraft in battles and accidents. For example, in the elite 200th regiment, formed from veteran pilots from different units, after a month of hostilities, only nine serviceable fighters remained in service. Nevertheless, noting the successes of the Japanese pilots who fought over the Philippines on the Hayat, it is worth mentioning Satoshi Anabuki (6 victories, 51 in total) and Katsuaki Kira (5 victories, 21 in total).
In the last months of the war, the Japanese experienced difficulties with the supply of fuel and spare parts, as a result of which many Hayates were chained to the ground. Nevertheless, other fighters of this type performed well in combat, and some pilots achieved significant success on the Ki-84.
Although the Ki-84 fighters could not completely replace the Hayabuses, which were widely used in the Army Air Forces, they were nevertheless used on many fronts, including in Manchuria and China. They played a prominent role during the battle for Okinawa, when they carried out daylight raids on American airfields. In air battles, the Hayate lagged behind the Mustangs and Thunderbolts in a dive and was slightly inferior to them in horizontal speed, but it outperformed enemy fighters in maneuverability and rate of climb.
In August 1945, several Ki-84 aircraft became trophies of the Red Army, but they did not arouse the interest of Soviet aviation specialists. By that time, jet aircraft were already in the spotlight.