A plane which since July 1932 the Nakajima Aircraft Mfg. Company had designed and manufactured for trial under the name of KI-84 was officially adopted in April 1944 by the Army as the Fighter Type 4 "Hayate" and the mass production was started. The number of the Hayate produced by the end of World War II totaled about 3,500 which ranks next to that of the Zero and the Hayabusa but is the largest in the Japanese aircraft history in view of the number produced in about a year. The performance of the Hayate was equal to, or higher than that of the Allies' fighters of those days. This was the first fighter worthy of the name having excellent speed (climbing ability), firepower and maneuverability that became available to the Army. Those days when Japan feared she might lose the command of the air even over Japan proper, the Hayate called "the Decisive fighter to turn the fate of the Greater East Asia" was accepted by fighter units with hopes as a new fighter to beat enemy combat planes. It made its first campaign over Central China as a member of the 22nd Air Flotilla.
As the main-strength fighter of the Japanese Army, it later showed activity against overwhelming American planes in the Battle of Leyte in the Philippines and the Battle of Okinawa. Many were used as bomb-laden suicide attack planes to smash bodily into the enemy. The Hayate also bravely intercepted B29 bombers and ship-planes of US task forces invading Japan proper. The Allies' pilots had an extreme horror of the Japanese fighter and called it " Frank". The Hayate had a maximum speed of 624 km/h, which was higher than that of any other fighter in Japan. The high speed was much due to the excellent performance of the Nakajima's HA - 45 engine employed. The engine had take-off output of 2,000 hp and was 1,180 mm in maximum diameter, i.e. output per unit front area was 1,83 hp/sq cm, which was remarkably high for an air-cooled engine. Thus the engine was ideal for a fighter that was expected to fly faster. (A large number of the HA-45 engines were also mounted on the Navy's famous high-speed reconnaissance planes such as the Sain and the Shidenkai under towards of Homare engine.) Many of the engines produced towards the end of the war, however, did not whow such high performance as originally designed because of the shortage of materials and lowered working technique.
Consequently, the Hayate's working ratio and flying performance were extremely lowered, and the fighter could not display its ability in full. The bad condition of the engines also resulted from the fact that the octane rating of fuel was lowered towards the end of the war. When the Hayate using fuel of 140 octane rating and high-quality ignition plugs was tested in the United States after the war, it made a record of a maximum speed of 689 km/h, and was praised as "the best one of all Japanese fighters appeared in the Pacific War.
Nakajima KI.84-IA Frank
Plastic model kit.