The Nakajima Ki-43 was the most produced aircraft of the Japanese Imperial Army Air Force. It´s first flight was in 1939, and production began at the beginning of the year 1941.
The allied codename was "Oscar".
The criteria for development of the Ki-43 were:
- It should be as manoeuvreable as the Ki-27
- Maximum speed of 500 km/h
- It must climb to a ceiling of 5000 m in 5 minutes
- A range of 800 km
- Its armament should be composed of two 7.7 mm machine guns
To develop an aircraft with those specification was no problem for Nakajima Hikōki. The needed manoeuvreability could be only fullfilled with the use of special flaps, which are pushed backwards from the cross section area. Those flaps were also used in later Nakajima aircraft.
After Japan entered World War II, they were able use their Ki-43 successful against enemies, the main reason for that was that Japan had many experienced pilots (for excampel over China). But the American Volunteer group (Flying Tigers), which were fighting for the Republic of China used the superior flight performance of the Curtiss P-40 successful against the more manoeuvreable Ki-43.
Because of many similarities with the Mitsubishi A6M Zero, the Americans didn´t notice that the Ki-43 was a different aircraft. Both, the USAAF pilots and the RAF pilots reported the Ki-43 to be a Zero, which was dreaded since the attack on Pear Harbour.
Despite upgrades with more powerful engines, heavier machine guns, self-healing fuel tanks and armor to protect the pilot, the Ki-43 was outdated quickly, because flight performance became more important than manoeuvreability, while the Ki-43 was only designed to be manoeuvreable.
The replacement for the Ki-43, in that flight performance had priority, was the Nakajima Ki-44 Shoki, however it was unsuccessful and unable to replace the Ki-43. Even with the appearance of the much more advanced Nakajima Ki-84 Hayate, production of the Ki-43 was still continued. The reason for that was that the Ki-43 needed unlike the Ki-44 and Ki-84 high performance engines, which were not advanced enough in Japan.
Like most of the Japanese fighters, the Ki-43 was used at the end of the War for Kamikaze missions.