Nakajima Ki-27

The Nakajima Ki-27 (Allied codename Nate) was the main fighter aircraft used by the Japanese Imperial Army up until 1940, and the Army's first monoplane. The Army designation was Type 97 Fighter (九七式戦闘機).

Development

In 1935, the Japanese Army held a competition between Nakajima, Mitsubishi, and Kawasaki to design a low-wing monoplane to replace the Kawasaki Ki-10 (Type 95 Fighter) biplane. The results were Nakajima Ki-27, Kawasaki Ki-28, and Mitsubishi Ki-33 (a modification of the Mitsubishi A5M carrier-based fighter). Nakajima design was based on its earlier Ki-11 monoplane fighter which lost to Ki-10 in the Type 95 Fighter competition. Since the follow-up Nakajima Ki-12 proposal with a liquid-cooled engine and retractable landing gear was deemed too complex by the Japanese officials, Ki-27 was designed by Koyama Yasushi to have air-cooled radial engine and fixed landing gear. The aircraft had the Nakajima trademark wing with a straight leading edge and tapered trailing edge which would reappear again on K-43, Ki-44, and Ki-84. Ki-27 made its first flight on October 15, 1936. Although it had slower top speed and worse climb performance that its competitors, the army chose the Nakajima design for its outstanding turning ability granted by its remarkably low wing loading and officially accepted it into service in 1937. In addition to Nakajima, Ki-27 was also manufactured by Tachikawa Hikoki and Manshu, with a total of 3,368 built.

Operational history

The Ki-27 was the army's main fighter until the start of World War II. In the 1939 Battle of Khalkhin Gol against USSR in Mongolia, Ki-27 faced I-15 biplanes and I-16 monoplanes and suffered from lack of armor protection for the pilot and absence of self-sealing or fire suppression in the fuel tanks. In addition, the airframe could not handle the stress of high speeds and Soviet pilots routinely escaped Ki-27 attacks in a dive. In addition, the armament of two rifle-caliber machine guns was weak. That is why, in spite of Ki-27 excellent turning performance, the Japanese claim of 1,252 downed enemy aircraft (6 times of official Soviet number) is unrealistic.([1][2]).

The Ki-27's high turn performance caused the Army to focus almost exclusively on maneuverability, a decision which came back to haunt them later as it handicapped the development of more heavily armed and faster fighters. The Ki-27 served until the beginning of World War II in the Pacific, escorting bombers attacking Singapore. After it was replaced by the Ki-43, Ki-27 continuing to serve as a trainer. It was also exported for use with Manchukuo and Thai armed forces, seeing combat with both. In Thai service, the Ki-27 reportedly damaged a P-51 Mustang and shot down one P-38 Lightning. Near the end of World War II, a few Ki-27 were equipped with up to 500 kg (1,100 lb) of explosives for Kamikaze duty.

Variants

Ki-27a - first production version
Ki-27b - improved canopy and oil cooler, provision for 4x 25 kg (55 lb) bombs or fuel tanks under the wings
Ki-27 Kai - lightened version developed as an interim solution when Ki-43 development was delayed, top speed 475 km/h (295 mph), 2 aircraft built