The Nakajima Ki-4 Army Type 94 Reconnaissance Aircraft was a multi-purpose Army support biplane that was the first aircraft to be designed by a private firm but with direct Army involvement in the design process.
The Ki-4 was developed to replace the Mitsubishi Army Type 92 Reconnaissance parasol aircraft. The army wanted a light-weight aircraft with the manoeuvrability of a fighter but that could still perform ground-attack missions as well as more traditional reconnaissance roles.
The design team was led by Shigejiro Ohwada, while the army was represented by an army engineer, Nario Ando. They produced a sesquiplane with elliptical wings, an all-metal monocoque (as used on the Nakajima Type 91 Fighter) and a radial engine. The wings had a mixed wood and metal structure and were fabric-covered. The prototypes had wheel fairings, a divided landing gear and tandem open cockpits for the pilot and observer.
Three prototypes were built, the first in March 1934 and the last in May. The Army supplied its own test pilots who worked with the Nakajima team. As a result of these tests the fuselage was lengthened in an attempt to improve both stability and manoeuvrability, and after these modifications were made the aircraft was accepted as the Army Type 94 Reconnaissance Aircraft (Ki-4).
The first production aircraft were given the designation Type 94-Ko. The wheel fairings were removed, although they could be used if required. Bomb racks could be installed under the wings. One of the early aircraft was used to test a float-plane adaptation of the aircraft, with a single main float and smaller wingtip floats. The -Ko entered service in 1935.
The Type 94-Otsu was the second production version. It had an engine exhaust collector ring (the -Ko had individual exhaust stacks for each cylinder). The bomb racks were installed on all aircraft but the wheel fairings were removed. The -Otsu entered service in 1937
One Otsu was used to test out a twin-float floatplane. Another was given compressed air powered flotation bags for use if the aircraft had to ditch. Neither of these modifications was adopted for production.
Type 94-T Multi-purpose Aircraft
This was a civil conversion that turned the Type 94 into a three-seater, with two in the observer's position. It was intended for use on geographical surveys.
A total of 516 Ki-4s were built between March 1934 and February 1939. Nakajima built 333, mainly of the -Ko type. Tachikawa built 57 and Manshu built 126, and these accounted for most of the -Otsu types.
The Type 94 Reconnaissance Aircraft was used for a wide range of missions during the first half of the Sino-Japanese War. Their original role was reconnaissance, both long range and over the battlefield, but they were also used as light bombers and to pick up and drop message containers. As a result losses were fairly heavy.
The Ki-4 was the last general purpose biplane reconnaissance aircraft to be used by the Japanese Army. After it came a series of more specialised monoplane aircraft, splitting the close air support role from tactical observation and long range photographic reconnaissance aircraft.
Engine: Ha-8 radial engine
Span: 39ft 4.5in
Length: 25ft 4.25in
Height: 11ft 5.75in
Empty weight: 3,668lb
Maximum take-off weight: 5,511lb
Max speed: 186mph
Climb Rate: 9 minutes to 9,843ft
Service ceiling: 26,246ft
Armament: Four 7.7mm machine guns (two fixed forward firing, two flexibly mounted)
Bomb load: 110lb