The Nakajima E4N was a reconnaissance biplane that went through two very different designs before entering service with the Japanese Navy during the 1930s.
In 1930 the Japanese Navy required a new reconnaissance aircraft to replace the Nakajima Type 15 Reconnaissance Seaplane (E2N) that had entered service in 1927.
Both of Nakajima's designs were influenced by the Vought O2U Corsair, a biplane observation biplane. Nakajima purchased one example of the Corsair, and later gained a licence to produce the design.
Nakajima's first attempt to satisfy the Navy requirement was the E4N1 biplane. This aircraft had a welded chromium molybdenum steel tube structure with fabric covering at the rear and aluminium sheet covering at the front. It was a standard biplane, with fabric covered wings with a wooden structure. The Vought Corsair used a single central float. The E4N1 was a twin float aircraft, but the two floats were very similar to the Vought design. Bombs were carried on the underside of the fuselage. It was powered by a 420-520hp Nakajima Jupiter VI radial engine, and reached 130mph.
Two prototypes of the E4N1 were built. They were given the official designation Navy Type 90-2-1 Reconnaissance Seaplane - Aichi had already had a reconnaissance seaplane accepted in 1930, and that became the Type 90-1. The E4N1 was tested by the Japanese Navy early in 1931, but the design was rejected because it wasn't very manoeuvrable.
Nakajima responded with the E4N2. This was very similar to the Vought O2U Corsair, reflecting Nakajima's purchase of a manufacturing licence. The new aircraft was also a fairly conventional biplane. This time the fuselage structure was a mix of wood and metal. Once again the forward fuselage was metal covered but the rest of the fuselage and the wings were fabric covered. The wings had a wooden structure and were rearward folding. It has a single main central float with wing-tip stabilisers. The E4N2 was powered by the Nakajima Kotobuki 2-kai-I nine-cylinder air-cooled radial, and reached a top speed of 144mph. More importantly it was much more manoeuvrable than the E4N1. The first prototype was tested late in 1930, suggesting that it was already under development before the E4N1 had been rejected. A stronger version was produced and in December 1941 was accepted as the Type 90-2-2 Reconnaissance Seaplane, E4N2. It could also be used with wheels, when it became the Type 90-2-3 E4N3.
Nakajima produced eighty E4N2s between 1931 and 1936 and Kawanishi produced another 67 aircraft between 1932 and 1934.
Nakajima also produced five of the E4N2-C carrier variant. This had wheels and carrier arrestor gear. They underwent service trials but weren't accepted.
The E4N2 was the Japanese Navy's main ship-borne reconnaissance aircraft from 1932 until it was replaced by the Nakajima Type 95 Reconnaissance Seaplane (E8N) in the mid 1930s. It was used on battleships and cruisers and was a popular aircraft with a good combination of manoeuvrability and strength. It saw combat during the Shanghai Incident
Nine of these landplanes were converted into night mail carriers, with the new designation P-1. They were turned into single-seaters, with an enclosed cockpit and were used to carry mail between the main Japanese islands.
Engine: Nakajima Kotobuki 2-kai-I nine-cylinder radial engine
Length: 29ft 1.25in
Empty weight: 2,760lb
Maximum take-off weight: 3,968lb
Max speed: 144mph
Climb Rate: 10 min 34 sec to 9,843ft
Service ceiling: 18,832ft
Range: 633 miles
Armament: One fixed forward firing 7.7mm machine gun, one flexibly mounted 7.7mm machine gun
Bomb load: Two 66lb bombs