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The Watanabe E9W1 Navy Type 96 Small Reconnaissance Seaplane was the first aircraft to be designed and built by Watanabe, and was carried on the large Jun Sen Type 3 submarines.
The Japanese Navy had already produced aircraft for submarines to its own designs, and the Yokosho 2-go Reconnaissance Seaplane of 1929 had entered limited service as the Type 91 Reconnaissance Seaplane. In the mid 1930s the Japanese Navy began work on a new class of large crusier submarines (the Junsen sensuijan Type 3 or J3 class submarines I-7 and I-8). These were designed to carry larger aircraft, and so Watanabe was given the task of designed a two-seat reconnaissance aircraft suitable for use from a submarine.
This would be the first Watanabe designed aircraft to enter production. It was designed by a team led by Ryohochiro Higuchi, and work began on the new aircraft in March 1934. The design was ready by August 1934. The first airframe was completed in November 1934, but was used for structural tests. The first flying prototype was ready in February 1935. Two more prototypes were built, and the type entered production in October 1935. In July 1936 it had been given the official designation Type 96 Small Reconnaissance Seaplane, soon changed to Type 96 Small Seaplane, and the short designation E9W1.
The E9W1 was designed to be assembled or disassembled easily in the cramped conditions on even a large submarine. It only took 2 minutes 30 seconds to assemble the aircraft and 1 minute 30 seconds to disassemble it for storage in the deck hanger (although even this was far too long if the submarine was under attack).
The E9W was a single-engine twin-float single-bay sesquiplane (with a larger upper and smaller lower wing). It has a mixed wood and metal structure, with a fabric covering. The crew of two sat in open cockpits. It was powered by a radial engine with a cowling ring.
The E9W1 saw service on three types of Japanese cruiser submarines (Junsen sensuikan). The first to receive it were the large J3 class submarines I-7 and I-8 (Junsen-gata sensuikan). These were long range scout submarines that were also equipped to serve as flagships.
Next came the Type A submarines (Junsen Ko-gata sensuikan). These were also built as flagships, starting with I-9 to I-11 in 1940-41.
Finally came the Type B submarines (Junsen Otsu-gata sensuikan), which were long range cruiser submarines similar to the Type A, but without the facilities to act as a flagship. This started with the twenty members of the B1 type (I-15, I-17, I-19, I-21, I-23 and I-25 to I-39), of 1939-1942.
The Ko-gata and Otsu-gata designations were the first two letters in the Ten Stems, part of the Japanese Zodiac that was often used in military designations. Ko is normally translated as 'A', and Otsuas 'B', although '1', '2' would probably be more accurate.
The E9W1 entered service on the I-7 and I-8. A total of thirty three aircraft were built, and they were issued to the Type B and Type A submarines as they entered service.
The E9W1 was finally replaced by the Yokosuka E14Y Type 9 Small Reconnaissance Seaplane ('Glen'), which appeared in 1940. Although the E14Y was designed by the Navy's own Yokosuka team, it was built by Watanabe.
Engine: Gasuden Tempu 11 or 12 nine-cylinder air-cooled radial engine
Power: 300-340hp
Crew: 2
Span: 32ft 9in
Length: 25ft 0 3/4in
Height: 10ft 9 1/2in
Empty weight: 1,867lb
Loaded weight: 2,667lb
Maximum take-off weight:
Max speed: 145mph at sea level
Climb Rate: 9min 41 sec to 9,843ft
Service ceiling: 22,112ft
Endurance: 4.9 hours
Range: 368-454 miles
Armament: One dorsal mounted 7.7mm machine gun