The Yokosuka E6Y aka Yokosuka Navy Type 91-1 Reconnaissance Seaplane, was developed by the Yokosuka Naval Air Technical Arsenal for the Imperial Japanese Navy during the 1920s.
The prototype, initially named the Yokosho 2-Go aka Yokosuka Arsenal No. 2 Reconnaissance Seaplane, took its first flight in 1929.
This single-seat biplane was designed for quick assembly and disassembly, allowing it to be stored on submarines.
Two prototypes were built, differing in power plant and design details.
Eight production models, designated E6Y and built by Kawanishi in the 1930s, were deployed on Japanese submarine aircraft carriers I-5, I-6, I-7, and I-8.
The E6Y saw limited action during the January 28 incident and the Second Sino-Japanese War, with the last example being retired in 1943.
The Imperial Japanese Navy was a pioneer in naval aviation, purchasing two floatplanes from Britain and one from the United States as early as 1912.
By December 1922, Japan had completed Hōshō, the first ship purpose-designed for aircraft operations.
Alongside this development, the Navy sought to extend the operational reach of their large submarine force by exploring aircraft as a reconnaissance tool.
The Navy acquired a German Caspar U.1 and a Parnall Peto from Britain, both early submarine-based reconnaissance aircraft, to inform the development of two prototype Japanese aircraft for submarine-based reconnaissance.
The 1-Go was based on the former, while the latter heavily influenced the 2-Go.
The Yokosuka Naval Air Technical Arsenal developed the 2-Go as a smaller aircraft than the Peto.
It was a biplane of mixed construction, with a steel frame and wooden-framed wings covered in canvas.
The wings and twin float assembly were designed to detach for storage.
The first prototype was powered by an Armstrong Siddeley Mongoose five-cylinder radial engine, rated at 130 hp (97 kW), but manufactured under license by Mitsubishi.
The second prototype, designated 2-Go Kai, differed in several details.
Lateral stability issues were resolved by increasing the tail fin and rudder, extending them upward.
The aircraft was fitted with a more powerful Japanese Gasuden Jimpu seven-cylinder radial, rated at 160 hp (120 kW), which gave a maximum speed of 169 km/h (105 mph) and four and a half hours endurance.
In 1931, the Kawanishi Aircraft Company was commissioned to produce eight production machines, designated E6Y1, based on the 2-Go Kai, which were built between 1932 and 1934.
The Navy took delivery of the 2-Go in May 1929 and initially tested it aboard the submarine I-51.
Testing was completed by September 1931.
The 2-Go Kai commenced testing in 1931 initially also on board I-51 and then subsequently the Junsen I Mod type submarine I-5.
Launch was initially from the water, but a catapult was fitted to I-5 in 1933 and this was found more satisfactory.
All subsequent Japanese aircraft-carrying submarines used catapults.
The first production E6Y entered service in 1933, and the eight aircraft were deployed to the three Junsen II and III submarines, I-6, I-7, and I-8.
The aircraft also saw surface ship use.
They saw limited service during the January 28 incident in 1932, providing reconnaissance, and subsequently there are reports that they served on submarines that operated during the Second Sino-Japanese War.
Between 1937 and 1938, submarines I-5 and I-6 were assigned to the Third Fleet (China Theatre Fleet) based at Hong Kong to patrol and blockade the central and southern Chinese coasts.
As the Japanese Navy introduced larger aircraft-carrying submarines, the E6Y was superseded by the Watanabe E9W.
The last example retired in 1943.
Variants
Yokosho 2-Go
First prototype equipped with a 130 horsepower (97 kW) Mitsubishi-licensed Armstrong Siddeley Mongoose.
Yokosho 2-Go Kai
Second prototype equipped by a 160 horsepower (120 kW) Gasuden Jimpu
E6Y1
Production version of the 2-Go Kai manufactured by Kawanishi.
Specifications
Crew
1
Length
6.69 m (21 ft 11 in)
Wingspan
8 m (26 ft 3 in)
Height
2.87 m (9 ft 5 in)
Wing area
26.70 m2 (287.4 sq ft)
Empty weight
570 kg (1,257 lb)
Max take-off weight
750 kg (1,653 lb)
Powerplant
1 × Gasuden Jimpu 7-cylinder radial,
120 kW (160 hp)
Performance
Maximum speed
169 km/h (105 mph, 91 kn)
Range
600 km (370 mi, 320 nmi)
Endurance
4.4 hours
Service ceiling
4,800 m (15,700 ft)
Time to altitude
3,000 m (9,800 ft) in 20 minutes 14 seconds
Power/mass
5.77 kg (12.7 lb)/hp.
Sources Japanese Aircraft, 1910-1941-Robert Mikesh & Shorzoe Abe The Mainichi Newspapers Co Ltd Yushukan War Memorial Museum Japanese Aircraft of the Pacific War-Rene Francillon, Japanese Aircraft-John Stroud, Japanese Military Aircraft Illustrated.
