R.Mikesh, A.Shorzoe Japanese Aircraft, 1910-1941 (Putnam)

Experimental Yokosho Twin-engined Seaplane

   This aeroplane not only has significance in being the first twin-engined aeroplane built in Japan, but, once completed, no one would fly it. Few pilots in Japan, if any, had ever seen a twin-engined aeroplane. However, it did influence future designs as a result of the experience gained in its design and ground testing.
   Intrigued with the idea of launching torpedoes from aircraft, Nakajima pursued this idea, beginning in about 1914. To explore this concept, he designed an aeroplane for this purpose in April 1916 at the Yokosuka Naval Arsenal. This twin-float biplane could carry a modified version of a 14-inch torpedo which was shortened from a standard torpedo-boat weapon.
   When the aeroplane was completed it was claimed to be the most powerful and the fastest aeroplane in Japan. But their claims were never substantiated, since none of the thirty Navy pilots stationed at the Oppama Naval Air Base would volunteer to fly the aeroplane. None had acquired twin-engine flying experience even while studying in other countries. As a result, only water taxi-ing tests were made, and the aeroplane was eventually stored in the South Hangar at Oppama.

   Twin-engined twin-float biplane with tail float. Wooden structure with fabric covering. Crew of two in open cockpit.
   Two 200hp Salmson 2M-7 seven-cylinder water-cooled radial engines, driving two-bladed wooden propellers.
   Torpedo weighing 350kg (771lb) having a range of 500 to 600m (1,640 to 1,968ft).
   Span 20m (65ft 7 1/2in); length 12m (39ft 4 3/4in); aspect ratio 12.
   Estimated maximum speed 70kt (81 mph) at sea level; endurance 4hr.
   One built in April 1916.