who designed it?
The Sopwith Aviation Company
Sopwith Triplane
The Sopwith Triplane was a British single seat fighter aircraft designed and manufactured by the Sopwith Aviation Company during the First World War. 
who was roderic dallas? An Australian fighter ace of World War I where is he from? Australia was his job related to planes? Yes, Dallas became one of the best-known pilots of Sopwith Triplanes in the RNAS.
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Sopwith Triplane [SEP] Introduction
The Sopwith Triplane was a British single seat fighter aircraft designed and manufactured by the Sopwith Aviation Company during the First World War. It has the distinction of being the first military triplane to see operational service. The Triplane was developed by the firm's experimental department as a private venture, the project was headed by the designer Herbert Smith. Aside from its obvious difference in wing configuration, the aircraft shared many similarities with the company's successful biplane fighter, the Sopwith Pup. The prototype Triplane performed its maiden flight on 28 May 1916 and was dispatched to the French theatre two months later, where it garnered high praise for its exceptional rate of climb and high manoeuvrability.