Evening All,
This was my subject for a GB on another site - the Short S39 Triple Twin.
The Short brothers were pioneers in aircraft design and experimentation before 1914, and although they did not originate the twin engine aircraft, they were the first to produce a successful design. The S 39 was structurally the same as the Farmen-Sommer type Short S27 biplane of 1911, but the S 39 had a stronger undercarriage,3 rudders under the tailplane, a front elevator, nacelle with two seats side by side, and two 50 hp Gnome rotary engines, one at the front and the other at the rear of the nacelle.
The rear engine drove a pusher propellor, while the front engine drove 2 tractor propellors via chains and gears. The engines rotated in opposite directions to counter the effects of torque. The S39 was first flown on 18 September 1911 by F. McClean who was able to throttle back each engine in our and still maintain a safe speed in level flight. H. Short had hoped that by placing the control surfaces in the slipstream of the propellors, lateral control would be improved, but the results were disappointing.
Originally the S 39 had equal span wings and 2 fuel tanks, but in December 1911 the span of the upper wing was increased to 50 feet and fuel capacity doubled by adding two extra tanks. Later the lower wings were also increased to 50 feet span.
The machine was bought by the Admiralty in June 1912 and used as a trainer at Eastchurch. In the spring of 1913 it was completely remodelled as a two seat tandem pusher.
Thanks for looking.
Stephen.
