Bristol Tramp

The Bristol Tramp was a British passenger and airmail transport triplane designed by the Bristol Aeroplane Company as a steam powered aircraft and built but never flown. It was a development of the earlier Pullman. In 1919 Frank Barnwell discussed with the Royal Mail Steam Packet Company the idea of flying boats as auxiliaries to ocean liners, and the company, experienced with steam turbines, suggested a steam turbine powerplant, planned as two 1,500 hp Ljungstrom type turbines with flash boilers driving four bladed tractor propellers. The turbine proved to deliver far too much power for the airframe. Two examples were completed in 1921 with four 230 hp Siddeley Puma piston engines, but troublesome clutches in the power transmission meant neither ever flew.