Bristol Siddeley Orpheus - Design and Development

Design and Development

The engine had its genesis in a 1952 request by Folland for an engine in the 5,000 pounds (22 kN) class to power a new trainer and lightweight fighter-bomber they were developing. Stanley Hooker, relatively new to the company after an earlier career at Rolls-Royce, took the project under his wing. He delivered a relatively simple and easy to maintain engine, which was put into use in the Folland Gnat, flying in 1955. Developing a Sea Level Static thrust of 4,520 lbf (20.1 kN), the Orpheus 701 had a 7 stage axial compressor driven by a single stage turbine.

Other users, mostly trainers, soon followed, including the Fuji T-1, Hindustan Marut, HA-300,and the experimental Hunting H.126 and Short SB5. In 1957 NATO ran a competition for a light fighter design, asking for entries in both engine and airframe categories. The Orpheus was the unanimous winner of the engine contest, and was thus selected to power the Fiat G.91R and G.91T using Fiat-built versions of the engine.

Many companies in the 1950s were looking at ways of producing a vertical take off and landing aircraft. Michel Wibault had the idea of using a turboshaft engine to drive four large centrifugal blowers which could be swivelled to vector the thrust. Hooker's engineers decided on using the Orpheus to drive a single large fan that would supply air to a pair of rotating nozzles, while the exhaust flow from the Orpheus was split into two and would supply another pair of nozzles at the rear of the engine. This experimental system developed into the Pegasus.