The advances made in the development of gas turbine engines during the past two decades have been remarkable. The engines have been improved tremendously in terms of power, weight, efficiency and cost. They are now being applied successfully as the prime movers for helicopters, VTOL aircraft, ground power units and for many other diverse purposes, besides the more conventional military and civil aircraft.

There have been parallel advances in the development of gas turbine engine fuel systems (which for convenience may be subdivided into the “control” and the “pumping arrangement”). These systems were originally wholly hydro-mechanical in nature. Sixteen or so years ago, the first supplementary electronic devices were introduced into fuel control systems. Since then, progressively more complex hybrid electronic/hydro-mechanical systems have been employed, with a corresponding easement of the demands on the hydro-mechanical portion. In 1957 Sturrock described to this Society what is now the classic Proteus engine control system used in Britannia aircraft. The satisfactory experience gained with the Proteus system led to the adoption of a comprehensive electronic fuel control system, coupled to a relatively simple fuel pumping system, for the supersonic Olympus engine. This system has been described by Hunt and by Colburn, Tweedy and Dent in papers presented at the joint RAeS/IEE conference “The Importance of Electricity in Aircraft” in 1962. Further papers by Rush presented at the same conference and by Airey in 1963, were devoted to the more general aspects of control.