FADEC is the acronym for Full Authority Digital Engine Control. It is a system consisting of a digital computer (called EEC /Electronic Engine Control/ or ECU /Electronic Control Unit/) and its related accessories which control all aspects of aircraft engine performance. FADECs have been produced for both piston engines and jet engines, their primary difference due to the different ways of controlling the engines.
Electronics' superior accuracy led to early generation analogue electronic control first used in Concorde's Rolls-Royce Olympus 593 in the 1960s. Later in the 1970s NASA and Pratt and Whitney experimented with the first experimental FADEC, first flown on an F-111 fitted with a highly modified Pratt & Whitney TF-30 left engine. The experiments led to Pratt & Whitney F100 and Pratt & Whitney PW2000 being the first military and civil engines respectively fitted with FADEC and later the Pratt & Whitney PW4000 as the first commercial 'Dual FADEC' engine.
The aircraft's thrust lever sends electrical signals (pilot's command, may also be the autothrottle) to the FADEC. The FADEC digitally calculates and precisely controls the fuel flow rate to the engines giving precise thrust. In addition to the fuel metering function, the FADEC performs numerous other control and monitoring functions such as Variable Stator Vanes (VSV's) and Variable Bleed Valves (VBV's) control, cabin bleeds and power off-takes control, control of starting and re-starting, turbine blade and vane cooling and blade tip clearance control, thrust reversers control, engine health monitoring, oil debris monitoring and vibration monitoring. The inputs come from various aircraft and engine sensors. Apart from the key parameters that are monitored for a safe thrust control (shaft rotational speeds, pressures and temperatures at various points along the gas path) the FADEC also monitors hundreds of various analog, digital and discrete data coming from the engine subsystems and related aircraft systems, providing a fully redundant and fault tolerant engine control