Full authority digital engine control system for aircraft engine

A digital engine control system for an aircraft engine comprising:

• two redundant electronic control units configured to control the engine of the aircraft, each electronic control unit being configured to determine a speed measurement of the engine from an output signal from a respective speed sensor representative of the speed of the engine;
• a selection unit configured to select one or the other of the electronic control units to control the engine as a function of an operating state of the electronic control units;
• and
• an electronic overspeed protection system configured to protect the engine of the aircraft from overspeeds, from the output signal from at least one respective protection speed sensor representative of the speed of the engine, wherein the selection unit comprises a monitoring module configured to determine a speed measurement of the engine from the output signal from the or each protection speed sensor and compare the or each speed measurement determined by the monitoring module with the speed measurements supplied by each electronic control unit to determine an operating state of each electronic control unit, and wherein the monitoring module is configured to inhibit the selection of an electronic control unit while the electronic control unit does not provide the monitoring module with a speed measurement.