A system (SYS1, SYS2) having at least one digital computer suitable for controlling an engine in an aircraft, each digital computer comprising: • at least one input (ENT1 i) suitable for receiving data (DON i) representative of the state of a sensor (CAP i); • at least one output (SOR1 j) suitable for being connected to at least one actuator (ACTj); and • a regulation module (MREG1) suitable for sending at least one command (COM i,j) via a said output (SOR1 j) to said at least one actuator (ACT j) as a function of data (DON i, DSU i) received by at least one input (ENT1 i); said system being characterized in that it comprises: • a selection module (MSEL1) included in said at least one digital computer and suitable for switching said input (ENT1 i) either to said sensor (CAP i) or else to a substitution bus as a function of an instruction from an operator; • a real time simulator for simulating at least some of the environment of said engine and of said aircraft, the simulator comprising: • a digital output suitable for sending at least one substitution item of digital data (DSU i) over said substitution bus to said input (ENT i) of said at least one digital computer; and • a digital input connected to said at least one output (SOR1 j) of the digital computer and suitable for receiving said at least one command (COM i,j) issued by said at least one digital computer, said real time simulator being designed to simulate the reaction of said engine and of said aircraft to said command (COM i,j); and • a verification module embedded in said at least one digital computer, suitable for implementing a verification procedure for preventing said at least one input (ENT1 i) of the digital computer from being switched to said substitution bus by said selection module (MSEL1) when said aircraft is in flight. • at least one input (ENT1 i) suitable for receiving data (DON i) representative of the state of a sensor (CAP i); • at least one output (SOR1 j) suitable for being connected to at least one actuator (ACTj); and • a regulation module (MREG1) suitable for sending at least one command (COM i,j) via a said output (SOR1 j) to said at least one actuator (ACT j) as a function of data (DON i, DSU i) received by at least one input (ENT1 i); • a selection module (MSEL1) included in said at least one digital computer and suitable for switching said input (ENT1 i) either to said sensor (CAP i) or else to a substitution bus as a function of an instruction from an operator; • a real time simulator for simulating at least some of the environment of said engine and of said aircraft, the simulator comprising: • a digital output suitable for sending at least one substitution item of digital data (DSU i) over said substitution bus to said input (ENT i) of said at least one digital computer; and • a digital input connected to said at least one output (SOR1 j) of the digital computer and suitable for receiving said at least one command (COM i,j) issued by said at least one digital computer, said real time simulator being designed to simulate the reaction of said engine and of said aircraft to said command (COM i,j); and • a digital output suitable for sending at least one substitution item of digital data (DSU i) over said substitution bus to said input (ENT i) of said at least one digital computer; and • a digital input connected to said at least one output (SOR1 j) of the digital computer and suitable for receiving said at least one command (COM i,j) issued by said at least one digital computer, said real time simulator being designed to simulate the reaction of said engine and of said aircraft to said command (COM i,j); and • a verification module embedded in said at least one digital computer, suitable for implementing a verification procedure for preventing said at least one input (ENT1 i) of the digital computer from being switched to said substitution bus by said selection module (MSEL1) when said aircraft is in flight.