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A FADEC on a gas turbine engine:
  • A
    is a single channel system.
  • B
    is single fault tolerant.
  • C
    is a three channel system.
  • D
    consists of two identical channels cross linked through an non engine related aircraft computer.
FADEC stands for Full Authority Digital Engine Control and is basically a digital control system mounted on the engine’s fan case, that performs the entire engine management tasks. The FADEC has a dual channels Electronic Control Unit (ECU) for redundancy, with one channel always active and a second one on standby. If one channel fails, the other automatically takes control and performs the exact same functions. In addition to the ECU, all the FADEC peripherals such as actuators, solenoids, electrical wiring, sensors, and fuel metering are also part of the FADEC system and are used for control and monitoring.

The system has a three-phase permanent magnetic alternator for an internal power source. This independent alternator is also the electrical power source for all the FADEC sensors as well as the ECUs. By interfacing with other aircraft systems and its own engine sensors, the FADEC system provides the following functions:
  • Automatic thrust rating control.
  • Engine operation within safe limits.
  • Fully automatic engine starting.
  • Thrust Reverser Control.
  • Engine overspeed and/or an EGT protection function.
  • Engine monitoring and help for maintenance and troubleshooting.

To make the FADEC’s operation more reliable, the system uses the dual inputs logic. All control inputs to the FADEC system are dual, with the exception of some secondary parameters used for monitoring and indicating (that are single). To increase the fault-tolerant design where the engine will still be able to operate within a required reliability and safety range, the parameters are exchanged between the two control channels (inside the ECU) via a cross-channel data link. Therefore, if one input parameter fails to be delivered, the input parameter from the other channel will be used to allow the correct computation of the engine parameters by the FADEC. This means that the FADEC is a single fault-tolerant, and it will ensure the efficient and correct running of the engine even in case of a detected malfunction.

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