전자식 엔진 제어 시스템 (FADEC)

Overview

Full Authority Digital Engine Control (FADEC) is the computerized engine management system that governs every aspect of a jet engine's operation from initial start through normal flight to shutdown. FADEC replaced the hydromechanical fuel controllers and analog supervisory electronics of earlier engine generations with a redundant digital system that continuously optimises fuel flow, variable geometry, ignition, bleed extraction, and starting sequences based on real-time sensor data. The "full authority" designation means the system has unrestricted command over all engine actuators — there is no mechanical backup or manual override available to the flight crew.

FADEC systems entered widespread commercial service in the 1980s and are now standard on all new commercial turbofan engines. Their adoption has contributed significantly to improvements in fuel efficiency, reliability, and engine life, while simultaneously reducing the complexity of pilot engine management tasks. A modern FADEC system typically monitors 100 or more engine parameters at rates of tens of samples per second, executing thousands of control law calculations per second to maintain optimal engine performance across every flight phase.

How It Works

Each FADEC consists of two fully independent Electronic Engine Controllers (EECs) or Engine Control Units (ECUs) operating in parallel, with one designated as the active (primary) channel and the other as the standby channel. Both channels continuously receive sensor inputs and execute control algorithms; the standby channel monitors the active channel's outputs for any anomaly and takes over seamlessly in the event of a primary channel fault. This dual-channel architecture achieves the failure rate required for aircraft certification without a conventional mechanical backup.

The primary control parameter is Engine Pressure Ratio (EPR) on some engines, or fan speed (N1) on others, with the FADEC translating the pilot's thrust lever angle into the appropriate fuel flow command. Around this primary loop, the system manages variable stator vane angles in the compressor, compressor bleed scheduling, turbine cooling flows, start sequencing, ignition, and — on geared turbofan engines — the fan speed relative to the low-pressure turbine. The FADEC also enforces engine protection limits, preventing exceedance of exhaust gas temperature (EGT), compressor discharge temperature (T3), shaft speeds, and vibration limits, regardless of pilot inputs.

Key Components

• Electronic Engine Controllers (EECs): Redundant computing modules containing the control laws, sensor interfaces, and actuator drive circuits. Typically housed in environmentally controlled enclosures on the engine fan case.
• Sensors: Thermocouples, pressure transducers, accelerometers, and speed pickups providing N1, N2, N3 (where applicable), EGT, compressor inlet temperature and pressure, fan inlet temperature, and vibration signals.
• Hydromechanical Unit (HMU) / Fuel Metering Unit (FMU): The electro-hydraulic interface between the FADEC and the fuel system. Converts FADEC electrical commands into precise fuel flow rates using servo valves and metering orifices.
• Variable Geometry Actuators: Electro-hydraulic or pneumatic actuators that position variable stator vanes and compressor bleed valves per FADEC commands.
• ARINC 429 / AFDX Databus Interface: Communications links connecting the FADEC to aircraft-level systems including the Flight Management System, Engine Indicating and Crew Alerting System (EICAS/ECAM), and the thrust management computer.

Aircraft Applications

• Boeing 737-800 — CFM56-7B FADEC; EEC manages start, idle, thrust limits, and bleed scheduling
• Airbus A320-200 — CFM56-5B or IAE V2500 FADEC; integrated with ECAM for crew alerts
• Boeing 777-300ER — GE90 FADEC; manages the world's largest commercial turbofan
• Boeing 787-9 — GEnx or Trent 1000 FADEC; coordinated with electric engine start and bleed-free architecture
• Airbus A350-900 — Trent XWB FADEC; integrated with Airbus's three-axis fly-by-wire and open-world avionics

Advantages and Limitations

FADEC provides consistent, optimised engine management that no human operator could replicate across the full flight envelope. It reduces pilot workload, eliminates the need for complex throttle management procedures, enables engine health monitoring, and enforces operating limits that protect engine hardware from damage. Modern FADEC systems achieve mean time between failures measurable in tens of thousands of flight hours, contributing directly to the excellent reliability rates of contemporary turbofan engines.

The elimination of a mechanical backup means that a complete dual-channel FADEC failure would result in loss of engine control — an event that must be demonstrably improbable through redundancy design. Software integrity is critical: FADEC software is certified to the most stringent avionics software standard (DO-178C Level A), requiring exhaustive testing and documentation. The self-contained nature of FADEC also means that troubleshooting requires specialised equipment and access to engine parameter data recorded by the controller, increasing the technical sophistication required of maintenance personnel.