Propulsion control system
- 1. FADEC (Propulsion Control System) Milind D Patil
- 2. FOR TRAINING PURPOSE ONLY 2 FADEC (Propulsion Control System) Contents 1 Definition 2 Description 3 Safety 4 Applications 5 Advantages 6 Disadvantages 7 FADEC Faults
- 3. FOR TRAINING PURPOSE ONLY 3 Definition FADEC is a system consisting of a digital computer, called an electronic engine controller (EEC) or engine control unit (ECU), and its related accessories that control all aspects of aircraft engine performance.
- 4. FOR TRAINING PURPOSE ONLY 4 True full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer. If a total FADEC failure occurs, the engine fails. If the engine is controlled digitally and electronically but allows for manual override, it is considered solely an EEC or ECU. An EEC, though a component of a FADEC, is not by itself FADEC. When standing alone, the EEC makes all of the decisions until the pilot wishes to intervene. Description
- 5. FOR TRAINING PURPOSE ONLY 5 FADEC works by receiving multiple input variables of the current flight condition including air density, throttle lever position, engine temperatures, engine pressures, and many other parameters. The inputs are received by the EEC and analyzed up to 70 times per second. Engine operating parameters such as fuel flow, stator vane position, bleed valve position, and others are computed from this data and applied as appropriate. FADEC also controls engine starting and restarting. The FADEC's basic purpose is to provide optimum engine efficiency for a given flight condition. Description
- 6. FOR TRAINING PURPOSE ONLY 6 FADEC not only provides for efficient engine operation, it also allows the manufacturer to program engine limitations and receive engine health and maintenance reports. For example, to avoid exceeding a certain engine temperature, the FADEC can be programmed to automatically take the necessary measures without pilot intervention. Description
- 7. FOR TRAINING PURPOSE ONLY 7 With the operation of the engines so heavily relying on automation, safety is a great concern. Redundancy is provided in the form of two or more separate but identical digital channels. Each channel may provide all engine functions without restriction. FADEC also monitors a variety of data coming from the engine subsystems and related aircraft systems, providing for fault tolerant engine control. Safety
- 8. FOR TRAINING PURPOSE ONLY 8 A typical civilian transport aircraft flight may illustrate the function of a FADEC. The flight crew first enters flight data such as wind conditions, runway length, or cruise altitude, into the flight management system (FMS). The FMS uses this data to calculate power settings for different phases of the flight. At takeoff, the flight crew advances the throttle to a predetermined setting, or opts for an auto-throttle takeoff if available. The FADECs now apply the calculated takeoff thrust setting by sending an electronic signal to the engines; there is no direct linkage to open fuel flow. This procedure can be repeated for any other phase of flight. In flight, small changes in operation are constantly made to maintain efficiency. Maximum thrust is available for emergency situations if the throttle is advanced to full, but limitations can not be exceeded; the flight crew has no means of manually overriding the FADEC. Applications
- 9. FOR TRAINING PURPOSE ONLY 9 • Better fuel efficiency • Automatic engine protection against out-of-tolerance operations • Safer as the multiple channel FADEC computer provides redundancy in case of failure • Care-free engine handling, with guaranteed thrust settings • Ability to use single engine type for wide thrust requirements by just reprogramming the FADECs • Provides semi-automatic engine starting • Better systems integration with engine and aircraft systems • Can provide engine long-term health monitoring and diagnostics • Number of external and internal parameters used in the control processes increases by one order of magnitude • Reduces the number of parameters to be monitored by flight crews • Due to the high number of parameters monitored, the FADEC makes possible "Fault Tolerant Systems" (where a system can operate within required reliability and safety limitation with certain fault configurations) • Saves weight Advantages
- 10. FOR TRAINING PURPOSE ONLY 10 • Full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer. • If a total FADEC failure occurs, the engine fails. • Upon total FADEC failure, pilots have no manual controls for engine restart, throttle, or other functions. • Single point of failure risk can be mitigated with redundant FADECs (assuming that the failure is a random hardware failure and not the result of a design or manufacturing error, which may cause identical failures in all identical redundant components). • High system complexity compared to hydromechanical, analogue or manual control systems • High system development and validation effort due to the complexity • Whereas in crisis (for example, imminent terrain contact), a non-Fadec engine can produce significantly more than its rated thrust, a FADEC engine will always operate within its limits. Disadvantages
- 11. FOR TRAINING PURPOSE ONLY 11 • The FADECs have two redundant channels; loss of a single channel does not generally require crew action. Single channel FADEC faults during start may be considered spurious on successful application of the reset procedure detailed in FCOM PRO.AEP.ENG • If both channels of a FADEC are lost, the thrust lever should be set to idle. Engine indications will be lost. If all other parameters are normal (check all ECAM system pages), the engine can be left running. Otherwise, shut it down. • If a FADEC overheats, reducing engine power may reduce temperature in the ECU area sufficiently to prevent shutdown. If on the ground the engine must be shut down and the FADEC depowered. FADEC faults
Editor's Notes
- #8: Engine control problems simultaneously causing loss of thrust on up to three engines have been cited as causal in the crash of an Airbus A400M aircraft at Seville Spain on 9 May 2015. Airbus Chief Strategy Officer Marwan Lahoud confirmed on 29 May that incorrectly installed engine control software caused the fatal crash. "There are no structural defects [with the aircraft], but we have a serious quality problem in the final assembly.